JPS6046477A - Radar equipment - Google Patents

Abstract

PURPOSE:To measure the elevation of a low-elevation target on the surface of sea accurately by generating two beams which have a vertical different orientating direction slightly shifted, and measuring the amplitude ratio and phase difference of the received wave of the two beams. CONSTITUTION:RF electric power from a transmitter 6 is shaped into a pencil beam which is directed upward and downward off the axial direction of a reflecting mirror 2 and radiated through a primary radiator 3a and the reflecting mirror 2. The RF pulses reflected by the target return to an antenna 1 as a direct or an indirect wave, and are received together and mixed by mixers 7 (7a and 7b) with the output of a local oscillator 8. The obtained IF pulse outputs are amplified and detected to obtain video pulse voltages V1 and V2. The outputs of amplifiers 9 (9a and 9b) are sent to a phase detector 13 to extract the phase difference between the voltages V1 and V2. Those voltages V1 and V2, and data on the phase difference are inputted to a servo/calculating circuit 14 to obtain the elevation of the target by an operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radar device that precisely measures the elevation angle of a low elevation angle target on a calm sea surface.

[Prior Art] Conventionally, in order to precisely measure the angle of a target, a voltage (angular error voltage) that increases as the target shifts from the beam center direction to the periphery within the radiation beam of a radar antenna is measured and its value is calculated. It depended on the size.

Methods for generating such voltages include the monopulse method in which a sum pattern and a difference pattern are formed on the antenna, the conical scan method in which the radiation beam is continuously rotated around the antenna axis, and the antenna method in which the radiation beam is rotated in a 1n11 angular plane. A loaf switching method was used to continuously deflect the beam in the axial direction, and another method for precise measurement was using multiple antennas.

There was also a method of arranging the antennas in the angle measurement plane by changing the spacing little by little, and measuring the reception phase difference between each antenna to determine the angle. If the beam encompasses both the target and the image of the target created by the sea surface, the direct wave from the target and
Interference with indirect waves via the sea surface occurs, making accurate angle measurement impossible, and under certain conditions, the target falls within the null point of the interference pattern, making it impossible to even receive a received wave. .

[Summary of the Invention] In order to eliminate these drawbacks, the present invention forms two beams with slightly shifted vertical directions, and generates received waves from these two beams (a composite wave of a direct wave and an indirect wave). ] By measuring the amplitude ratio and phase difference of
[Embodiment of the invention] Fig. 1 is a τ diagram showing an embodiment of the radar equipment of this invention, and (1) in Fig. 9 shows the parabolic reflector (2) and its focal point. Two primary radiators (3
Antenna (4a) composed of a) and (3b).

(4b) is a transmitter/receiver switch, (5) is a variable frequency transmitter (
A high-power switch that switches and supplies the output of 6) to the transmitter/receiver switchers (4a) and (4b), <7a> and <7b) are mixers, (8) is a local oscillator, and (9a) and (9b) are xy amplifier, (1oa), (10b) is a detector, and a range gate circuit that follows the target distance and extracts only the signal within the range cell that includes the target.

H is an engineer F amplifier (based on the output of the range gate circuit I).
9a), AGO circuit that automatically controls the gain of (9b).

a3 converts the output signal of the engineering F amplifier (9b) into the engineering F amplifier (9b).
9a) is a phase detector which detects the phase of the output signal and extracts the phase difference β between the two output signals.α(a) is a detector (10).

(iob) (7) Output voltage V1. V217) ratio v2/
Generation of a signal for correcting the elevation angle of the antenna 100 based on v1 and phase difference β.

This is a servo/calculation circuit that calculates the target elevation angle Ov.

First, the RF power of 9 frequencies f1 (wavelength λ1) is transmitted to the transmitter (6
) is pulsed from terminal A of the high power switch (5).

Transmission/reception switching device (4 ways), the primary radiator (3a) emits the wave to the parabolic reflector (2).The emitted wave is transmitted to the reflector (2).
The RF pulse reflected by the target is shaped into a pencil beam pointing upward from the mirror axis direction and radiated into the air, as shown in Figure 2.
Antenna (1) with one part as a direct wave and one part as an indirect wave.
9 are combined, focused by a reflecting mirror (2), and received by the 111st-order radiators (3a) and (3b).

The received waves pass through transmission/reception switching devices (4a) and (4b), respectively, and are mixed with the output of the local oscillator (8) in mixers (7a) and (7b). The obtained F pulse outputs are amplified by F amplifiers (9a) and (9b), respectively, and then sent to a detector (10).
a), (10b) is detected and the video pulse voltage V1
t V2 . Here, 1 of the output of the detector (1oa)
The signal is sent to the AGO circuit (12) via the range gate circuit αυ and used for gain control of the IP amplifier (9st (9b)).

A part of the outputs of the IP amplifiers (9a) and (9b) are sent to the phase detector Is, and the phase difference β between vl and v2 is extracted.

These vl, v2, and β become input data to the servo/calculation circuit I.

By the way, the antenna beams corresponding to the primary radiators (3a) and (3b) are deflected at the same angle up and down with respect to the mirror axis direction AV, as shown by beam I and beam ■ in Fig. 2, respectively. . In Figure 2, ha is the antenna (1)
, ht is the height of the target T, R is the distance at the target reed,
Ot is the deviation angle of the target from the mirror axis direction A. t OV is the elevation angle of the target, M is the image of the target T on the sea surface, and M is the reflection point B in the horizontal direction.

Therefore, as shown in Figure 3, the video pulse voltages Vi and v2 received by beams ■ and beam ■, respectively, are voltages proportional to the combined value of the reflected waves from both the target and the image. l-6 In Figure 3, TI
, T2 are beams I, respectively.

Target received video voltage by beam n, f1. Technique 2 is the received video voltage of the image by beam ■ and beam ■, respectively, the horizontal axis 0 is the elevation angle, and the dashed line indicates that the mirror axis direction A is the target T.
Indicates the case where it shifts to the side.

Now, consider the case in which the mirror axis direction A of the antenna (11) in FIG. 2 points toward the center of the target T and the image plane.

The combined value of the direct wave and the indirect wave is equal for beam I and beam l, and v2/v1=1. Therefore, if we express the phase of the indirect wave with respect to the direct wave by α, the relationship shown in FIG. 4 can be obtained.

Here, if the change in phase angle at the nine reflection points M is ψ and -[, then α is expressed by the following equation.

This uses the condition of V2/V1 = 1.

sin 2ψ=sin2(π-β-ψ)-2sin (
π−β−ψ) sin (π−α) cosψ ten sjn 2
(π-4) (21 relational expressions are obtained.

Furthermore, when the No. 4 voltage received by Beam ■ is normalized by the No. 4 voltage received by Beam I from a single target, as shown in FIG. 5, as the target elevation angle 0 increases.

A monotonically decreasing output curve is obtained. Therefore, by expressing this curve as y=f(o) 141, 0-Ot can be uniquely determined for 7=T2/TI.

Also, from Figure 2, hj is ht=ha+Rtanov=ha+Rtan (Ot-
r ) (5).

In the above equation (11 to equation (5)), R1λ1.ha, f
(0), r is known as a radar parameter, and can be obtained by measuring ψ, π, and β, so in Equation 9, ht
Assuming the value of
By substituting C1b from T into equation (5), a new htO value can be obtained. Substituting this into equation (1) again,
By repeating similar calculations, the convergence value of ht is finally obtained, and the target elevation angle Ov can be obtained from Equation 9 (5).

In addition, in order to direct the mirror axis direction of the antenna (11) to the center of the target T and image l, the servo/calculation circuit +14 is used to (
Vl-V2)/(Vl +V2)", and set the servo motor and antenna so that this value is the minimum (
You can change the elevation angle of 11.

Also, the above (vl-V2) / (Vl +V2)
The value of can take the minimum value depending on the value of α even if the mirror axis direction of the antenna (11) is not directed at the center of the target T and the imager, so in order to exclude such cases.

Re-measure with a different value of α. Specifically, the transmitter (6)
Transmission frequency wo f, (wavelength λ1) to f2 (wavelength λ2)
Change to ■1. ■2. It is good to re-measure β.

FIG. 6 shows another embodiment of this invention, in which (11
~(lj corresponds to the part with the same number in FIG. 1.

Among the newly added parts in Figure 6, αe is the transmitter (6)
A divider that equally distributes the outputs of (17a3.(17b
).

(17C), (17d)! -1 low power switch, α
& is terminal B of low power switch (17a), (17b)
The sum (Σ) and difference (Δ) of the RF received electric field obtained from
The resulting monopulse coupler.

First, the RIt'' power of one frequency f1 (wavelength λ1) is transmitted in pulses from the transmitter (6), and is divided into in-phase and equal parts by one distributor (161). The radiators (k) and (5b) radiate to the parabolic reflector (2).The radiated waves are synthesized in space and shaped by the reflector into a pencil beam (beam I in Figure 6) directed in the direction of the mirror axis. and radiates into the air.

Below, the processing of the obtained RF reception pulses is as follows: low power switch (17a), (17b), (17c), (17
d) If the circuit is connected to terminal A, the procedure is exactly the same as described above. ■1. V2. The measuring force of β can therefore be claimed.

Low power switch (17a), (17b), (17c
), (17 (1) +7) If a circuit is connected to terminal B, the RF received pulse is connected to the monopulse coupler (I
It is changed to Σ and △ signals by l, and becomes a normal monopulse radar.

In other words, according to the embodiment shown in FIG. It is possible to do so.

[Effects of the Invention] As described above, this invention receives a composite wave of direct waves and indirect waves using two beams, and removes the influence of indirect waves by comparing and processing them. , it has the advantage of being able to precisely measure the elevation angle of a low-elevation target on a calm sea surface.

Of the two embodiments, the one shown in Fig. 1 transmits independently with two beams and simultaneously utilizes the reception signals of both beams, so that no interference occurs as in the case of a normal single beam radar. There is an advantage that there is no interruption in the received No. 4 due to pattern mull. Furthermore, the method shown in FIG. 6 has the advantage that it can be used interchangeably with the conventional monopulse angle measurement method.

Incidentally, this invention can also be used for angle measurement of high elevation angle targets where no image exists within the beam by directly utilizing the relationship t between T2/TI and Ot shown in FIG. Furthermore, although a reflector type antenna is used for the antenna (11), it is clear that a similar beam can be formed using a phased array.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of a radar device according to the present invention, FIGS. 2 to 5 are diagrams for explaining the operation according to the present invention, and FIG. 6 is a diagram showing another embodiment of the present invention. FIG. In the figure (11 is the antenna, (91L) (9b) is the engineering F
Step width switch, (10a) and (10b) are detectors, aυ is range gate circuit or AGO circuit, (I3 is phase detector, 04+ is servo/calculation circuit, α9 is servo motor. (17+ is low power It is a switch. Identical or equivalent parts in the diagram are indicated by the same reference numerals. Agent Masuo Oiwa

Claims (2)

[Claims] (1) An antenna that forms two independent beams that are close to each other and alternately directed at different elevation angles, a means for amplifying and detecting waves received by these two beams, two video voltages obtained by this means, and a mechanism for adjusting the direction of the antenna so that the two video voltages are approximately equal; and means for calculating the target elevation angle from the ratio of the target signals received by the two beams and the phase difference. A radar device for low elevation angle measurement characterized by: (2) An antenna that forms two independent beams that are close to each other and directed at different elevation angles, a low power switch that switches and supplies the received waves from these two beams to a monopulse coupler, and amplification and detection of the received waves from the two beams, respectively. the two video voltages obtained by this means, a mechanism for obtaining the phase difference Z between them and adjusting the direction of the antenna so that the two video voltages are approximately equal; A radar device comprising means for calculating a target elevation angle from a signal ratio and the phase difference, and for switching to a monopulse angle measurement function based on the low power switch.