CN101995565B - Method for searching and detecting anti-jamming synthetic aperture radar signal - Google Patents

Abstract

The invention relates to a method for searching and detecting an anti-jamming synthetic aperture radar (SAR) signal, which belongs to the field of radar signal detection. The method comprises the following steps of: searching the SAR signal by a frequency sweeping method; scanning in a specified frequency range by a narrow-band filter, wherein the step band width of the scanning is equal to pass band width of the narrow-band filter; judging whether the narrow-band filter outputs a signal at each frequency point and measuring pulse width (PW) and pulse repetition time (PRT) of the narrow-band signal when the narrow-band filter outputs the signal; considering the frequency of search exceeds the range of the frequency of the SAR signal when the signal does not exist in a continuous frequency range and calculating the parameters of the SAR signal according to the measured narrow-band signal parameters; and removing a jam signal by a two search comparison method according to a given SAR signal parameter threshold and locking the SAR signal. The method has high search flexibility and anti-jamming capacity. The method is used for searching of the narrow-band filter and has high flexibility and anti-jamming capacity, and various anti-jam measures are adopted.

Description

A kind of jamproof synthetic-aperture radar signal search detection method

Technical field

The present invention relates to a kind of jamproof synthetic-aperture radar signal search detection method, belong to radar signal and scout the field.

Background technology

The time wide bandwidth of synthetic-aperture radar is long-pending greatly, peak power ratio is low; So intercepting and capturing, analysis to its signal have certain difficulty; Especially in complex electromagnetic environments; A large amount of undesired signals superposes, and has increased the detection difficulty of echo signal greatly, causes perhaps intercepting and capturing undesired signal by intercepted signal.

Present intercept receiving method since its antijamming capability a little less than, can't adapt in complex electromagnetic environments the scouting of SAR radar signal is used.

Summary of the invention

The present invention provides a kind of jamproof synthetic-aperture radar signal search detection method; Solving prior art than the problem that is difficult under the strong jamming SAR radar signal is detected in real time, and centre frequency (CF), bandwidth (BW), pulsewidth (PW) and the repetition period (PRT) that can record the SAR signal.

For realizing above-mentioned purpose, a kind of jamproof synthetic-aperture radar signal search detection method of the present invention may further comprise the steps:

The first step: with frequency sweep method search SAR signal, to scanning in the designated frequency range, scanning stepping frequency range equals the narrow band filter passband width through a narrow band filter;

Second step: judge whether narrow band filter has signal output at each frequency,, measure the PW and the PRT of this narrow band signal when determining narrow band filter when having signal to export;

The 3rd step: when thinking in the continuous band frequency scope that the frequency of search has exceeded the scope of SAR signal frequency during no signal, this moment is according to the parameter of this SAR signal of narrow band signal calculation of parameter that records;

The 4th step: exclude the interference signal locking SAR signal through the method for twice search comparison and according to given SAR signal parameter thresholding.

Wherein adopt the narrow band filter search in the first step;

Judge in second step wherein whether narrow band filter has the method for signal output following:

1) narrow band filter detects two more than the pulse in the time that this frequency stops;

2) PRT that records the signal pulse of this frequency satisfies the PRT scope of setting;

3) judge the PRT of the detected signal pulse of this frequency and the PRT of previous frequency,, otherwise think there is not signal output if its difference, judges then that signal output is arranged in specified scope.

Wherein get rid of in the 4th step and disturb the method for locking SAR signal following:

1) with judging in search procedure in the parameter area whether the SAR signal parameter that records is being set, if then record should the group parameter; Impose a condition if there are many group parameters to satisfy, one group that then only keeps the pulse height maximum as this Search Results;

2) after twice search, the comparison search result, if the centre frequency difference that records in given range then think and search target SAR signal, otherwise is done search for the third time, and with the result of search for the second time relatively, by that analogy.

Advantage of the present invention is following: the present invention adopts the method for narrow band filter frequency sweep that the SAR signal is detected, and can in very wide frequency range, detect the SAR signal, and to the bandwidth of SAR signal and the time wide susceptibility less, wide accommodation.This invention search sensitivity is high, and antijamming capability is strong.The present invention searches for narrow band filter, and is highly sensitive, takes multiple interference protection measure, and antijamming capability is strong.

Description of drawings

Fig. 1-frequency sweep method search principle synoptic diagram

Fig. 2-to the I after the AD sampling, the processing synoptic diagram of Q two paths of signals

Fig. 3-to crossing the smoothing processing synoptic diagram of thresholding detection signal

Fig. 4-search once obtains a plurality of signal schematic representations.

Embodiment

Below in conjunction with accompanying drawing SAR input anti-interference method of the present invention is described in detail.

The present invention adopts the fixed narrow wave filter, the radiofrequency signal down coversion is realized the scanning process of narrow band filter through low-converter.As shown in Figure 1.

Main during detection according to crossing the thresholding indicator signal; The production method of crossing the thresholding indicator signal is following: as shown in Figure 2; At first to adopt rotation of coordinate digital computation (CORDIC) algorithm to ask mould, obtain the envelope of signal I, the Q two-way narrow band signal of SAR receiver output; Then signal envelope is done LPF, filter away high frequency noise; Then filtered signal envelope is crossed Threshold detection and obtained the thresholding indicator signal; Thresholding can adopt adaptive threshold and fixed threshold; The average that the thresholding thres of some a should equal bc segment signal amplitude is multiplied by COEFFICIENT K, adds parameter D gained, i.e. thres=K*mean (b～c)+D; Do the shaping processing to crossing the thresholding indicator signal at last, recess is mended in promptly first deburring again, and is as shown in Figure 3.

In scanning process, judge that according to the method in the summary of the invention whether narrow band filter has signal output, if signal is arranged, then writes down the pulsewidth (fi_pw) and the repetition period (fi_prt) of this frequency narrow band signal pulse.And in whole search procedure, want the initial frequency (fi_begin) of tracer signal and the end frequency (fi_end) of signal.

When thinking that the frequency of current search has exceeded the highest frequency of SAR signal during no signal in the continuous 20MHz scope; Because the SAR pulse signal is a linear FM signal; Characteristics according to linear FM signal; The calculation of parameter of each arrowband in-band signal that can the time record according to search the parameter of SAR signal, and formula is following:

BW＝fi_end-fi_begin

$\mathrm{PW}=\underset{i}{\overset{N}{\mathrm{\Σ}}}\mathrm{fi}\_\mathrm{pw}$

$\mathrm{PRT}=\frac{\underset{i}{\overset{N}{\mathrm{\Σ}}}\mathrm{fi}\_\mathrm{prt}}{N}$

$\mathrm{CF}=\frac{\mathrm{fi}\_\mathrm{begin}+\mathrm{fi}\_\mathrm{<figure-callout\; id="2"\; label="end"\; filenames="HSA00000327956900011.png"\; state="\{\{state\}\}">end</figure-callout>}}{2}$

At last, as shown in Figure 4 owing in the hunting zone, may search out a plurality of signals, thus need exclude the interference signal through method that twice Search Results compared and according to given SAR signal parameter thresholding, locking SAR signal, concrete steps are following:

1. in a same search procedure; When searching the end frequency of pulse signal; The parameter value of judging this pulse signal whether in the parameter area of setting, if the range value of the range value of this pulse signal and previous pulse signal would relatively write down the parameter value and the range value of that bigger group pulse signal of amplitude; And continue search until the end frequency of setting, if not do not write down and continue to search for until the end frequency of setting; 2. after twice search, the comparison search result, if the centre frequency difference that records less than 20MHz then think and search target SAR signal, otherwise is done search for the third time, and with the result of search for the second time relatively, by that analogy.

In above-mentioned steps, the range value measuring method of pulse signal is following:

1. measure the amplitude equalizing value of the pulse signal of each arrowband frequency; 2. when searching the end frequency of pulse signal, obtain the amplitude equalizing value of broadband signal according to the amplitude equalizing value of the pulse signal of each arrowband frequency, promptly to the amplitude equalizing value summation of the pulse signal of arrowband frequency, then divided by the frequency number.

Claims (3)

1. jamproof synthetic-aperture radar signal search detection method is characterized in that: may further comprise the steps:

The first step: with frequency sweep method search SAR signal, to scanning in the designated frequency range, scanning stepping frequency range equals the narrow band filter passband width through a narrow band filter;

Second step: judge whether narrow band filter has signal output at each frequency,, measure the pulsewidth PW and the repetition period PRT of the narrow band signal that this narrow band filter exports when determining narrow band filter when signal output is arranged;

The 3rd step: when thinking in the continuous band frequency scope that the frequency of search has exceeded the scope of SAR signal frequency during no signal, this moment is according to the parameter of this SAR signal of narrow band signal calculation of parameter that records;

The 4th step: exclude the interference signal locking SAR signal through the method for twice search comparison and according to given SAR signal parameter thresholding;

Get rid of and disturb the method for locking SAR signal following:

1) with judging in search procedure in the parameter area whether the SAR signal parameter that records is being set, if then record should the group parameter; Impose a condition if there are many group parameters to satisfy, one group that then only keeps the pulse height maximum as this Search Results;

2) after twice search, the comparison search result, if the centre frequency difference that records in given range then think and search target SAR signal, otherwise is done search for the third time, and with the result of search for the second time relatively, by that analogy.

2. a kind of jamproof synthetic-aperture radar signal search detection method according to claim 1 is characterized in that: wherein adopt the narrow band filter search in the first step.

3. a kind of jamproof synthetic-aperture radar signal search detection method according to claim 1 is characterized in that: judge in second step wherein whether narrow band filter has the method for signal output following:

1) narrow band filter detects two more than the pulse in the time that this frequency stops;

2) PRT that records the signal pulse of this frequency satisfies the PRT scope of setting;

3) judge the PRT of the detected signal pulse of this frequency and the PRT of previous frequency,, otherwise think there is not signal output if its difference, judges then that signal output is arranged in specified scope.

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