CN117805756A - Noise interference identification method and system with low false alarm rate in clutter - Google Patents
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Abstract
The invention discloses a method and a system for identifying noise interference with low false alarm rate in clutter, wherein the method comprises the following steps: judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration; judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration; after judging that the radar is possibly interfered by noise, the pulse compression result is subjected to modulo conversion, the modulo conversion is carried out on the pulse compression result to a frequency domain, and whether the radar is interfered by noise is judged by judging whether the amplitude of the zero frequency component of the frequency domain is larger than a preset threshold or not. The invention realizes the real-time detection and recognition of noise interference, reduces the false alarm of interference detection caused by clutter, and provides decision basis for the radar to take effective anti-interference measures in time.
Description
Technical Field
The invention belongs to the field of radar anti-interference, and particularly relates to a clutter low false alarm rate noise interference identification method and system.
Background
The development of modern electronic countermeasure technology makes the electromagnetic environment facing the radar more and more complex, and various high-tech means and devices against the radar are continuously appeared, so that the working environment of the radar is more and more complex and deteriorated. Electronic interference is one of four threats of radar, and is the most important threat to military radar due to the characteristics of multiple styles, flexible use, strong resistance and the like.
Noise interference is one of the most common active interference types faced by radar, and is characterized in that by raising the radar echo noise base, the target echo signal-to-noise ratio is reduced, and even the target is submerged in noise, so that the radar cannot detect the existence of the target. Noise interference is very difficult to realize for jammers, so that the interference type is widely applied to various jammers.
In the radar anti-interference process, interference sensing comprises detection of interference, identification of interference types and the like; interference suppression means that proper anti-interference measures are adopted manually/adaptively according to interference sensing results; interference perception is a precondition for interference suppression.
The existing noise interference detection and identification method is difficult to be widely applied to equipment due to high calculation complexity; and is susceptible to clutter, and detection false alarms occur. The radar is difficult to accurately sense whether the radar is in a noise interference state or not, so that an operator cannot be timely and automatically or prompted to adopt anti-interference measures. Under the condition, the radar is extremely easy to leak and alarm, namely, the target is effectively shielded by the self-defense jammer so as to be successfully burst-protected, and the radar is extremely easy to be beaten by the burst-protected target in a short distance.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for identifying noise interference with low false alarm rate in clutter, comprising the following steps:
the radar transmits a linear frequency modulation signal;
preprocessing the radar echo signal to obtain a baseband complex signal, calculating the amplitude envelope of the baseband complex signal, and judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration;
if the average amplitude of the amplitude envelope of the baseband complex signal does not exceed the corresponding threshold and the duration of the amplitude envelope is not longer than the corresponding duration, the radar is not interfered by noise;
if the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold or the duration of the amplitude envelope is longer than a corresponding duration, the radar is possibly interfered by noise, and pulse compression processing is carried out on the baseband complex signal to obtain a pulse compression result; judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration;
if the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing does not exceed the corresponding threshold and the duration of the amplitude envelope is not longer than the corresponding duration, the radar is not interfered by noise;
if the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing exceeds a corresponding threshold or the duration of the amplitude envelope is longer than a corresponding duration, the radar is likely to be interfered by noise, the pulse compression result is subjected to modulo conversion, the modulo value is converted into a frequency domain, and whether the radar is interfered by noise is judged by judging whether the amplitude of zero frequency component of the frequency domain is greater than a preset threshold or not;
if the amplitude of the zero frequency component of the frequency domain is smaller than or equal to a preset threshold, the radar is not interfered by noise, and if the amplitude of the zero frequency component of the frequency domain is larger than the preset threshold, the radar is interfered by noise.
Further, the preprocessing of the radar echo signal includes: the echo signal is processed through amplification, down-conversion, sampling and orthogonal double-channel processing.
Further, according to whether the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold and whether the average amplitude of the amplitude envelope of the baseband complex signal before and after the pulse compression processing exceeds the corresponding threshold in the corresponding threshold, the corresponding threshold is a fixed value VT0, and the fixed value VT0 is equal to the radar echo noise base plus a fixed value.
Further, the pulse width TT0 of the radar transmitting signal is determined according to whether the amplitude envelope duration of the baseband complex signal is larger than the corresponding duration and whether the amplitude envelope duration of the baseband complex signal before and after the pulse compression processing is larger than the corresponding duration in the corresponding durations.
Further, the pulse compression result is modulo, and the modulo value is transformed to the frequency domain, comprising the following steps:
pulse pressure results are denoted by s1 (t);
windowing a modulus value obtained after modulus of a pulse pressure result s1 (t);
and transforming the signal obtained after the windowing processing into a frequency domain by using FFT (fast Fourier transform), and normalizing according to the FFT point number to obtain a frequency domain spectrum result S (f).
Further, the windowing process specifically includes that a modulus value obtained by modulo the pulse pressure result s1 (t) is multiplied by a window function with the same length point by point.
Further, the method for obtaining the preset threshold specifically includes:
on the basis of radar echo noise base, adding a fixed value as noise interference detection threshold VT; the noise interference detection threshold VT is a preset threshold.
The invention also provides a system for identifying the noise interference of the low false alarm rate in the clutter, which is characterized in that the system identifies the radar noise interference according to any method.
Compared with the prior art, the invention has the advantages that:
the high-efficiency and real-time noise interference detection and identification method provided by the invention can prompt whether the radar is in a noise interference state or not in real time, and can effectively inhibit interference detection false alarms caused by clutter; the radar can be enabled to resist noise interference automatically in time or manually through an operator when noise interference is received, so that the radar can continuously and effectively detect targets of a high-performance jammer carrying noise interference, and the information guarantee capability of the radar in a complex electromagnetic environment can be better supported.
Drawings
Fig. 1 is a flowchart of a clutter low-false early warning noise interference recognition method according to an embodiment of the present invention.
Fig. 2 is a graph showing typical radar baseband echo complex signal amplitude as a function of range bin when undisturbed by noise.
Fig. 3 is a graph showing the amplitude of the echo signal in fig. 2 as a function of distance units after pulse compression processing when the echo signal is not interfered by noise.
Fig. 4 shows the result obtained by processing the radar echo by the method of the present embodiment when the radar echo is not interfered by noise in the application example.
Fig. 5 is a graph showing typical radar baseband echo complex signal amplitude as a function of range bin when disturbed by noise.
Fig. 6 is a graph showing amplitude of the echo signal in fig. 2 as a function of distance units after pulse compression processing when the echo signal is interfered by noise.
Fig. 7 shows the result obtained by processing the radar echo by the method of the present embodiment when the radar echo is interfered by noise in the application example.
Detailed Description
Aiming at the problems that the current noise interference detection method is complex in calculation and is easily influenced by clutter to cause noise detection false alarm, the method for identifying low-false early warning noise interference in clutter is provided. Firstly, calculating envelope of signals before pulse compression and after pulse compression by utilizing the time domain characteristics of radar echo interfered by noise, comparing the envelope with a transmitting pulse width, and preliminarily judging whether noise interference exists or not; then, the distribution of the amplitude of the radar baseband echo data along with time is transformed into a frequency domain, the frequency spectrum characteristics of the radar baseband echo data are counted, and whether noise interference signals exist in the radar echo is judged according to the counting result. The method realizes the real-time detection and recognition of noise interference by the combined treatment of two modes, reduces the false alarm of interference detection caused by clutter, provides decision basis for the radar to take effective anti-interference measures in time, and has important innovative significance and practical value.
In order to facilitate an understanding of the present application, a more complete description of the present application will now be provided with reference to the relevant figures. Examples of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
The embodiment provides a noise interference identification method with low false alarm rate in clutter, which specifically comprises the following steps:
step 1, a radar transmits a linear frequency modulation signal to search and detect a certain airspace, and an echo signal is amplified, down-converted, sampled, subjected to orthogonal double-channel processing and the like to obtain a baseband complex signal s (t);
step 2, processing the baseband complex signal s (t) obtained in the step 1 by an interference detection and identification processing branch, calculating an amplitude envelope of the baseband complex signal s (t), and if the average amplitude of the amplitude envelope is greater than a certain value V T0 (V T0 Equal to the radar echo noise floor plus a fixed value) and a duration greater than the pulse width of the transmitted signal; step 3 is carried out, otherwise, the radar is directly judged not to be interfered by noise;
step 3, pulse compression processing is carried out on the baseband complex signal s (t) obtained in the step 1 to obtain a pulse pressure result s 1 (t) calculating the amplitude envelope thereof.
Step 4, if the average amplitude of the echo signal amplitude envelope is greater than the threshold V before and after pulse compression T0 And the amplitude envelope duration is greater than the pulse width T of the transmitted signal T0 Step 5, processing is carried out; otherwise, giving an indication that the radar does not receive noise interference;
step 5, for the pulse pressure result s obtained in step 3 1 (t) obtaining a modulus value;
step 6, windowing the modulus value obtained in the step 6, namely multiplying the modulus value with a window function of the same length point by point;
step 7, transforming the signal obtained in the step 7 into a frequency domain by using Fast Fourier Transform (FFT), and normalizing according to the FFT point number to obtain a frequency domain spectrum result S (f);
step 8, adding a fixed value as a noise interference detection threshold V on the basis of the radar echo noise base T ；
And 9, taking the amplitude of the zero frequency component in the step 8, comparing the amplitude with a noise detection threshold, and if the amplitude is smaller than the noise detection threshold, considering that the radar is not interfered by noise, otherwise, judging that the radar is interfered by noise.
The method can be used for detecting the root cause of noise interference, and is characterized in that the whole amplitude of the echo time domain is estimated through the amplitude of the zero frequency component of the frequency by transforming the amplitude of the echo signal to the frequency domain; after the radar is interfered by noise and the amplitude of all or part of the distance section is too high, the amplitude of the zero frequency component of the frequency domain is raised; if the radar is interfered by the sheet clutter, the amplitude of the zero frequency component of the frequency domain is limited because the amplitudes of other distance units are not raised.
The embodiment also provides a noise interference recognition system with low false alarm rate in clutter, which is used for carrying out radar noise interference recognition according to the method.
One of the applications of this embodiment is specifically as follows: the method of the embodiment is applied to the radar subjected to noise interference, and takes actual measurement data recorded when the radar is used for resisting a self-defense interference source (applying noise interference) as an example.
(1) In a certain experiment, a certain radar works in a searching state, a linear frequency modulation signal is transmitted, a self-defense type jammer carried by a target is not started, and the radar is not interfered by noise and the like. The amplitude of the radar baseband echo complex signal is shown in fig. 2, and it can be seen that the amplitude is raised at the distance units 1-140 and 420-590 at this time; the pulse compression processing result of the frame echo data is shown in fig. 3, and it can be seen from the combination of fig. 1 and fig. 2 that sheet clutter exists at distance units 1-140 and 420-590.
(2) The data of figure 2 is processed by steps 2 and 3 of the embodiment of the invention, and the detection threshold V is set at the same time T0 Adding 10 (dB) to the radar echo noise substrate, and performing step 4 processing to obtain the frame echo signal amplitude envelope average amplitude which is larger than the threshold V T 0 and the amplitude envelope duration is greater than the pulse width T of the transmitted signal T 0；
(3) The data of fig. 3 are processed in steps 5, 6 and 7 to obtain the result shown in fig. 4, where a noise detection threshold V is set T 45dB, it can be seen that the zero frequency component amplitude in FIG. 4 is less than the threshold V T And giving a detection result that the radar is not interfered by noise.
(4) In the same test, a certain radar works in a search state, a linear frequency modulation signal is transmitted, a self-defense type jammer carried by a target is started, and the radar is interfered by noise and the like. The amplitude of the radar baseband echo complex signal is shown in fig. 5, and it can be seen that the amplitude of the echo is raised in the whole distance section at the moment; the pulse compression processing result of the frame echo data is shown in fig. 6, and it can be seen from the comprehensive fig. 1 and 2 that the radar receives noise interference in all distance segments.
(5) The data of fig. 5 is processed by steps 2 and 3 of the embodiment of the invention, and the detection threshold V is set at the same time T0 Adding 10 (dB) to the radar echo noise substrate, and performing step 4 processing to obtain the frame echo signal amplitude envelope average amplitude which is larger than the threshold V T 0 and the amplitude envelope duration is greater than the pulse width T of the transmitted signal T 0；
(6) The data of fig. 6 are processed in steps 5, 6 and 7 to obtain the result shown in fig. 7, where the noise detection threshold V is set T 45dB, canIt can be seen that the zero frequency component amplitude in fig. 4 is less than the threshold V T And giving a detection result that the radar is interfered by noise.
The method and the system for identifying the low-false early warning noise interference in the clutter are efficient and real-time, can prompt whether the radar is in a noise interference state or not in real time, and can effectively inhibit interference detection false alarms caused by the clutter. The radar can be enabled to resist noise interference automatically in time or manually through an operator when noise interference is received, so that the radar can continuously and effectively detect targets of a high-performance jammer carrying noise interference, and the information guarantee capability of the radar in a complex electromagnetic environment can be better supported.
The foregoing description of the preferred embodiment of the invention is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Claims (8)
1. The noise interference identification method for the low false alarm rate in the clutter is characterized by comprising the following steps of:
the radar transmits a linear frequency modulation signal;
preprocessing the radar echo signal to obtain a baseband complex signal, calculating the amplitude envelope of the baseband complex signal, and judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration;
if the average amplitude of the amplitude envelope of the baseband complex signal does not exceed the corresponding threshold and the duration of the amplitude envelope is not longer than the corresponding duration, the radar is not interfered by noise;
if the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold or the duration of the amplitude envelope is longer than a corresponding duration, the radar is possibly interfered by noise, and pulse compression processing is carried out on the baseband complex signal to obtain a pulse compression result; judging whether the radar is likely to be interfered by noise according to whether the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing exceeds a corresponding threshold or whether the duration of the amplitude envelope is longer than a corresponding duration;
if the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing does not exceed the corresponding threshold and the duration of the amplitude envelope is not longer than the corresponding duration, the radar is not interfered by noise;
if the average amplitude of the amplitude envelope of the baseband complex signals before and after the pulse compression processing exceeds a corresponding threshold or the duration of the amplitude envelope is longer than a corresponding duration, the radar is likely to be interfered by noise, the pulse compression result is subjected to modulo conversion, the modulo value is converted into a frequency domain, and whether the radar is interfered by noise is judged by judging whether the amplitude of zero frequency component of the frequency domain is greater than a preset threshold or not;
if the amplitude of the zero frequency component of the frequency domain is smaller than or equal to a preset threshold, the radar is not interfered by noise, and if the amplitude of the zero frequency component of the frequency domain is larger than the preset threshold, the radar is interfered by noise.
2. The method for identifying noise interference with low false alarm rate in clutter according to claim 1, wherein the preprocessing of the radar echo signal comprises: the echo signal is processed through amplification, down-conversion, sampling and orthogonal double-channel processing.
3. The method for identifying noise interference with low false alarm rate in clutter according to claim 1, wherein,
according to whether the average amplitude of the amplitude envelope of the baseband complex signal exceeds a corresponding threshold and whether the average amplitude of the amplitude envelope of the baseband complex signal before and after pulse compression processing exceeds the corresponding threshold in the corresponding threshold, the average amplitude of the amplitude envelope of the baseband complex signal is a fixed value V T0 Constant value V T0 Equal to the radar echo noise floor plus a fixed value.
4. The method for identifying noise interference with low false alarm rate in clutter according to claim 1, wherein,
according to whether the amplitude envelope duration of the baseband complex signal is greater than the corresponding time length and according to whether the amplitude envelope durations of the baseband complex signal before and after the pulse compression process are both greater than the corresponding time length in the corresponding time lengthPulse width T of radar emission signal T0 。
5. The method for identifying noise interference with low false alarm rate in clutter according to claim 1, wherein the pulse compression result is modulo and the modulo value is transformed to the frequency domain, comprising the following steps:
pulse pressure results are s 1 (t) represents;
for pulse pressure result s 1 (t) windowing the obtained module value after module calculation;
and transforming the signal obtained after the windowing processing into a frequency domain by using FFT (fast Fourier transform), and normalizing according to the FFT point number to obtain a frequency domain spectrum result S (f).
6. The method for noise interference identification with low false alarm rate in clutter according to claim 5, wherein the windowing process is specifically to obtain the pulse pressure result s 1 And (t) multiplying the modulus value obtained by the modulus by a window function with the same length point by point.
7. The method for identifying noise interference with low false alarm rate in clutter according to claim 1, wherein the method for obtaining the preset threshold is specifically as follows:
on the basis of radar echo noise base, a fixed value is added as noise interference detection threshold V T The method comprises the steps of carrying out a first treatment on the surface of the The noise interference detection threshold V T The preset threshold is obtained.
8. A clutter low false alarm rate noise interference recognition system, characterized in that the system is configured to perform radar noise interference recognition according to the method of any one of claims 1-7.
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| CN118050716A (en) * | 2024-04-16 | 2024-05-17 | 湖南赛能环测科技有限公司 | Sodar signal processing method for multi-scale morphological processing |
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| CN118050716A (en) * | 2024-04-16 | 2024-05-17 | 湖南赛能环测科技有限公司 | Sodar signal processing method for multi-scale morphological processing |
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