JPH0792257A - Radar equipment - Google Patents

Abstract

PURPOSE:To precisely compensate a fluctuation and to prevent the degradation of the cross range resolution by a method wherein a predetermined reference point of a reflected signal from a target is detected and the phase of the output at a range compression means is compensated on the basis of the reference point. CONSTITUTION:Reference-point detection means 10a to 10N detect each one reference point, which shows a feature as compared with the circumference on a target and which is used as a phase compensation reference, from a complex signal Q (c,gamma) after subjected to cross range compression by a means 4. A selection means 19 selects one reference point from the detected reference points. At this time, when algorithms for the detection means 10a to 10N are different, the algorithms which are provided with two or more conditions for the reference points (e.g. whose range gets a perfect score and which are situated in a brightest point) are detected according to decision by majority. Consequently, the fluctuation compensation is resistant to interference. Then, a fluctuation compensation means 11 detects, on the basis of the selected reference point, a phase change as a phase compensation amount at every bit of the reference point from a signal after cross range compression by a means 3, and the phase of a received signal is compensated by a cross-range compression means 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a change in a reflected signal based on a change in a relative positional relationship between a target and a radar device and a change in a reflected signal based on a change in a transmission frequency to achieve a high resolution. The present invention relates to a radar device that can obtain

[0002]

2. Description of the Related Art A conventional radar device of this type is generally called a high resolution radar device, for example, Donald
R. Wehner, "High Resolution"
Radar ", Artech House, INC.
1987 pp302, ISAR (In
Verse Synthetic Aperture
Radar) and Japanese Patent Application No. 3-333473. In FIG. 45, reference numeral 1 denotes a transmitting / receiving antenna that radiates high-frequency power to space and receives a signal reflected by a target, and 2 denotes power that is radiated by the transmitting / receiving antenna 1.
A coherent transceiver that supplies the received signal and performs phase detection / amplification of the received signal. Reference numeral 3 is a range compression unit that improves the resolution related to the distance between the transmission / reception antenna 1 and the target. Reference numeral 4 is a cross-range compression unit that improves the resolution related to the target azimuth. Reference numeral 5 denotes range compression means 3 and cross-range compression means 4.
A monitor display 8 for displaying the radar image created by 1. is a target such as an aircraft or a ship.

Next, the operation will be described. The coherent transceiver 2 in FIG. 45 generates a high frequency pulse modulated into a signal (chirp) whose frequency changes with time as shown in FIG. 46, and supplies it to the transmitting / receiving antenna 1. The signal (echo) reflected by the target enters the transmitting / receiving antenna 1 and is demodulated by the coherent transceiver 2.

Since the demodulated signal is delayed by the time required for round trip of radio wave propagation between the transmitting / receiving antenna 1 and the target 8 with respect to the instantaneous frequency of the transmitting signal, the transmitting signal s ( Matching the received signal r (t) with t),
As shown in (1), the conjugate signal s * of the transmission signal s (t)
By obtaining the convolution of (t) and the received signal r (t), the impulse v
(T) can be obtained. This improves range resolution.

[0005]

[Equation 1]

Since a range-compressed signal is obtained each time the radar repeats transmission, a two-dimensional complex having the range r and the hit h as axes is obtained by collecting the range-compressed signals for each radar transmission (hit). Signal P (h, r)
Is obtained. Between the range r and the time t, r = (Δr
There is a relationship of / Δt) · t. Where Δt is the sampling interval of the A / D converter (= 1 / B, B is the transmission band)
And Δr is the range resolution (= C / 2B). Here, it is assumed that the range movement of the echo accompanying the movement of the target has been corrected in advance by the range compression means 3.

The cross-range compression means 4 uses the complex signal P
By Fourier transforming (h, r) on the hit h according to the equation (2), the complex signal Q (c, r) compressed for both the range and the cross range is obtained. Here, c indicates a cross range (azimuth direction).

[0008]

[Equation 2]

This processing has the same effect as the range compression means 3, that is, the effect of improving the resolution in the cross range direction. Hereinafter, this principle will be described.

FIG. 47 shows the geometry of the transmitting / receiving antenna 1 and the target 8 (ship). In FIG. 47, 42 and 43
Indicate the tip (bow) and tail (stern) of the target, respectively. Now, assuming that the target 8 does not move but is rotating (yaw motion) about an axis perpendicular to the sea surface, the Doppler frequency fd of the signal reflected at a certain part on the target is expressed by the following formula. It

[0011]

[Equation 3]

Where λ is the transmission wavelength, x is the radius of gyration of the reflected portion, ω is the angular velocity of rotation, and θ (h) is the target angle based on the line LOS (Line of Slight) which is the reference for observation. Is.

From equation (3), it can be seen that the Doppler frequency of the reflected signal from each part on the target differs depending on the distance x from the rotation axis. For example, in FIG. 48, the reflected signal Doppler frequency fd from the target tip and tail is shown.
Indicates. In the figure, 44 and 45 respectively indicate the Doppler frequencies of the reflected signals from the tip and tail of the target.

That is, different Doppler frequencies are generated depending on the target position in the front-rear direction. Therefore, the received signal is Fourier-transformed according to the equation (2) to improve the resolution in the cross-range direction more than the transmission beam width of the antenna. be able to.

The absolute value of the complex signal Q (c, r) whose resolution is improved in both the range direction and the cross range direction by the range compression means 3 and the cross range compression means 4 corresponds to the target radar reflection cross section. Therefore, by displaying on the two-dimensional plane of the range r and the cross range c on the monitor display 5 with the brightness corresponding to the absolute value of Q (c, r) or the square thereof, both the range and the cross range are increased. A resolution-resolved target image can be displayed.

[0016]

By the way, in general, a target targeted by this type of radar is moving, but when the speed with respect to the transmitting / receiving antenna 1 changes during observation, it is reflected at a certain point on the target. The Doppler frequency of the signal changes over time. FIG. 49 shows an example of the Doppler frequency of the reflected wave from the tip and the tail of the target in such a case. In the figure, 46 and 47 are examples of the Doppler frequencies of the reflected waves from the target tip and tail, respectively.

In such a case, even if the cross range compression is performed according to the equation (2), the target cross range resolution is not improved. This is compared to the case where the target is not moving
This is because the phase error Δφ (h) shown in (4) is generated and the Doppler frequency becomes the value of fd ′ (h) shown in equation (5).

[0018]

[Equation 4]

Here, Δr (h) is a change in distance between the transmitting / receiving antenna 1 and the target 8 caused by the movement of the target.

Therefore, when the target is moving, in order to improve the cross range resolution, it is necessary to obtain the phase error Δφ (h) by some means and compensate it. Upset caused by Δr
You must know (h). However, it is generally very difficult to know the fluctuation of the goal. As described above, in the conventional radar device, it is difficult to accurately perform the motion compensation and prevent the deterioration of the performance.

[0021]

According to a first aspect of the present invention, reference point detecting means for detecting one predetermined reference point of a reflection signal from a target based on the output of the cross range compressing means, and a reference point detecting means. On the basis of the points, the fluctuation compensating means for compensating the phase of the output of the range compressing means is provided.

According to a second aspect of the present invention, a plurality of reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of the cross-range compression means, and the plurality of reference points. It is provided with a selecting means for selecting the output of 1 according to a predetermined reference from the output of the point detecting means, and a swing compensating means for compensating the phase of the output of the range compressing means based on the output of the selecting means. is there.

According to a third aspect of the present invention, the first reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output of the range compressing means, and the cross range compressing means. Based on the output, the second reference point detecting means for detecting one predetermined reference point of the reflection signal from the target, and the outputs of the first reference point detecting means and the second reference point detecting means Selecting means for selecting the output of 1 according to a predetermined standard;
A fluctuation compensating means for compensating the phase of the output of the range compressing means based on the output of the selecting means is provided.

According to a fourth aspect of the present invention, a plurality of first reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of the range compression means, and a cross range. Based on the output of the compression means, a plurality of second reference point detection means for respectively detecting a predetermined one reference point of the reflection signal from the target, the plurality of first reference point detection means and the plurality of reference points. Selector means for selecting the output of 1 according to a predetermined reference from the output of the second reference point detecting means, and swing compensating means for compensating the phase of the output of the range compressing means based on the output of the selecting means. Be prepared.

According to a fifth aspect of the invention, a display device for displaying the output of the range compression means, a reference point input means for inputting a reference point from the outside, and the range compression means based on the output of the reference point input means. Is provided with a fluctuation compensating means for compensating the phase of the output of.

According to a sixth aspect of the present invention, the display device for displaying the output of the cross range compression means, the reference point input means for inputting a reference point from the outside, and the range compression based on the output of the reference point input means are used. The fluctuation compensating means for compensating the phase of the output of the means is provided.

According to a seventh aspect of the present invention, the first reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output of the range compressing means and the cross-range compressing means. Second reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output, and image formation for determining the image forming state at the reference point of the second reference point detecting means. Based on the determination means, the re-detection instructing means for instructing the first reference point detecting means to re-detect the reference point based on the determination result, and the range compression based on the reference point of the first reference point detecting means. The fluctuation compensating means for compensating the phase of the output of the means is provided.

The present invention according to claim 8 is characterized in that, based on the output of the range compression means, the first reference point detection means for detecting one predetermined reference point of the reflection signal from the target and the cross range compression means. Based on the output, a plurality of second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target and a connection at each reference point of the plurality of second reference point detecting means. A plurality of image forming determination means for determining an image state; a selecting means for selecting one output from outputs of the plurality of image forming determination means according to a predetermined reference; and a first output based on the output of the selecting means. Re-detection instructing means for instructing the reference point detecting means to re-detect the reference point, and a shake compensating means for compensating the phase of the output of the range compression means based on the reference point of the first reference point detecting means. It is those with a.

According to a ninth aspect of the present invention, the first reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output of the range compressing means, and the cross range compressing means. Based on the output, a plurality of second reference point detecting means for respectively detecting a predetermined one reference point of the reflection signal from the target, and a predetermined number from the outputs of the plurality of second reference point detecting means Based on the output of the selection means for selecting the output of 1 according to the reference, the image formation determination means for determining the image formation state at the reference point selected by the selection means, and the first reference point detection based on the output of the image formation determination means. The re-detection instructing means for instructing the means to re-detect the reference point, and the shake compensating means for compensating the phase of the output of the range compression means based on the reference point of the first reference point detecting means. Than it is.

According to a tenth aspect of the present invention, first reference point detecting means and second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of the cross range compression means. Point detecting means, and the second
Imaging determination means for determining the imaging state at the reference point of the reference point detection means, and re-detection instruction means for instructing the first reference point detection means to re-detect the reference point based on the determination result. A fluctuation compensating means for compensating the phase of the output of the range compressing means based on the reference point of the first reference point detecting means is provided.

According to an eleventh aspect of the present invention, first reference point detecting means and a plurality of second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of the cross range compression means. Reference point detecting means, selecting means for selecting one output from the outputs of the plurality of second reference point detecting means in accordance with a predetermined reference, and an image formation state at the reference point selected by the selecting means. Of the first reference point detecting means and the re-detection instructing means for instructing the first reference point detecting means to re-detect the reference point based on the output of the image forming determining means. A fluctuation compensating means for compensating the phase of the output of the range compressing means on the basis of the reference point is provided.

According to a twelfth aspect of the present invention, first reference point detecting means and a plurality of second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of the cross range compression means. Reference point detection means, a plurality of image formation determination means for determining image formation states at the reference points of the plurality of second reference point detection means, and outputs from the plurality of image formation determination means. Selection means for selecting the output of 1 according to the reference, re-detection instruction means for instructing the first reference point detection means to re-detect the reference point based on the output of the selection means, and the first reference. A fluctuation compensating means for compensating the phase of the output of the range compressing means based on the reference point of the point detecting means is provided.

According to a thirteenth aspect of the present invention, reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output of the cross range compressing means, and the output of the reference point detecting means. Based on the above, the fluctuation compensating means for compensating the phase of the output of the range compressing means, the display for displaying the output of the cross range compressing means, and the re-detection for instructing the reference point detecting means to re-detect the reference point It is provided with an instruction input means.

[0034]

According to the present invention, the reference point detecting means detects the reference point of 1 based on the output of the cross range compressing means, and the oscillation compensating means detects the phase of the output of the range compressing means based on the reference point. To compensate.

According to the second aspect of the invention, based on the output of the cross range compression means, the plurality of reference point detection means detect a plurality of reference points, and the selection means selects one reference point from the plurality of reference points. The fluctuation compensating means compensates the phase of the output of the range compressing means based on the output of the selecting means.

In the third aspect of the invention, the first reference point detecting means detects one reference point based on the output of the range compressing means, and the second reference point detecting means detects the second reference point based on the output of the cross range compressing means.
The reference point detecting means detects one reference point, the selecting means selects one reference point from the outputs of the first reference point detecting means and the second reference point detecting means, and the output of the selecting means. Based on the above, the fluctuation compensating means compensates the phase of the output of the range compressing means.

In the invention of claim 4, the plurality of first reference point detecting means detect a plurality of reference points on the basis of the output of the range compression means, and the plurality of second reference points on the basis of the output of the cross range compression means. The reference point detecting means detects a plurality of reference points, and the selecting means detects one reference point from the outputs of the plurality of first reference point detecting means and the plurality of second reference point detecting means. Based on the output of the selecting means, the fluctuation compensating means compensates the phase of the output of the range compressing means.

In the invention of claim 5, the display device displays the output of the range compression means, the operator judges the reference point based on the display, and the reference point is input from the outside by using the reference point input means. The fluctuation compensating means compensates the phase of the output of the range compressing means based on the output of the reference point inputting means.

In the invention of claim 6, the display device displays the output of the cross-range compression means, the operator judges the reference point based on the display, and the reference point is input from the outside by using the reference point input means. Then, the motion compensation means compensates the phase of the output of the range compression means based on the output of the reference point input means.

In the invention of claim 7, the first reference point detecting means detects one reference point based on the output of the range compressing means, and the second reference point detecting means detects the cross range compressing means. Based on the output, one reference point is detected, the imaging determination means determines the imaging state at the reference point of the second reference point detection means, and the re-detection instructing means determines the first reference point based on the determination result. The reference point detecting means is instructed to re-detect the reference point, and the motion compensating means compensates the phase of the output of the range compressing means based on the reference point of the first reference point detecting means.

In the eighth aspect of the present invention, the first reference point detecting means detects one reference point based on the output of the range compressing means, and the plurality of second reference point detecting means cross-range compresses. Detects multiple reference points based on the output of the means,
The plurality of image forming determination means determines the image forming state at each reference point of the second reference point detecting means, the selecting means selects one output from the outputs of the plurality of image forming determination means, and the re-detection instruction is given. Based on the output of the selecting means, the means instructs the first reference point detecting means to re-detect the reference point, and the motion compensation means based on the reference point of the first reference point detecting means, the range compression is performed. Compensate the phase of the output of the means.

In the ninth aspect of the present invention, the first reference point detecting means detects one reference point based on the output of the range compressing means, and the plurality of second reference point detecting means detects the cross range compression. Based on the output of the means, each of the plurality of reference points is detected, the selection means selects one output from the outputs of the plurality of second reference point detection means, and the image formation determination means is selected by the selection means. Determine the image formation state at the reference point,
The re-detection instructing means instructs the first reference point detecting means to re-detect the reference point based on the output of the image formation determining means, and the motion compensation means becomes the reference point of the first reference point detecting means. Based on this, the phase of the output of the range compression means is compensated.

In the tenth aspect of the present invention, the first reference point detecting means and the second reference point detecting means respectively detect the reference points based on the output of the cross-range compressing means, and the image forming determining means described above. The image forming state at the reference point of the second reference point detecting means is determined, and the re-detection instructing means instructs the first reference point detecting means to re-detect the reference point based on the determination result, and the motion compensation means. However, the phase of the output of the range compression means is compensated based on the reference point of the first reference point detection means.

In the eleventh aspect of the present invention, the first reference point detecting means and the plurality of second reference point detecting means respectively detect the reference points on the basis of the output of the cross-range compressing means, and the selecting means described above. One output is selected from the outputs of the plurality of second reference point detection means, the image formation determination means determines the image formation state at the reference point selected by the selection means, and the re-detection instruction means determines the image formation determination. Based on the output of the means, the first reference point detection means is instructed to re-detect the reference point, and the motion compensation means is based on the reference point of the first reference point detection means,
The phase of the output of the range compression means is compensated.

According to the twelfth aspect of the present invention, the first reference point detecting means and the plurality of second reference point detecting means respectively detect the reference points based on the output of the cross range compressing means, and the image forming determining means. Determines the image forming state at each reference point, the selecting means selects one output from the outputs of the plurality of image forming determining means, and the re-detection instructing means determines the first output based on the output of the selecting means. The one reference point detecting means is instructed to re-detect the reference point, and the motion compensating means compensates the phase of the output of the range compressing means based on the reference point of the first reference point detecting means.

In the thirteenth aspect of the present invention, the reference point detecting means detects one reference point based on the output of the cross range compressing means, and the motion compensation means based on the output of the reference point detecting means. Compensating the phase of the output of the compression means, the display device displays the output of the cross-range compression means,
The operator judges the image formation state based on the display screen and uses the re-detection instruction input means to instruct the reference point detection means to re-detect the reference point.

[0047]

【Example】

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the reference point is detected based on the output of the cross range compression means, and the motion compensation is performed.

In FIG. 1, 1 is a transmission / reception antenna, 2 is a coherent transceiver that generates and supplies electric power to be radiated by the transmission / reception antenna 1, and amplitude-detects a reception signal and also detects a phase, and 3 is a transmission-reception antenna and a target. The range compression means 4 for improving the resolution with respect to the distance between and the cross compensating the phase of the signal on the basis of the phase compensation amount of the output of the motion compensating means 11, thereby performing the motion compensation and improving the resolution for the target azimuth. Range compression means, 5 is a monitor display for displaying radar images, 8
Are targets of aircraft, ships, etc., 10a, 10b, ... 10
N is a reference point detecting means for detecting a reference point based on the cross-range compressed signal, 11 is a shake compensating means for obtaining a phase compensation amount based on the reference point selected by the selecting means 19, and 19 are N reference values. Point detection means 10a, 10b, ...
.... Selection means for selecting one reference point from the output of 10N.

Next, the operation will be described. The high frequency pulse generated in the coherent transceiver 2 of FIG. 1 is modulated into a signal (chirp) whose frequency changes with time,
It is radiated from the transmitting / receiving antenna 1. The signal (echo) reflected by the target enters the transmitting / receiving antenna 1 again and is demodulated by the coherent transceiver 2. When the transmission pulse is repeatedly generated at fixed time intervals, a reception signal is obtained according to the transmission pulse.

This received signal is further compressed in the range direction, and a signal P (h, r) with improved resolution in the range direction (radio wave emission direction) is obtained. Further, a compression operation in the cross range direction is performed by the cross range compression means 4, and the cross range direction (direction perpendicular to the range direction)
The resolution of is improved. These processes improve the resolution of the entire observation area and reproduce the image. Since the phase compensation is not performed in the first process, the same operation as the conventional radar device is performed.

Reference point detecting means 10a, 10b, ... 1
0N detects a reference point of 1 on the target from the complex signal Q (c, r) after cross-range compression, and outputs the range r0 in which the reflection signal from that point exists. Where r0
Is the range bin number (r0 is one point within r) in the array Q (c, r) where the reference point exists. The reference point is a specific range on the array Q (c, r) for taking out the input of the motion compensation means. This corresponds to an echo from a site that shows some feature on the target compared to the surroundings. The specific part differs depending on the reference point detection algorithm described below. In the present embodiment, since the reference point is obtained using the output of the cross range compression means 4 with improved cross range resolution and the complex signal Q (c, r), the reference point detection means 10a, 10b, ... Selects a reference point using the target shape in the cross-range direction. The plurality of reference point detecting means 10a, 10b, ..., 10N independently detect one reference point.

A plurality of reference point detecting means 10a, 10b ,.
.. The 10N algorithms may be different or the same. When a different algorithm is used, the selecting means 19 can detect the one having two or more conditions of the reference point (for example, the one which is the end point of the range and is the brightest point) by the majority vote, and the fluctuation is caused. There is an effect that the compensation becomes stronger against the influence of interference.

On the other hand, when the same algorithm is used,
By changing each parameter, it is possible to provide a wide range of conditions for detecting the reference point, and it is possible to reduce the probability of detection failure. For example, Example 6 described later
In the stable reflection point detecting means, the plurality of reference point detecting means 1 are changed by changing the combination of the average power of the parameter and its variance.
0a, 10b, ..., 10N, even if the reference point detection means 10a cannot detect the reference point because the reference point is too strict, the reference point detection means 10b has a slightly looser detection reference. Can detect a suboptimal reference point, which increases the probability of successful detection of the reference point. In this case, the selection means 19 includes the reference point detection means 10a, 10
The output of b ... 10N may be prioritized and the output of 1 may be selected.

Reference point detecting means 10a, 10b, ... 1
0N shows some features on the target compared to the surroundings,
It detects a reference point serving as a reference for phase compensation, and a specific means therefor is means for detecting a cross range end point. FIG. 4 is a flow chart showing the detailed operation of the reference point detecting means by detecting the cross range end point.

In FIG. 4, step 1 (ST1): a pointer is set at the end of the image in the cross range direction (r = 1, c = 1) step 2 (ST2): the brightness of the pixel pointed by the pointer is , Predetermined criteria (Q0)
Is checked, and if it is, this pixel is output as the cross range end point, and the operation ends. Step 3 (ST3): Without changing the cross range coordinates,
Repeat step 2 while moving the pointer in the range direction. Step 4 (ST4): Steps 2 and 3 are repeated while moving the cross-range coordinates of the pointer toward the center of the image.

In FIG. 4, r is the range coordinate of the pointer, c is the cross range coordinate, the absolute value of Q (c, r) is the luminance at the image coordinate (c, r), and Q0 is the predetermined reference luminance. , Rmax is the maximum value of the range coordinates of the image, cma
x is the maximum value of the cross range coordinates. With the above operation, the reference point detecting means for detecting the cross-range end point outputs the point (r0, c0) having a larger cross-range coordinate or a predetermined luminance at a smaller position, that is, the echo end point as the cross-range end point. To do. An example of the cross range end points is shown in FIG. In FIG. 5, 66 is the cross range end point.

The procedure shown in FIG. 6 may be used. Figure 6
In contrast to the case of FIG. 4, is a procedure for searching in order from the largest cross range axis. The specific procedure is the same as in the case of FIG.

In the following description, the cross range end point detected by the procedure of FIG. 4 will be referred to as the left cross range end point, and FIG.
The cross-range endpoint detected by the procedure of 1) will be referred to as the right cross-range endpoint. In FIG. 5, 67 is the right cross range end point.

The selection means 19 is a reference point detection means 10a,
The output of 1 is selected from the outputs of 10b, ..., 10N.
If the algorithms of the plurality of reference point detecting means 10a, 10b, ..., 10N are different, the selecting means 19 is provided with two or more conditions of the reference point by a majority decision (for example, it is a range end point and is the clearest). Point) is detected. In this case, the motion compensation is effective against the influence of interference.

On the other hand, when the same algorithm is used,
The selection means 19 includes reference point detection means 10a, 10b, ...
• Prioritize 10N output and select 1 output.

Next, the operation of the motion compensation means 11 will be described. The motion compensating means 11 detects the phase change for each hit of the reference point from the signal after range compression based on the one reference point r0 obtained by the selecting means 19, and performs the motion compensation in the cross range compression means 4. The phase compensation amount of is calculated. That is, the phase φ0 (h) of the complex signal P (h, r0) corresponding to the change in the distance of the reference point r0 is obtained according to the equation (6). The fluctuation compensating means is set to zero (no phase compensation) until the reference point detecting means outputs the coordinates of the reference point.

[0062]

[Equation 5]

In the equation (6), the function Image indicates an operation of taking an imaginary part of a complex number, and Real indicates an operation of taking a real part.
The cross-range compression unit 4 cancels the phase error due to the target fluctuation by using the phase φ0 (h), which is the output of the motion compensation unit 11, for the complex signal P (h, r) that is the output of the range compression unit 3. , Compensate according to equation (7), then
Use (2) to improve the cross range resolution.

[0064]

[Equation 6]

For example, assume that the target 90 translates and rotates during observation, as shown in FIG. There is a bright spot 91 having a significantly larger radar cross-sectional area than the surroundings on the target, and its coordinates are (x0, r0). The center coordinate of rotation 92 is (0, 0). In FIG.
R0 is the distance between the transmitting and receiving antenna and the center of rotation, Δr is the distance change due to translation, and dr is the distance change due to rotation (Δ
r, dr << R0). Now, the reference point detecting means 10
Suppose that the bright spot 91 is detected, the motion compensation means 11 outputs the next phase φ 0 (h).

[0066]

[Equation 7]

The phase φ (h) of the echo from the coordinates (x, r) on the target is expressed by the following equation.

[0068]

[Equation 8]

The cross-range compression means 4 has a phase φ (h).
Of the received signal is compensated by the phase φ0 (h) of the reference point, and further Fourier transformed to obtain a two-dimensional image. Compensated complex signal P '(h, r) and its Doppler frequency f
d'is represented by the following equation.

[0070]

[Equation 9]

Here, ω is the rotational angular velocity. When using a microwave, the target rotation angle required to achieve a resolution of, for example, 1 m may be about 1 degree, and the normal angle θ is sufficiently smaller than 1 radian. Therefore, in the equation (13), the second term on the right side is sufficiently smaller than the first term and can be ignored. Further, cos θ can be regarded as approximately 1. Therefore, there is a proportional relationship between the coordinate x of the cross range and the Doppler frequency f * d of the echo from that position. That is, it is possible to prevent the deterioration of the resolution by compensating the error caused by the translational movement of the target with the phase of the reference point.

When the reference point is detected based on the output of the cross range compression means 4 as in the embodiment of FIG. 1, the influence of the interference of echoes at the reflection points can be reduced more than when the reference point is detected based on the output of the range compression means 3. it can. For example, when signals from other reflection points are mixed in the range of the reference point and the reference point,
The effect of the interference of echoes of a plurality of reflection points appears, and the performance of the motion compensation deteriorates. Therefore, it is desirable to select a point where no other reflection point exists in the same range as the reference point. Such inconvenience can be avoided by using the signal after the cross range compression.

In this embodiment, the reference point detecting means 1
Although the case where there are a plurality of 0's has been described, it goes without saying that even if there is only one reference point detecting means 10 as shown in FIG. Further, as shown in FIG. 3, one reference point may be selected from the output of the range compression unit 3 and the output of the cross range compression unit 4.

Embodiment 2 In the above embodiment, the reference point detecting means 10 is the reference point detecting means by the cross range end point detection, but the reference point detecting means by the range end point detection may be used.

The reference point detected by the range end point performs the following operation as shown in the flowchart of FIG. Step 1 (ST1): The pointer is set at the end of the range of the image. Step 2 (ST2): The brightness of the pixel indicated by the pointer is
Examine whether it exceeds the predetermined standard. If it exceeds, this pixel is output as the range end point, and the operation ends. Step 3 (ST3): Step 2 is repeated while moving the pointer in the cross range direction without changing the range coordinates. Step 4 (ST4): Steps 2 and 3 are repeated while moving the range coordinates of the pointer toward the center of the image. An example of range end points is shown in FIG.

R is the range coordinate of the pointer, c is the cross range coordinate, Q (c, r) is the brightness of the image coordinate (c, r), Q0 is the predetermined standard brightness, and rmax is the range coordinate of the image. , Cmax is the maximum of the cross range coordinates.

Alternatively, the procedure shown in FIG. 9 may be used. Figure 9
Is a procedure for searching in order from the direction with the largest range axis, contrary to FIG.

The reference point detecting means 10 in FIG. 1 detects the reference point based on the output of the cross range compressing means 4, but the reference point detecting means by the range end point detection is based on the range compressing means 3 in FIG. As shown, the range end point may be detected from the signal P (h, r) before the cross range compression. The operation in that case is as follows.

Step 1 (ST1): The sum of the luminance of the pixels in the range r in the hit direction is calculated. Step 2 (ST2): When the sum exceeds the threshold value, the range coordinate r0 = r is output as the range coordinate of the range end point, and the operation is stopped. Step 3 (ST3): Steps 1 and 2 are repeated from the minimum or maximum of the range axis of the image toward the center. An example of the range end point in this case is shown in FIG.

In FIG. 10, h and r are pointers indicating the coordinates of hit and range, hmax and rmax are their maximum values,
sum (r) is a variable indicating the sum of the luminance of pixels in the range r in the hit direction, and the absolute value of P (h, r) is the coordinate (h, r).
, The pixel brightness, and P0 is the minimum brightness at the end of the range.

Further, another example of this concrete procedure is shown in FIG.
It is shown in the flowchart. FIG. 10 shows the procedure for detecting the range endpoint on the smaller range coordinate side, while FIG. 11 shows the procedure for searching for the range endpoint on the larger range coordinate side.

The range endpoints detected by the procedures of FIGS. 6 and 8 are called near range endpoints, and the range endpoints detected by the procedures of FIGS. 9 and 11 are called far range endpoints. In FIGS. 12 and 13, 65 is a near range endpoint and 64 is a far range endpoint.

Embodiment 3 As the reference point detecting means 10, there is a reference point detecting means for detecting the brightest point. The reference point detection by the brightest point detection is
The following operation is performed as shown in the flowchart of FIG. Step 1 (ST1): Compare the brightness of all pixels in the image. Step 2 (ST2): The coordinates of the pixel showing the maximum brightness are output as the brightest point, and the operation is stopped.

In FIG. 14, h and r are pointers indicating the coordinates of the hit and range of the image, max is a variable holding the maximum value of the brightness of the pixel, and the absolute value of P (h, r) is the coordinates (h, r). ), The luminance of the pixel, r0, h0 are the coordinates of the pixel having the maximum luminance, and rmax, hmax are the maximum values of the coordinates of the hit and range of the image.

An example of another operation of the brightest point detecting means is shown in the flowchart of FIG. Step 1 (ST1): Calculate the sum of image luminance in the hit direction for each range Step 2 (ST2): Compare the sum of luminance for each range to obtain the maximum. Step 3 (ST3): Output the range coordinate showing the maximum sum as the brightest point.

In FIG. 15, h and r are pointers indicating the coordinates of the hit and range of the image, max is a variable holding the maximum value of the brightness of the pixel, and the absolute value of P (h, r) is the coordinates (h, r). ) Pixel brightness, sum (r) is the sum of the brightness of pixels in the range r in the hit direction, rmax and hmax are the maximum values of the image hit and range coordinates, and r0 is the maximum of the brightness hit direction. The coordinates of the range.

An example of the brightest point is shown in FIG. In the figure, 60 is the brightest point. The reference point detecting means for detecting the brightest point may detect the brightest point from the complex signal Q (c, r) after the cross-range compression, as shown in the flowchart of FIG. An example of the brightest point in this case is shown in FIG.
8 shows.

Embodiment 4 Although the brightest point detecting means is used as the reference point detecting means 10, the reference point detecting means by the single bright point detection may be used as another means. Reference point detection by single bright spot detection
As shown in FIG. 19, the following operation is performed. Step 1 (ST1): On the image before cross-range compression, the absolute value of the brightness P (h, r0) exceeds the threshold value P0 and the vicinity on the range axis (Δr1> r−r0 absolute value> It is checked whether the brightness of .DELTA.r2) is smaller than the threshold value P1. Step 2 (ST2): If the condition of Step 1 is satisfied, Step 1 is repeated for the absolute value of the brightness P (h, r0) for all hits. Step 3 (ST3): If the condition of Step 2 is satisfied, the range coordinate of the single bright spot is output as r0 and the operation is stopped. Step 4 (ST4): If the conditions of Steps 1 and 2 are not satisfied, set range r = r + 1 and repeat Step 1.

In FIG. 19, h and r are pointers indicating the coordinates of hit and range, P0 is the minimum amplitude of a single bright spot, and P0 is
1 is the maximum amplitude of a single bright spot, Δr1 and Δr2 are range ranges that define the vicinity of the single bright spot, and the absolute value of P (h, r0) is the brightness of the pixel at coordinates (h, r).

FIG. 20 shows an example of a single bright spot. In the figure, 61 is a single bright spot. The reference point detection by the single bright spot detection is performed by the complex signal Q (c, r) after the cross range compression.
The single bright spot may be detected from FIG. 21 shows a flowchart. An example of a single bright spot in this case is shown in FIG.
Shown in.

Embodiment 5 Further, as the reference point detecting means 10, a reference point detecting means by local brightest point detection may be used. The reference point detection by the local brightest point detection performs the following operation as shown in the flowchart of FIG. Step 1 (ST1): Search for coordinates (h0, r0) of a pixel that gives the maximum brightness in the range of coordinates (h1 ≤ h ≤ h2, r1 ≤ r ≤ r2) of the image before cross-range compression Step 2 (ST2): (H0, r0) is output as the coordinates of the local brightest point, and the operation is stopped.

In FIG. 23, h and r are pointers indicating coordinates of hits and ranges, h1, h2 r1 and r2 are coordinates of hits and ranges for limiting the range for obtaining the local brightest point, and P.
The absolute value of (h, r) is the brightness of the pixel at coordinates (h, r), m
ax is a variable indicating the maximum brightness, and (h0, r0) is the coordinates of the local brightest point.

FIG. 25 shows an example of the local brightest point. In the figure, 62 is a local brightest point. It should be noted that the local brightest point detecting means 52 uses the complex signal Q (c, r) after the cross range compression.
You may make it detect the brightest point from this. FIG. 24 shows a flowchart. FIG. 26 shows an example of the local brightest point 62 in this case.

The reference point detection by the local brightest point detection is
As shown in the flowchart of FIG. 27, the following operation may be performed. Step 1 (ST1): In the range of the range coordinates (r1 ≤ r ≤ r2) of the image before the cross range compression, the sum of the luminance hit directions is obtained for (h1 ≤ h ≤ h2) and the array sum is calculated.
Store in (r) Step 2 (ST2): The range coordinate r0 that gives the maximum of sum (r) is determined, output as the range coordinate of the local brightest point, and the operation is stopped. In FIG. 27, sum (r) is the sum of luminance hits h (h1 ≤ h ≤ h2) at the range coordinates r.

Embodiment 6 Further, as the reference point detecting means, a reference point detecting means by stable reflection point detection may be used. The reference point detection by the stable reflection point detection performs the following operation as shown in the flowchart of FIG. Step 1 (ST1): If the brightness of the pixel at the coordinates (h, r) exceeds the threshold value P0, the counter s (r) is incremented. Step 2 (ST2): If the counter s (r) exceeds the threshold value s0 (s0≤hmax), r0 = r is output as the range coordinates of the stable reflection point, and the operation is stopped. Step 3 (ST3): Steps 1 and 2 are repeated for all hits h (1≤h≤hmax). Step 4 (ST4): Steps 1 to 3 are repeated for all ranges r (1≤r≤rmax).

In FIG. 28, h and r are pointers indicating the coordinates of hit and range, the absolute value of P (h, r) is the brightness of the pixel at coordinates (h, r), and P0 is the minimum brightness of the stable reflection point. Value, s (r) is the number of pixels whose brightness exceeds P0, S0 is the minimum value of pixels in the hit direction of the stable reflection point, hmax, rma
x is the maximum of the hit and range coordinates of the image. Figure 3
An example of a stable reflection point is shown in 0. In the figure, 63 is a stable reflection point.

Further, as for the reference point detection by the stable reflection point detection, the following operation may be performed as shown in the flowchart of FIG. Step 1 (ST1): For the pixel at the range coordinate r,
Calculate the average and variance of luminance in the hit direction. Step 2 (ST2): If it is larger than the average threshold value P0 and the variance is smaller than the threshold value σ0, then the range r0
= R is output as the range coordinate of the stable reflection point, and the operation is stopped. Step 3 (ST3): All ranges (1 ≦ r ≦ rmax
), Steps 1-2 are repeated. In FIG. 29, h and r are pointers indicating the coordinates of the hit and the range, hmax rmax is the maximum thereof, and the absolute value of P (h, r) is the brightness of the pixel at the coordinates (h, r), the average P (r), σ
(R) is the average and variance of the luminance of the pixels in the range r in the hit direction, and average P0 and σ0 are the thresholds of the average luminance and variance.

Embodiment 7 Further, as the reference point detecting means 10, a reference point detecting means for detecting a target tip may be used. The reference point detection by the target tip detection performs the following operation as shown in the flowchart of FIG. Step 1 (ST1): It is checked from the range tracking data whether the target is moving away or approaching at high speed. Step 2 (ST2): When the condition of Step 1 is satisfied, it is checked whether it is approaching or moving away. When approaching, a near range end point is detected from the image after cross range compression. If the distance is far, the far end of the range is detected. Step 3 (ST3): When the condition of Step 1 is not satisfied, the positive / negative of the second differential of the range is checked. If it is positive, the left cross-range end point is detected from the image after cross-range compression. If it is negative, the right cross-range endpoint is detected. Step 4 (ST4): The detected coordinates of the reference point are output to the motion compensation means to stop the operation. In FIG. 31, DR is the first derivative of the time between the antenna and the target distance R, DDR is its second derivative, and DR0 is the threshold of the first derivative of the distance R. Note that DR and DDR can be obtained from a block that performs range tracking processing in the transceiver.

An example of the target tip is shown in FIG. In the figure, reference numeral 68 is a target tip detected as a far range end point. FIG. 33 shows the positional relationship between the target and the antenna for explaining the operation of detecting the reference point by detecting the target tip.
In FIG. 33, 1 is a transmitting / receiving antenna, 8 is a target, and 70
Is a movement to start moving away, 71 is a movement to start approaching, 77
Is an approaching movement and 78 is a moving away movement.

In the first approaching motion 77, the target tip appears on the side of the reproduced image where the range coordinates are small, that is, on the side close to the antenna. Therefore, by detecting the range endpoint of the second embodiment, the target range endpoint is detected. It can be a tip.

Next, in the movement 70 that starts to move away, it is difficult to separate on the range axis because the distance from the antenna is not so different before and after the body. However, since the airframe is rotating, the speed at which the head moves away from the antenna is faster than that at the tail of the airframe, and therefore the Doppler frequency of the received signal varies greatly. That is, since the target tip appears on the negative side of the cross range coordinates of the reproduced image,
By detecting the left cross-range end point according to the procedure of the above-described embodiment, the target front end can be obtained. On the other hand, in the approaching movement 71, the head approaches the antenna faster than the tail of the body, and therefore the Doppler frequency of the received signal changes largely. That is, since the target tip appears on the positive side of the cross range coordinates of the reproduced image, the right cross range end point is detected by the procedure of the above embodiment,
Can be a target tip.

Embodiment 8 Further, as the reference point detecting means 10, a reference point detecting means by full range search may be used. The reference point detection by the full range search operates as follows, as shown in the flowchart of FIG. Step 1 (ST1): The range coordinates of the reference point are initialized (0). Step 2 (ST2): The range coordinates of the reference point are incremented and output to the motion compensation means. Step 3 (ST3): If the imaging determination unit or the observer determines that the imaging is defective, step 2 is repeated. Step 4 (ST4): When the range coordinates exceed the maximum value, the operation is stopped. That is, in the reference point detection by the full range search, all the reference points are sequentially selected, so that the motion compensation can be automatically attempted using all the reference points. In FIG. 34, r0 is the range coordinate of the reference point.

Example 9 In Examples 1 to 8 described above, the reference point was obtained by the reference point detecting means 10 and the motion compensation was performed. However, the motion compensation was performed based on the reference point input by the operator while observing the display on the display. You can go. In FIG. 35, 13 is an operator,
Reference numeral 16 is a reference point input device for inputting the coordinates of the reference point detected by the operator.

The monitor display 6 displays the absolute value of P (h, r) or P (h) on the display indicated by the two-dimensional coordinates of the hit h and the range r from the complex signal P (h, r) before range compression. , R) is displayed with a brightness proportional to the square of the absolute value of r. The operator 13 observes the display and judges / selects the reference point, and inputs the range number of the detected reference point to the reference point input device 16. The motion compensator 11 calculates the amount of phase compensation using the reference point detected by the operator 13. Therefore, the motion compensation can be performed using the reference point determined by the experience and intuition of the operator.

Embodiment 10 In the above embodiment, the monitor display 6 displays the output of the range compression means, but as shown in FIG.
The output signal of the cross range compression means may be displayed. The monitor display 6 displays the complex signal Q after cross range compression.
(C, r) is a luminance value proportional to the absolute value of Q (c, r) or the square of the absolute value of Q (c, r) on the display displayed in the two-dimensional coordinates of the cross range c and the range r. indicate. The operator 13 observes the display to judge and select the reference point, and inputs the range number to the reference point input device 16. The motion compensator 11 uses the reference point detected by the operator 13 to obtain the amount of phase compensation. Therefore, the reference point can be detected from the radar image obtained by the cross range compression, based on the experience and intuition of the operator.

Embodiment 11 In the above-mentioned Embodiments 1 to 10, the reference point detected by the reference point detecting means 10 was used for calculating the phase amount of the motion compensation, but the state of the obtained radar image (focus May be used as a reference point of the image forming determination means. In FIG. 38, reference numeral 12 is an image forming determination means. The determination of the image formation state means that the image formation state is bad when the spread of the brightness at a certain point is wider than the brightness spread of the actual reflection point (that is, when the focus is out of focus). is there.

As an example of the algorithm of the image formation judging means 12, there is one based on the point image response evaluation shown in the flowchart of FIG. Step 1 (ST1): Coordinates (c0, r) of the reference point selected by the reference point detecting means on the image after the cross range compression.
0) is read. Step 2 (ST2): Cross-range coordinate c (c <c0
), The absolute value of the brightness Q (c, r0) of the image at the range coordinate r0, and the absolute value of Q (c, r0) is αmax (α is a constant 0 <α <1, max = Q (c0, The maximum value c that is smaller than the absolute value of r0) is searched for and designated as c3. Step 3 (ST3): Cross-range coordinate c (c> c0)
), The absolute value of the brightness Q (c, r0) of the image of the range coordinate r0, and the value of c (4) in which the absolute value of Q (c, r0) is smaller than αmax is searched for and designated as c4. Step 4 (ST4): The difference .DELTA.c between c3 and c4 indicates the spread of the point image response at the reference point (c0, r0), and it is checked whether .DELTA.c exceeds a predetermined reference point .beta .. Δc
If it is> β, the point image response is poor, and if Δc ≦ β, the point image response is good and the operation is stopped. In FIG. 37, c0 and r0 are the cross range of the reference point,
The coordinates of the range, c is a pointer indicating the coordinates of the cross range, the absolute value of Q (c, r0) is the brightness of the pixel at the coordinates (c, r), α is a constant 0 <α <1, and max is the reference point. The brightness, Δc, is the spread of the brightness of the reference point in the cross range direction, and β is the threshold value of the spread of the point image in the cross range direction for determining the quality of the point image response.

Based on the output result of the image forming determination means 12, when the radar image obtained as a result of the motion compensation is not appropriate, the reference point used in the motion compensation means of the first to eighth embodiments is detected again. In FIG. 38, reference numeral 17 is a re-detection instructing means for instructing the reference point detecting means 10a, 10b to re-detect the reference point based on the result of the image formation determining means 12. Also,
The reference point detecting means 10 a is a first reference point detecting means for detecting a reference point for calculating the phase compensation amount in the motion compensating means 11, and the reference point detecting means 10 b is a reference point used for the image forming determining means 12. It is a second reference point detecting means for detecting.

Reference point detection means 10a and motion compensation means 11
The operation of is the same as the operation in the above-described embodiment. The re-detection instructing means 17 does not output the re-detection instruction because the reference point used is appropriate when the result of the imaging determination means 12 is good compared with a predetermined reference. On the other hand, when the result of the image forming determination means 12 is bad, the re-detection instruction signal is output to select another reference point.
This re-detection instruction signal is used as the reference point detection means 10a, 10b.
Entered in. Thereby, the reference point detecting means 10a, 10
b detects the reference point again. The re-detection instruction signal may be input only to the reference point detecting means 10a. Also, FIG.
As shown in 9, based on the output of the cross-range compression unit 4,
Two types of reference points are obtained by the reference point detection means 10b and 10c, the image formation determination means 12a and 12b determine the image formation state for each, and the two determination results are selected by the selection means 19.
Alternatively, the re-detection instructing means may instruct re-detection based on the output of the selected 1.

The re-detection instructing means 17 automatically re-detects the reference point when the imaging state is not appropriate, and a good radar image can be obtained. Further, in the embodiment of FIG. 39, the plurality of image forming determination means 12 determine the image forming state of the image from the complex signal Q (c, r) after the cross range compression. It is easy to know whether the image is obtained. At this time, if the algorithms or parameters of the plurality of image formation determination means 12 are changed, different determination results can be obtained, so that the image formation determination can be performed more stably.
For example, the overall judgment result can be determined by the majority decision of each judgment result.

Further, since a signal line for feeding back the output of the image formation determination means 12 to the reference point detection means 10 is provided, the reference point detection means 10 re-detects the reference point if the image formation determination result is bad. be able to. At this time, if the algorithm or the parameter of the reference point detecting means 10 is changed every time feedback is given, a different reference point can be detected each time, so a series of processing is performed until a target high resolution image is obtained. It can be repeated automatically. Also in this case, since the plurality of image forming determination means 12 output the respective determination results, the image forming determination can be performed more stably.

As described above, the selection means 19 makes a more appropriate determination of the image formation state by selecting based on the priority of the reference point detection means 10a and 10b. If the number of reference point detecting means 10 is 3 or more, the majority may be used for selection. Further, the selection criterion may be changed based on the output of the re-detection instructing means 17. Further, in FIG. 39, the outputs of the image formation judging means 12a and 12b are selected by the selecting means 19
However, the outputs of the reference point detecting means 10b and 10c may be selected, and in this case, only one image forming determining means 12 is required.

Twelfth Embodiment In the eleventh embodiment, the reference point used for the motion compensation is determined based on the output of the range compression means 3, but as shown in FIG. 40, the reference point determined based on the output of the cross range compression means 4. Perturbation compensation may be performed using points. In this case, FIG.
As shown in FIG. 5, the plurality of reference point detecting means 10b and 10c respectively obtain the reference points based on the output of the cross range compression means 4, the selecting means 19 selects the reference points, and the images are formed based on the selected reference points. The determination means 12 may determine the image formation state. Further, a plurality of image formation determination means may be provided, and the selection means may select the image formation determination result.

Embodiment 13 In the above embodiment, the re-detection of the reference point is automatically carried out based on the output of the image formation judging means. However, the operator manually instructs the re-detection while watching the radar image. Good. In FIG. 42, 6 is a monitor display for displaying the output of the cross-range compression means, 13 is an operator, and 1
Reference numeral 4 is a re-detection instruction input means.

The monitor display 6 outputs the complex signal Q (c, r) after cross range compression to the cross range c and range r.
It is displayed on the two-dimensional coordinates of X with the brightness proportional to the absolute value of Q (c, r) or its square, and the operator 13 judges from the display whether or not the target high-resolution image is formed and re-detects it. The instruction input device 14 is instructed whether re-detection is necessary. The reference point detecting means 10 re-detects another reference point based on the instruction. Therefore, a series of processes can be repeated until the operator 13 determines from experience and intuition that the target high-resolution image is formed. In FIG. 42, a plurality of reference point detecting means 10 may be used, or the reference points may be detected based on the output of the cross-range compressing means, and the same operation / effect can be obtained.

Embodiment 14 In addition, in the above Embodiments 1 to 13, the motion compensating means 11 is used.
However, instead of this, a Doppler-tracking means may be used. An example thereof is shown in FIG. In FIG. 43, 74 is Doppler frequency calculation means for calculating the Doppler frequency of the reference point, 75 is smoothing means for smoothing the time change of the Doppler frequency obtained in 74 with a low-order curve, and 76 is a phase for each hit. It is a phase compensation amount calculation means for calculating the compensation amount. In FIG. 43, the Doppler-tracking means has a complex signal P (h, r) before the cross-range compression by the reference point detection means 10 as in the motion compensation means 11.
The reference point detected based on the above is received, and the phase compensation amount is obtained with reference to the phase of the reflected wave at the reference point. The cross range compression means 4 compensates the received signal based on this phase compensation amount.

Next, the operation of the Doppler-tracking means will be described. The Doppler frequency calculator 74 receives the received signal P (h, r) reflected at the reference point (range r0) according to the equation (14).
0) with a length Δh and subjected to a piecewise Fourier transform to obtain a spectrum fs
Find (h ', f).

[0118]

[Equation 10]

Next, from the spectrum fs (h ', f), the expression
The Doppler frequency fd that maximizes the amplitude according to (15) or the average Doppler weighted by the amplitude according to equation (16).
The frequency fd is obtained and output.

[0120]

[Equation 11]

The Doppler frequency fd (h ') thus obtained is shown in FIG. In the figure, reference numeral 72 shows a plot of the Doppler frequency fd (h '). Next, the smoothing means 75 calculates the Doppler frequency fd.
Fds with (h ') smoothed in the hit direction
Find (h '). The situation is also shown in FIG.
In the figure, 73 is the Doppler frequency f after smoothing.
The graph of ds (h ') is shown.

Smoothing is performed by, for example, the least-squares method so as to minimize the square error Δe of the equation (17).
This can be realized by obtaining (h '). At this time, fd
s (h ') can be represented by a linear function of hit h', for example, as in Expression (18). Smoothing is a process performed based on a priori knowledge that the Doppler frequency of the echo of each target portion changes constantly or slowly with respect to time.

[0123]

[Equation 12]

Next, the phase compensation amount calculation means 76 obtains the phase compensation amount for each hit from the smoothed Doppler frequency fds (h ') according to the equation (19).

[0125]

[Equation 13]

By the way, in the above description, the smoothed Doppler frequency fds (h ') is explained as a linear function of the hit h', but it may be a quadratic function or a higher-order function.

As described above, in the Doppler-tracking means, since the signals of a plurality of hits are integrated by the Fourier transform of equation (14), the amount of phase compensation should be obtained even when the signal-to-noise ratio deteriorates. The target high resolution image can be obtained. The other operations in this embodiment are the same as those in the embodiment. Further, the reference point detecting means 10 is
The reference point may be detected from the absolute value of the image Q (c, r) after the cross range compression. Further, as the reference point detecting means used in the Doppler tracking means, the cross range end point detection, the range end point detection, the brightest point detection, the single bright point detection, the local brightest point detection, and the stable reflection point detection shown in Examples 1 to 8 are performed. Any of the algorithms for target tip detection and full range search may be used.

[0128]

As described above, according to the invention of claim 1, the reference point detecting means detects one predetermined reference point of the reflection signal from the target based on the output of the cross range compressing means. Since the motion compensator compensates the phase based on this reference point, the target high resolution image can be obtained without deteriorating the cross range resolution even if the target relative speed with respect to the transmitting / receiving antenna changes.

Further, according to the inventions of claims 2 to 4, the plurality of reference point detecting means detect a plurality of predetermined reference points of the reflection signal from the target, and the selecting means detects the plurality of reference points. Since a point is selected and the motion compensation means performs phase compensation based on the selected reference point, appropriate phase compensation can be performed and stable cross range resolution can be obtained.

According to the fifth and sixth aspects of the invention, since the reference point is input while checking the radar image, it is possible to select an appropriate reference point, perform appropriate phase compensation, and stabilize Excellent cross range resolution can be obtained.

Further, according to the inventions of claims 7 to 12, since the re-detection instructing means instructs the re-detection of the reference point based on the output of the image forming determination means, the automatic detection is performed until a proper radar image is obtained. By repeating the reference point detection, stable cross range resolution can be obtained.

According to the thirteenth aspect of the present invention, since it is possible to instruct re-detection of the reference point by the re-detection instruction input means while checking the radar image, the reference point is detected so that a desired radar image can be obtained. It is possible to obtain stable cross-range resolution.

According to the fourteenth aspect of the present invention, since the phase compensation is performed by the Doppler tracking means, it is possible to perform the appropriate phase compensation even when the signal-to-noise ratio deteriorates.
A stable cross range resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a radar device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a radar device according to another embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a radar device according to another embodiment of the present invention.

FIG. 4 is a flowchart showing an algorithm for detecting a cross range end point.

FIG. 5 is a diagram showing an example of a cross range end point.

FIG. 6 is a flowchart showing another algorithm for detecting a cross range end point.

FIG. 7 is an explanatory diagram of the principle of motion compensation.

FIG. 8 is a flowchart showing an algorithm for detecting a range end point.

FIG. 9 is a flowchart showing another algorithm for range end point detection.

FIG. 10 is a flowchart showing another algorithm for range end point detection.

FIG. 11 is a flowchart showing another algorithm for detecting a range end point.

FIG. 12 is a diagram showing an example of range end points.

FIG. 13 is a diagram showing another example of a range end point.

FIG. 14 is a flowchart showing an algorithm for detecting the brightest point.

FIG. 15 is a flowchart showing another algorithm for detecting the brightest point.

FIG. 16 is a flowchart showing another algorithm for detecting the brightest point.

FIG. 17 is a diagram showing an example of the brightest point.

FIG. 18 is a diagram showing another example of the brightest point.

FIG. 19 is a flowchart showing an algorithm for detecting a single bright spot.

FIG. 20 is a diagram showing an example of a single bright spot.

FIG. 21 is a flowchart showing another algorithm for detecting a single bright spot.

FIG. 22 is a diagram showing another example of a single bright spot.

FIG. 23 is a flowchart showing an algorithm for detecting a local brightest point.

FIG. 24 is a flowchart showing another algorithm for detecting the local brightest point.

FIG. 25 is a diagram showing an example of a local brightest point.

FIG. 26 is a diagram showing another example of the local brightest point.

FIG. 27 is a flowchart showing another algorithm for detecting the local brightest point.

FIG. 28 is a flowchart showing an algorithm for detecting stable reflection points.

FIG. 29 is a flowchart showing another algorithm for detecting stable reflection points.

FIG. 30 is a diagram showing an example of stable reflection points.

FIG. 31 is a flowchart showing an algorithm for detecting a target tip.

FIG. 32 is a diagram showing an example of a target tip.

FIG. 33 is an explanatory diagram of the principle of target tip detection.

FIG. 34 is a flowchart showing the algorithm of the full range search means.

FIG. 35 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 5;

FIG. 36 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 6;

FIG. 37 is a flowchart showing an algorithm for point image response determination.

FIG. 38 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 7;

FIG. 39 is a diagram showing the configuration of a radar device according to an embodiment of the invention as claimed in claim 8;

FIG. 40 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 10;

FIG. 41 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 11;

FIG. 42 is a diagram showing a configuration of a radar device according to an embodiment of the invention of claim 13;

FIG. 43 is a diagram showing a configuration of Doppler-tracking means.

FIG. 44 is a view showing the operation principle of the Doppler-tracking means.

FIG. 45 is a diagram showing a configuration of a conventional radar device.

FIG. 46 is a diagram showing the principle of chirp modulation.

FIG. 47 is a diagram showing a transmitting / receiving antenna and a target geometry.

FIG. 48 is a diagram showing Doppler of reflection signals from the tip and the tail of the target.

FIG. 49 is a diagram showing Doppler of reflection signals from the tip and tail of the target when the target moves.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting / receiving antenna 2 Coherent transmitter / receiver 3 Range compression means 4 Cross range compression means 5 Monitor display 8 Target 10 Reference point detection means 11 Motion compensation means 12 Image formation determination means 13 Operator 14 Redetection instruction input means 16 Reference point input device 17 Re Detection instruction means 19 Selection means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masafumi Iwamoto 5-1-1, Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Electronic Systems Laboratory (72) Inventor Takahiko Fujisaka 5-1-1, Ofuna, Kamakura-shi, Kanagawa No. Mitsubishi Electric Corporation, Electronic Systems Laboratory (72) Inventor, Yuasa Ohashi 5-1-1, Ofuna, Kamakura-shi, Kanagawa Prefecture Mitsubishi Electric Corporation, Electronic Systems Laboratory, (72) Inventor, Tomomasa Kondo, 5-chome, Ofuna, Kamakura, Kanagawa Prefecture No. 1 No. 1 Electronic Systems Laboratory, Mitsubishi Electric Corporation

Claims (14)

[Claims] 1. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means A reference point detecting means for detecting a predetermined one reference point of the reflection signal from the target based on the output of the above, and a shake compensating means for compensating the phase of the output of the range compressing means based on the reference point. A radar device comprising: 2. A transmitter, an antenna for radiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means A plurality of reference point detecting means for respectively detecting a predetermined one reference point of the reflection signal from the target based on the output of 1), and the outputs of the plurality of reference point detecting means according to the predetermined reference 1 A selection means for selecting an output of the range compression means and a fluctuation compensating means for compensating the phase of the output of the range compression means based on the output of the selection means. Radar system for the butterflies. 3. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; First reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output, and predetermined determination of the reflection signal from the target based on the output of the cross range compression means. Second reference point detecting means for detecting the one reference point
Selection means for selecting the output of 1 according to a predetermined reference from the outputs of the first reference point detection means and the second reference point detection means, and of the range compression means based on the output of the selection means A radar device comprising: a shake compensating means for compensating for an output phase. 4. A transmitter, an antenna for irradiating a high-frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; A plurality of first reference point detecting means for respectively detecting a predetermined one reference point of the reflection signal from the target based on the output, and a reflection signal from the target based on the outputs of the cross range compression means. A plurality of second reference point detecting means for respectively detecting a predetermined one of the reference points, the plurality of first reference point detecting means and the plurality of second bases. A selection means for selecting an output of 1 from the output of the point detection means according to a predetermined reference; and a fluctuation compensation means for compensating the phase of the output of the range compression means based on the output of the selection means. A radar device characterized by. 5. A transmitter, an antenna for radiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; A display device for displaying the output, a reference point input means for inputting a reference point from the outside, and a swing compensating means for compensating the phase of the output of the range compression means based on the output of the reference point input means are provided. A radar device characterized by. 6. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means A display device for displaying the output of the above, reference point input means for inputting a reference point from the outside, and wobbling compensation means for compensating the phase of the output of the range compression means based on the output of the reference point input means. A radar device characterized by the above. 7. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; First reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output, and predetermined determination of the reflection signal from the target based on the output of the cross range compression means. Second reference point detecting means for detecting the one reference point
Based on the image formation determination means for determining the image formation state at the reference point of the second reference point detection means and the determination result, the first
Re-detection instructing means for instructing the reference point detecting means to re-detect the reference point, and a shake compensating means for compensating the phase of the output of the range compressing means based on the reference point of the first reference point detecting means. A radar device comprising: 8. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflection signal from a target, a receiver for detecting the reflection signal, and an output signal of the receiver based on the output signal. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; First reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output, and predetermined determination of the reflection signal from the target based on the output of the cross range compression means. The plurality of second reference point detecting means for detecting the respective one reference points, and the image forming states at the respective reference points of the plurality of second reference point detecting means. A plurality of image forming determining means to be set, a selecting means for selecting one output from the outputs of the plurality of image forming determining means according to a predetermined reference, and a first reference inspection based on the output of the selecting means. The re-detection instructing means for instructing the output means to re-detect the reference point, and the fluctuation compensating means for compensating the phase of the output of the range compression means based on the reference point of the first reference point detecting means. A radar device characterized by the above. 9. A transmitter, an antenna for emitting a high-frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. A range compression means for improving the resolution in the irradiation direction of the high-frequency signal; a cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means; First reference point detecting means for detecting one predetermined reference point of the reflection signal from the target based on the output, and predetermined determination of the reflection signal from the target based on the output of the cross range compression means. A plurality of second reference point detecting means for respectively detecting the obtained one reference point, and a predetermined reference from the outputs of the plurality of second reference point detecting means. The selection means for selecting the output of 1 and the image formation determination means for determining the image formation state at the reference point selected by the selection means, and the first reference point detection means based on the output of the image formation determination means. Re-detection instructing means for instructing re-detection of the reference point, and the first
And a fluctuation compensating means for compensating the phase of the output of the range compressing means based on the reference point of the reference point detecting means. 10. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means Of the first reference point detecting means and the second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target based on the output of An image formation determination means for determining an image formation state at the reference point, a re-detection instruction means for instructing the first reference point detection means to re-detect the reference point based on the determination result, and Based on the reference point of the first reference point detecting means, the radar apparatus being characterized in that a perturbation compensation means for compensating the phase of the output of the range compression means. 11. A transmitter, an antenna for irradiating a high-frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means Based on the output of the target, first reference point detecting means and a plurality of second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target, and the plurality of second reference points. Selection means for selecting the output of 1 according to a predetermined reference from the output of the point detection means, and the image formation state at the reference point selected by the selection means are determined. An image forming determination means, a re-detection instructing means for instructing the first reference point detecting means to re-detect the reference point based on the output of the image forming determination means, and a reference point of the first reference point detecting means. Based on the above, there is provided a vibration compensating means for compensating for the phase of the output of the range compressing means. 12. A transmitter, an antenna for emitting a high-frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver based on the output signal. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means Based on the output of the target, first reference point detecting means and a plurality of second reference point detecting means for respectively detecting one predetermined reference point of the reflection signal from the target, and the plurality of second reference points. According to a plurality of image formation determination means for determining the image formation state at each reference point of the point detection means and a predetermined reference from the outputs of the plurality of image formation determination means. Selection means for selecting the output of the first reference point detection means, a re-detection instructing means for instructing the first reference point detection means to re-detect the reference point based on the output of the selection means, and a reference of the first reference point detection means. A radar device comprising a fluctuation compensating means for compensating the phase of the output of the range compressing means based on the above points. 13. A transmitter, an antenna for irradiating a high frequency signal generated by the transmitter and receiving a reflected signal from a target, a receiver for detecting the reflected signal, and an output signal of the receiver. Range compression means for improving the resolution in the irradiation direction of the high-frequency signal, cross-range compression means for improving the resolution in the direction intersecting the irradiation direction of the high-frequency signal based on the output of the range compression means, and the cross-range compression means Based on the output, the reference point detecting means for detecting one predetermined reference point of the reflection signal from the target, and the output from the reference point detecting means to compensate the phase of the output from the range compressing means. Vibration compensation means, a display for displaying the output of the cross range compression means, and re-detection instruction input means for instructing the reference point detection means to re-detect the reference point. Radar apparatus, comprising the. 14. A Doppler tracking unit for compensating the phase of the output of the range compression unit by a reflection signal reflected from a target a plurality of times based on a reference point instead of the motion compensation unit. The radar device according to claim 1.