CN103727960A - DRFM (digital radio frequency memory)-based jamming signal generation method for radio altimeter - Google Patents

Abstract

The invention discloses a DRFM (digital radio frequency memory)-based jamming signal generation method for a radio altimeter. The method comprises the following steps of generating a range deception jamming signal for the altimeter according to the DRFM-based data circulating storage and read-write signal delay accurate-control technology; generating a radio frequency noise jamming signal for the altimeter according to the DRFM-based digital noise modulation technology; generating a false target jamming signal for the altimeter according to the DRFM-based data circulating storage and digital convolution filter technology; generating a range-speed synchronous jamming signal for the altimeter according to the DRFM-based frequency-shifting jamming technology. According to the method, the generated jamming signals for the altimeter are integrated to meet the requirements of anti-jamming performance tests of the radio altimeter of an anti-ship missile; the technology is applied to a universal radio altitude simulation device developed by the Naval Aeronautical Engineering Academy to finish testing two types of radio altimeters and verify the accuracy of the method; the radio altimeter jamming signals are applied to a missile-borne radio altimeter, and can also be popularized to an airborne radio altimeter.

Description

A kind of radio altimeter undesired signal production method based on DRFM

Technical field

The present invention relates to a kind of radio altimeter undesired signal production method based on DRFM, belong to equipment Test technical field.Mainly for generation of the undesired signal to multiple system radio altimeter, for the interference free performance of measuring height table.

Background technology

China starts late to the research of radio altimeter Anti-Jamming Technique and undesired signal generating technique.The altitude signal simulator that domestic missile-borne height indicator performance test is used, equivalent cable box scheme, SAW (Surface Acoustic Wave) delay line scheme or fibre delay line scheme have successively been adopted, these interfere informations that all cannot superpose in altitude signal, interference free performance that also just cannot measuring height table.Therefore, the simulation of height indicator Research on anti-interference technique height indicator undesired signal in the urgent need to address has problems.

Summary of the invention

The present invention relates to a kind of missile-borne radio altimeter undesired signal production method based on DRFM technology.The ultimate principle of the method is on the basis that radio altimeter signal characteristic is analyzed, DRFM technology is applied to the simulation of height indicator undesired signal, utilize the technical characterstic of DRFM, produce the multiple jamming signal type of the different system radio altimeters such as paired pulses and continuous wave.1. adopt the circulation storage based on DRFM and the time delay precision Control Technology that reads and writes data, by continuously changing the time delay of the relative input signal of output signal, produce the distance deception jamming signal to height indicator; 2. adopt the digital noise modulation technique based on DRFM, utilize the Signal fine-feature copy function of DRFM, zoop amplitude modulation or the phase modulation factor on the decoding output signal of DRFM circuit, produce the radio noise modulated interferer signal to height indicator; 3. adopt datacycle memory technology and digital convolution wave filter technology, the storage data of DRFM are processed at the decoding row digital filtering that recovers to advance, produce the many false target jamming profile signal to height indicator; 4. adopt the shift frequency perturbation technique based on DRFM, utilize digital quadrature mixing mode to carry out shift frequency modulation to altitude signal, produce the distance-speed synchronous interference signal to height indicator.Comprehensive above every technical measures, the multiple jamming signal type of generation to radio altimeter, the satisfied demand that different system radio altimeters are carried out to interference free performance test of adopting.

Accompanying drawing explanation

Fig. 1 LFMCW time domain plethysmographic signal and spectrogram

Fig. 2 LFMICW signal time-frequency figure

Fig. 3 LFMICW time domain plethysmographic signal and spectrogram

The height indicator undesired signal of Fig. 4 based on DRFM produces block diagram

The cheating interference of Fig. 5 to linear frequency modulation continuous wave

Fig. 6 FIR filter construction

The false target jamming profile of Fig. 7 to linear frequency modulation continuous wave

The digital noise modulations achievement of Fig. 8 based on DRFM

The RF noise jamming of Fig. 9 to linear frequency modulation continuous wave height indicator

Figure 10 disturbs the noise phase modulation of linear frequency modulation continuous wave height indicator

The shift frequency modulations achievement of Figure 11 based on DRFM

Figure 12 disturbs the shift frequency of linear frequency modulation continuous wave height indicator

Embodiment

The present invention is on the basis that radio altimeter signal characteristic is analyzed, datacycle storage and read-write time delay precision Control Technology, digital noise modulation technique, digital convolution wave filter technology and the shift frequency modulation technique based on digital quadrature mixing of integrated use based on DRFM, realize the simulation of the undesired signals such as radio noise, noise phase modulation, range gate deception and decoy to radio altimeter, met the needs of different system radio altimeter interference free performance tests.

Particular content of the present invention is:

1, missile-borne radio altimeter signature analysis

According to the feature difference that transmits, radio altimeter is divided into pulse and two kinds of systems of continuous wave.

(1) the pulse signal feature of height indicator

The radio altimeter transmitting wireless pulse signal of pulse system irradiates ground (sea) face, by the flying height of determining guided missile time delay in the relative transponder pulse of detection of echoes pulse front edge forward position, comprise monopulse system, Linear FM pulse compression system, pseudo-random phase coding system etc., its feature that transmits is identical with pulsed radar with principle of work.

The most frequently used pseudo-random phase coded signal is pseudorandom Coded Signals, adopts the modulation of { 0, π } biphase coding, and the plural form of signal is:

The envelope function of signal is:

For biphase coding

the complex envelope of pseudorandom Coded Signals is:

$\tilde{U}\left(t\right)=\left\{\begin{array}{cc}\frac{1}{\sqrt{N}}\mathrm{\Σ}{C}_k\tilde{u}(t-{\mathrm{k\τ}}_1),& |0\≤t\≤\mathrm{\τ}|\\ 0,& 0\end{array}\right.---\left(3\right)$

In formula, complex envelope for pseudorandom Coded Signals subpulse function; τ ₁for signal subspace pulse width; N is signal subspace pulse number; τ=N τ ₁wide during for signal.

(2) the Continuous Wave with frequency modulation signal characteristic of height indicator

The radio altimeter emission signal frequency temporal evolution of continuous wave system, generally adopts linear frequency modulation continuous wave (LFMCW), and signal frequency is pressed triangular wave or sawtooth wave rule linear change.The swept-frequency signal on symmetrical triangle linear frequency modulation of take is example, and the complex expression of signal is:

In formula, A ₀for signal amplitude; f ₀for signal carrier frequency;

for signal initial phase; K=B/T is chirp rate, and B is modulating bandwidth, and T is that frequency sweep section is wide when effective.The instantaneous frequency of signal is f=f ₀+ Kt; The complex envelope of signal is:

$a\left(t\right)=A_0{e}^{\mathrm{j\πK}{t}^2}---\left(5\right)$

A (t) is through Fourier transform, obtains its frequency spectrum to be:

A(f)＝U ₀e ^-jπf(f/K-T){[c(v ₁)+c(v ₂)]+j[s(v ₁)+s(v ₂)]} (6)

In formula, c (v), s (v) are Fresnel integral,

$c\left(v\right)={\∫}_0^v\cos \left(\frac{\mathrm{\π}}{2}{x}^2\right)\mathrm{dx}$

(7)

$s\left(v\right)={\∫}_0^v\sin \left(\frac{\mathrm{\π}}{2}{x}^2\right)\mathrm{dx}$

$v_1=\sqrt{2K}(\frac{T}{2}-\frac{f}{K})=\sqrt{\frac{\mathrm{BT}}{2}}(1+2(f-f_0)/B)$

(8)

$v_2=\sqrt{2K}(\frac{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">T</figure-callout>}}{2}+\frac{f}{K})=\sqrt{\frac{\mathrm{BT}}{2}}(1+2(f-f_0)/B)$

The time domain waveform of linear frequency modulation altimeter signal and frequency spectrum are as shown in Figure 1.

(3) the frequency modulation quasi c. w. signal characteristic of height indicator

For making height indicator have the advantage of continuous wave system and pulse system concurrently, can adopt linear frequency modulation quasi c. w. (LFMICW) signal, on the basis of Linear Frequency Modulation continuous wave, add ripple gate control pulse, with rect.p. string P _t(t) remove to block linear frequency modulation continuous wave signal S (t), LFMICW signal indication is:

S _T(t)＝P _T(t)·S(t) (9)

Wherein, P _t(t) be rect.p. function,

$P_T\left(t\right)=\left\{\begin{array}{cc}1,& {\mathrm{iT}}_P\&le;t\&le;T_f-{\mathrm{<figure-callout\; id="0"\; label="iT\; P"\; filenames="HSA00000849433800011.png,HSA00000849433800023.png"\; state="\{\{state\}\}">iT</figure-callout>}}_P\\ 0,& T_f+{\mathrm{iT}}_P<t<(i+1)T_P\end{array}\right.--\left(10\right)$

In formula, T _pfor the pulse repetition time; T _ffor pulse width; Dutycycle η=T _f/ T _p.As shown in Figure 2, time domain plethysmographic signal and frequency spectrum are as shown in Figure 3 for the time-frequency figure of LFMICW signal.

2, the height cheating interference signal based on DRFM produces

Height cheating interference to height indicator is similar to the distance deception jamming to radar.Height indicator to linear frequency modulation system, by the difference on the frequency transmitting and receive between signal, detect elevation information, the frequency deviation that superposes in altitude signal can realize the height cheating interference to height indicator, also can realize height cheating interference by altitude signal being carried out to time delay.For the height indicator of pulse system, can only produce height cheating interference by the latter.For taking into account the height indicator of different systems, the present invention adopts the method generation height cheating interference signal that altitude signal is carried out to time delay control.

Height indicator undesired signal based on DRFM produces theory diagram as shown in Figure 4, and its core is DRFM circuit.The principle of work of DRFM circuit is: height indicator is transmitted and is down-converted to baseband signal, then by A/D converter, it sampled and quantize, and depositing sampled data in data-carrier store.Under the control of delay control circuit, after one period of time delay, by the data reading in data-carrier store, by decoding restoring circuit, revert to baseband signal, then be converted to radiofrequency signal output through upconverter.If signal sample circuit and decoding restoring circuit adopt identical clock signal, and clock frequency is not less than the twice of base-band signal frequency, according to nyquist sampling theorem, signal after decoding the recovers information entrained with input signal is identical, just there is in time a delay, the size of the numerical value representative simulation height of this time delay.If control signal time delay changes, change that just can simulated altitude, reaches height indicator is carried out to the effect of highly cheating.To the interference effect of the height cheating interference signal of linear frequency modulation continuous wave system height indicator as shown in Figure 5.

3, the decoy signal based on DRFM produces

Height cheating interference signal to height indicator can be regarded a decoy as, if will produce a plurality of false target jamming profile signals to height indicator, can realize by the digital filtering technique based on DRFM.

By DRFM circuit, input signal is converted to digital signal, utilizes the filter function of digital signal processing, by digital convolution wave filter, produce a plurality of false target jamming profile to height indicator.If adopt FIR wave filter to produce N decoy:

$X\left(n\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}\mathrm{\&beta;}\left(i\right)x(n-\mathrm{mi}),$ n＝0，1，……(11)

Wherein, N is decoy quantity; M is the mistiming between adjacent decoy;

for the Amplitude Ratio between each decoy, if require each decoy amplitude identical, β (i) ≡ 1; The structure of FIR wave filter as shown in Figure 6.

A plurality of decoys that realize by convolution filter method can keep the correlativity transmitting with height indicator, after a plurality of false target jamming profile signals are processed by matched filtering, the coherent accumulation of radio altitude sheet receiver, can present the upper peak value echo that produces different amplitudes at various height, reach the effect to the many false target jamming profile of height indicator.To the false target jamming profile effect of linear frequency modulation continuous wave system radio altimeter as shown in Figure 7.

4, the radio noise signal based on DRFM produces

Radio noise is, with wave filter, white noise is carried out to filtering, and through amplifying the band-limited noise obtaining, its probability distribution Normal Distribution:

Wherein, phase place

in (π, π), be uniformly distributed, and and A _n(t) separate; ω _jfor carrier frequency, numerical value is much larger than S _j(t) spectrum width; Envelope function A _n(t) Rayleigh distributed, that is:

$P\left(A_n\right)=\frac{A_n}{{\mathrm{\&sigma;}}^2}{e}^{-\frac{{\mathrm{<figure-callout\; id="2"\; label="A\; n"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">A</figure-callout>}}_n^{}}{{2\mathrm{\&sigma;}}^2}}---\left(13\right)$

Utilize DRFM can retain the feature of radiofrequency signal fine feature, produce the noise interferences to height indicator.Height indicator is transmitted by after down coversion and analog to digital conversion, be converted to numerical information and store accurately.During output, from data-carrier store, read the data of storage, utilize digital noise modulation technique, by the two-way quadrature information S of DRFM circuit output _i(n), S _q(n), as carrier signal, in carrier signal, modulate a digital noise signal, that is:

In formula,

for equally distributed phase sequence in (π, π); A (n) is the envelope sequence of Rayleigh distributed.Digital noise modulation principle block diagram based on DRFM as shown in Figure 8.

Two paths of signals S ' through digital noise modulation _i(n), S ' _q(n) after orthogonal modulation, decoding recovery, up-conversion and power are synthetic, as the radio noise signal output to height indicator.The convolution that interfering signal power spectrum after modulation is altitude signal power spectrum and zoop power spectrum.To the radio noise signal of linear frequency modulation continuous wave system height indicator as shown in Figure 9, wherein the jamming-to-signal ratio JSR=0dB of (a) figure, (b) the jamming-to-signal ratio JSR=10dB of figure.

5, the noise phase modulation undesired signal based on DRFM produces

Noise phase modulation undesired signal is that the phase place of signal is subject to noise modulated, and its complex expression is:

Wherein, A _jfor interference signal amplitude; ω _jfor carrier frequency; β _pmfor coefficient of phase modulation; U (t), for needing the noise signal of modulation, is that average is 0 generalized stationary random process;

for being uniformly distributed in [0,2 π], and with u (t) mutually independent random variables.

If u (t) for variance be σ _ngaussian noise, define effective phase shift D=β _pmσ _n, the power spectrum of noise phase modulation signal is:

$G_j\left(f\right)=A_{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">j</figure-callout>}}^2{\&Integral;}_0^{\&infin;}[\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}(f-f_j)+\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}(f+f_j)]{\mathrm{\&tau;e}}^{-D^2(1-\frac{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&pi;\&Delta;}{F}_n\mathrm{\&tau;}}{2\mathrm{\&pi;\&Delta;}{F}_n\mathrm{\&tau;}})}\mathrm{d\&tau;}---\left(16\right)$

The general power of noise phase modulation signal is:

$P_t={\&Integral;}_0^{+\&infin;}{G}_j\left(f\right)\mathrm{df}\&ap;\frac{A_{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">j</figure-callout>}}^2}{2}---\left(17\right)$

Utilize the coherent copy function of DRFM, in altitude signal, carry out noise phase modulation modulation, in DRFM circuitry stores data, be multiplied by the noise phase modulation factor, that is:

Wherein,

u (n) is noise signal.Seemingly, difference, will just using A wherein (n) as constant for the implementation method of noise phase modulation undesired signal and noise AM interference class signal

as modulation signal, altitude signal is modulated.While Figure 10 shows that effective phase shift D=10, the phase modulation of linear frequency modulation continuous wave height indicator is disturbed (a) the jamming-to-signal ratio JSR=0dB of figure, (b) the jamming-to-signal ratio JSR=10dB of figure.

6, the shift frequency undesired signal based on DRFM produces

It is that the carrier frequency of altitude signal is changed to a frequency displacement f up or down that the shift frequency of height indicator is disturbed _d, on the basis of former altitude signal S (t), be multiplied by a phase shift factor:

$S_J\left(t\right)=S\left(t\right)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000849433800043.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{d}t}---\left(19\right)$

For the height indicator of linear frequency modulation continuous wave system, the shift frequency of altitude signal is disturbed to the effect that can play height cheating interference, for the height indicator that has speed measuring function concurrently, can also play the effect that velocity gate deception disturbs.

The implementation method that shift frequency based on DRFM disturbs is to utilize digital quadrature mixing technology, realizes the shift frequency to altitude signal.If the altitude signal after DRFM sampling is:

The in-phase component of carrying out after orthogonal transformation is:

Quadrature component after conversion is:

By in-phase component S _iand quadrature component S (n) _q(n) be multiplied by respectively cos (2 π f _dn) and sin (2 π f _dn), then two paths of signals is subtracted each other and can be obtained:

From formula 23, after digital quadrature mixing, output signal S _j(n) than former altitude signal S (n) many a frequency-shifted components f _d, having realized the shift frequency of altitude signal has been disturbed, implementation method is as shown in figure 11.To the shift frequency interference effect of linear frequency modulation continuous wave height indicator as shown in figure 12.

The present invention has been applied to the radio altimeter global altitude analogue means of naval aviation engineering college development, the motor-driven Support Equipment of Bing Sui naval and guided missile repair track universal test system pay naval warehouse and ordnance maintenance depot is used, complete the test to amphitypy guided missile radio altimeter, obtained the favorable comment of applying unit.Application units are thought: the height indicator undesired signal production method based on DRFM of naval aviation engineering college design, meet missile-borne radio altimeter serviceability and interference free performance testing requirement, can directly apply to the test of radio altimeter interference free performance and test.

The radio altimeter undesired signal that the present invention produces, is not only applicable to missile-borne radio altimeter, can be applied to airborne radio height indicator yet, and popularizing application prospect is wide.

Claims (1)

1. the present invention relates to a kind of radio altimeter undesired signal production method based on DRFM technology.The ultimate principle of the method is on the basis that radio altimeter signal characteristic is analyzed, and DRFM technology is applied to the simulation of height indicator undesired signal, utilizes the technical characterstic of DRFM, produces the multiple jamming signal type to different system radio altimeters.1. adopt datacycle storage and read-write time delay precision Control Technology based on DRFM, by changing data reading and signal release time of storer, change the time delay of the relative input signal of output undesired signal, produce the distance deception jamming signal to height indicator; 2. adopt the digital noise modulation technique based on DRFM, utilize the Signal fine-feature copy function of DRFM, sample signal after DRFM recovers, as carrier wave, is modulated a noise amplitude modulation or the phase modulation factor thereon, realizes the radio noise modulated interferer to height indicator; 3. adopt sampled data circulation memory technology and digital convolution wave filter technology, the digital signal of DRFM storage is processed by digital filtering before decoding recovers, produce a plurality of false target jamming profile signals to height indicator; 4. adopt the shift frequency perturbation technique based on DRFM, utilize digital quadrature mixing mode to carry out shift frequency modulation, realize the distance-speed synchronous interference to height indicator.Comprehensive above every technical measures, the undesired signal of generation to the multiple pattern of height indicator, the satisfied demand to different system radio altimeter interference free performance tests of adopting.

Images