RU2494412C2 - Method of protecting radar station from pulse interference and apparatus for realising said method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: signal reflected from a target is detected by filtering the received signal matched with a probing signal, followed by selection of the envelope and comparing with a detection threshold. The detection threshold is set in accordance with the level of interference measured by filtering the received signal, matched with pulse interference, based on interference reduction during filtering, matched with the probing signal.

EFFECT: high protection of radar stations from high-power pulse interference of a known structure.

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Description

The invention relates to the field of radar and can be used in radar stations (radar) to protect against impulse noise of a known structure.

There is a method of protecting the radar from impulse noise, which consists in tuning the operating frequency of the radar from pulse to pulse according to the pseudorandom law (Theoretical Foundations of Radar. Edited by V.E. Dulevich, Sov. Radio, 1978, p.453).

A device is known that implements the known method of protection against impulse noise, comprising a series-connected unit for calculating the carrier frequency and the unit issuing commands (ibid.).

A known device that implements the known method of protection against impulse noise, works as follows. In the block for calculating the carrier frequency, before each radiation of the probe signal, the carrier frequency is calculated according to the pseudo-random law. The calculated value of the carrier frequency is sent to the command issuing unit, from where a command is issued to restructure the transmitter and receiver, as well as to emit a sounding signal at this carrier frequency.

A disadvantage of the known technical solutions is that since the carrier frequency of the impulse noise is not measured, it is possible that the carrier frequency of the interference coincides with the selected carrier frequency of the radar. In this case, the pulse interference will not be suppressed and will interfere with the processing of the radar signal.

The closest way to protect the radar from impulse noise includes filtering the received signal that is consistent with the probing signal, extracting the envelope of the filtered signal, comparing it with the detection threshold, deciding whether to detect the signal from the target (Theoretical Foundations of Radar. Edited by Y.D. Shirman, Sov Radio, 1970, pp. 110-114).

The closest protection device against impulse noise contains (Fig. 1) a series-connected filter matched with the probe signal 1, an envelope detector 2 and a comparison unit with a detection threshold 3, the output of which is the output of the device for protection against impulse noise (Theoretical Basics of Radar. Ed. Ya.D. Shirman, Sov. Radio, 1970, p. 114, fig. 3.19).

The value of the detection threshold in the closest technical solutions is set equal to the value of the threshold q ₀ corresponding to a given level of false alarms in the absence of signal and interference.

The closest technical solutions allow suppressing impulse noise, including impulse noise with a known structure. Such interference includes, for example, impulse noise caused by radio equipment located in the vicinity of the radar. However, if the level of interference is large enough, then at the output of the filter matched with the probe signal, the interference may exceed the detection threshold and will be taken as the target. This is a disadvantage of the closest technical solutions.

The problem being solved (technical result) is to increase the radar protection from impulse noise of a known high-power structure.

The specified technical result is achieved in that in a method for protecting a radar station from impulse noise, including filtering the received signal matched to the probing signal, isolating the envelope of the filtered signal, comparing it with the detection threshold, making a decision to detect the signal from the target, characterized in that both the interval equal to the duration of the probe signal, carry out the filtering of the received signal, consistent with the known impulse noise, select the envelope of the filter U _n Nogo signal level of the detection threshold is determined from the formula:

$$Q_0=max(q_0,U_P\times k),(\mathrm{one})$$

where q ₀ is the value of the detection threshold corresponding to a given level of false alarms in the absence of signal and interference;

k is a coefficient characterizing the attenuation of the level of impulse noise during its filtering, which is consistent with the probe signal, relative to the level of interference when it is filtered, consistent with the impulse noise, is calculated in advance based on the type of impulse noise and filter characteristics.

The indicated result is also achieved by the fact that in the impulse noise protection device comprising a series-connected filter, matched with the probing signal, an envelope detector and a detection threshold comparison unit, the output of which is the output of the impulse noise protection device, according to the invention, a series-connected filter matched to the impulse noise, a second envelope detector and a detection threshold selection unit, while the filter input matched to the probing interconnected signal, and the input of the filter, matched with the impulse noise, form the input of the impulse noise protection device, the second input of the detection threshold selection unit is designed to supply a detection threshold value corresponding to a given level of false alarms in the absence of signal and interference, the output of the detection threshold selection unit is connected with the second input of the comparison block with the detection threshold.

Let us explain the essence of the invention.

In the claimed invention, the received signal is processed by two channels. In the first (main) channel, the signal reflected from the target is extracted from the received signal. To do this, filter the received signal, consistent with the probing signal, followed by the allocation of the envelope U _with . In the case when the impulse noise is at a sufficiently high level, the signal at the filter output, in addition to the signal from the target, also contains residual noise. To suppress these residues, the detection threshold Q _{0 is} set in accordance with the interference level allocated in the second (additional) channel.

The separation of interference in the second channel is carried out by filtering the received signal, consistent with the interference of a known structure, and the subsequent selection of the envelope U _p .

Since the interference in the main channel is suppressed for the most part, and the interference in the secondary channel is optimally processed, the detection threshold Q ₀ must be set (in accordance with formula (1)) equal to the noise level at the output of the secondary channel multiplied by the coefficient k, where k - the coefficient characterizing the attenuation of the level of impulse noise during its filtering, consistent with the probe signal, relative to the level of interference when it is filtered, consistent with the pulse interference, is calculated in advance based on the type lsnoy interference and filter characteristics.

Consider several options for the received signal and the results of its processing of the claimed method.

If the received signal contains only the signal reflected from the target, then at the output of the filter matched with the probe signal (in the main channel), the optimally processed signal reflected from the target will be present. At the output of the filter, matched with the impulse noise (in the additional channel), the signal from the target will be significantly suppressed. The detection threshold Q ₀ will be set in accordance with the level of this suppressed signal (1) and practically will not make any deterioration in the detection of the signal from the target in the main channel.

If the received signal contains only impulse noise, then the suppressed impulse noise will be present at the output of the filter matched with the probing signal (in the main channel) (in accordance with the problem being solved, the interference power is such that the suppressed it exceeds the threshold level q ₀ ). At the output of the filter, matched with the impulse noise (in the additional channel), an optimally processed impulse noise will be present. The detection threshold Q ₀ will be set in accordance with the level of this interference (1), therefore, interference in the main channel will be suppressed.

If the received signal contains a mixture of the signal reflected from the target and the interference, then the output of the filter, matched with the probing signal (in the main channel), will contain the optimally processed signal from the target and the suppressed impulse noise (in accordance with the problem being solved, the interference power is such that suppressed, it exceeds the threshold level q ₀ ). At the output of the filter, matched with the impulse noise (in the additional channel), the optimally processed impulse noise and the suppressed signal will be present. The detection threshold Q ₀ will be set mainly by the interference level (1), therefore, the signal in the main channel will be detected, and the impulse noise is suppressed.

Thus, the claimed technical result is achieved.

The invention is illustrated by the following drawings.

Figure 1 - the closest protection device against impulse noise, implementing the closest method.

Figure 2 - the claimed device protection against impulse noise that implements the inventive method.

An impulse noise protection device that implements the inventive method comprises (Fig. 2) a series-connected filter matched with a probe signal 1, an envelope detector 2 and a comparison unit with a detection threshold 3, as well as a series-connected filter matched with a pulse interference 4, the second an envelope detector 5 and a detection threshold selection unit 6, wherein the input of the filter matched with the probing signal 1 and the input of the filter matched with the impulse noise 4 are connected to each other and form the input of the protection device o t of impulse noise, the output of the detection threshold selection block 6 is connected to the second input of the comparison unit with the detection threshold 3, the output of the comparison block with the detection threshold 3 is the output of the impulse noise protection device.

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

The filter matched with the probing signal 1, and the filter matched with the impulse noise 4 - digital filters (Kuzmin SZ Fundamentals of designing systems for digital processing of radar information, M., "Radio Communication", 1986, p. 38-45).

Envelope detector 2 and second envelope detector 5 - devices that produce output voltages that are linear functions of the envelopes of the intermediate frequency signals (Radar Reference, edited by M. Skolnik, vol. 3, M., Sov. Radio, 1979, p. 163 )

The comparison block with the detection threshold 3 is a threshold device (Integrated circuits. Handbook edited by BV Tarabrin, M., Radio and Communications, 1984), in which the received signal in each discrete is compared with the level of the detection threshold Q ₀ coming from output of the detection threshold selection block 6.

The detection threshold selection unit 6 is a device in which the detection threshold Q ₀ is selected as the largest of q ₀ and U _s × k (in accordance with formula (1)).

The protection device from impulse noise, works as follows. The received signal (which is a probe signal reflected from the target, impulse noise, or a mixture of the signal reflected from the target and the impulse noise) is sampled in range by the input of the filter matched with the probe signal 1 and the filter matched with the impulse noise 4. Using envelope detectors 2 and 5, the corresponding envelopes U _c and U _p are highlighted. The envelope U _with from the output of the envelope detector 2 is fed to the first input of the comparison unit with the detection threshold 3, and the envelope U _p from the second detector of the envelope 5 is fed to the first input of the detection threshold 6 unit. A pre-calculated value is supplied to the second input of the detection threshold 6 unit detection threshold q ₀ corresponding to a given level of false alarms in the absence of signal and interference. In the detection threshold selection block 6, in accordance with formula (1), the detection threshold value Q ₀ , which is supplied to the second input of the comparison block with detection threshold 3, is determined for each discrete in range.

In the comparison unit with the detection threshold 3, the envelope U _{s is} compared with the detection threshold Q ₀ . If the specified threshold is exceeded, a decision is made to detect the target and the signal from the target is output to the device. Since in the presence of impulse noise, the detection threshold Q _{0 is} set in accordance with its level, the interference is suppressed.

Thus, the claimed technical result is achieved.

Claims (2)

1. A method of protecting a radar station from impulse noise, including filtering the received signal consistent with the probing signal, isolating the envelope of the filtered signal, comparing it with the detection threshold, deciding whether to detect the signal from the target, characterized in that at the same time in an interval equal to the duration of the probing signal filter the received signal, consistent with the impulse noise of a known structure, filter out the envelope of the filtered signal U _p , detection threshold level determined from the formula
Q ₀ = max (q ₀ , U _p · k),
where q ₀ is the value of the detection threshold corresponding to a given level of false alarms in the absence of signal and interference;
k is a coefficient characterizing the attenuation of the level of impulse noise during its filtering, which is consistent with the probe signal, relative to the level of interference when it is filtered, consistent with the impulse noise, is calculated in advance based on the type of impulse noise and filter characteristics. 2. An impulse noise protection device comprising a series-connected filter matched with a probing signal, an envelope detector and a detection threshold comparison unit, the output of which is an output of an impulse noise protection device, characterized in that a filter connected in series with an impulse noise is introduced , a second envelope detector and a detection threshold selection unit, wherein the input of the filter matched with the probing signal and the input of the filter matched with it are interconnected pulse interference, form the input of the device for protection against impulse noise, the second input of the detection threshold selection unit is designed to supply a detection threshold value corresponding to a given level of false alarms in the absence of signal and interference, the output of the detection threshold selection unit is connected to the second input of the comparison unit with the detection threshold.

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