CN105223553A - A kind of half frequency range matched filtering realizes shift-frequency jamming recognition methods - Google Patents

Abstract

A kind of half frequency range matched filtering realizes shift-frequency jamming recognition methods, and it has four large steps: the signal one, received by radar carries out pre-service, is divided into three tunnels before matched filtering; Two, three road signals are passed through complete matched filter, and extract each matched filtering output voltage peak value; Three, thresholding is set; Four, export the ratio of peak value according to the coupling of target under Different matching wave filter and combine whether set thresholding determination target is shift-frequency jamming decoy.The present invention overcomes in frequency displacement mensuration, the drawback that jammer causes identifying that shift-frequency jamming lost efficacy by controlling undesired signal centre frequency, can realize the detection identification to active leading false target jamming profile; Performing step of the present invention is few, calculated amount is little, can meet radar to multiobject Real time identification, and to hardware system without extra demand, be easy to Project Realization.

Description

A kind of half frequency range matched filtering realizes shift-frequency jamming recognition methods

Technical field

The invention belongs to Radar cross-section redaction field, relate to radar jamming decoydiscrimination, more specifically linear frequency modulated(FM) radar, provide a kind of half frequency range matched filtering and realize shift-frequency jamming recognition methods.

Background technology

Linear FM signal (abroad also known as chirp signal) studies the earliest and applies the widest a kind of pulse compression signal.And have comparatively large action-range; shift-frequency jamming is very easily subject to again compared with the linear FM radar of the plurality of advantages such as high resolution; namely when the stable detection of the target detection such as aircraft, guided missile enemy radar, tracking signal; in identification, it is usually can use shift-frequency jamming technology before and after self, produce remote decoy true to nature at once after linear frequency modulation detectable signal; radar is made to be difficult to identify real goal; the undesired signal of some sides of disturbing to different shift frequency amount repeats to forward, then the leading produced and delayed decoy group greatly will consume radar resource.The great challenge for existence that linear FM radar faces makes to seek effective shift-frequency jamming decoy recognition methods in real time and is provided with important application value in army.

The method of existing radar identification shift-frequency jamming decoy mainly contains two kinds: frequency displacement mensuration, Fractional Fourier Transform method (FRFT).Frequency displacement mensuration utilizes digital receiver treatment technology calculate the centre frequency of echoed signal and calculate undesired signal shift frequency amount by centre frequency thus judge whether this target is shift-frequency jamming decoy.The weak point of the method be its when assume that shift-frequency jamming signal and real goal echo wide identical, bandwidth is identical, and jammer uses DRFM technology can change the time wide and bandwidth of institute's retransmitted jamming signal completely, control the centre frequency of undesired signal, ensure that it is identical with target echo signal, frequency displacement mensuration was lost efficacy.Fractional Fourier Transform method by Fractional Fourier Transform is combined with the matching result in radar receiver, the shift-frequency jamming decoy that the range information identification jammer that the target speed information utilizing Fractional Fourier Transform to estimate to obtain and pulse compression obtain is launched.And the method needs a large amount of best FRFT rotation angle search work in practical application, have impact on decoy identification ageing.As fully visible, the recognition methods of current shift-frequency jamming decoy all has respective deficiency and shortcoming, does not still have a kind of effective shift-frequency jamming decoy recognition methods to be applied to linear FM radar.

Summary of the invention

The object of the invention is to enable radar implement the decoy effectively identifying that shift-frequency jamming generates, for follow-up antijamming measure provides support, this is also important key point in Radar Anti shift-frequency jamming (decoy identification).The technical problem to be solved in the present invention is: utilize target echo signal, shift-frequency jamming signal and the difference of matched filter in frequency characteristic, adopt half frequency range coupling and mate the method combined completely, contrast radar return signal is by the ratio of half frequency range matched filter with the output peak value of complete matched filter, strict by ensureing to this ratio of target echo under ideal conditions then will be greater than or less than this ratio of shift-frequency jamming difference can realize the quick identification to shift-frequency jamming distance decoy accordingly.

Technical scheme of the present invention is: a kind of half frequency range matched filtering realizes shift-frequency jamming recognition methods, and it comprises the following steps:

Step one: the signal received by radar carries out pre-service, is divided into three tunnels before matched filtering.

First the signal received radar receiver carries out filtering and low noise amplification etc. and anticipates, and then the radar signal received is divided into three tunnels, can carries out matched filtering respectively after making it, and extracts peak value and makes comparisons, and identifies whether target is decoy.

Step 2: by three road signals by complete matched filter, and extract each matched filtering output voltage peak value.

Left and right half frequency range matched filter is respectively complete matched filter near low, high frequency side on frequency domain, and width is the half of complete matched filter.If linear FM signal x (t), bandwidth is B, and pulsewidth is T, then its complete matched filter and left and right half frequency range matched filter impulse response are:

h ₀(t)＝kx ^*(t ₀-t),-T/2≤t＜T/2

H _l(t)=kx ^*(t ₀-t) ,-T/2≤t < 0 (formula one)

h _R(t)＝kx ^*(t ₀-t),0≤t＜T/2

Wherein " * " represents conjugation, t ₀for matched filtering exports peak value moment, k is normalization coefficient.

Linear FM signal x (t) is by No. three matched filter h ₀(t), h _l(t), h _rt frequency domain that () exports and time-domain expression are:

Y ₀(f)＝X(f)H ₀(f)

Y _l(f)=X (f) H _l(f) (formula two)

Y _R(f)＝X(f)H _R(f)

And Fourier inverse transformation is carried out to the result of formula two, calculate Signal Matching and export peak value:

(formula three)

If coupling exports peak value and is respectively y _0max,y _lmax,y _rmax, y here _xmax=max (| y _x(t) |).

Step 3: setting thresholding.

Consider the Doppler shift f that target velocity is brought _d=2v _max/ λ=2v _maxf ₀the mismatch that/c causes, determine thresholding:

(formula four)

Wherein, v _maxfor radar can survey target maximum speed, λ is radar emission signal wavelength, f ₀for radar emission signal carrier frequency, c is the light velocity, and B is radar emission FM signal bandwidth, f _dfor the Doppler shift that target velocity is brought, n _cl, n _crfor left and right thresholding.

Step 4: export the ratio of peak value according to the coupling of target under Different matching wave filter and combine whether set thresholding determination target is shift-frequency jamming decoy.

H ₀: and target is true target;

H ₁: or or or target is decoy.

Beneficial effect of the present invention:

One, ingeniously make use of that shift-frequency jamming signal begins, end frequecy characteristic, on the identifying of decoy by the impact of shift-frequency jamming signal center frequency.The method effectively overcomes in frequency displacement mensuration, the drawback that jammer causes identifying that shift-frequency jamming lost efficacy by controlling undesired signal centre frequency.

Two, applied range, identifiable design multiple interfering bodies false making target.The present invention can to interrupted sampling repeater jammer, and the distance multi-false targets that the application such as shift-frequency jamming linear FM signal range-Doppler coupling characteristic produces identifies.

Three, compensate for the deficiency that anti-interference method is followed the tracks of in radar forward position, the detection identification to active leading false target jamming profile can be realized;

Four, radar can be met to multiobject Real time identification.The performing step that the present invention relates to is few, calculated amount is little, is easy to Project Realization.Can differentiate that target is true and false with a signal echo in theory, resource when saving radar is empty, efficiency is high, speed is fast, can meet radar to multiobject Real time identification.

Accompanying drawing explanation

Fig. 1 is the decoy recognition methods overview flow chart that the present invention proposes;

Fig. 2 is the shift-frequency jamming decoy identification system design frame chart that the present invention proposes;

Fig. 3 is each matched filter of proposing of the present invention and radar return signal Spectrum Relationship schematic diagram; In figure, B is bandwidth, and f is frequency, H ₀(f), H _l(f), H _rf () is respectively the left and right half frequency range matched filter designed by complete matched filter and the present invention;

Fig. 4 (a) carries out emulation experiment undesired signal and echoed signal by the amplitude contrast schematic diagram after complete matched filter for utilizing the present invention;

Fig. 4 (b) carries out emulation experiment undesired signal and echoed signal by the amplitude contrast schematic diagram after left half frequency range matched filter for utilizing the present invention.

Fig. 4 (c) carries out emulation experiment undesired signal and echoed signal by the amplitude contrast schematic diagram after right half frequency range matched filter for utilizing the present invention.

Embodiment

Fig. 1, Fig. 2 are that the present invention proposes decoy recognition methods overview flow chart and radar linear frequency-modulated signal shift-frequency jamming decoy identification system design frame chart, are described further embodiments of the present invention below in conjunction with accompanying drawing.

Emulation experiment is based on multi-purpose computer, and adopt Matlab emulation platform to realize, simulation parameter is set to: radar emission signal pulsewidth T=50us, bandwidth B=10MHz, carrier frequency f ₀=3000MHz, interference frequency shift amount f _dj=-1Mhz ,-3MHz, the decoy leading now produced distance is 750m, 2250m.

A kind of half frequency range matched filtering of the present invention realizes shift-frequency jamming recognition methods, and the method concrete steps are as follows:

Step one: the signal first received radar receiver carries out filtering and low noise amplification etc. and anticipates, and then the radar signal received is divided into three tunnels, can carries out matched filtering respectively after making it.

Complete matched filter H herein ₀(f) and left and right half frequency range matched filter H _l(f), H _rf the Spectrum Relationship of () as shown in Figure 3.Fig. 3 is each matched filter of proposing of the present invention and involved radar return signal Spectrum Relationship, can find out when target echo signal X (f) passes through H from this Spectrum Relationship figure _l(f), H _rf () outputs signal peak value afterwards and X (f) will keep strict by the ratio of the output peak value of complete match wave filter (do not consider noise, shift frequency that target velocity causes time, should give consideration in practical application), and shift-frequency jamming signal X _jf () passes through H _l(f) or H _rf () outputs signal peak value and X (f) afterwards by complete match filters H ₀f the ratio of the output peak value of () will be greater than or less than this is the foundation that the present invention differentiates shift-frequency jamming decoy.

Step 2: three road signals are carried out matched filtering process respectively, and get matched filtering output peak value.

By radar return signal after pretreatment respectively through complete match filters H ₀(f), left half frequency matched filter H _l(f), right half matched filter H frequently _rf (), obtains coupling and exports peak value y ₀, y _l, y _r.

Step 3: setting thresholding.

If radargrammetry target maximum radial velocity v _max=3400m/s (10 times of velocities of sound), the Doppler shift frequency amount that target velocity causes is f _d=68kHz (visible, the mismatch caused by target velocity is very limited), consider that thresholding can slightly relax by the environmental factors such as noise, thresholding is set to n herein _cl=49.0%, n _cr=51.0%.

Step 4: also combine set threshold discrimination target according to the ratio of the coupling output peak value of target under Different matching wave filter true and false.

Will with n _cl, n _crcontrast, if H ₀set up and then judge that target is as true target, otherwise be decoy (as shown in Figure 2).Illustrate the present invention to decoy recognition effect for clear, under the prerequisite not affecting emulation correctness, this place establishes radar return signal to pass through H ₀(f), H _l(f) and H ₀f the output peak value of () is 1, see Fig. 4 (a), and utilizes this peak value to H _l(f) and H ₀f the corresponding target of () exports peak value and is normalized.H is passed through by Fig. 4 (b) visual target echo _l(f) and H ₀f the ratio of () amplitude is afterwards about this ratio of shift-frequency jamming signal then no longer keeps being less than be about 44.4%, 28.6% respectively; In like manner as Fig. 4 (c), shift-frequency jamming signal passes through H _rf after (), this ratio is about 55.6%, 72.4% respectively, all far exceed set thresholding n _cl, n _cr, can judge that it is decoy, achieve the identification to shift-frequency jamming decoy.

Claims (1)

1. half frequency range matched filtering realizes a shift-frequency jamming recognition methods, it is characterized in that: it comprises the following steps:

Step one: the signal received by radar carries out pre-service, is divided into three tunnels before matched filtering;

First the signal received radar receiver carries out filtering and low noise amplification is anticipated, and then the radar signal received is divided into three tunnels, carries out matched filtering respectively to make it rear, extracts peak value and also makes comparisons, and identifies whether target is decoy;

Step 2: by three road signals by complete matched filter, and extract each matched filtering output voltage peak value;

Left and right half frequency range matched filter is respectively complete matched filter near low, high frequency side on frequency domain, width is the half of complete matched filter, if linear FM signal x (t), bandwidth is B, pulsewidth is T, then its complete matched filter and left and right half frequency range matched filter impulse response are:

h ₀(t)＝kx ^*(t ₀-t),-T/2≤t＜T/2

H _l(t)=kx ^*(t ₀-t) ,-T/2≤t < 0 (formula one)

h _R(t)＝kx ^*(t ₀-t),0≤t＜T/2

Wherein " * " represents conjugation, t ₀for matched filtering exports peak value moment, k is normalization coefficient;

Linear FM signal x (t) is by No. three matched filter h ₀(t), h _l(t), h _rt frequency domain that () exports and time-domain expression are:

Y ₀(f)＝X(f)H ₀(f)

Y _l(f)=X (f) H _l(f) (formula two)

Y _R(f)＝X(f)H _R(f)

And Fourier inverse transformation is carried out to the result of formula two, calculate Signal Matching and export peak value:

$\left|y_0\left(t\right)\right|=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{\mathrm{\&infin;}}{Y}_0\left(f\right)e^{j2\mathrm{\&pi;}ft}df\right|$

$\left|y_L\left(t\right)\right|=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{\mathrm{\&infin;}}{Y}_L\left(f\right)e^{j2\mathrm{\&pi;}ft}df\right|$ (formula three)

$\left|y_R\left(t\right)\right|=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{\mathrm{\&infin;}}{Y}_R\left(f\right)e^{j2\mathrm{\&pi;}ft}df\right|$

If coupling exports peak value and is respectively y _0max, y _lmax, y _rmax, y here _xmax=max (| y _x(t) |);

Step 3: setting thresholding;

Consider the Doppler shift f that target velocity is brought _d=2v _max/ λ=2v _maxf ₀the mismatch that/c causes, determine thresholding:

$n_{cl}=\frac{B/2-f_d}{B-f_d}=\frac{1}{2}-\frac{f_d}{2(B-f_d)}$

(formula four)

$n_{cr}=\frac{B/2}{B-f_d}=\frac{1}{2}+\frac{f_d}{2(B-f_d)}$

Wherein, v _maxfor radar can survey target maximum speed, λ is radar emission signal wavelength, f ₀for radar emission signal carrier frequency, c is the light velocity, and B is radar emission FM signal bandwidth, f _dfor the Doppler shift that target velocity is brought, n _cl, n _crfor left and right thresholding;

Step 4: export the ratio of peak value according to the coupling of target under Different matching wave filter and combine whether set thresholding determination target is shift-frequency jamming decoy;

H ₀： $n_{cl}\&le;\frac{\left|y_L\right|}{\left|y_0\right|}\&le;n_{cr}$ And $n_{cl}\&le;\frac{\left|y_R\right|}{\left|y_0\right|}\&le;n_{cr}$ Target is true target;

H ₁： $\frac{\left|y_L\right|}{\left|y_0\right|}\&le;n_{cl}$ Or $\frac{\left|y_R\right|}{\left|y_0\right|}\&le;n_{cl}$ Or $\frac{\left|y_R\right|}{\left|y_0\right|}\&GreaterEqual;n_{cr}$ Or $\frac{\left|y_L\right|}{\left|y_0\right|}\&GreaterEqual;n_{cr}$ Target is decoy.