RU2428712C1 - Method for radar detection of signals reflected from targets, and device for realising said method - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: in the inventions, after matched filtering, a final decision on the received signal which exceeds the detection threshold is made after additional analysis, where the degree of mismatch between the received signal and the matched filter is evaluated. For range samples in which the detection threshold has been exceeded, the ratio of the value of the signal envelope before matched filtering, delayed by signal processing time during matched filtering, to the value of the signal envelope after matched filtering is determined. The obtained ratio is compared with a given threshold value established based on the acceptable mismatch of the received signal which is reflected from the target. A decision is made on detection of the signal which is reflected from the target if the said threshold value was not exceeded. ^ EFFECT: high protection of radar stations from pulse interference in form of high-power mismatched signals. ^ 2 cl, 2 dwg

Description

The invention relates to the field of radar and can be used in radar stations (radar) to detect targets under conditions of pulsed interference.

In modern radars, probing signals with intra-pulse modulation and a sufficiently long duration are widely used. A known method for detecting such signals reflected from targets involves temporarily compressing the received signal using matched filtering (Radar Reference, edited by M. Skolnik, vol. 3, M., Sov. Radio, 1979, p. 400).

A device for radar detection of signals reflected from targets, containing a matched filter (Reference radar, edited by M. Skolnik, t.3, M., Sov. Radio, 1979, p. 400-402).

The known method and device can significantly reduce the influence of impulse noise in the form of interfering signals that are not consistent with the filter, but have low immunity from impulse noise in the form of interfering signals of high power, mismatched with the filter. The term "mismatched received signal", borrowed from the source: Modern radar. Analysis, calculation and design of systems. Per. from English. Ed. Yu.B. Kobzareva, M., Sov. Radio, 1969, p. 222, denotes a received signal that is not fully consistent with the filter.

The closest way to detect the signal reflected from the target involves temporarily compressing the received signal using matched filtering, extracting the envelope of the signal and then comparing it with the detection threshold q ₀ , above which the decision is made to detect the target (Theoretical Basics of Radar. Edited by Y. Shirman. D., "Sov. Radio", 1970, p.110-114). The detection threshold q _{0 is} set based on a given level of false alarms.

The closest device (Fig. 1) contains a matched filter 1 in series, a signal envelope detector 2, and a threshold device 3 (Theoretical Foundations of Radar. Edited by Shirman Y.D., Sov. Radio, 1970, p. 114, fig. .3.19).

The closest technical solutions can effectively detect probe signals reflected from targets, and suppress impulse noise in the form of signals that are not consistent with the filter. However, if the impulse noise is a signal that is inconsistent with the filter, and at the same time its power is high enough, then at the output of the matched filter its envelope can exceed the detection threshold, and in this case it will be detected as a signal reflected from the target. This is a disadvantage of the closest technical solutions.

The problem being solved (technical result) is to increase the radar security from impulse noise in the form of mismatched high power signals.

The specified technical result is achieved by the fact that in the method of radar detection of signals reflected from targets, which includes coordinated filtering of the received signal with subsequent separation of the envelope of the signal and comparing it in each discrete in range with the detection threshold, according to the invention, for a discrete in range in which exceeding the detection threshold, determine the ratio of the envelope of the signal to the matched filtering delayed by the signal processing time with the matched filter To the value of the envelope of the signal after matched filtering, the obtained ratio is compared with a predetermined threshold value established on the basis of the permissible mismatch of the received signal reflected from the target, a decision is made to detect a signal reflected from the target if the specified threshold value is not exceeded.

The indicated result is also achieved by the fact that in the device for radar detection of signals reflected from targets, containing a matched filter, a signal envelope detector and a threshold device in accordance with the invention, a second signal envelope detector, a delay device, an envelope amplitude ratio calculator for calculating the ratio of the signal envelope value to the matched filter to the signal envelope value after the matched filter, the second time The device and circuit “I”, while the matched filter input and the input of the second envelope signal detector are connected to each other and are the input of the radar detection device, the output of the second signal envelope detector is connected to the input of the delay device, the first and second inputs of the envelope amplitude ratio calculator are connected respectively with the output of the envelope detector of the signal and the output of the delay device, and its output is connected to the input of the second threshold device, the output of the threshold device and d second threshold devices connected respectively to the first and second inputs of "AND" circuit, whose output is the output of the radar detection device.

Let us explain the essence of the invention.

It is known that with matched filtering, the level of a compressed signal with intrapulse modulation depends on how close the received signal is in structure to the probing signal.

If the impulse noise is a signal mismatched with the filter and has a sufficiently large power, then after filtering it can create a compressed signal whose envelope exceeds the detection threshold q ₀ and can be detected as a signal reflected from the target.

As already noted, the received signal is considered inconsistent if it is not fully consistent with the filter (Modern radar. Analysis, calculation and design of systems. Translated from English. Edited by Yu.B. Kobzarev, M., Sov. Radio, 1969, p.222).

In the invention, in order to reduce the influence of interference in the form of signals mismatched with the filter, the final decision on the received signal that exceeds the detection threshold q ₀ is made after additional analysis, in which the degree of mismatch of the received signal with the matched filter is evaluated. As a measure of the mismatch of the received signal with the matched filter, the ratio of the envelope value of the received signal to the matched filter U _og to the envelope value of the signal after the matched filter U _{og is used. f} :

In this case, the signal U _og before calculation (1) is delayed by a time equal to the time of its processing with matched filtering.

The greatest mismatch of the received signal with the matched filter corresponds to a value of δ equal to unity, the smallest - the value inversely proportional to the compression coefficient of the matched filter (significantly less than unity).

When deciding whether to detect a target, the mismatch value δ for the range discrete in which the detection threshold q _{0 is} exceeded is compared with a predetermined threshold value δ ₀ , which is set based on the permissible mismatch of the received signal reflected from the target with a matched filter. If the mismatch δ does not exceed the threshold value δ ₀ (δ≤δ ₀ ), the signal after matched filtering is considered to be a probe signal reflected from the target, otherwise (δ> δ ₀ ) - impulse noise.

The invention is illustrated by the following drawings:

Figure 1 - the closest device for radar detection of signals reflected from targets, implementing the closest method.

Figure 2 - the inventive device radar detection of signals reflected from targets that implements the inventive method.

A device for radar detection of signals reflected from targets that implements the inventive method comprises (Fig. 2) a matched filter 1, a signal envelope detector 2 and a threshold device 3, a second signal envelope detector 4, a delay device 5, and an envelope amplitude ratio calculator 6 , the second threshold device 7 and the circuit "And" 8, while the interconnected input of the matched filter 1 and the input of the second envelope detector of the signal 4 are the input of the radar detection device the output of the second envelope detector of signal 4 is connected to the input of the delay device 5, the first and second inputs of the calculator of the ratio of the amplitudes of the envelope of signals 6 are connected respectively to the output of the envelope detector of the signal 2 and the output of the delay device 5, and its output is connected to the input of the second threshold device 7, the output of the threshold device 3 and the output of the second threshold device 7 are connected respectively to the first and second inputs of the AND circuit 8, the output of which is the output of the radar detection device.

The inventive device can be performed using the following functional elements.

Consistent filter 1 - digital filter (Kuzmin SZ. Fundamentals of designing systems for digital processing of radar information, M., "Radio Communication", 1986, p. 38-45).

The envelope detector of signal 2 and the second detector of envelope of signal 4 are devices that generate output voltages that are a linear function of the envelope of the intermediate frequency signal (Radar Reference, edited by M. Skolnik, vol. 3, M., Sov. Radio, 1979, p. .163).

Threshold device 3 - a threshold device in which the incoming signal is compared with the level of the detection threshold q ₀ , selected on the basis of a given probability of false alarm, above which a signal is generated at the output of the device (Integrated circuits. Handbook edited by B.V. Tarabrin, M ., Radio and Communications, 1984).

Delay device 5 - device for the time delay of the signal (ibid.). The delay time is set equal to the delay time of the signal when it is processed in the matched filter 1.

The calculator of the ratio of the amplitudes of the envelope of the signals 6 - a digital computer that calculates the ratio of the envelope of the received signal before the matched filtering to the envelope of the signal after the matched filtering (1), is performed on standard microcircuits (ibid.).

The second threshold device 7 is a threshold device in which the ratio of the envelope value of the received signal before the matched filtering to the value of the envelope of the signal after the matched filtering is compared with the threshold value δ ₀ . If the threshold value δ _{0 is} not exceeded, a signal is generated at the output of the device (ibid.).

Scheme "And" 8 - a digital element made on a standard chip (ibid.).

A device for radar detection of signals reflected from targets works as follows. The received signal is obtained in a discrete range at the input of the matched filter 1, where the signal is compressed. Next, the envelope detector of the signal 2 selects its envelope, which is then fed to the input of the threshold device 3, where it is compared with the detection threshold q ₀ . If the envelope of the compressed signal exceeds the detection threshold q ₀ , a signal is generated at the output of the threshold device 3, which is fed to the first input of the And circuit 8.

The received signal is also fed to the input of the second envelope detector of the signal 4, from the output of which the envelope of the received signal is supplied to the delay device 5, where it is delayed by a time equal to the delay time of the signal in the matched filter 1.

From the output of the envelope detector of signal 2 and from the output of the delay device 5, signals corresponding to the same discrete in range are supplied respectively to the first and second inputs of the calculator of the ratio of the amplitudes of the envelopes of the signals 6, in which their ratio δ (1) is calculated. From the output of the calculator 6, a signal proportional to the ratio δ is fed to the input of the second threshold device 7, where it is compared with the threshold value δ ₀ . If the value of δ does not exceed the specified threshold value, then a signal is generated at the output of the device 7, which is fed to the second input of the AND circuit 8.

The output of the circuit "And" 8 generates a signal about the detection of the target in the discrete range, if both of its inputs are signals.

Thus, the decision that the received signal is a signal reflected from the target is made if it has exceeded the detection threshold q ₀ and the value of the signal mismatch with the matched filter δ does not exceed the permissible value δ ₀ .

Thus, the claimed technical result is achieved.

Claims (2)

1. The method of radar detection of signals reflected from targets, including coordinated filtering of the received signal, followed by highlighting the envelope of the signal and comparing it in each discrete in range with the detection threshold, characterized in that for the discrete in range in which the detection threshold is exceeded, determine the ratio of the signal envelope to the matched filtering, delayed by the signal processing time for matched filtering, to the signal envelope after the matched f iltration, the obtained ratio is compared with a predetermined threshold value established on the basis of the permissible mismatch of the received signal reflected from the target, a decision is made to detect a signal reflected from the target if the specified threshold value is not exceeded. 2. A device for radar detection of signals reflected from targets, comprising a matched filter, a signal envelope detector, and a threshold device, characterized in that a second signal envelope detector, a delay device, a signal envelope amplitude ratio calculator, are used to calculate a signal envelope value ratio before the matched filter to the value of the envelope of the signal after the matched filter, the second threshold device and circuit And, while connected the input of the matched filter and the input of the second signal envelope detector are the input of the radar detection device, the output of the second signal envelope detector is connected to the input of the delay device, the first and second inputs of the signal envelope amplitude ratio calculator are connected respectively to the output of the signal envelope detector and the output of the delay device, and its output is connected to the input of the second threshold device, the output of the threshold device and the output of the second threshold device are connected respectively only with the first and second inputs of the AND circuit, the output of which is the output of the radar detection device.

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