RU1840916C - Moving target selection apparatus - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: apparatus comprises a device for delaying probing signals by a repetition period, a synchronous detector and a subtractor, the first input of which is connected to the input of the delay device, and the second input is connected to the output of the delay device and the input of the synchronous detector, the second input of which is connected to the output of the subtractor; the apparatus also includes a second synchronous detector, the inputs of which are connected to the input of the delay device and the output of the subtractor, and a second subtractor, the inputs of which are connected to the outputs of the synchronous detectors, wherein the output of the second subtractor is the output of the apparatus.

EFFECT: high efficiency of rejecting passive jamming.

1 dwg

Description

The present invention relates to the field of radar and can be used to protect coherent-pulse radar from passive interference.

A device is known (US patent No. 3042915 class. 343-7.7, 1962) for the selection of moving targets on one delay line, containing an inter-period subtraction circuit at an intermediate frequency, followed by multiplication of the delayed limited signal and the output signal of the subtraction circuit.

The device, according to its author, is equivalent to a two-period inter-period subtraction scheme on two delay lines.

The aim of the present invention is to provide a selection circuit for moving targets on the same delay line with increased passive interference suppression efficiency.

This goal is achieved by the fact that in the device for selection of moving targets, containing an antenna, receiving, transmitting and indicating device, a device for delaying received signals, a subtracting device and a synchronous detector, in which the outputs of the receiving device are connected to a subtracting device, a synchronous detector and a delay device, subtracting the device is connected to the output of the delay device and a synchronous detector, a second synchronous detector connected to the outputs of the subtraction devices and rzhki, and a second subtractor connected to the outputs of synchronous detectors and the input of the indicator device.

In addition, the output of the receiving device and the output of the delay device are connected respectively to the first synchronous detector and the second synchronous detector through amplitude limiters. The structural diagram of the proposed device for the selection of moving targets is presented in figure 1.

The device for moving targets contains

1 - antenna device;

2 - transmitter;

3 - receiver;

4 - indicator device;

5 - delay device for the repetition period of the probe pulses;

6, 7 - subtraction schemes;

8, 9 - synchronous detectors;

10, 11 - amplitude limiters.

The presented scheme works as follows.

High-power radar pulses generated in the transmitter 2 are sent by a directional antenna 1 into space with moving targets. The signals reflected from the target are received by antenna 1 and fed to receiver 3.

At the output of the receiver, the signals are divided into two channels.

In one of the channels, using the delay device 5, the signal is delayed by the period of the probing signals and one part of the signal energy from the output of the delay device goes directly to the subtraction circuit 6, and the other through the amplitude limiter 11 enters the synchronous detector 9.

In the second channel, one part of the undelayed signal goes directly to the subtraction circuit 6, and the other part is fed through the amplitude limiter 10 to the synchronous detector 8.

The output of the subtraction circuit 6 is received at the other inputs of the synchronous detectors. The multiplication products of devices 8 and 9 are fed to the subtraction circuit 7, after which it is fed to indicator 4 or another output device.

The effectiveness of the proposed, compared with the known scheme can be determined by the formula:

$$\alpha =\frac{I}{I_n}=\frac{\mathrm{one}-\mathrm{1,5}{r}_{\mathrm{at}x}(T)+\frac{\mathrm{one}}{2}{r}_{\mathrm{at}x}^2(T)}{{{\text{[1-r}}_{\text{in}}\text{(T)]}}^{\text{2}}};\text{(one)}$$

where r _in (T) is the correlation coefficient of the input process as a function of the pulse repetition period;

I and I _n are the improvement coefficients of the proposed scheme and prototype, respectively, which are determined by the ratio (2).

(see D. Barton "Radar Systems", Military Publishing House of the USSR Ministry of Defense, Moscow, 1967)

$$I=\frac{{\overline{C}}_{\mathrm{at}sx}{}^2/{\overline{P}}_{\mathrm{at}sx}{}^2}{{\overline{\mathrm{FROM}}}_{\mathrm{at}x}{}^2/{\overline{P}}_{\mathrm{at}x}{}^2};\text{(2)}$$

и $${\overline{C}}_{вх}$$

- усредненная по всем возможным скоростям цели мощность сигнала на выходе и входе схемы соответственно,Where $${\overline{\mathrm{FROM}}}_{\mathrm{at}sx}$$

and $${\overline{C}}_{\mathrm{at}x}$$

- averaged over all possible target speeds signal power at the output and input of the circuit, respectively,

и $${\overline{П}}_{вх}$$

- мощность помехи на выходе и входе схемы соответственно. $${\overline{P}}_{\mathrm{at}sx}$$

and $${\overline{P}}_{\mathrm{at}x}$$

- interference power at the output and input of the circuit, respectively.

As follows from the above expression (1), the effectiveness of the proposed device can never be worse than the effectiveness of the prototype. With the values of inter-period correlation of passive interference equal to 0.9 and 0.95, the gain in the improvement coefficient is 7.4 and 10.2 dB, respectively, and monotonically increases when the correlation coefficient of passive interference is closer to unity (the most interesting case for selecting moving targets) . The frequency response of the proposed device is described, like the prototype, by a sine-square function.

Thus, the introduction of additional schemes and a certain order of their inclusion provides a significant increase in the efficiency of the device for selecting moving targets, which compares favorably with the specified prototype. Using the proposed device allows, with a slight complication in comparison with the known prototypes, to increase by an order of magnitude the efficiency of distinguishing moving targets against the background of passive interference, to avoid the need for expensive, complex and unreliable schemes of repeated inter-period subtraction and to obtain an equivalent economic effect. The additional effect cannot be accurately calculated due to the a priori uncertainty of the conditions and field of use of the proposed device).

Claims (1)

A moving target selection device comprising a delay device for the period of probing signals, a synchronous detector and a subtraction device, the first input of which is connected to the input of the delay device, and the second input is connected to the output of the delay device and the input of the synchronous detector, the second input of which is connected to the output of the subtraction device characterized in that, in order to increase the efficiency of suppressing passive interference, a second synchronous detector is introduced into its composition, the inputs of which are connected to the input of the device a delay and subtracting the output device and a second subtractor having inputs connected to the outputs of the synchronous detectors, and the output of the second subtracting unit is an output device.

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