JPH0454481A - Clutter suppression device - Google Patents

Abstract

PURPOSE:To obtain excellent suppression performance to a clutter which varies in center frequency in a distance direction by providing a filter position memory stored with a phase variation quantity corresponding to the center frequency of a filter over the entire range and a register stored with a phase variation quantity corresponding to the shape of a filter. CONSTITUTION:The clutter suppression device in a figure has the exactly the same device as before as to 1 - 10. In this device, the output of the filter position memory 11 stored with the center frequency of the filter can be varied, range by range, so the sum of the above output and the output of the register 7 stored with the filter shape is supplied to a complex multiplier 5 to vary the center frequency of the filter, range by range, while the filter shape is fixed. Consequently, the non-erasure of even a clutter which varies in the center frequency in the distance direction is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a radar clutter suppression device mounted on the ground, on an aircraft, on a vehicle, on a ship, etc.

[Conventional technology]

FIG. 9 is a block diagram of a conventional clutter suppression device. (
1) is an antenna that receives reflected waves from the target, (2) is a receiver that performs video processing on the received signal from antenna (1), and (3) is a receiver that converts the analog video signal from receiver (2) into a digital signal. (4) A/D converter for converting into
is a series-connected delay memory that stores the digital signal from the A/D converter (3) for all ranges during one pulse repetition time, and (5) is the output from the A/D converter (2). and a complex multiplier that multiplies the output from each delay memory (4) connected in series by a complex multiplier; For example, when configuring a double cancellation MTI filter without feedback at the Doppler frequency O position, 3
1 for each of the up to the th complex multipliers (5). 2. 1
Output. (6) is a complex adder that adds the outputs from each biplane multiplier. For example, in this figure, a 3-pulse canceler filter is configured by adding the outputs of three complex multipliers (5). ing. (8) is a complex adder (
(6) is an amplitude detector that detects the amplitude with respect to the output, and (9) is a target detector that detects a target for the amplitude detector (8). For example, the average amplitude value of 16 range pins is calculated and the average value is constant It is multiplied by a coefficient 1, for example 10, and those with larger amplitude values are detected as targets. (10)
calculates the distance error, angle error, etc. of the target based on the output from the target detector (9), and provides it to other equipment as necessary target information for the radar system.

For example, in the case of a tracking radar, it is a target information processing lid device that outputs to a filter calculation processor that predicts the target position.

In the clutter suppression device configured as above, the receiver (
The analog video signal from 2) is converted into a digital signal by the A/D converter (3) and sequentially enters the delay memory (4).The data stored in the delay memory (4) is converted to an A/D signal at each pulse repetition time. The output from the D converter (2) is complex multiplied by the complex data stored in the register (7) in the complex multiplier (5), and then added in the complex adder (6). A 3-pulse canceller filter is formed.In this case, the data stored in the register (7) is the phase change amount corresponding to the center frequency position on the frequency axis of the filter and the filter shape, for example, the position of the Doppler frequency O. When configuring a double cancellation MTl filter without feedback, the first to third registers (7
) for each 1. 2. Set 1.

has been completed.

FIG. 10 is a diagram illustrating the operation of the filter formed by the clutter suppression device shown in FIG. 9. Same figure (1)
is the clutter received power shown on the frequency axis, (2) in the figure is, for example, the pulse repetition time of 400 μs, and the setting values of the first to third registers (7) are set to 1.
2. The filter shape when set to 1 is shown.
A double cancellation MTI filter without feedback having a null point at the Doppler frequency O is formed. The same figure (3) is the same figure (
It shows the power of clutter suppressed by the filter shown in 2).

[Invention or problem to be solved]

In the conventional clutter suppression device configured as described above, the register (7) that stores and outputs the amount of phase change corresponding to the center frequency position on the frequency axis of the filter is fixed at all range pins. For clutter whose center frequency changes in the distance direction, there is a problem in that the clutter suppression performance deteriorates as the center frequency of the clutter moves away from the null point of the filter. FIG. 11 is a diagram illustrating deterioration in clutter suppression performance of a conventional clutter suppression device. In the same figure (
1) shows an example of the clutter power at four different points, with frequency 0 in the order of a, b, c, and d.
The center frequency changes from The electric power generated is e in Figure (3).

It can be seen that the remaining clutter increases as f, g, and h.

In addition, in the conventional clutter suppression device configured as described above, the register (7) that stores and outputs the amount of phase change corresponding to the filter shape is fixed on all range pins, so the clutter frequency axis For clutter whose shape changes in the distance direction, there is a problem in that the clutter suppression performance deteriorates as the filter shape spreads beyond the set filter shape.

FIG. 12 is a diagram illustrating deterioration in clutter suppression performance of a conventional clutter suppression device. In the figure, (1) shows an example of clutter power at four different points, and shows how the shape of clutter spreads in the order of a, b, c, and d. The clutter input shown in (1) of the same figure has a frequency f as shown in (2) of the same figure. The power output when entering a filter that has a null point is shown in the same figure (
3), e, f, g, and h, and it can be seen that the amount of clutter remaining is increasing.

Furthermore, in the conventional clutter suppression device configured as described above, a register (7) stores and outputs the amount of phase change corresponding to the center frequency position on the frequency axis of the filter and the amount of phase change corresponding to the filter shape. All range pins are fixed, so the shape of the clutter on the frequency axis changes in the distance direction, and the shape of the clutter on the frequency axis changes in the distance direction. However, as the center frequency of the clutter moves away from the null point of the filter, and as the shape of the clutter becomes wider than the set filter shape, the clutter suppression performance deteriorates. FIG. 13 is a diagram illustrating deterioration in clutter suppression performance of a conventional clutter suppression device. In the figure, (1) shows an example of clutter power at four different points, a, b, c,
The figure shows how the center frequency of the clutter moves in the order of d, and the shape of the clutter becomes wider. When the clutter input shown in (1) in the same figure enters a filter that has a null point at frequency O as shown in (2) in the same figure, the output power is e, f, g, in (3) in the same figure, It can be seen that the amount of remaining clutter increases as shown in h.

The present invention has been made to solve such problems, and aims to suppress clutter whose center frequency and shape change in the range direction, and furthermore, to suppress clutter whose shape changes in the range direction. The objective is to control the gain so that target detection can be performed stably.

[Means to solve the problem]

The clutter suppression device according to the present invention has an antenna that receives reflected waves from a target, a receiver that performs video processing on the signal received from the antenna, and an A/C converter that converts the analog video signal from the receiver into a digital signal. It has a D converter, has a delay memory connected in series to store the digital signal from the A/D converter over all ranges during one pulse repetition time, and has a delay memory connected in series with the output from the A/D converter. It has a complex multiplier that multiplies the output from each connected delay memory by a complex multiplier.

It has a complex adder that adds the amount of phase change across all range pins to create a complex multiplier.The complex adder stores and outputs the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over all ranges. It has a filter position memory that stores and outputs the amount of phase change corresponding to the filter shape for the complex adder, and has a complex adder that adds the outputs from each complex multiplier. It has an amplitude detector that detects the amplitude based on the output of the radar system, and a target detector that detects the target relative to the amplitude detector. It outputs necessary target information.

Another embodiment of the present invention provides a register for storing and outputting the amount of phase change corresponding to the center frequency position on the frequency axis of the filter for the complex adder, and a phase change corresponding to the shape of the filter for the complex adder. It has a filter shape memory that stores and outputs the amount over the entire range, and the other parts have the same structure as the above invention.

Another embodiment of the present invention provides a filter position memory for storing and outputting the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range to the complex adder, and a phase change corresponding to the filter shape. It has a filter shape memory that stores and outputs the amount of change over the entire range, and the other parts have the same structure as the above invention.

Furthermore, another embodiment of the present invention has a gain controller that performs gain control to perform target detection while maintaining a constant gain over all range pins when performing target detection calculations on the amplitude detector. .

[Effect]

In the clutter suppression device configured as described above.

By having a filter position memory that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range, and a register that stores the amount of phase change that corresponds to the filter shape, it is possible to null at different frequencies for each range pin. It is possible to form a filter with a fixed shape, such as having points.

Furthermore, by having a register that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter and a filter shape memory that stores the amount of phase change that corresponds to the filter shape over the entire range.

It is possible to form a filter that has a null point at a fixed frequency and has a different shape for each range pin.

In addition, by having a filter position memory that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range, and a filter shape memory that stores the amount of phase change that corresponds to the filter shape over the entire range. , it is possible to form filters with different shapes so that each range pin has a null point at a different frequency.

In addition, by having a gain controller that performs gain control over all range pins during target detection calculation for the amplitude detector output, it is possible to use different filters depending on the filter shape even when performing clutter suppression using filters with different shapes for each range pin. The difference in gain can be corrected.

〔Example〕

FIG. 1 is a block diagram of a clutter suppressing device showing an embodiment of the present invention, and (1) to (1o) are exactly the same as the conventional device described above. (11) is a filter position memory that stores and outputs the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range, and a register (11) that stores and outputs the amount of phase change that corresponds to the filter shape.
7) is calculated by a complex adder (6), and is provided to a complex multiplier (5).

In the above clutter suppression device, since the output of the filter position memory (11) that stores the center frequency of the filter can be changed for each range, the sum of the output of the register (7) that stores the filter shape is By applying this to the complex multiplier (5), the center frequency of the filter can be changed for each range while keeping the filter shape fixed. By changing the center frequency of the filter for each range, it is possible to minimize the amount of clutter remaining even when the center frequency has a property of changing in the distance direction.

FIG. 5 is a diagram illustrating the effect of the clutter suppression performance of the clutter suppression device. In the same figure, (1) shows an example of clutter power at four different points, for example, a,
It shows how the center frequency changes from frequency 0 in the order of b, c, and d. By forming a filter with null points such as e, f, g, and h as shown in (2) in the same figure for the clutter input shown in (1) in the same figure, the output power can be reduced as shown in the figure (2). If i, j, k, and l in (3) are satisfied, good ripple suppression performance can be obtained.

FIG. 2 is a block diagram of a clutter suppressing device showing another embodiment of the present invention, and (1) to (10) are exactly the same as the conventional device described above. (12) is a filter shape memory that stores and outputs the amount of phase change corresponding to the filter shape over the entire range, and the output of register (7) that stores and outputs the amount of phase change that corresponds to the center frequency position of the filter. The configuration is such that a complex adder (6) calculates the sum of , and provides the sum to a complex multiplier (5).

In the above clutter suppression device, since the output of the filter shape memory (12) that stores the filter shape can be changed for each range, the sum with the output of the register (7) that stores the center frequency of the filter is a complex multiplier (5
), the shape of the filter can be changed for each range while keeping the center frequency of the filter fixed.

By changing the filter shape for each range, it is possible to minimize the amount of clutter that remains undisappeared, even for clutter whose shape changes in the distance direction.

FIG. 6 is a diagram illustrating the effect of the clutter suppression performance of the clutter suppression device. In the same figure, (1) shows an example of clutter power at four different points, for example, a,
It shows how the clutter shape changes in the order of b, c, and d. As shown in (2) of the same figure for the clutter input shown in (1) of the same figure.

By forming filters with different shapes such as e, f, g, and h, the output power is i,
j, k, r, and good rutter suppression performance can be obtained.

FIG. 3 is a block diagram of a clutter suppressing device showing another embodiment of the present invention, and 5(1) to 5(1o) are exactly the same as the conventional device. (11) is a filter position memory that stores and outputs the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range, and (1
2) is a filter shape memory that stores and outputs the amount of phase change corresponding to the filter shape over the entire range. The outputs of the filter position memory (11) and filter shape memory (12) are added by a complex adder (6), and the outputs of the filter position memory (11) and filter shape memory (12) are
).

In the above clutter suppression device, the output of the filter position memory (11) that stores the center frequency of the filter can be changed for each range, and the output of the filter shape memory (11) can be changed for each range.
Since the output of 2) can also be changed for each range, the center frequency of the filter and the shape of the filter can be changed for each range. By changing the filter center frequency and filter shape for each range, it is possible to eliminate residual clutter even for clutter that has a property that the clutter center frequency changes in the distance direction and the clutter shape changes in the distance direction. can be minimized.

FIG. 7 is a diagram illustrating the effect of the clutter suppression performance of the clutter suppression device. In the figure, (1) shows an example of clutter power at three different points, a,
The clutter center frequency and clutter shape change in the order of b and c. By forming filters with different shapes at and at the center of the filter.

The output power is as shown in g, h, and i in the figure (3), and good rutter suppression performance can be obtained.

FIG. 4 is a block diagram of a clutter suppressing device showing another embodiment of the present invention, and CI) to (12) are exactly the same as the above device. (13) is a gain controller that performs gain control so that target detection can be performed while maintaining a constant gain over all range pins when performing target detection calculations on the amplitude detector.

In the above clutter suppression device, since the output of the filter shape memory (12) can be changed for each range, the shape of the filter can be changed for each range. If the filter shape differs for each range, the average gain of the filter will also differ for each range.1 For example, by controlling the noise level for each range to be constant using a gain controller (13), the target detector (9) The detection performance can be stabilized.

FIG. 8 is a diagram illustrating the effect of the gain controller (13) of the clutter suppression device. In (1) of the same figure, for example, a
indicates the average gain of the filter for each range due to different filter shapes, and means that the noise level also changes in conjunction with this, for example, as shown in b. On the other hand, by performing gain control as shown in (2), the noise level can be made constant, for example, as shown in C in (3) of the figure.

Changes in the CFAR threshold level for each range are made constant, and stable detection performance can be obtained in the target detector (9).

By the way, in the above description, the filter configuration has two delay memories (4) and three complex multipliers (5), but there are even more delay memories (4) and complex multipliers (5).
It goes without saying that the same effect as described above can be obtained with the configuration using 5).

Furthermore, in the above explanation, the delay memory (4) and the complex multiplier (
5) is a filter configuration in which there are a plurality of filters, but it goes without saying that the same effect as described above can be obtained even if the filter position and shape are made variable over the entire range by other means. Nor.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the following effects.

The center frequency changes in the distance direction using a filter position memory that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range and a register that stores the amount of phase change that corresponds to the filter shape. Good rutter suppression performance can be obtained even for clutter having such characteristics.

Furthermore, by having a register that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter and a filter shape memory that stores the amount of phase change that corresponds to the filter shape over the entire range.

Good rattling suppression performance can be obtained even for clutter that has a different shape for each range pin.

In addition, by having a filter position memory that stores the amount of phase change corresponding to the center frequency position on the frequency axis of the filter over the entire range, and a filter shape memory that stores the amount of phase change that corresponds to the filter shape over the entire range. Good ripple suppression performance can be obtained even for clutter whose center frequency and shape change in the distance direction.

In addition, by having a gain controller that performs gain control over all range pins during target detection calculation for the amplitude detector output, it is possible to use different filters depending on the filter shape even when performing clutter suppression using filters with different shapes for each range pin. It becomes possible to correct the difference in gain between the two and obtain stable target detection performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a clutter suppression device showing one embodiment of the invention, FIG. 2 is a block diagram of a clutter suppression device showing another embodiment of the invention, and FIG. 3 is a block diagram of a clutter suppression device showing another embodiment of the invention. FIG. 4 is a configuration diagram of a clutter suppression device showing still another embodiment of the present invention;
5 is a diagram explaining the operation of the clutter suppression device in FIG. 1, FIG. 6 is a diagram explaining the operation of the clutter suppression device in FIG. 2, and FIG. 7 is a diagram explaining the operation of the clutter suppression device in FIG. 3. 8 is a diagram illustrating the operation of the clutter suppression device shown in FIG. 4, FIG. 9 is a block diagram of a conventional clutter suppression device, and FIGS. 10, 11, and 12. and FIG. 13 are diagrams illustrating the operation of a conventional clutter suppression device. In the figure, (1) is the antenna, (2) is the receiver, and (3)
A/D converter, (4) delay memory, (5) complex multiplier, (6) complex adder, (7) register, (8) amplitude detector, (9) target detector, (10) is the target information processing type device, (11) is the filter position memory, (12)
) is a filter shape memory, and (13) is a gain controller. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (3)

[Claims] (1) An antenna that receives reflected waves from the target, a receiver that performs video processing on the signal received from the antenna, an A/D converter that converts the analog video signal from the receiver into a digital signal, and an A/D converter. series-connected delay memories that store the digital signals from the A/D converter over all ranges during one pulse repetition time, and a complex multiplier for the output from the A/D converter and the output from each series-connected delay memory. A complex multiplier that multiplies, a complex adder that adds the amount of phase change across all range pins to create a complex multiplier, and a complex adder that adds the amount of phase change corresponding to the center frequency position on the frequency axis of the filter to all ranges to create a complex multiplier. A filter position memory that stores and outputs the transition, a register that stores and outputs the amount of phase change corresponding to the filter shape for the complex adder, a complex adder that adds the outputs from each complex multiplier, and the output of the complex adder. an amplitude detector that detects the amplitude for
Equipped with a target detector that detects a target using an amplitude detector, and a target information processor that calculates target distance error, angle error, etc. from the output from the target detector, and calculates necessary target information for the radar system. A clutter suppression device characterized by: (2) An antenna that receives reflected waves from the target, a receiver that performs video processing on the signal received from the antenna, an A/D converter that converts the analog video signal from the receiver into a digital signal, and an A/D converter. series-connected delay memories that store the digital signals from the A/D converter over all ranges during one pulse repetition time, and a complex multiplier for the output from the A/D converter and the output from each series-connected delay memory. A complex multiplier that multiplies, a complex adder that adds the amount of phase change across all range pins to create a complex multiplier, and a complex adder that stores and outputs the amount of phase change that corresponds to the center frequency position on the frequency axis of the filter. A register that stores and outputs the amount of phase change corresponding to the filter shape for the complex adder over the entire range, a complex adder that adds the outputs from each complex multiplier, and the output of the complex adder. an amplitude detector that detects the amplitude for
Equipped with a target detector that detects a target using an amplitude detector, and a target information processor that calculates target distance error, angle error, etc. from the output from the target detector, and calculates necessary target information for the radar system. A clutter suppression device characterized by: (3) An antenna that receives reflected waves from the target, a receiver that performs video processing on the signal received from the antenna, an A/D converter that converts the analog video signal from the receiver into a digital signal, and an A/D converter. series-connected delay memories that store the digital signals from the A/D converter over all ranges during one pulse repetition time, and a complex multiplier for the output from the A/D converter and the output from each series-connected delay memory. A complex multiplier that multiplies, a complex adder that adds the amount of phase change across all range pins to create a complex multiplier, and a complex adder that adds the amount of phase change corresponding to the center frequency position on the frequency axis of the filter to all ranges to create a complex multiplier. A filter position memory that stores and outputs the phase change corresponding to the filter shape for the complex adder over the entire range and outputs it, a complex adder that adds the outputs from each complex multiplier. , an amplitude detector that detects the amplitude from the output of the complex adder, a target detector that detects the target for the amplitude detector, and a radar that calculates the distance error, angle error, etc. of the target from the output from the target detector. A clutter suppression device comprising a target information processor that calculates target information necessary for the system.