CN105071830B - A kind of detection recognition method of direct sequence signal - Google Patents
A kind of detection recognition method of direct sequence signal Download PDFInfo
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- CN105071830B CN105071830B CN201510422676.4A CN201510422676A CN105071830B CN 105071830 B CN105071830 B CN 105071830B CN 201510422676 A CN201510422676 A CN 201510422676A CN 105071830 B CN105071830 B CN 105071830B
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Abstract
Include the invention provides a kind of detection recognition method of direct sequence signal, the step of this method：1st, the power spectrum for receiving signal is calculated, and logarithm operation is carried out to the power spectrum；Then using the logarithm operation result as detection signal, and the power spectrum of the detection signal is composed as detection；2nd, detection spectrum is filtered；3rd, maximum V is searched in signal after the filteringmax, and ask for the average V of the filtered signalmean；4th, with maximum VmaxWith average VmeanRatio is used as detection characteristic value E, i.e. E=Vmax/Vmean；5th, the detection characteristic value E and threshold value e of settingthresholdIt is compared judgement：If E>ethreshold, then judge to receive signal for direct sequence signal.This method takes full advantage of in Direct Sequence Spread Spectrum Signal pseudo-code component in frequency domain and the periodicity of time domain, and the discrete component being submerged in continuous quantity is lifted using logarithm operation, so as to reduce influence of the noise to recognition performance, method realization is simple, be easy to Project Realization and signal identification efficiency high.
Description
Technical field
The present invention relates to signal of communication process field, more particularly to a kind of detection recognition method of direct sequence signal, for area
Divide general communication signal and direct sequence signal.
Background technology
The detection identification of signal of communication is one of the key technology in single star electronic reconnaissance field.The task of signal detection identification
Seek to determine to receive to whether there is useful signal in signal, and identify the modulation system of signal.Detect that identification process may
It can be disturbed by noise, and need known portions modulation intelligence.Effective detection identification can be demodulation, analysis or be done
The follow-up work such as disturb and foundation is provided.
The detection recognition method of early stage is mostly that the high-frequency signal received first is changed into intermediate frequency, then inputs different demodulation
Device obtains the signal of observable, finally by operating personnel according to obtained signal time and frequency domain characteristics, temporal characteristics and sound messenger
To judge the modulation system of signal.Use at present it is mostly be automatic detection recognition methods, can substantially be divided into two classes：Based on decision-making
The statistical model detection recognition method that theoretical maximum likelihood hypothesis testing method and feature based are extracted.
DSSS (DSSS) is a kind of channel transmission technique wide variety of in modern communicationses, with very high
Processing gain.Source signal is often hidden among noise after DS is handled, and this special nature determines that it is difficult to detect.Mesh
Before, it is usually used in detecting that the method for direct sequence signal includes auto-correlation accumulation, cyclic stationary spectrum correlation, Higher Order Cumulants etc..These sides
Method all has to the characteristic of insensitive for noise, it is possible to compared with realizing detection of DS under low signal-to-noise ratio.But this kind of side
Method there is also it is certain the problem of, for these methods, general communication signal and direct sequence signal have similar characteristic, so
Although these methods can detect that signal whether there is, cannot distinguish between echo signal is normal signal or direct sequence signal,
That is such method is easily influenceed by normal signal.
The content of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of detection recognition method of direct sequence signal.
This method is analyzed by docking the secondary power spectrum of the collection of letters number, and the feature that extraction normal signal does not have is special as detection
Levy, so as to determine whether echo signal is direct sequence signal while signal presence or absence is detected, it is to avoid the shadow of normal signal
Ring.Method realization is simple, be easy to Project Realization, and to insensitive for noise, signal identification efficiency high.
The above-mentioned purpose of the present invention is realized by following scheme：
A kind of detection recognition method of direct sequence signal, it is characterised in that comprise the following steps：
(1) power spectrum for receiving signal, is calculated, and logarithm operation is carried out to the power spectrum；Then the logarithm is transported
Result is calculated as detection signal, and the power spectrum of the detection signal is composed as detection；
(2) the detection spectrum, obtained to step (1) is filtered；
(3) maximum V, is searched in step (2) filtered signalmax, and ask for the average of the filtered signal
Vmean；
(4), with maximum VmaxWith average VmeanRatio is used as detection characteristic value E, i.e. E=Vmax/Vmean；
(5), the detection characteristic value E for obtaining step (4) and the threshold value e of settingthresholdIt is compared judgement：If E>
ethreshold, then judge to receive signal for direct sequence signal.
The detection recognition method of above-mentioned direct sequence signal, in step (1), in received signal power spectrum calculating is carried out,
The docking collection of letters number first carries out a piecemeal, then calculates the power spectrum of each data block, then the power spectrum of multiple data blocks is superimposed
The spectra calculation result for receiving signal is used as after averaging.
The detection recognition method of above-mentioned direct sequence signal, in step (1), detects that the calculation formula of spectrum is as follows：
P (t)=| FFT [lg | FFT [f (t)] |2]|2
Wherein, P (t) composes to calculate obtained detection；F (t) is reception signal；FFT represents FFT computing；Lg is represented
Logarithm operation.
The detection recognition method of above-mentioned direct sequence signal, in step (2), using high-pass filter to detection signal power
Spectrum is filtered.
The detection recognition method of above-mentioned direct sequence signal, the cut-off frequency of high-pass filter is two points of system sampling frequency
One of.
The detection recognition method of above-mentioned direct sequence signal, in step (5), threshold value ethresholdSpan for 20~
25。
The present invention compared with prior art, with advantages below：
(1), the present invention calculates the power spectrum for receiving signal first, obtains detecting signal after then taking the logarithm, and again to inspection
The power spectrum for surveying signal analyze and obtains characteristic value, take full advantage of in Direct Sequence Spread Spectrum Signal pseudo-code component in frequency domain and
The periodicity of time domain, method realization is simple, be easy to Project Realization and signal identification efficiency high；
(2) method for, being averaging power spectrum in the present invention by repeatedly calculating obtains receiving the power spectrum of signal, can be effective
Elimination noise, in addition, extract detection compose high-frequency characteristic to insensitive for noise, another reduces noise to recognition performance
Influence, twice noise reduction process can make this method compared with realized under low signal-to-noise ratio direct sequence signal effective detection recognize；
(3), the present invention removes DC component and low frequency part by high-pass filtering, so that by HFS and other parts
Separated and extract signal characteristic, and normal signal and noise do not have this feature.DC terms and low frequency term are reduced to expansion
The influence of frequency signal characteristic identification, and take full advantage of direct sequence signal and general communication signal and the signal structure of white Gaussian noise
Difference, the identification of direct sequence signal is realized while effective detection echo signal whether there is, improve direct sequence signal inspection
Survey recognition efficiency.
Brief description of the drawings
Fig. 1 a are the corresponding detection spectrograms of direct sequence signal DS-BPSK；
Fig. 1 b are the corresponding detection spectrogram of white Gaussian noise；
Fig. 1 c are the corresponding detection signal power spectrograms of general communication signal BPSK；
Fig. 2 is the process chart of the detection of DS recognition methods of the present invention；
Distribution figure of characterized values Fig. 3 a is detect to 1.4MHz signals in the embodiment of the present invention when；
Distribution figure of characterized values Fig. 3 b is detect to 2.8MHz signals in the embodiment of the present invention when；
Distribution figure of characterized values Fig. 3 c is detect to 5.6MHz signals in the embodiment of the present invention when.
Embodiment
The present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings：
The detection of DS recognition methods of the present invention takes full advantage of in Direct Sequence Spread Spectrum Signal pseudo-code component in frequency
Domain and the periodicity of time domain, extract characteristic quantity identification direct sequence signal.Concrete principle is as follows：
The power spectrum P of direct sequence signals(f) it is：
Wherein,A is signal amplitude, and p is the cycle of PN sequences, TcIt is the symbol width of PN sequences, f0It is
Signal center frequency, pTcIt is the time cycle of PN sequences, Sa(f) be information code d (t) power spectrum.
The logarithmic spectrum that power spectrum signal to more than obtained after logarithm operation is as follows：
Contain three components in the logarithmic spectrum that above formula is provided：(1) DC terms of signal power spectral amplitude, are represented；(2),
Represent the low frequency term of the pseudo- bit rate of spread-spectrum signal；(3) high frequency of PN-code capture, is represented.
Logarithmic spectrum to more than carries out FFT and obtains accordingly also containing three in detection spectrum, detection spectrum again：First
Item is located at the pulse of 0 position, represents the constant of signal power spectral amplitude；Section 2 represents the speed of pseudo-code close to 0；Section 3
Positioned at higher position, and with period p TcInterval is repeated, and represents signal PN-code capture frequency.Wherein, Section 2 is leaned on very much
Nearly 0 position, is difficult to separate in detection spectrum, and Section 3 is to repeat item with pseudo-code time cycle interval, and can be obtained
Higher processing gain is obtained, is easy to detection, and pass through the interval estimation pseudo-code time cycle between them.
Detection analysis of spectrum is carried out to direct sequence signal using the analysis method of the above, as a result as shown in Figure 1a, the figure is with DS-
Exemplified by bpsk signal analysis, wherein can substantially distinguish one in detection spectrum, two, three.And same method is used to height
This white noise and general communication signal carry out detection analysis of spectrum, in the absence of above-mentioned feature, as a result as shown in fig. 1b and fig. lc, its
Middle Fig. 1 c are the detection spectrum analyzed bpsk signal.
As seen through the above analysis, can using detection spectrum in Section 3 as direct sequence signal personal feature, from
And realize the differentiation of direct sequence signal and noise and general communication signal.As shown in Fig. 2 the detection of DS identification side of the present invention
Method comprises the following steps：
(1), obtain receiving the power spectrum of signal by repeatedly calculating the method for averaging, and to power spectrum progress pair
Number computing；Then using the logarithm operation result as detection signal, and the power spectrum of the detection signal is composed as detection.
The detection spectrum calculation formula provided in the present embodiment is as follows：
P (t)=| FFT [lg | FFT [f (t)] |2]|2
Wherein, P (t) composes to calculate obtained detection；F (t) is reception signal；FFT represents FFT computing；Lg is represented
Logarithm operation.
(2) the detection spectrum, obtained using high-pass filter to step (1) is filtered；
(3) maximum V, is searched in step (2) filtered signalmax, and ask for the average of the filtered signal
Vmean；
(4), with maximum VmaxWith average VmeanRatio is used as detection characteristic value E, i.e. E=Vmax/Vmean；
(5), the detection characteristic value E for obtaining step (4) and the threshold value e of settingthresholdIt is compared judgement：If E>
ethreshold, then judge to receive signal for direct sequence signal.Wherein, typically according to signal environment given threshold ethresholdEqual to 20~
25.In the present embodiment, above analysis is carried out to the signal with a width of 1.4MHz, 2.8MHz and 6MHz respectively, in signal to noise ratio snr
The feature Distribution value obtained during=- 10~10dB as shown in Figure 3 a, 3b and 3c as shown in, there it can be seen that can be with given threshold
ethreshold=25, so as to realize the detection of direct sequence signal.
It is described above, it is only an embodiment of the invention, but protection scope of the present invention is not limited thereto, and is appointed
What those familiar with the art the invention discloses technical scope in, the change or replacement that can be readily occurred in, all
It should be included within the scope of the present invention.
The content not being described in detail in description of the invention belongs to the known technology of professional and technical personnel in the field.
Claims (5)
1. a kind of detection recognition method of direct sequence signal, it is characterised in that comprise the following steps：
(1) power spectrum for receiving signal, is calculated, and logarithm operation is carried out to the power spectrum；Then by the logarithm operation knot
Fruit is composed as detection signal, and using the power spectrum of the detection signal as detection；
(2) the detection spectrum, obtained using high-pass filter to step (1) is filtered；
(3) maximum V, is searched in step (2) filtered signalmax, and ask for the average V of the filtered signalmean；
(4), with maximum VmaxWith average VmeanRatio is used as detection characteristic value E, i.e. E=Vmax/Vmean；
(5), the detection characteristic value E for obtaining step (4) and the threshold value e of settingthresholdIt is compared judgement：If E>
ethreshold, then judge to receive signal for direct sequence signal.
2. a kind of detection recognition method of direct sequence signal according to claim 1, it is characterised in that：In step (1),
Carry out in received signal power spectrum calculating, the docking collection of letters number first carries out piecemeal, then calculates the power spectrum of each data block, then
The spectra calculation result for receiving signal is used as after the power spectrum superposition of multiple data blocks is averaging.
3. a kind of detection recognition method of direct sequence signal according to claim 1, it is characterised in that：In step (1), inspection
The calculation formula for surveying spectrum is as follows：
P (t)=| FFT [lg | FFT [f (t)] |2]|2
Wherein, P (t) composes to calculate obtained detection；F (t) is reception signal；FFT represents FFT computing；Lg represents logarithm
Computing.
4. a kind of detection recognition method of direct sequence signal according to claim 1, it is characterised in that：Section of high-pass filter
Only frequency is 1/2nd of system sampling frequency.
5. a kind of detection recognition method of direct sequence signal according to claim 1, it is characterised in that：In step (5), threshold
Value ethresholdSpan be 20~25.
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| CN105959035B (en) * | 2016-06-14 | 2018-04-03 | 东南大学 | A kind of direct sequence signal intercepts and captures detection method |
| CN106849992B (en) * | 2016-12-12 | 2019-06-18 | 西安空间无线电技术研究所 | A kind of detection method of the direct sequence signal based on Generalized Quadratic power spectrum |
| CN106899324B (en) * | 2017-03-13 | 2018-12-28 | 广西翼界科技有限公司 | A kind of detection recognition method of long code direct sequence signal |
| CN106877901B (en) * | 2017-03-30 | 2019-05-24 | 南京格外信息技术有限公司 | A kind of detection method of low noise than direct sequence signal |
| CN112684251B (en) * | 2019-10-17 | 2022-07-12 | 武汉瑞天波谱信息技术有限公司 | Target signal frequency domain detection method based on power spectrum template |
| CN112436863B (en) * | 2020-10-29 | 2023-05-02 | 西安空间无线电技术研究所 | Signal rapid detection search method based on frequency spectrum dispersion analysis |
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| JP2000252876A (en) * | 1999-03-03 | 2000-09-14 | Asahi Chem Ind Co Ltd | Spread spectrum signal, processor and spread spectrum communication system |
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