JP2618984B2 - Pulse Doppler radar device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulse Doppler radar device having a Doppler filter constituted by an FFT, and particularly focuses on a data input setting period to the Doppler filter, and sets the setting period. The present invention relates to an improvement in the method of applying AGC for the purpose of suppressing generation of an erroneous target caused by intermodulation due to reception system saturation as a processing unit.

[Conventional technology]

Conventional pulsed Doppler radar and IAGC
Examples of (Instantaneous AGC) are shown in FIGS. 3 and 4, respectively. Fig. 3 is a diagram of the document "Radar Technology (No. 2)" published by the Institute of Electronics and Communication Engineers, for example, Fig. 12.6 of Chapter 12.3, and Fig. 4 is a diagram of the document "Radar Handbook"("RADARHANDBOOK") published by McGraw-Hill Book Company. Similar circuits are shown in each case.

In FIG. 3, (1) is an antenna, (2) is a transmission / reception switch, (3) is a transmitter, (4) is an IF amplifier, and constitutes a reception system together with a detector (6). (9) is a range gate, (10) is a Doppler filter composed of an n-point FFT, and (11) is a detector group connected to the Doppler filter (10).

FIG. 4 shows that an ATT (ATTenuater) circuit (5) is inserted between the IF amplifier (4) and the detector (6) in FIG. 3, and the ATT is instantaneously changed according to the output of the detector (6). Circuit (5)
This is an IAGC that is configured by adding an ATT control circuit (12) that adjusts the gain and adjusts the reception system gain.

 Next, the operation will be described.

The transmission wave generated by the transmitter (3) is transmitted and received by the transmission / reception switch (2).
From the antenna (1), is radiated into the air via the antenna (1), is reflected by the target, is received again as a reception wave, passes through the transmission / reception switch (2) from the antenna (1), is amplified by the IF amplifier (4), and is detected by the detector (6) Is a received video signal. The received video signal is selected on the time axis by the range gate (9) and input to the Doppler filter (10).

For the sake of simplicity, it is assumed that the number of targets is two and the Doppler frequencies are f ₁ and f ₂ at the same distance R. Do).

If the receiving system is not saturated with the received waves from the two targets, the received video appears on the time axis as beat frequencies f ₁ and f ₂ as shown in FIG. 5 (a). The range gate (9) performs n data samplings at every radar pulse repetition period T from the time corresponding to the distance R, and uses this as a processing unit (hereinafter referred to as a burst) for n points.
Send to the Doppler filter (10) composed of FFT.
The received video is separated by the Doppler filter (10) into Doppler frequencies f ₁ and f ₂ as shown in FIG.
Each is detected in 1).

However, if the received wave is strong enough to saturate the receiving system, the received video will be distorted on the time axis and cause intermodulation as shown by a solid line in FIG.
0) In addition to f ₁ and f ₂ , the output is 2f ₁ −f as shown in FIG.
_2, resulting in unnecessary wave of 2f ₂ -f _1. These unnecessary waves may be detected as wrong targets by the detector group (11).

Therefore, it is necessary to consider AGC as a method of not saturating the receiving system. Conventionally, an IAGC as shown in FIG. 4 has been provided as this type of method. The IAGC is instantaneous according to the output of the detector (6) in a control loop composed of the detector (6), the ATT control circuit (12) and the ATT circuit (5) as shown in FIG.
The ATT amount of the ATT circuit (5) is set, and gain control of the receiving system is performed. However, in this method, the reception system gain of the n data samplings changes at the output of the detector (6) during the burst period described above, so that the data does not become the same, and the time becomes the same as in FIG. The waveform is distorted, and unnecessary waves are generated on the frequency axis.

[Problems to be solved by the invention]

As described above, when the conventional IAGC is combined with a radar apparatus that performs detection on the frequency axis like a pulse Doppler radar apparatus, when the gain control of the receiving system is performed instantaneously, the burst period, that is, data setting of the n-point FFT is performed. Period (n.
In T), the receiving system gain of each data is different, and intermodulation occurs due to waveform distortion, an unnecessary wave appears in the FFT output, and there is a problem that it is detected as an erroneous target.

The present invention has been made in order to solve the above-described problems of the related art, and is realized by a method different from the IAGC, and is also applicable to a radar apparatus that performs target detection on a frequency axis such as a pulse Doppler radar apparatus. The purpose is to obtain a pulsed Doppler radar device having an AGC that can be used.

[Means for solving the problem]

A pulse Doppler radar device according to the present invention is a pulse Doppler radar device that performs target detection using a Doppler filter configured by an n-point FFT (Fast Fourier Transform), wherein a data input setting period to the Doppler filter is set as a processing unit. A saturation level detecting means for detecting a saturation level of the receiving system between processing units, and setting an automatic gain control (AGC) amount in accordance with the saturation level, and setting the set amount of AGC constant during the next processing unit period AGC amount setting means for setting the receiving system, and attenuating means for attenuating the signal of the receiving system according to the AGC amount setting of the AGC amount setting means and preventing saturation of the receiving system due to a strong received signal. It is a thing.

[Action]

In the present invention, the AGC detects the saturation level of the received wave, sets the AGC amount for each burst period, and sets the receiving system gain at the constant AGC amount during the next burst period. An erroneous target caused by intermodulation due to saturation of the receiving system is suppressed, and a decrease in detection performance of the pulse Doppler radar device is prevented.

〔Example〕

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

FIG. 1 shows a pulse Doppler radar apparatus according to an embodiment of the present invention. In the figure, (1) to (4), (6) and (9) to (11) show a conventional pulse Doppler radar apparatus, 5) is the same as that of IAGC, respectively.
(7) a saturation level detector (saturation level detection means) for detecting the saturation level when the level of the received wave is higher than the maximum input level at which no intermodulation occurs in the reception system;
(8) stores the maximum value of the detection value of the saturation level detector (7) in the burst period, and uses the maximum value as the AGC control amount.
This is a maximum value storage circuit (AGC amount setting means) for setting the circuit (5).

 Next, the operation will be described.

In FIG. 1, the operation from the transmission of the radar to the reception of the received wave and the exit from the transmission / reception switch (2) is the same as that of the conventional art, and therefore the description thereof is omitted.

The received wave that has passed through the transmission / reception switch (2) is split into two, and one is input to the saturation level detector (7). When the received wave input level is higher than the maximum input level of the receiving system, the saturation level detector (7) detects the saturation level and sends it to the maximum value storage circuit (8).

The maximum value storage circuit (8) stores the maximum value from among the saturation levels sent from the saturation level detector (7) with the burst period as one processing unit, and uses the maximum value to set the AT.
The AGC amount required to control the T circuit (5) is set.

The operation described above is now described in burst (1) shown in FIG.
In this case, the AGC control amount during the burst (1) of the maximum value storage circuit (8) in the burst (1) is ATT1. This control amount ATT1 is the next burst (2)
In the burst period, the ATT circuit (5) is used during the burst period to prevent the saturation of the receiving system for the burst (2) period, suppress the generation of unnecessary waves due to intermodulation as in FIG. To prevent the detection performance from decreasing.

Thereafter, similarly, the ATT circuit is controlled within the next burst period with the AGC control amount set one burst before, and operates as an AGC that prevents saturation of the reception system.

In addition to the above embodiment, (i) the method of setting the burst period (= processing unit) is as follows. When the output data of the n-point FFT is integrated, if the number of integrations is m, the burst The period is m
By using n · T, the sampling period of the time axis waveform is increased as compared with the case of n · T in FIG. 2, and the setting accuracy of the maximum saturation level of the received wave (set by the maximum value storage circuit (8))
AGC control amount) is improved (see FIG. 7).

(Ii) For the AGC set amount, instead of using the maximum saturation level of the received wave in the burst period, the storage capacity of the maximum value storage circuit is increased, and the maximum value in the burst period is set for each range gate in the pulse repetition period T. The saturation level is stored, and 1 is stored in the next burst period.
Based on the maximum saturation level of each range gate in the pulse repetition cycle before the burst, the ATT circuit (5) is controlled so that the same AGC amount is set for the same range gate in each pulse repetition cycle. Therefore, during the same burst period, AG
Since the C setting does not change and remains constant, and the AGC setting is optimal for each range gate, the small signal detection performance can be improved as compared with the above embodiment (FIG. 8). Also, the AGC amount is not always constant during the same burst period, but the AGC amount is constant at each range gate during the same burst period. However, generation of unnecessary waves is hardly a problem.

(Iii) Regarding the correction of the prediction error due to the difference between the AGC amount measurement period and the AGC amount setting period by one burst, in the above embodiment, strictly, the AGC amount set in the next burst before one burst is measured. Because that AGC
The amount is a predicted value, and although it is close in time, it cannot be guaranteed that the receiving system will not saturate at all. (However, since the AGC is multiplied by the predicted value, compared to the case without this method, , The amount of saturation is much smaller), so that the probability of saturation can be reduced by correcting the prediction error.

As the correction method, the prediction set one burst before
That is, the AGC amount is slightly added to the AGC amount.

An appropriate correction amount 補正 obtained by the computer simulation and the experimental circuit is △ ≒ 3 dB, and a satisfactory result can be obtained by adding this value to the AGC amount of the maximum value storage circuit (8) of the experimental circuit. ing.

〔The invention's effect〕

As described above, according to the pulse Doppler radar device according to the present invention, in the Doppler filter configured by the n-point FFT, the input data setting period is set as a processing unit, and the AGC amount of the receiving system is kept constant during that period. Therefore, it is possible to suppress the saturation of the receiving system, prevent the generation of unnecessary waves due to intermodulation, and provide an AGC that does not cause deterioration in detection performance even for radar devices that detect on the frequency axis like pulsed Doppler radar devices. it can.

[Brief description of the drawings]

FIG. 1 is a system diagram of a pulse Doppler radar device having an AGC according to an embodiment of the present invention, FIG. 2 is a diagram illustrating the operation of the AGC according to the present invention, FIG. 3 is a system diagram of a conventional pulse Doppler radar device, FIG. The figure is a system diagram in which the conventional IAGC is added to the receiving system of the conventional pulsed Doppler radar device, FIG. 5 is an explanatory diagram of the received signal when the receiving system is not saturated, and FIG. 6 is the receiving system is saturated. FIG. 7 is a diagram showing another setting for the AGC processing unit (= burst) according to the present invention, and FIG. 8 is a diagram showing another embodiment for setting the AGC amount of the AGC according to the present invention. FIG. In the figure, (1) is an antenna, (2) is a duplexer,
(3) is a transmitter, (4) is an IF amplifier, (5) is an ATT circuit (attenuation means), (6) is a detector, (7) is a saturation level detector (saturation level detection means), (8) Is a maximum value storage circuit (AGC amount setting means), (9) is a range gate, (10) is a Doppler filter, and (11) is a detector group. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kinoshita 8-1-1, Tsukaguchi-Honcho, Amagasaki-shi, Hyogo Ryoden Toki Co., Ltd. (72) Inventor Masanobu Tsuto 8-1-1, Tsukaguchi-Honcho, Amagasaki-shi, Hyogo 1 Mitsubishi Electric Corporation Communication Equipment Works (72) Inventor Masaki Anfuku 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Mitsubishi Electric Corporation Communication Equipment Works (72) Inventor Kazumi Yamaguchi Tsukaguchi Honmachi, Amagasaki City, Hyogo Prefecture 8-1-1, Mitsubishi Electric Corporation Communication Equipment Works (56) References JP-A-61-79178 (JP, A) JP-A-63-36176 (JP, A) JP-A-62-170867 (JP, A) A) Japanese Patent Publication No. 61-61071 (JP, B2) Japanese Patent Publication No. 2-42438 (JP, B2) Japanese Patent Publication No. 4-78950 (JP, B2)

Claims (1)

(57) [Claims] 1. An n-point FFT (Fast Fourier Transfor
m) a pulse Doppler radar device for performing target detection using a Doppler filter, wherein a data input setting period to the Doppler filter is set as a processing unit, and a saturation level for detecting a saturation level of a receiving system between the processing units is set. AGC (Automatic Gain Control) according to the detection means and the saturation level
AGC amount setting means for setting the amount, setting the set AGC amount constant during the next processing unit period, and setting the AGC amount in the receiving system, and attenuating the signal of the receiving system according to the AGC amount setting of the AGC amount setting means. And a damping means for preventing the reception system from being saturated by a strong reception signal.