JPS63221274A - Target azimuth detecting circuit - Google Patents

Abstract

PURPOSE:To decide the azimuth of a target with high accuracy even from a small input by finding the quadrant of the phase of each video by using only sign bits of a sum video signal and a difference video signal after digital conversion, and making a decision from a quadrant difference. CONSTITUTION:A quadrant converter 3a inputs only a sign between the sign and amplitude after the bipolar A/D conversion of a sum pattern video from a monopulse antenna receiver to find a quadrant where the phase of the video is present. Similarly, a quadrant converter 3b finds a quadrant from the size of a difference pattern video. Then a quadrant difference detector 4 finds the quadrant difference and a right-left decision device 5 decides three conditions, i.e. right, left, and unknown conditions from the output of the detector 4. Then latch circuits 11 in an integrator 6 and an integral decision device 7 are stored with a right, a left, or an unknown signal and an adder 10b performs integration to decide right when the integral value is larger than a specific value or left in other cases.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to target direction detection for determining whether a reflected wave from a target is from the left or right direction in a radar device using a monopulse antenna. It is related to circuits.

[Conventional technology]

Conventionally, this type of circuit has been shown in Figure 4. In Figure 0, 1a and 1b are sum pattern videos (hereinafter ΣI video, ΣQ) from a monopulse antenna receiver.
It is called video, and ■video and Q video have a phase difference of 90°. ) and difference pattern video (hereinafter Δ■ video, Δ
It's called Q-video. ) is a phase angle detector for determining the phase angle of Σ video and the phase angle of Δ video, respectively, using a signed video signal converted from an analog video to a digital signal for each distance gate, and 2 is a phase angle detector. The phase angle φΣ(O
~360°) and Δvideo phase angle φΔ(O~36
This is a phase difference determiner that determines the phase difference from 0°) and determines the left and right orientation.

Here, the concept of orientation determination using a general monopulse antenna will be briefly explained with reference to FIGS. 6(a), (b), and (C). (Communications Association Research Radar Technology [Part 2] First Edition 11
．． 4 monopulse method) Two partially overlapping monopulse antenna patterns (
Using FIG. 6(a), a sum pattern in which two antenna patterns are combined in the same phase and a difference pattern in which they are combined in opposite phases are used.

Phase difference between Σ video phase and Δ video a phase φΔ−φΣ
is from -90@ to +90” (or +9
0″ to 190＠, here the right side is +90° and the left side is -
When the phase difference φΔ−φΣ in FIG. 6(b) is +90°, the target is determined to be on the right, and when it is −90°, it is determined that the target is on the left. (Although it may be assumed that +90' is the left direction and -90" is the right direction, here, the right direction is +90°, and -90" is the right direction.
90” is assumed to be the left direction).

Therefore, the conventional circuit operation will be explained next.

In a monopulse antenna receiver, the Σ pattern and the Δ pattern are combined into I and Q videos with a phase difference of 90'' using a phase detector. That is, the amplitude is Avp-r, and the target angular frequency is ω. Then, the video signal is AVF-P (CO3(ωt+θo) + jsin
(ω is 10)) is expressed as a complex number. Among these video signals, the one on the real axis A cos (ω is 10) is called ■video, and the one on the imaginary axis As1n (ω is 10) is called Q video.

The four analog videos ΣI, ΣQ, Δ■, and ΔQ are A/D converted, and the phase angle is detected using the sign and amplitude value. The phase angle detector 1a determines whether it is the right half plane or the left half plane in FIG. 5 from the mark.

The conditions of ROM (Read Only Memory
) and output the phase angle (φΣ) of Σ from the ROM.

Similarly, the phase angle of Δ (φΔ) is also output from the phase angle detector 1b.

In the phase difference determiner 2, the phase of Σ (φΣ) is subtracted from the phase of Δ (φΔ) and expressed as between -180° and +180'', and when it is between 0° and +180'', it is set as 1 (right). −
When the angle is between 180'' and 0°, the left/right direction determination result is output as O (left).

[Problem that the invention seeks to solve]

Since the conventional target direction detection circuit is configured as described above, it is possible to obtain the phase angle when the input amplitude of the radar received video is at a large level, but it is difficult to calculate when the input amplitude is at a small level close to noise. Can not do it. Therefore, since the phase difference between the videos Δ and Σ (phase of Δ−phase of Σ) cannot be calculated accurately, there is a problem that the left and right directions may be incorrectly determined.

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to obtain a target direction detection circuit that can determine the direction of a target with high precision.

[Means for solving problems]

The target direction detection circuit according to the present invention includes a bipolar A/D
(analog/digital) Using only the sign bits of the sum video signal and difference video signal after conversion, find the quadrant in which the phase of each video is located, and use the quadrant difference between the phases of the sum video signal and difference video signal to find the target. It is designed to determine the direction.

[Effect]

In this invention, the target direction is determined using only the phase codes of the sum video signal and the difference video signal, so even if the level of the received video is close to noise, the left and right direction of the target can be determined with high accuracy. can be determined.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1) are block diagrams and circuit diagrams showing a target direction detection circuit according to a first embodiment of the present invention, and in both figures, 3a and 3b are a sum video (Σ video) signal and a difference video signal. (ΔVideo) Using the codes after A/D conversion of I and Q videos, each having a 90° phase difference, the sum,
quadrant converter for determining the phase quadrants of the difference video; 4;
5 is a quadrant difference detector that calculates the difference between the quadrant of Σ video and the quadrant of Δ video and outputs the result in 2 bits. 6 is an integrator for integrating the judgment of right, left, and unknown; 7 is an integral judge for obtaining the final discrimination result of left and right from the integrated result; 8a is ΣI; 8b is an exclusive OR circuit into which the sign of Q is input, ΔI is input, and the sign of Q is input, 10a is Bz, the input signal of the B+ terminal is input to the upper,
2-bit signal as lower bit, A t , A I
Add "1" to a 2-bit signal whose upper and lower bits are the input signal of the terminal, and convert the lower 2 bits of the addition result to 82
, S, and the sign of ΣQ is input to the B+ terminal via the inverter circuit 9a.
, the output of the OR circuit 8a is input to the terminal via the inverter circuit 9b, the sign of ΔQ is input to the A2 terminal,
The output of the OR circuit 8b is input to the A terminal, and "1" is always input to the CO terminal via the inverter circuit 9C. 12 is an AND circuit which receives as input the inverted signal from the inverter circuit 9d of the output of the SZ terminal of the adder 10a and the output of the S terminal, and 9e is an AND circuit 81 of the adder 10a.
Inverter circuit that inverts the output of the terminal, 11 is -AND
A launch circuit 10b stores a 2-bit signal in which the output of the circuit 12 is the upper bit and the output of the inverter circuit 9e is the lower bit. Reference numeral 10b is an adder that integrates the stored 2-bit signal a predetermined number of times.

Next, the operation will be explained.

In the quadrant converter 3a, bipolar A of ΣI, ΣQ video
Of the sign and amplitude after /D conversion, only the sign is input,
converted into quadrants. That is, as shown in FIG. 1('b), a 2-bit signal consisting of the sign of ΣQ and the output of the exclusive OR circuit 8a is output. Here (Σ■, ΣQ)
-(0,0) is the first quadrant, (1,O) is the second quadrant, (1,1) is the third quadrant, and (0,1) is the fourth quadrant.

Similarly, quadrants are determined from the codes of the Δ■ and ΔQ videos by the quadrant converter 3b, and similar signals are output.

Next, the quadrant difference detector 4 determines the phase quadrant of the quadrant difference -Δ and the phase quadrant of -Σ. That is, the adder 10a receives the inverted signal of the output of the quadrant converter 3a, the output of the quadrant converter 3b, and "
1'' are input, a predetermined addition is performed, and S
,,S, terminals output the addition result as a 2-bit signal.

Then, in the left/right discriminator 5, the quadrant difference is expressed as a 2-bit signal based on the 2-bit signal and output. Here, when the phase quadrant of Δ is one quadrant ahead, 2(1
0) signal, 0 (00) when Σ is one quadrant ahead
signal is output, and the phase quadrant difference is O or 2 (same -
quadrant or 180＠ deviation), the cause is monopulse.
It is assumed that this is due to a phase shift of the Σ and Δ videos of the antenna or a conversion error during A/D conversion of the Σ and Δ videos, and a signal of 1 (01) is output as unknown.

Next, in the integrator 6 and the integral determiner 7, the latch circuit 1
1 stores the signals 2 (right), O (left), and 1 (unknown), and the adder 10b performs integration, and when the value is greater than a predetermined value, it is determined as right, and when it is not, it is determined as left. . For example, if you integrate 8 times, the integration result will be 8
If it is above, it is right.

In this way, in this embodiment, the target direction is determined using only the phase codes of the sum video signal and the difference video signal, so even if the level of the received video is close to noise, it is possible to Since the direction can be determined and the determination result is obtained by integrating it multiple times, the effects of phase shifts between the sum video and difference video and conversion errors of the A/D converter can be reduced, increasing reliability. It is possible to obtain highly accurate judgment results.

FIG. 2 is a block diagram showing a target direction detection circuit according to a second embodiment of the present invention.
(This is a configuration in which the integrator 6 and the integral determiner 7 are removed from the embodiment shown in bl.) In this embodiment, the monopulse antenna's Σ and Δ video phase shifts and Σ and Δ video's A If the conversion error during /D conversion is within the allowable value, accurate direction determination can be performed.

FIG. 3 is a circuit diagram showing a target direction detection circuit according to a third embodiment of the present invention. This example is shown in Figs. 1(a) and (b).
) The quadrant converters 3a, 3b and the quadrant difference detector 4 of the embodiment shown in FIG. This is replaced with a ROM (Read Only Memory) circuit 13 that outputs a discrimination signal.
As in the embodiments shown in FIGS. (a) and (b), accurate determination can be made.

〔Effect of the invention〕

As described above, according to the target direction detection circuit of the present invention,
The quadrant in which the video phase is located is determined using only the sign bits of the sum video signal and the difference video signal after bipolar A/D conversion, and the target direction is determined from the quadrant difference between the phases of the sum video signal and the difference video signal. This has the advantage that even if the level of the received video is close to noise, the left and right direction can be determined accurately.

[Brief explanation of drawings]

1(a) and (b) are block diagrams and circuit diagrams showing a target direction detection circuit according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing a target direction detection circuit according to a second embodiment of the present invention. 3 is a circuit diagram showing a target direction detection circuit according to a third embodiment of the present invention, FIG. 4 is a block diagram showing a conventional target direction detection circuit, and FIG. 5 is a circuit diagram showing a conventional target direction detection circuit. Diagram for explaining phase difference calculation, FIG. 6(a),
(b) and (C) are diagrams for explaining the concept of left/right direction detection in a monopulse antenna. In the figure, 3a and 3b are quadrant converters, 4 is a quadrant difference detector, 5 is a left/right discriminator, 6 is an integrator, 7 is an integral determiner, and 8
a, 8b are exclusive OR circuits, and 9a. 9b, 9c, 9d, 9e are inverter circuits, 10a, l
Qb is an adder, 11 is a latch circuit, 12 is an AND circuit,
13 is ROM (Read Only Memory)
It is a circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (4)

[Claims] (1) In a target orientation detection circuit that detects the target orientation using the error sensitivity curves of the sum pattern and difference pattern of the monopulse antenna, I and Q videos with a 90° phase difference between the sum video signal and the difference video signal are used. A quadrant converter that calculates phase quadrants of the sum video and the difference video using codes after A/D conversion; a quadrant difference detector that detects the quadrant difference between the sum video and the difference video; and a quadrant difference detector that detects the quadrant difference between the sum video and the difference video. 1. A target orientation detection circuit comprising: left and right discrimination means for determining left and right based on the left and right discrimination means. (2) A patent characterized in that the left/right discrimination means is equipped with an integrator that integrates a signal indicating the discrimination result multiple times, and an integral determiner that discriminates between left and right based on the integration result. A target direction detection circuit according to claim 1. (3) The quadrant converter includes first and second exclusive OR circuits to which the A/D converted codes of each I and Q video of the sum video signal and the difference video signal are input, respectively; The quadrant difference detector detects a 2-bit signal in which the upper bit is an inverted signal of the sign of the Q video of the sum video signal and the lower bit is an inverted signal of the output of the first exclusive OR circuit, and the difference video signal. The above second exclusive OR with the code of the Q video of
The left/right discrimination means includes an adder that adds a 2-bit signal whose lower bit is the output of the circuit and a carry input signal "1" and outputs a signal of the lower 2 bits of the addition result, and the left/right discrimination means is configured to perform the addition. Claim 1, characterized in that the invention comprises an AND circuit receiving an inverted signal of the upper bit signal of the output of the device and a lower bit signal, and an inverter circuit receiving the lower bit signal. The target direction detection circuit described in item 1. (4) The left/right discrimination means includes a latch circuit that stores a 2-bit signal in which the output of the AND circuit is the upper bit and the output of the inverter circuit is the lower bit, and the signal stored in the latch circuit is integrated a predetermined number of times. 4. The target direction detection circuit according to claim 3, further comprising an adder for calculating the target direction.