CN103780462A - Satellite communication signal modulation identification method based on high-order cumulants and spectrum characteristics - Google Patents

Abstract

The invention discloses a satellite communication signal modulation identification method based on high-order cumulants and spectrum characteristics. The method includes the following steps of carrying out signal band-pass filtering, estimating carrier frequency, estimating the symbol rate, obtaining high-order cumulant parameters, identifying APSK or 16QAM signals, obtaining the number of spectral peaks of a quadratic spectrum, identifying BPSK or MSK signals, obtaining a quadruplicate spectrum, obtaining the number of spectral peaks of the quadruplicate spectrum, identifying pi/4DQPSK signals, obtaining the number of spectral peaks of the quadratic spectrum of a base band, and identifying 6PSK, 8PSK, OQPSK, QPSK signals. According to the satellite communication signal modulation identification method, total blindness identification of a satellite communication signal modulation mode can be achieved, and the method is simple, easy to carry out and high in accuracy.

Description

Satellite communication signal Modulation Identification method based on Higher Order Cumulants and spectrum signature

Technical field

The invention belongs to satellite communication and digital signal processing technique field, particularly a kind of satellite communication signal Modulation Identification method based on Higher Order Cumulants and spectrum signature.

Background technology

Conventional satellite communication signal comprises BPSK (Binary Phase Shift Keying binary phase shift keying), QPSK(Quadrature Phase Shift Keying quaternary phase shift keying), OQPSK(Offset QPSK skew quaternary phase shift keying), π/4DQPSK(π/4Difference Quadrature Phase Shift Keying π/4 differential quadrature phase shift keying), 6PSK(6Phase Shift Keying six phase place phase shift keyings), 8PSK(8Phase Shift Keying octal system phase shift keying), MSK(Minimum Shift Keying minimum shift keying), 16QAM(16Quadrature Amplitude Modulation16 quadrature amplitude modulation), APSK(Amplitude Phase Shift Keying APK amplitude phase shift keying) signal.In non-cooperative communication situation, monitoring and identification communication signal, have using value very widely in civil and military field effectively.Take satellite communication as example, at civil area, whether signal is cognitive is operated in legal running parameter for user in monitor satellite net, detects disabled user's occupying and usurping satellite repeater resource simultaneously; In its military domain, signal cognition is accurately the precondition that realizes space electromagnetic countermeasure and obtain information weight processed.

In the document of the relevant Modulation Identification of having delivered both at home and abroad at present, signal Modulation Identification method roughly can be divided: the maximum likelihood hypothesis testing method based on decision theory and the statistical pattern recognition method based on feature extraction.Maximum likelihood hypothesis detection method is the test problem of the many hypothesis of a kind of likelihood, is characterized in, by observing signal waveform to be identified, being assumed to be a certain candidate's modulation system, is then judged and is determined its modulation system by similitude.These class methods are normally analyzed and obtain certain decision rule for the statistical property of the concrete modulation signal of certain class, thereby are only applicable to the identification of such modulation signal, and identification range is narrow, and algorithm complexity, are difficult for realizing.Know method for distinguishing based on statistical model and comprise the method based on instantaneous temporal signatures, the method based on signal statistics feature and the method based on transform domain feature etc.

For this specific communication scene of satellite communication, these methods also come with some shortcomings: 1, the extraction of institute's use characteristic parameter often needs more priori, is difficult to accomplish total blindness's Modulation Identification; 2, do not consider the impact that raised cosine is shaped on signal characteristic of division, satellite communication signal generally all adopts raised cosine to be shaped, and algorithm identified rate is declined and even lost efficacy; 3, identification kind is few, and the restricted application of algorithm does not have to form the identification system for satellite communication signal.4, algorithm complexity, is difficult to accomplish real-time Modulation Mode Recognition.

Summary of the invention

The object of the present invention is to provide a kind of satellite communication signal Modulation Identification method based on Higher Order Cumulants and spectrum signature, can realize total blindness's Modulation Identification, algorithm simple, be easy to realize, accuracy rate is high.

The technical solution that realizes the object of the invention is: a kind of satellite communication signal Modulation Identification method based on Higher Order Cumulants and spectrum signature, comprises the steps:

10) signal bandpass filtering: receive pending signal data, and it is carried out to bandpass filtering;

20) estimating carrier frequency: filtered signal is carried out to segment processing, calculate the power spectrum of every segment signal, and power spectrum is carried out to smoothing processing, utilize the carrier frequency of frequency algorithm estimated signal placed in the middle;

30) estimate symbol speed: filtered signal is carried out to a square processing, calculate its quadratic power spectrum, detect the baseband spectrum line structure of quadratic power spectrum, utilize the character rate of the line structure characteristic estimating signal of character rate;

40) obtain Higher Order Cumulants parameter: calculate Higher Order Cumulants, obtain Higher Order Cumulants parameter, provide threshold value;

50) APSK or the identification of 16QAM signal: if according to signal Higher Order Cumulants parameter and threshold value comparison, identify APSK or 16QAM signal, identifying finishes, otherwise continues;

60) obtain quadratic power spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal quadratic power spectrum of signal quadratic power spectrum;

70) BPSK or msk signal identification: if identify BPSK or msk signal identification according to quadratic power spectrum peak number order, identifying finishes, otherwise continues;

80) obtain biquadratic spectrum: square signal after treatment is carried out to the high-pass filtering that cut-off frequency is carrier frequency, and then carry out a square processing, calculate the biquadratic spectrum of signal;

90) obtain biquadratic spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal biquadratic spectrum of signal biquadratic spectrum;

100) π/4DQPSK signal identification: if identify π/4DQPSK signal according to biquadratic spectrum peak number order, identifying finishes, otherwise continues;

110) obtain base band quadratic power spectrum spectrum peak number order: according to the baseband spectrum line structure characteristic of signal quadratic power spectrum, detect the ratio of the interior spectral line peak value of base band quadratic power spectrum band limits and average, if be greater than a certain thresholding, adjudicate as spectrum peak, finally calculate the baseband spectrum peak number order of signal quadratic power spectrum;

120) 6PSK, 8PSK, OQPSK, the identification of QPSK signal: according to biquadratic spectrum spectrum peak number order and base band quadratic power spectrum spectrum peak number order, finally identify 6PSK, 8PSK, OQPSK, QPSK signal.

The present invention compared with prior art, its remarkable advantage:

1, be applicable to satellite communication channel feature: satellite communication channel is awgn channel, signal shaping generally all adopts raised cosine to be shaped, and the present invention has taken into full account the impact that raised cosine is shaped on signal Higher Order Cumulants and spectrum signature, is applicable to the feature of satellite communication channel;

2, identify without priori total blindness: the present invention does not rely on priori, comprise rolloff-factor or modulation index, signal to noise ratio, carrier frequency, carrier phase, symbol synchronization etc. accurately, accomplished total blindness's Modulation Mode Recognition;

3, the modulation system kind of identification is many: set up the conventional satellite communication signal Modulation Mode Recognition set of comparatively perfect, conventional satellite communication signal comprises BPSK, QPSK, OQPSK, π/4DQPSK, 6PSK, 8PSK, MSK, 16QAM, APSK signal;

4, implementation complexity is low: the present invention proposes the feature extraction based on base band quadratic power spectrum, omit the calculating of traditional envelope spectrum, quadratic power spectrum, biquadratic spectrum all adopt unified spectrum peak decision method simultaneously, simplify decision rule, reduce the complexity that algorithm is realized, can complete the quick Real time identification of modulation system;

5, recognition accuracy is high: the present invention has introduced Line enhancement algorithm, makes spectral line characteristic more obvious, and the spectrum peak decision method of proposition is more practical, adopts self-adaptive decision threshold simultaneously, has improved Low SNR modulated mode recognition accuracy.

Below in conjunction with the drawings and specific embodiments, the present invention is done further and illustrated.

Accompanying drawing explanation

Fig. 1 is the flow chart that the present invention is based on the satellite communication signal Modulation Identification method of Higher Order Cumulants and spectrum signature.

Fig. 2 is the flow chart of estimating carrier frequency step in Fig. 1.

Fig. 3 is the flow chart of estimate symbol speed step in Fig. 1.

Fig. 4 is the flow chart that obtains Higher Order Cumulants parameter step in Fig. 1.

Fig. 5 is the flow chart that obtains quadratic power spectrum spectrum peak number order step in Fig. 1.

Fig. 6 is the flow chart that obtains biquadratic spectrum spectrum peak number order step in Fig. 1.

Fig. 7 A, 7B are the level and smooth front and back contrast of power spectrum schematic diagrames.

Fig. 8 A, 8B are contrast schematic diagrames before and after bpsk signal square spectrum Line enhancement.

Fig. 9 is simulation result figure of the present invention.

Figure 10 is various modulation system higher order cumulants value tables.

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.

Embodiment

As shown in Figure 1, the present invention is based on the satellite communication signal Modulation Identification method of Higher Order Cumulants and spectrum signature, comprise the steps:

10) signal bandpass filtering: receive pending signal data, and it is carried out to bandpass filtering;

20) estimating carrier frequency: filtered signal is carried out to segment processing, calculate the power spectrum of every segment signal, and power spectrum is carried out to smoothing processing, utilize the carrier frequency of frequency algorithm estimated signal placed in the middle;

As shown in Figure 2, described estimating carrier frequency (20) step comprises:

21) signal subsection: filtered signal data is divided into L section, and calculates the power spectrum X of every segment signal data _i;

22) ask level and smooth power spectrum: multiple power spectrum stacks, be averaging, obtain level and smooth power spectrum

23) intercept effective bandwidth: intercept level and smooth power spectrum effective bandwidth according to the Welch algorithm of simplifying;

Described intercepting effective bandwidth (23) step is specially: start search from level and smooth power spectrum two ends, find out all minimum points, find the minimum point of peak value both sides by adaptive threshold is set, retain the frequency component between minimum point, all the other component zero setting.

24) obtain carrier frequency: utilize frequency algorithm estimated signal placed in the middle carrier frequency.

Described carrier frequency (24) step of obtaining is specially:

The carrier frequency of signal is

$f_c=\frac{\underset{i=1}{\overset{N/2}{\mathrm{\Σ}}}i{\left|X\left(i\right)\right|}^2}{\underset{i=1}{\overset{N/2}{\mathrm{\Σ}}}{\left|X\left(i\right)\right|}^2}\×\frac{f_s}{N}---\left(1\right),$

Wherein, X (i) is the power spectrum of signal, and N is total sampling number, f _sit is sample frequency.

30) estimate symbol speed: filtered signal is carried out to a square processing, calculate its quadratic power spectrum, detect the baseband spectrum line structure of quadratic power spectrum, utilize the character rate of the line structure characteristic estimating signal of character rate;

As shown in Figure 3, described estimate symbol speed (30) step comprises:

31) quadratic power spectrum is calculated: filtered signal is carried out to a square processing, calculate its quadratic power spectrum;

32) Line enhancement: to each sample value of quadratic power spectrum pin, the relatively difference of the mean value of all sample points in it and adjacent domain, thus realize the Line enhancement of quadratic power spectrum;

Described Line enhancement (32) step is specially:

$\mathrm{Env}\_\mathrm{new}\left(k\right)=\frac{\mathrm{Env}\left(k\right)}{\underset{n=1}{\overset{L}{\mathrm{\Σ}}}w\left(n\right)\mathrm{Env}(k+n)},k\∈(0,N/2]---\left(2\right),$

Wherein, N is total sampling number,

for the weighted average of signal envelope, filter length L × N, w (n) is mean filter weights,

The main thought of Line enhancement is exactly each sample value for square spectrum, the relatively difference of the mean value of all sample points in it and adjacent domain, thus and then the result after is relatively carried out to maximum value search and determine character rate information.

33) symbol rate estimation: according to the position of the line structure Characteristics Detection base band quadratic power spectrum spectral line peak value of character rate, if the ratio of the interior peak value of search bandwidth and average is greater than decision threshold, the frequency values that spectrum peak position is corresponding is character rate.

40) obtain Higher Order Cumulants parameter: calculate Higher Order Cumulants, obtain Higher Order Cumulants parameter, provide threshold value;

As shown in Figure 4, described in, obtaining Higher Order Cumulants parameter (40) step comprises:

41) calculate Higher Order Cumulants: the fourth order cumulant C that calculates signal ₄₀, C ₄₂with six rank cumulant C ₆₃;

42) obtain Higher Order Cumulants parameter: measure Higher Order Cumulants parameter by higher order cumulants

F ₁＝|C ₆₃|， (4)

${\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="HDA0000460336970000033.png,HDA0000460336970000041.png"\; state="\{\{state\}\}">F</figure-callout>}}_2=\frac{\left|{\mathrm{<figure-callout\; id="42"\; label="C"\; filenames="HDA0000460336970000023.png"\; state="\{\{state\}\}">C</figure-callout>}}_{42}\right|}{\left|{\mathrm{<figure-callout\; id="40"\; label="C"\; filenames="HDA0000460336970000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_{40}\right|};$

43) provide threshold value: the Variation Features according to the Higher Order Cumulants parameter F 1 of raised cosine shaped signal, F2 with signal to noise ratio, provides threshold value th1, th2.

50) APSK or the identification of 16QAM signal: if according to signal Higher Order Cumulants parameter and threshold value comparison, identify APSK or 16QAM signal, identifying finishes, otherwise continues;

60) obtain quadratic power spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal quadratic power spectrum of signal quadratic power spectrum;

As shown in Figure 5, described in, obtaining quadratic power spectrum spectrum peak number order (60) step is specially:

61) detection bandwidth is set: detect the line structure feature of quadratic power spectrum, set monitoring bandwidth B ₂;

62) maximum time maximum value search: with twice carrier frequency 2F _ccentered by certain band limits (2F of frequency _c-B ₂, 2F _c+ B ₂) interior search maximum and time maximum;

63) spectrum peak judgement: calculate respectively the ratio of maximum and average and time maximum and average, if be greater than a certain thresholding, adjudicating is a spectrum peak;

64) spectrum peak number order calculates: gather and obtain total spectrum peak number order C2.

70) BPSK or msk signal identification: if identify BPSK or msk signal identification according to quadratic power spectrum peak number order, identifying finishes, otherwise continues;

80) obtain biquadratic spectrum: square signal after treatment is carried out to the high-pass filtering that cut-off frequency is carrier frequency, and then carry out a square processing, calculate the biquadratic spectrum of signal;

As shown in Figure 6, described in, obtaining biquadratic spectrum spectrum peak number order (80) step comprises:

81) detection bandwidth is set: detect the line structure feature of biquadratic spectrum, set monitoring bandwidth B ₄;

82) maximum time maximum value search: with four times of carrier frequency 4F _ccentered by certain band limits (4F of frequency _c-B ₄, 4F _c+ B ₄) interior search maximum and time maximum;

83) spectrum peak judgement: calculate respectively the ratio of maximum and average and time maximum and average, if be greater than a certain thresholding, adjudicating is a spectrum peak;

Judgement (83) step in described spectrum peak is specially:

Extract n power spectrum discrete spectrum peak detection parameter as follows

$C_n=\frac{\mathrm{Max}\left({\mathrm{spec}}_n\left(i\right)\right)}{\frac{1}{i_2-i_1}(\underset{i=i_1}{\overset{i=i_2}{\mathrm{\&Sigma;}}}{\mathrm{spec}}_n\left(i\right)-\mathrm{Max}\left({\mathrm{spec}}_n\left(i\right)\right))},i\&Element;[{\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="HDA0000460336970000041.png,HDA0000460336970000043.png"\; state="\{\{state\}\}">i</figure-callout>}}_1,i_2]---\left(5\right),$

Wherein,

the exponent number that wherein n is higher-order spectrum, spec _nfor signal n power spectrum, f _cfor carrier frequency, B is detection bandwidth, and N is that Fourier transform is counted, f _sfor sample frequency.

Often there is adjacent one another are or close maximum and time maximum in the spectrum peak place of actual raised cosine shaping satellite communication signal, if press peak-to-average force ratio threshold judgement, can be mistaken for two spectrum crest lines, for avoiding this situation to occur, spectrum is set peak-to-peak every determination point dn, if two spectral line intervals that rule out are less than the peak-to-peak dot interlace of spectrum, shows that actual is a spectrum crest line, otherwise, be two spectrum crest lines.

84) spectrum peak number order calculates: gather and obtain total spectrum peak number order C4.

90) obtain biquadratic spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal biquadratic spectrum of signal biquadratic spectrum;

100) π/4DQPSK signal identification: if identify π/4DQPSK signal according to biquadratic spectrum peak number order, identifying finishes, otherwise continues;

If C4=2, this signal is π/4DQPSK signal, process ends.

110) obtain base band quadratic power spectrum spectrum peak number order: according to the baseband spectrum line structure characteristic of signal quadratic power spectrum, detect the ratio of the interior spectral line peak value of base band quadratic power spectrum band limits and average, if be greater than a certain thresholding, adjudicate as spectrum peak, finally calculate the baseband spectrum peak number order of signal quadratic power spectrum;

The baseband spectrum peak number order C2_bd of signal quadratic power spectrum.

120) 6PSK, 8PSK, OQPSK, the identification of QPSK signal: according to biquadratic spectrum spectrum peak number order and base band quadratic power spectrum spectrum peak number order, finally identify 6PSK, 8PSK, OQPSK, QPSK signal.

In the time of C4=0, if C2_bd=0, this signal is 6PSK signal, if C2_bd=1, this signal is 8PSK signal, process ends; In the time of C4=1, if C2_bd=0, this signal is OQPSK signal, if C2_bd=1, this signal is QPSK signal, process ends.

The present invention is directed to this application scenarios of satellite communication, take into full account satellite channel feature, by the method that adopts Higher Order Cumulants and spectrum signature to combine, build the satellite communication signal identification set of a comparatively perfect, by introducing power spectrum smoothly and Line enhancement algorithm, improve the accuracy rate of parameter Estimation and Modulation Mode Recognition, realized the accurate Real time identification to conventional satellite communication signal in the situation that there is no priori.

Fig. 7 provided power spectrum of the present invention level and smooth before and after contrast situation, Fig. 8 has provided spectrum improvement situation after employing Line enhancement method.Fig. 9 has provided and has adopted the Modulation Mode Recognition simulation result based on Higher Order Cumulants and spectrum signature.Emulated data is 400 emulation symbols, and the raised cosine roll off factor is 0.35.Can be found out by result, 6PSK and APSK signal recognition accuracy in the time that signal to noise ratio is greater than 8dB reach more than 95%, except 6PSK and APSK signal, other signal is in the time that signal to noise ratio is greater than 5dB, recognition accuracy is more than 95%, BPSK, MSK and π/4DQPSK signal recognition accuracy in the time that signal to noise ratio is greater than 1dB reach more than 95%, have verified the feasibility of the method.

The invention provides a kind of satellite communication signal Modulation Mode Recognition method based on Higher Order Cumulants and spectrum signature; should be understood that; for those skilled in the art; under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.In addition, in the present embodiment not clear and definite each part all available prior art realized.

Claims (10)

1. the satellite communication signal Modulation Identification method based on Higher Order Cumulants and spectrum signature, is characterized in that, comprises the steps:

10) signal bandpass filtering: receive pending modulation signal data, and it is carried out to bandpass filtering;

20) estimating carrier frequency: filtered signal is carried out to segment processing, calculate the power spectrum of every segment signal, and power spectrum is carried out to smoothing processing, utilize the carrier frequency of frequency algorithm estimated signal placed in the middle;

30) estimate symbol speed: filtered signal is carried out to a square processing, calculate its quadratic power spectrum, detect the baseband spectrum line structure of quadratic power spectrum, utilize the character rate of the line structure characteristic estimating signal of character rate;

40) obtain Higher Order Cumulants parameter: calculate Higher Order Cumulants, obtain Higher Order Cumulants parameter, provide threshold value;

50) APSK or the identification of 16QAM signal: if according to signal Higher Order Cumulants parameter and threshold value comparison, identify APSK or 16QAM signal, identifying finishes, otherwise continues;

60) obtain quadratic power spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal quadratic power spectrum of signal quadratic power spectrum;

70) BPSK or msk signal identification: if identify BPSK or msk signal identification according to quadratic power spectrum peak number order, identifying finishes, otherwise continues;

80) obtain biquadratic spectrum: square signal after treatment is carried out to the high-pass filtering that cut-off frequency is carrier frequency, and then carry out a square processing, calculate the biquadratic spectrum of signal;

90) obtain biquadratic spectrum spectrum peak number order: according to the spectrum peak number order of the line structure property calculation signal biquadratic spectrum of signal biquadratic spectrum;

100) π/4DQPSK signal identification: if identify π/4DQPSK signal according to biquadratic spectrum peak number order, identifying finishes, otherwise continues;

110) obtain base band quadratic power spectrum spectrum peak number order: according to the baseband spectrum line structure characteristic of signal quadratic power spectrum, detect the ratio of the interior spectral line peak value of base band quadratic power spectrum band limits and average, if be greater than a certain thresholding, adjudicate as spectrum peak, finally calculate the baseband spectrum peak number order of signal quadratic power spectrum;

120) 6PSK, 8PSK, OQPSK, the identification of QPSK signal: according to biquadratic spectrum spectrum peak number order and base band quadratic power spectrum spectrum peak number order, finally identify 6PSK, 8PSK, OQPSK, QPSK signal.

2. satellite communication signal Modulation Identification method according to claim 1, is characterized in that, described estimating carrier frequency (20) step comprises:

21) signal subsection: filtered signal data is divided into L section, and calculates the power spectrum X of every segment signal data _i;

22) ask level and smooth power spectrum: multiple power spectrum stacks, be averaging, obtain level and smooth power spectrum

23) intercept effective bandwidth: intercept algorithm according to the Welch power spectrum of simplifying and intercept level and smooth power spectrum effective bandwidth;

24) obtain carrier frequency: utilize frequency algorithm estimated signal placed in the middle carrier frequency.

3. satellite communication signal Modulation Identification method according to claim 2, it is characterized in that, described intercepting effective bandwidth (23) step is specially: first start search from level and smooth power spectrum two ends, find out all minimum points, by being set, adaptive threshold finds the minimum point of peak value both sides, then retain the frequency component between minimum point, all the other component zero setting.

4. satellite communication signal Modulation Identification method according to claim 2, is characterized in that, described in obtain carrier frequency (24) step and be specially:

The carrier frequency of signal is

$f_c=\frac{\underset{i=1}{\overset{N/2}{\mathrm{\&Sigma;}}}i{\left|X\left(i\right)\right|}^2}{\underset{i=1}{\overset{N/2}{\mathrm{\&Sigma;}}}{\left|X\left(i\right)\right|}^2}\&times;\frac{f_s}{N}---\left(1\right),$

Wherein, X (i) is the power spectrum of signal, and N is total sampling number, f _sit is sample frequency.

5. satellite communication signal Modulation Identification method according to claim 1, is characterized in that, described estimate symbol speed (30) step comprises:

31) quadratic power spectrum is calculated: filtered signal is carried out to a square processing, calculate its quadratic power spectrum;

32) Line enhancement: to each sample value of quadratic power spectrum pin, the relatively difference of the mean value of all sample points in it and adjacent domain, thus realize the Line enhancement of quadratic power spectrum;

33) symbol rate estimation: according to the position of the line structure Characteristics Detection base band quadratic power spectrum spectral line peak value of character rate, if the ratio of the interior peak value of search bandwidth and average is greater than decision threshold, the frequency values that spectrum peak position is corresponding is character rate.

6. satellite communication signal Modulation Identification method according to claim 5, is characterized in that, described Line enhancement (32) step is specially:

$\mathrm{Env}\_\mathrm{new}\left(k\right)=\frac{\mathrm{Env}\left(k\right)}{\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}w\left(n\right)\mathrm{Env}(k+n)},k\&Element;(0,N/2]---\left(2\right),$

Wherein, N is total sampling number, for the weighted average of signal envelope, filter length L × N, w (n) is mean filter weights,

7. satellite communication signal Modulation Identification method according to claim 1, is characterized in that, described in obtain Higher Order Cumulants parameter (40) step and comprise:

41) calculate Higher Order Cumulants: the fourth order cumulant C that calculates signal ₄₀, C ₄₂with six rank cumulant C ₆₃;

42) obtain Higher Order Cumulants parameter: measure Higher Order Cumulants parameter by higher order cumulants

F ₁＝|C ₆₃|， (4)

$F_2=\frac{\left|C_{42}\right|}{\left|C_{40}\right|};$

43) provide threshold value: the Variation Features according to the Higher Order Cumulants parameter F 1 of raised cosine shaped signal, F2 with signal to noise ratio, provides threshold value th1, th2.

8. satellite communication signal Modulation Identification method according to claim 1, is characterized in that, described in obtain quadratic power spectrum spectrum peak number order (60) step and be specially:

61) detection bandwidth is set: detect the line structure feature of quadratic power spectrum, set monitoring bandwidth B ₂;

62) maximum time maximum value search: with twice carrier frequency 2F _ccentered by certain band limits (2F of frequency _c-B ₂, 2F _c+ B ₂) interior search maximum and time maximum;

63) spectrum peak judgement: calculate respectively the ratio of maximum and average and time maximum and average, if be greater than a certain thresholding, adjudicating is a spectrum peak;

64) spectrum peak number order calculates: gather and obtain total spectrum peak number order C2.

9. satellite communication signal Modulation Identification method according to claim 1, is characterized in that, described in obtain biquadratic spectrum spectrum peak number order (80) step and comprise:

81) detection bandwidth is set: detect the line structure feature of biquadratic spectrum, set monitoring bandwidth B ₄;

82) maximum time maximum value search: with four times of carrier frequency 4F _ccentered by certain band limits (4F of frequency _c-B ₄, 4F _c+ B ₄) interior search maximum and time maximum;

83) spectrum peak judgement: calculate respectively the ratio of maximum and average and time maximum and average, if be greater than a certain thresholding, adjudicating is a spectrum peak;

84) spectrum peak number order calculates: gather and obtain total spectrum peak number order C4.

10. satellite communication signal Modulation Identification method according to claim 9, is characterized in that, judgement (83) step in described spectrum peak is specially:

Extract n power spectrum discrete spectrum peak detection parameter as follows

$C_n=\frac{\mathrm{Max}\left({\mathrm{spec}}_n\left(i\right)\right)}{\frac{1}{i_2-i_1}(\underset{i=i_1}{\overset{i=i_2}{\mathrm{\&Sigma;}}}{\mathrm{spec}}_n\left(i\right)-\mathrm{Max}\left({\mathrm{spec}}_n\left(i\right)\right))},i\&Element;[i_1,i_2]---\left(5\right),$

Wherein,

the exponent number that wherein n is higher-order spectrum, spec _nfor signal n power spectrum, f _cfor carrier frequency, B is detection bandwidth, and N is that Fourier transform is counted, f _sfor sample frequency, often there is adjacent one another are or close maximum and time maximum in the spectrum peak place of actual raised cosine shaping satellite communication signal, if press peak-to-average force ratio threshold judgement, can be mistaken for two spectrum crest lines, for avoiding this situation to occur, spectrum is set peak-to-peak every determination point dn, if two spectral line intervals that rule out are less than the peak-to-peak dot interlace of spectrum, showing actual is a spectrum crest line, otherwise, be two spectrum crest lines.

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