CN101325431B - A Method of Intercepting Pulse Radio Signals Based on Amplitude Statistics - Google Patents

Abstract

The invention discloses a pulse radio signal interception method based on amplitude statistics, which is characterized in that the pulse radio signal has the characteristics of low duty cycle and large instantaneous amplitude, carries out amplitude statistics on the sampling sequence of the received signal, and utilizes the small-amplitude point middle signal The active ingredient is low, and after taking it out, it has little effect on signal energy collection, but it can effectively remove most of the noise energy, thereby improving the signal-to-noise ratio of spectrum analysis and improving the impossibility of pulsed radio signals due to extremely low power spectral density. intercepted problem. It solves the problem that the traditional interception method cannot intercept the pulsed radio signal under the condition of low duty cycle.

Description

A kind of method for interception of the impulse radio signal based on amplitude statistics

Technical field

The invention belongs to the radio communication field of information security technology, particularly the method for interception of impulse radio signal.

Background technology

U.S.'s " international electronics and The Institution of Electrical Engineers's wall bulletin " (IEEE Communication Letter) 1998 the 2nd phase 36-38 beginnings of the page have proposed the notion of impulse radio earlier.Impulse radio signal has the characteristics of typical low power spectral density, and impulse radio communications is the important technical of current ultra-wideband communications, has a wide range of applications in short haul connection.

The method for interception research of paired pulses radio signal is the major issue of information security field.Have not yet to see open source literature the intercepting and capturing problem of paired pulses radiocommunication signals is discussed, the research that the paired pulses radio is intercepted and captured problem still is in space state.

Summary of the invention

The objective of the invention is to propose a kind of method for interception of the impulse radio signal based on amplitude statistics, to solve the problem that traditional method for interception under the low duty ratio condition can't the paired pulses radio signal be intercepted and captured.

The method for interception based on the impulse radio signal of amplitude statistics that the present invention proposes is characterized in that:

To obtained from received signal r (t) from antenna square after sampling sequence r _e(n)=r ²(nT) carry out amplitude statistics, the n in the formula is the sampling point sequence number, and T is the sampling interval; And will square after sampling sequence r _e(n) according to amplitude it is arranged in from small to large and increases preface collating sequence A _q(n); Delete factor P and increase preface collating sequence A according to noise spot _q(n) select corresponding deletion thresholding A _Th=A _q([PN]), the N in the formula are the sampling point sums, [ ] expression and the immediate integer of variable; Will square after sampling sequence r _e(n) with deletion thresholding A _ThCompare and obtain denoising sequence r _q(n) be: work as r _e(n)＞A _ThThe time, denoising sequence r _q(n)=r _e(n); Work as r _e(n)≤A _ThThe time, denoising sequence r _q(n)=0; To denoising sequence r _q(n) carry out discrete Fourier transform (DFT) (DFT) and obtain transform sequence d _r(k)=DFT (r _q(n)), k is the label of transform sequence; Further to transform sequence d _r(k) delivery and remove DC component after, select M maximum point, the position of M maximal point is recorded as initial position sequence s (m), m is the sequence number of maximum point here; Initial position sequence s (m) is increased the preface ordering obtain position sequence p (m), if δ (m)=p (m+1)-p (m) is a certain constant C to the adjacent position of position sequence p (m) difference _δIntegral multiple, for different maximum point sequence number m, δ (m) is C _δDifferent integral multiples, then adjacent position difference δ (m) and constant C _δRatio delta (m)/C _δWith its near integer [δ (m)/C _δ] between depart from absolute value | δ (m)/C _δ-[δ (m)/C _δ] | less than permissible error C _ErrThe time, adjudicate to intercepting and capturing; If depart from absolute value more than or equal to permissible error C _ErrThen be not judged to be and intercept and capture.

Described to from received signal r (t) from antenna, can adopt one of following dual mode to obtain square after sampling sequence r _e(n): a kind of is will carry out from the received signal r (t) of antenna obtaining quadrature signal r behind the square operation earlier ²(t), again to quadrature signal r ²(t) take a sample obtain square after sampling sequence r _e(n)=r ²(nT); Or another kind is will carry out analog digital from the received signal r (t) of antenna earlier and be converted to sampling sequence r _Ne(n)=and r (nT), again to r _Ne(n) carry out square obtaining square after sampling sequence

Here T is the sampling interval.

Above-mentioned processing method of the present invention is owing to utilized the characteristics that the impulse radio signal duty ratio is low, instantaneous amplitude is big, sampling sequence to received signal carries out amplitude statistics, signal active ingredient is low in utilizing by a small margin, it is little to signal energy collection influence to take out the back, but can effectively remove entering of most of noise energy, thereby improved the signal to noise ratio of spectrum analysis, improved impulse radio signal because the extremely low caused problem that can't intercept and capture of power spectral density.

Description of drawings

Fig. 1 is based on the capture device block diagram 1 of the impulse radio signal of noise spot removal.

Fig. 2 is based on the capture device block diagram 2 of the impulse radio signal of noise spot taking-up.

Fig. 3 is the impulse radio signal frequency spectrum that does not adopt noise spot to remove.

Fig. 4 adopts noise spot to remove the frequency spectrum that method for interception obtains.

Fig. 5 adopts noise spot to remove the alarm dismissal probability curve of method for interception.

Embodiment:

Embodiment 1: the intercepting and capturing based on the impulse radio signal of amplitude statistics of taking a sample behind the first square operation

The intercepting and capturing based on the impulse radio signal of amplitude statistics that present embodiment is taked to take a sample behind the first square operation, accompanying drawing 1 has provided the intercepting and capturing processing block Fig. 1 based on the impulse radio signal of amplitude statistics.Concrete processing procedure is: the radio wave that exists in the space that receives by antenna 0, and after amplification procedure 1 amplifies, send into filter step 2 and carry out filtering and obtain received signal r (t), signal r (t) obtains quadrature signal r through square operation 4 _e(t)=r ²(t), at 3 couples of quadrature signal r of sampling procedure _e(t) sampling sequence r after sampling obtains square _e(n), will square after sampling sequence r _e(n) deliver to intercepting and capturing treatment step 5 and intercept and capture algorithm process, promptly obtain court verdict; Here the amplifier that is adopted in the amplification procedure 1 can be any linear amplifier that covers the detection signal frequency range; The filter that is adopted in the filter step 2 is that passband is any band pass filter or any low pass filter that covers the detection signal frequency range, the square law device that is adopted in the described square operation 4 can be arbitrary square law device that working band covers detection signal place frequency range, for example, for frequency band is the pulse signal of 1-2GHz, the Max109 that sampler can select for use Maxim company to produce utilizes multi-phase clock to realize, amplifier is selected the AD8353 of ADI (Analog Device), ADA9537 realizes that square law device is selected the MTD001 of Wei Yin Xie Er company (AeroFlex); Spendable device includes but not limited to above-mentioned device in the present embodiment.

The part of dotted line institute frame is for intercepting and capturing treatment step 5 among Fig. 1, and it specifically comprises amplitude statistics 51, thresholding selection 52, noise spot removal 53, discrete Fourier transform (DFT) 54 and adjudicates 55 processing procedures: sampling sequence r after described square _e(n) after amplitude statistics process 51 is carried out amplitude statistics, output increase preface collating sequence A _q(n) be sent to thresholding selection course 52, this thresholding selection course 52 is deleted factor P and is increased preface collating sequence A according to the noise spot of default _q(n) obtain deleting thresholding A _Th, square after sampling sequence r _e(n) and deletion thresholding A _ThSampling sequence r after noise spot is removed process 53 and removed square _e(n) amplitude is less than removing thresholding A in _ThSampling point after, obtain denoising sequence r _q(n); This denoising sequence r _q(n) d as a result after discrete Fourier transform (DFT) process 54 _r(k) be input to judging process 55, according to d _rWhether whether the alternate position spike between the maximum point of amplitude (k) satisfies the judgement of multiple relation has impulse radio signal and exports the result.

It is as follows that but the impulse radio based on the noise spot removal of above-mentioned intercepting and capturing treatment step 5 is intercepted and captured the processing procedure concrete operations:

1, will square after sampling sequence r _e(n) be input to amplitude statistics 51, according to square after sampling sequence r _e(n) amplitude from small to large to square after sampling sequence r _e(n) sort, obtain increasing preface collating sequence A _q(n), n is the sampling point sequence number here;

2, calculate the sampling point sum n that needs deletion ₁=[PN], N is the total number of sampling point here, and P is the noise spot deletion factor, i.e. and subsequent operation process is prepared the sampling point ratio of deletion, and [PN] is near the integer of PN;

3, will increase preface collating sequence A _q(n) be input to thresholding and select 52, obtain thresholding A _Th:

A _th＝A _q(n ₁)＝A _q([PN])

4, list entries r _e(n) in denoising point 53 with A _ThCompare, obtain denoising sequence r _q(n):

$r_q\left(n\right)=\left\{\begin{array}{c}{r}_e\left(n\right),r_e\left(n\right)>A_{\mathrm{<figure-callout\; id="0"\; label="th"\; filenames="S2008101231614E00021.png,S2008101231614E00022.png"\; state="\{\{state\}\}">th</figure-callout>}}\\ 0,r_e\left(n\right)\&le;A_{\mathrm{th}}\end{array}\right.$

5, with denoising sequence r _q(n) being input to discrete Fourier transform (DFT) 54 carries out the discrete time Fourier transform and obtains transform sequence d _r(k), k is the sequence number of transform sequence:

$d_r\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{r}_q\left(n\right)W_N^{\mathrm{nk}},$ Here $W={\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="S2008101231614E00021.png,S2008101231614E00022.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$

6, with transform sequence d _r(k) be input to judgement 55, to d _r(k) delivery and remove DC component, seek M maximal point then, the position of maximal point is recorded as initial position sequence s (m) (0≤m≤M-1), here m is the maximal point sequence number, s (m) is arranged and to obtain position sequence p (m) according to increasing preface, and (0≤m≤M-2) is a certain constant C if a little bigger alternate position spike δ (m)=p (the m+1)-p (m) of consecutive roots _δIntegral multiple, for different maximum point sequence number m, δ (m) is C _δDifferent integral multiples: i.e. adjacent position difference δ (m) and constant C _δRatio delta (m)/C _δWith its near integer [δ (m)/C _δ] between depart from absolute value | δ (m)/C _δ-[δ (m)/C _δ] | less than permissible error C _ErrThe time, adjudicate to intercepting and capturing; If depart from absolute value more than or equal to permissible error C _ErrThen be not judged to be and intercept and capture; Here [δ (m)/C _δ] represent near δ (m)/C _δInteger.

Embodiment 2: the intercepting and capturing based on the impulse radio signal of amplitude statistics of sampling back square operation earlier

The intercepting and capturing based on the impulse radio signal of amplitude statistics that present embodiment is taked to take a sample behind the first square operation, accompanying drawing 2 has provided the intercepting and capturing processing block Fig. 2 based on the impulse radio signal of amplitude statistics.Concrete processing procedure is: the radio wave that exists in the space that receives by antenna 0, and after amplification procedure 1 amplifies, send into filter step 2 and carry out filtering and obtain received signal r (t), obtain sampling sequence r through sampling procedure 3 _Ne(n)=r (nT), sampling sequence r after square operation step 4 obtains square again _e(n), deliver to intercepting and capturing treatment step 5 and intercept and capture algorithm process, promptly obtain court verdict; Here the amplifier that is adopted in the amplification procedure 1 can be any linear amplifier that covers the detection signal frequency range; The filter that is adopted in the described filter step 2 is that passband is any band pass filter or any low pass filter that covers the detection signal frequency range, for example, for frequency band is the pulse signal of 1-2GHz, the Max109 that sampler can select for use Maxim company to produce utilizes multi-phase clock to realize, amplifier is selected the AD8353 of ADI (Analog Device), ADA9537 realizes that spendable device includes but not limited to above-mentioned device in the present embodiment.

That describes among the concrete processing procedure of the intercepting and capturing treatment step 5 in the present embodiment and the embodiment 1 is in full accord.

Consider such impulse radio signal:

$r\left(t\right)+\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\mathrm{ad}}_l{w}_{\mathrm{rec}}(t-{\mathrm{lT}}_f-C_l{T}_c)+n\left(t\right)$

Here a is the received signal amplitude, w _Rec(t) be the impulse waveform that receives, d _lBe the 1st pulse modulated data, d _l∈+1,0} or d _l∈+1 ,-1}, T _fBe the pulse repetition period, C _lBe time-hopping sequence, T _cAt interval, l is the pulse sequence number when being jumping.

Suppose that traffic rate is B _d, pulse energy is E _p, then signal energy is B _dE _p, bandwidth is B, so obtain the spectrum density signal to noise ratio is

Consider bit signal to noise ratio E generally speaking _b/ N ₀But proper communication during ≈ 15dB is as traffic rate B _dLess than 20Mbps, during signal bandwidth B=2GHz, can calculate the spectrum density signal to noise ratio snr＜-5dB, use the existence that traditional frequency spectrum analysis method can't be found out data-signal this moment.Accompanying drawing 3 has provided bit signal to noise ratio E _b/ N ₀=15dB, time-hopping sequence C _l=2,1,2,0,0}, pulse repetition period T _f=210ns, interval T during jumping _cThe amplitude part of discrete Fourier transform (DFT) result during=42ns, abscissa are frequency, and unit hertz, ordinate are the normalization amplitudes, use logarithmic coordinates, can't judge whether to exist impulse radio signal this moment.

Consider that impulse radio signal is a signal that duty ratio is very low, a lot of sampling points do not include the signal message of usefulness.Energy is evenly distributed in the each point of Fourier transform results.Therefore remove most sampling points that does not comprise signal message after adopting amplitude statistics, will reduce noise contribution part in the Fourier transform each point, and signal contribution partly is able to the reservation of largest portion.Accompanying drawing 4 has provided the amplitude part that adopts the resulting Fourier transform results of the inventive method under the same parameter, and abscissa is a frequency, the unit hertz, ordinate is a relative amplitude, adopt logarithmic coordinates, as can be seen from the figure have some discrete spectral lines, spectral line just in time is 1/T at interval _c, can effectively judge whether to exist impulse radio signal thus and extract time parameter T _c

Accompanying drawing 5 has provided at bit signal to noise ratio E _b/ N ₀Intercepting and capturing performance from 4dB to 12dB, abscissa are bit signal to noise ratio E _b/ N ₀, the dB of unit, ordinate are alarm dismissal probability, adopt logarithmic coordinates.It must be noted that, in the case Dui Ying spectrum density signal to noise ratio snr excursion be-16dB is to-8dB.Noise spot deletion factor P=0.99 in the numerical simulation, maximum point number M=3,, given permissible error C _Err=0.01.This moment, corresponding false alarm probability was 0.0014.The maximum point number M increases or given permissible error C _ErrReduce all will improve alarm dismissal probability, reduce false alarm probability; Otherwise if the maximum point number M reduces or given permissible error C _ErrIncrease and all will reduce alarm dismissal probability, improve false alarm probability.

Claims (3)

1. method for interception based on the impulse radio signal of amplitude statistics is characterized in that: to obtained from received signal r (t) from antenna square after sampling sequence r _e(n)=r ²(nT) carry out amplitude statistics, the n in the formula is the sampling point sequence number, and T is the sampling interval; And will square after sampling sequence r _e(n) according to amplitude it is arranged in from small to large and increases preface collating sequence A _q(n); Delete factor P and increase preface collating sequence A according to noise spot _q(n) select corresponding deletion thresholding A _Th=A _q([PN]), the N in the formula are the sampling point sums, [ ] expression and the immediate integer of variable; Will square after sampling sequence r _e(n) with deletion thresholding A _ThCompare and obtain denoising sequence r _q(n) be: work as r _e(n)＞A _ThThe time, denoising sequence r _q(n)=r _e(n); Work as r _e(n)≤A _ThThe time, denoising sequence r _q(n)=0; To denoising sequence r _q(n) carry out discrete Fourier transform (DFT) (DFT) and obtain transform sequence d _r(k)=DFT (r _q(n)), k is the label of transform sequence; Further to transform sequence d _r(k) delivery and remove DC component after, select M maximum point, the position of M maximal point is recorded as initial position sequence s (m), m is the sequence number of maximum point here; Initial position sequence s (m) is increased the preface ordering obtain position sequence p (m), if δ (m)=p (m+1)-p (m) is a certain constant C to the adjacent position of position sequence p (m) difference _δIntegral multiple, for different maximum point sequence number m, δ (m) is C _δDifferent integral multiples, then adjacent position difference δ (m) and constant C _δRatio delta (m)/C _δWith its near integer [δ (m)/C _δ] between depart from absolute value | δ (m)/C _δ-[δ (m)/C _δ] | less than permissible error C _ErrThe time, adjudicate to intercepting and capturing; If depart from absolute value more than or equal to permissible error C _ErrThen be not judged to be and intercept and capture.

2. according to claim 1 based on the method for interception of the impulse radio signal of amplitude statistics, be characterised in that described to sampling sequence r after obtaining from received signal r (t) square from antenna _e(n), be to carry out from the received signal r (t) of antenna obtaining quadrature signal r behind the square operation earlier ²(t), again to quadrature signal r ²(t) take a sample obtain square after sampling sequence r _e(n)=r ²(nT), T is the sampling interval here.

3. according to claim 1 based on the method for interception of the impulse radio signal of amplitude statistics, be characterised in that described to sampling sequence r after obtaining from received signal r (t) square from antenna _e(n), be to carry out analog digital from the received signal r (t) of antenna earlier to be converted to sampling sequence r _Ne(n)=and r (nT), again to r _Ne(n) carry out square obtaining square after sampling sequence Here T is the sampling interval.

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