CN101388688B - Frequency scanning interference suspending method for direct sequence spread spectrum communication system - Google Patents

Abstract

The invention provides a method for disturbing and inhibiting fractional fourier transformation through adding window segmentation overlapped processing, which comprises: firstly, utilizing the differences between the noise characteristics of a direct-spread communication signal on a fractional fourier region and the energy focusing characteristics of a sweep frequency interfering signal on a corresponding order, finishing the separation between the communication signal and the sweep frequency interference, then, utilizing window functions to inhibit the characteristics of side lobes of the sweep frequency interference, reducing the side lobe leakage of the interfering signal after transformation, enabling the energy of the sweep frequency interference on the fractional fourier region to focus on a major lobe, thereby effectively separating the interference and an useful signal, finally, adopting a method of segmentation overlapped processing, solving the problem that the energy of an edge signal is low due to adding window, inhibiting the energy of the sweep frequency interfering signal to the maximum, simultaneously, guaranteeing signal energy loss as little as possible, achieving higher code error rate performance, and guaranteeing reliable communication of a direct-spread system.

Description

A kind of frequency scanning interference suspending method that is used for direct sequence spread spectrum communication system

Affiliated technical field

The present invention relates to a kind of disturbance restraining method, belong to communication Anti-Jamming Technique field, be used for the inhibition that direct sequence spread spectrum communication system is disturbed frequency sweep.

Background technology

Resistant DS Spread Spectrum System (abbreviation directly-enlarging system) has that antijamming capability is strong, information signal is hidden, is convenient to encryption, random access discrete address and be easy to distinct advantages such as networking, and therefore straight expansion technology is widely used in communication equipment at present.Spread spectrum system is because himself coding gain and processing gain; Has certain anti-interference capability; But the complexity of emittor/receiver and the bandwidth that can supply utilize define the upper limit of processing gain; Thereby when the strong jamming that is exceeded jamming margin, the spread spectrum system performance can severe exacerbation.

It is that a kind of common non-stationary disturbs that linear FM signal (being called LFM again, the Chirp signal) is disturbed, and its energy is dispersed in whole time domain or frequency domain, and directly-enlarging system is had very big harmfulness.For this reason, occurred utilizing in a large number the method for Digital Signal Processing that it is disturbed the research of inhibition (frequency sweep is disturbed and suppressed) cancellation techniques both at home and abroad, and obtained certain achievement.

But prior art and method are disturbed frequency sweep and are suppressed mainly to exist following problem:

(1) traditional converter technique is not good to the frequency sweep interference suppressioning effect, though because fourier transform technique can to a certain degree suppress the arrowband steadily to be disturbed, disturb this broad-band interference that becomes when quick to suppress to have little effect to frequency sweep; And wavelet transformation and Short Time Fourier Transform are suitable for suppressing to have the pulsed interference of burst characteristic; Disturb though become dry when the swept-frequency signal broadband to a certain degree discerned and rejected to the Time-Frequency Analysis Method of propositions such as Amin M G, Ouyang X M, Barbarossa S can; But when a plurality of frequency sweeps interference exist simultaneously; Wigner-Ville distributes because a plurality of interference can't be correctly distinguished in the cross term puzzlement that exists; In addition; The method that suppresses a plurality of interference through the tracking instantaneous frequency only is suitable for the situation that each has only an interference to exist constantly; Barbarossa S etc. has proposed the method that a plurality of interference are discerned in based on WVD-Hough conversion, thereby but the cross term of WVD can form pseudo-spike after the Hough conversion cause the mistake identification to disturbing.

(2) a kind of Adaptive Suppression algorithm that disturbs based on frequency sweep in the DSSS system of fraction Fourier conversion of proposing such as Qi Lin frequency sweep disturbed have certain inhibition effect, but the snr loss is bigger after the conversion.Because when carrying out fraction Fourier conversion because swept-frequency signal has been carried out limited intercepting; Interference signal has produced spectral leakage; Caused bigger snr loss after swept-frequency signal suppressed, when especially existing a plurality of frequency sweeps to disturb, owing to need carry out fraction Fourier conversion and contrary fraction Fourier conversion continuously; The snr loss accumulates obviously, and the directly-enlarging system bit error rate performance worsens obviously.

The present invention is by selecting suitable window function;, the direct-sequence spread-spectrum communication signal that the stack frequency sweep is disturbed carries out the windowing computing earlier before carrying out fraction Fourier conversion; The discontinuous influence that causes in edge when reducing limited intercept signal; Effectively suppress frequency sweep interfering signal secondary lobe; Frequency sweep is disturbed in the fractional order Fourier domain concentration of energy at main lobe, disturbed and useful signal thereby effectively separate; Handle by segmentation overlay again, further reduce the snr loss after suppressing to handle, make system have better bit error rate performance.

In order to understand the present invention better, briefly introduce in the face of fraction Fourier conversion down:

In recent years, (Fractional Fourier Transform FRFT) as a kind of new time frequency analyzing tool, has obtained application more and more widely in the signal processing field to fraction Fourier conversion, has caused the extensive concern of signal processing circle.Fraction Fourier conversion has extensive use at optical field at first, and Almeida was interpreted as the rotation of signal at time-frequency plane to fraction Fourier conversion in 1993, was the popularization of classical Fourier transform; After Turk Ozaktas had proposed a kind of discrete sampling type algorithm suitable with the FFT computational speed in 1996, fraction Fourier conversion just began to be applied in the signal processing field.Fraction Fourier conversion can be regarded a kind of unified time-frequency conversion as; Reflected simultaneously signal the time, frequency domain information; Different with quadratic form time-frequency distributions commonly used is that it representes time-frequency information with unitary variant, and does not have the cross term puzzlement, compares with traditional Fourier transform (being a special case of fraction Fourier conversion in fact); It is suitable for handling non-stationary signal; Especially Chirp class signal, and many free parameters (the conversion exponent number a), thus fraction Fourier conversion often can access traditional time-frequency distributions or effect that Fourier transform can not get under certain conditions; And, therefore when obtaining better effect, need not pay too many calculation cost because it has the fast discrete algorithm of comparative maturity.

It is typical case and effective method that employing carries out based on the fraction Fourier conversion instrument that frequency sweep disturb to suppress; Because the basic function of fraction Fourier conversion is the Chirp base of one group of quadrature on the fractional order frequency domain; Fraction Fourier conversion has the advantage of energy accumulating characteristic to given swept-frequency signal in certain fractional order Fourier domain, so fraction Fourier conversion is particularly suitable for handling swept-frequency signal.Fraction Fourier conversion is a kind of generalized form of Fourier transform.As a kind of new time frequency analyzing tool, fraction Fourier conversion can be interpreted as signal in the rotation of time-frequency plane internal coordinate axle around initial point.

The fraction Fourier conversion of signal x (t) is defined as:

$X_p\left(u\right)=\left\{F_p\right[x\left(t\right)\left]\right\}\left(u\right)={\∫}_{-\∞}^{+\∞}x\left(t\right)\·K_p(t,u)\mathrm{dt}---\left(1\right)$

Wherein: p=2 α/π is the order of fraction Fourier conversion, and α is the anglec of rotation, F _p[] is the fraction Fourier conversion operator notation, K _p(t u) is the transformation kernel of fraction Fourier conversion:

$K_p(t,u)=\left\{\begin{array}{cc}\sqrt{\frac{1-j\&CenterDot;\cot \mathrm{\&alpha;}}{2\mathrm{\&pi;}}}\&CenterDot;\exp (j\&CenterDot;\frac{{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000094885090000031.png,HDA0000094885090000032.png"\; state="\{\{state\}\}">t</figure-callout>}}^2+u^2}{2}\&CenterDot;\cot \mathrm{\&alpha;}-j\&CenterDot;u\&CenterDot;t\&CenterDot;\csc \mathrm{\&alpha;})& \mathrm{\&alpha;}\&NotEqual;\mathrm{n\&pi;}\\ \mathrm{\&delta;}(t-u)& \mathrm{\&alpha;}=2\mathrm{n\&pi;}\\ \mathrm{\&delta;}(t+u)& \mathrm{\&alpha;}=(2n\&PlusMinus;1)\mathrm{\&pi;}\\ & \end{array}\right.---\left(2\right)$

Being inversely transformed into of fraction Fourier conversion:

$x\left(t\right)={\&Integral;}_{-\&infin;}^{+\&infin;}{X}_p\left(u\right)\&CenterDot;K_{-p}(t,u)\mathrm{du}---\left(3\right)$

Summary of the invention

In Resistant DS Spread Spectrum System, suppress to exist the snr loss to cause the problem of error rate of system decreased performance too greatly in order to solve the frequency sweep interference, the present invention proposes the fraction Fourier conversion disturbance restraining method of a kind of windowing, segmentation overlay processing.Frequency sweep interference signal energy being carried out in as far as possible the inhibition the least possible signal energy is run off,, ensure the reliable communication of Resistant DS Spread Spectrum System to reach the higher bit error rate performance more.

Basic principle of the present invention is: at first utilize noise characteristic and frequency sweep interference signal the difference the energy focusing characteristic of corresponding scores rank order between of Resistant DS Spread Spectrum System signal of communication at fractional order Fourier domain, accomplish separating signal of communication and frequency sweep interference; Secondly, the Sidelobe Suppression characteristic of utilizing window function that frequency sweep is disturbed reduces the secondary lobe of interference signal after the FRFT conversion and leaks, and frequency sweep is disturbed in the fractional order Fourier domain concentration of energy at main lobe, disturbs and useful signal of communication thereby effectively separate frequency sweep; At last, the way that adopts segmentation overlay to handle has solved because the problem that the margin signal energy that windowing causes reduces ensures the least possible signal energy loss more when frequency sweep interference signal energy being carried out the as far as possible inhibition.

The present invention realizes through following technical scheme: a kind of frequency scanning interference suspending method that is used for Resistant DS Spread Spectrum System comprises following nine steps:

(1) be that the pending signal f (x) that frequency sweep disturbs that contains of N carries out p rank fraction Fourier conversion with length, p ∈ (0,1) wherein, stepping is Δ p, carries out the frequency sweep interference signal parameters through two-dimentional peak value searching and estimates, draws the frequency modulation rate parameter μ of swept-frequency signal ₀If exist m frequency sweep to disturb, remember that their frequency modulation rate is { μ ₀, μ ₁..., μ _M-1;

(2) be that the pending signal f (x) that frequency sweep disturbs that contains of N is divided into the k section with length, every segment length is M, and each segment data is designated as { f ₀(x), f ₁(x) ..., f _K-1(x) }; KM=N;

(3) data 0 that are M/4 in the preceding benefit length of signal f (x) are removed last M/4 the data of signal f (x), form new data a (x), and a (x) signal length still is N, and it is divided into the k section, and every segment length is M, and each segment data is designated as { a ₀(x), a ₁(x) ..., a _K-1(x) };

(4) remove signal f (x) front M/4 data, mending length in signal f (x) back is the data 0 of M/4, forms new data b (x), and signal b (x) length still is N, and it is divided into the k section, and every segment length is M, and each segment data is designated as { b ₀(x), b ₁(x) ..., b _K-1(x) };

(5) to 2k data segment { a ₀(x), a ₁(x) ..., a _K-1(x); b ₀(x), b ₁(x) ..., b _K-1(x) } multiply by window function w (x) respectively, be p ₀Rank fraction Fourier conversion (p wherein ₀=-2arc cot (μ ₀)/π) obtains p ₀Rank fractional order Fourier domain data { A ₀(ω), A ₁(ω) ..., A _K-1(ω); B ₀(ω), B ₁(ω) ..., B _K-1(ω) };

(6) to 2k data segment { A ₀(ω), A ₁(ω) ..., A _K-1(ω); B ₀(ω), B ₁(ω) ..., B _K-1(ω) }, ask the mould value respectively, calculate the adaptive threshold T=θ+K σ (wherein T is a threshold value, and θ is an average, and σ is a variance, and K is a regulatory factor) of each data segment, the data that surpass thresholding T in the data segment are changed to threshold T, suppress the frequency sweep interference signal;

(7) with the result of step (6), promptly 2k data segment after the mistake threshold processing carries out p ₀The contrary fraction Fourier conversion in rank (p wherein ₀=-2arc cot (μ ₀)/π), obtain time domain data a ' ₀(ω), a ' ₁(ω) ..., a ' _K-1(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' _K-1(ω) };

(8) to 2k data segment a ' ₀(ω), a ' ₁(ω) ..., a ' _K-1(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' _K-1(ω) } go overlapping processing, at first 2k data segment is arranged as a ' ₀(ω), b ' ₀(ω), a ' ₁(ω), b ' ₁(ω) ..., a ' _K-1(ω), b ' _K-1(ω) }, each data segment, length is M, and 2k data segment total length is 2kM=2N; M/4 data of preceding M/4 that removes each data segment again and back, obtain a new 2k data segment a " ₀(ω), b " ₀(ω), a " ₁(ω), b " ₁(ω) ..., a " _K-1(ω), b " _K-1(ω) }, be designated as f ' (x), each data segment, length becomes M/2, and 2k data segment total length is kM=N, and f ' is (x) consistent with the length of handling preceding f (x) signal;

(9) if exist a plurality of frequency sweeps to disturb repeating step (2)-(8).Conversion exponent number in the step each time (5) is: p _i=-2arccot (μ _i)/π, wherein μ _i∈ { μ ₀, μ ₁..., μ _M-1.

Theoretical foundation of the present invention and derivation process are following:

(1) swept-frequency signal is at the focus characteristics of corresponding scores rank Fourier domain;

The basic function of fraction Fourier conversion is the Chirp base of one group of quadrature on the fractional order frequency domain; A swept-frequency signal will show as an impulse function in suitable fractional order Fourier domain; When getting order is p ∈ (0; 1) time, swept-frequency signal frequency modulation rate μ and focusing order p existence following corresponding relation: μ=-cot (p pi/2).

Do theoretical derivation in the face of swept-frequency signal at the focus characteristics of corresponding fractional order Fourier domain down, establish swept-frequency signal and be:

With the theoretical formula (3) of following formula substitution fraction Fourier conversion, then its p rank fraction Fourier conversion is shown below, wherein p=α 2/ π:

When μ=-cot α, f _mDuring=ucsc α, the fractional Fourier amplitude spectrum of g (t) (fraction Fourier conversion mould square) obtains peak value, and peak value is:

${\left|G_{\mathrm{\&alpha;}}\left(u\right)\right|}_{\mathrm{<figure-callout\; id="2"\; label="max"\; filenames="HDA0000094885090000031.png,HDA0000094885090000032.png"\; state="\{\{state\}\}">max</figure-callout>}}^2={\left|G_{\mathrm{\&alpha;}}\left(u\right)\right|}^2{|}_{\mathrm{\&mu;}=-\cot \mathrm{\&alpha;},f_m=u\csc \mathrm{\&alpha;}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="HDA0000094885090000031.png,HDA0000094885090000032.png"\; state="\{\{state\}\}">A</figure-callout>}}^2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000094885090000031.png,HDA0000094885090000032.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{\left|\sin \mathrm{\&alpha;}\right|}---\left(6\right)$

According to swept-frequency signal frequency modulation rate μ, can be through making p rank (fraction Fourier conversion of p=-2arccot (μ)/π), the main energy of extraction swept-frequency signal.The fractional order Fourier domain focus characteristics of swept-frequency signal is shown in accompanying drawing 1.And the statistical property of DS spread spectrum signal does ..., it is in that fractional order Fourier domain is equal arbitrarily ..., therefore can utilize fraction Fourier conversion that the focusing of Chirp signal is separated the frequency sweep interference with spread-spectrum signal.

(2) Fourier domain adds window property to swept-frequency signal on the corresponding scores rank;

Swept-frequency signal is sampled; Get limited data and carry out fraction Fourier conversion, the process of signal cutout is equivalent to signal times with rectangular window function, and the signal windowing is inevitable; Signal is multiplied each other by a window function and means that total conversion is the convolution of desired conversion and window function conversion; If the real power concentration of signal is in a frequency band, this convolution algorithm will cause the spectral leakage in fractional order territory this arrowband power expansion to the scope of closing on.Revealing effect is that discrete fraction rank Fourier transform is intrinsic; Can adopt the window function weighting technique; Reduced the caused secondary lobe component of brink than rectangular window function is slick and sly on the edge of through selecting suitable window function to make, reached the purpose that suppresses spectral leakage by weighted signal.

With the rectangular window is example, and only than the low 13.46dB of main lobe, promptly the Sidelobe Suppression degree has only 13.46dB to its first secondary lobe; For the interference bigger tens decibels than useful signal; Its secondary lobe is also big a lot of than signal, when disturbing inhibition, just causes the not thorough of interference eliminated; Or increased the bandwidth range of eliminating, thereby increased the weight of damage to useful signal.For the spectral leakage that reduces to disturb, must adopt the lower window function of secondary lobe.But when secondary lobe reduced, main lobe broadened rapidly, therefore needed to select suitable window function.Fig. 2 provides the amplitude spectrum characteristic of various window functions at fractional order Fourier domain, can find out that the rectangular window sidelobe performance is not as the other types window function.Table 1 is that the parameter of various window functions compares, and according to directly-enlarging system and frequency sweep characteristics of interference, the present invention selects for use Hamming window as the signal weighting window function.

The various window functions of table 1 relatively

Window function	Main lobe width	Side lobe peak decay (dB)	Stopband minimal attenuation (dB)
				Rectangle	4π/N	-13	-21
The Chinese is peaceful	8π/N	-31	-44
				Hamming	8π/N	-41	-53
Blacknam	12π/N	-57	-74

(3) segmentation overlay handling principle

Carry out the discontinuous influence that windowing has reduced MARG to received signal, but can twist signal to a certain extent after windowing is blocked.Accompanying drawing 2 (c) disturbs the windowing result for frequency sweep, can find out that by figure tangible distortion has appearred in the edge of signal, has caused the snr loss.

In order to reduce this distortion, can adopt overlapping treatment technology.Adopt the two paths of signals treatment channel, the first via is at first added the inhibit signal that primary signal M/4 is ordered that is input as of M/4 individual zero, the second tunnel before primary signal; Two-way carries out after the conversion process; Abandon the sampling point of each M/4 of front and back, M/2 sampling point in the middle of keeping, then that two paths of signals is synthetic.The purpose of doing like this is to remove owing to bigger signal component is twisted in windowing, keeps the very little signal of loss, and is when two-way synthesizes one the tunnel, just less to the distortion of whole signal.Accompanying drawing 3 (d) has provided through overlapping processing back signal waveform, compares accompanying drawing 2 (c), and the waveform of handling the back signal more solves primary signal.Accompanying drawing 4 has provided the realization block diagram, and accompanying drawing 5 has provided the flow chart of overlapping processing.

In the interference of fractional order Fourier domain suppresses; Adopt threshold detection method, because spread-spectrum signal adds that the frequency spectrum of Gaussian noise is comparatively smooth, and the frequency sweep interference has aggregation properties; So set a rational threshold value as the case may be; Data point to surpassing threshold value is carried out zero setting or clamper, and this method is simple, be applicable to require to eliminate fast interference effect occasion.Obviously, the whether suitable of selection of threshold is the key of this algorithm.To this; Can utilize the K-Sigma algorithm; Thresholding is set is: Th=E+K σ, and wherein E and σ receive average and the standard deviation of signal at fractional order Fourier domain, and K changes adaptively selected quantizing factor with σ; Choose corresponding K according to performance requirement and just can calculate the interference eliminated thresholding, accomplish elimination disturbing.

The swept-frequency signal disturbance restraining method that the present invention proposes based on Resistant DS Spread Spectrum System, its beneficial effect is:

(1) the present invention has utilized the Resistant DS Spread Spectrum System signal of communication in the noise characteristic of fractional order Fourier domain and the difference between the energy focusing characteristic of frequency sweep interference signal at corresponding order; Completion separates signal of communication and frequency sweep interference; A swept-frequency signal will show as an impulse function in suitable fractional order Fourier domain; Shown in accompanying drawing 1, so select for use this instrument of fraction Fourier conversion to disturb the time frequency analyzing tool of handling than adopting other that remarkable advantages is arranged to frequency sweep.

(2) the swept-frequency signal disturbance restraining method based on Resistant DS Spread Spectrum System of the present invention's proposition; The Sidelobe Suppression characteristic of having utilized window function that frequency sweep is disturbed; Reduce the snr loss who causes after suppressing to disturb, handle through segmentation overlay again, when frequency sweep interference signal energy being carried out the as far as possible inhibition, ensure the least possible signal energy loss more; To reach the higher bit error rate performance, ensured the reliable communication of Resistant DS Spread Spectrum System.Shown in accompanying drawing 6; Simulation parameter is: the PN code length is 64; Signal to noise ratio is-10dB that jamming-to-signal ratio is changed by 0-30dB, single frequency sweep interference; By adopting fraction Fourier conversion to disturb rejection to be superior to adopting Fourier transform among the figure, has more dominance ability and adopt the windowing segmentation overlay to handle fraction Fourier conversion.

(3) frequency scanning interference suspending method based on Resistant DS Spread Spectrum System of the present invention's proposition disturbs advantages more obvious to a plurality of frequency sweeps.Because when existing a plurality of frequency sweeps to disturb, need carry out fraction Fourier conversion and contrary fraction Fourier conversion at different orders, owing to be serial process, the snr loss has the accumulation benefit, and is very big to the bit error rate performance influence of system.The inventive method is owing to adopted windowing and the segmentation overlay processing, and the mid portion of each intercepting concentration of energy has reduced the snr loss.Shown in accompanying drawing 7, simulation parameter is consistent with Fig. 6, but exists two frequency sweeps to disturb.There is figure to know, when having a plurality of interference, adopts the windowing segmentation overlay to handle fraction Fourier conversion and disturb the bit error rate performance of inhibition obviously to be superior to original method.

(4) method that proposes of the present invention can parallel work-flow, helps flowing water and realizes, is fit to the Rapid Realization of hardware platform.Because the two paths of signals that segmentation overlay is divided into, its processing method is consistent, so be fit to the hardware continuous productive process.In addition, fraction Fourier conversion has the fast discrete algorithm to support, and amount of calculation and FFT are suitable, realize simple.

Description of drawings

The fractional order Fourier domain focus characteristics of Fig. 1-swept-frequency signal;

Fig. 2-swept-frequency signal time-domain windowed sketch map: (a) swept-frequency signal time domain waveform, (b) window function waveform, (c) swept-frequency signal waveform after the windowing;

The overlapping processing sketch map of Fig. 3-swept-frequency signal piecemeal: (a) swept-frequency signal time domain waveform, (b) first via signal windowing waveform, (c) the second road signal windowing waveform (d) goes overlapping processing postwave shape;

Fig. 4-based on the overlapping processing of the windowing in the fraction Fourier conversion interference mitigation technology;

Fig. 5-overlapping handling process;

Fig. 6-single frequency sweep disturbs rejection relatively;

Fig. 7-two frequency sweep disturbs rejection relatively.

Embodiment

Based on the argumentation in front " summary of the invention " part, the inventive method is elaborated below in conjunction with accompanying drawing and actual example.

The frequency scanning interference suspending method that the present invention proposes based on Resistant DS Spread Spectrum System, its theory diagram can be referring to accompanying drawing 4 and accompanying drawing 5, and concrete implementation is summarized as follows:

Suppose that input signal f (x) is for being mixed with 2 different frequency modulation rate { μ ₀, μ ₁Direct-sequence spread-spectrum communication signal that frequency sweep is disturbed, and length N is 8192 points, performing step is following:

(1) gets stepping Δ p=0.01; P ∈ (0; 1); Input signal f (x) is carried out p rank totally 100 fraction Fourier conversions, carry out the frequency sweep interference signal parameters through two-dimentional peak value searching and estimate, the frequency modulation rate parameter that can draw 2 frequency sweep interference signals is for

(2) be that 8192 signal f (x) is divided into 8 sections with length, every segment length M is 1024, and each segment data is designated as { f ₀(x), f ₁(x) ..., f ₇(x) };

(3) before f (x) signal, mending length is the data 0 of M/4=256, removes the data of f (x) signal last 256, forms new data a (x), and a (x) signal length is 8192 still, is divided into 8 sections, and every segment length is 1024, and each segment data is designated as { a ₀(x), a ₁(x) ..., a ₇(x) };

(4) data of removal f (x) signal front 256, benefit length is 256 data 0 behind f (x) signal, forms new data b (x), and b (x) signal length is 8192 still, is divided into 8 sections, and every segment length is 1024, and each segment data is designated as { b ₀(x), b ₁(x) ..., b ₇(x) };

(5) to 16 data segment { a ₀(x), a ₁(x) ..., a ₇(x); b ₀(x), b ₁(x) ..., b ₇(x) } multiply by Hamming window function w (x) respectively, be p ₀The rank fraction Fourier conversion (wherein

), obtain p ₀Rank fractional order Fourier domain data { A ₀(ω), A ₁(ω) ..., A ₇(ω); B ₀(ω), B ₁(ω) ..., B ₇(ω) };

(6) to 16 data segment { A ₀(ω), A ₁(ω) ..., A ₇(ω); B ₀(ω), B ₁(ω) ..., B ₇(ω) }, ask the mould value respectively, calculate the adaptive threshold T=θ+K σ (wherein T is a threshold value, and θ is an average, and σ is a variance, and K is a regulatory factor) of each data segment, the data that surpass thresholding in the data segment are changed to threshold value, suppress the frequency sweep interference signal;

(7) 16 data segments will crossing after the threshold processing carry out p ₀The contrary fraction Fourier conversion in rank (wherein

), obtain time domain data a ' ₀(ω), a ' ₁(ω) ..., a ' ₇(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' ₇(ω) };

(8) to 16 data segments a ' ₀(ω), a ' ₁(ω) ..., a ' ₇(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' ₇(ω) } go overlapping processing, at first 16 data segments are arranged as a ' ₀(ω), b ' ₀(ω), a ' ₁(ω), b ' ₁(ω) ..., a ' ₇(ω), b ' ₇(ω) }, each data segment, length is that 1024,16 data segment total lengths are 16382; Remove again each data segment preceding 256 with back 256 data, obtain 16 new data segments a " ₀(ω), b " ₀(ω), a " ₁(ω), b " ₁(ω) ..., a " ₇(ω), b " ₇(ω) }, be designated as f ' (x), it is 8192 that each data segment, length becomes 512,16 data segment total lengths, and f ' is (x) consistent with the length of handling preceding f (x) signal;

(9) be that to exchange frequency be μ more than ₀Frequency sweep disturb and to suppress repeating step (2)-(8), the wherein p in step (5) and (7) ₀Change p into ₁,

Through above 9 steps, accomplish input signal f (x) is separated 2 different frequency modulation rate { μ ₀, μ ₁Frequency sweep interference and direct-sequence spread-spectrum communication signal, having suppressed the frequency sweep interference at different fractional order Fourier domains simultaneously, windowing and segmentation overlay are handled and have been reduced the snr loss, guarantee the proper communication of directly-enlarging system.

Above-described specific descriptions; Purpose, technical scheme and beneficial effect to invention have carried out further explain, and institute it should be understood that the above is merely specific embodiment of the present invention; And be not used in qualification protection scope of the present invention; All within spirit of the present invention and principle, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1. a frequency scanning interference suspending method that is used for direct sequence spread spectrum communication system is characterized in that, comprises following nine steps:

(1) be that the pending signal f (x) that frequency sweep disturbs that contains of N carries out p rank fraction Fourier conversion with length, p ∈ (0,1) wherein, stepping is Δ p, carries out the frequency sweep interference signal parameters through two-dimentional peak value searching and estimates, draws the frequency modulation rate parameter μ of swept-frequency signal ₀If exist m frequency sweep to disturb, remember that their frequency modulation rate is { μ ₀, μ ₁..., μ _M-1;

(2) be that the pending signal f (x) that frequency sweep disturbs that contains of N is divided into the k section with length, every segment length is M, and each segment data is designated as { f ₀(x), f ₁(x) ..., f _K-1(x) }; KM=N;

(3) data 0 that are M/4 in the preceding benefit length of signal f (x) are removed last M/4 the data of signal f (x), form new data a (x), and a (x) signal length still is N, and it is divided into the k section, and every segment length is M, and each segment data is designated as { a ₀(x), a ₁(x) ..., a _K-1(x) };

(4) remove signal f (x) front M/4 data, mending length in signal f (x) back is the data 0 of M/4, forms new data b (x), and signal b (x) length still is N, and it is divided into the k section, and every segment length is M, and each segment data is designated as { b ₀(x), b ₁(x) ..., b _K-1(x) };

(5) to 2k data segment { a ₀(x), a ₁(x) ..., a _K-1(x); b ₀(x), b ₁(x) ..., b _K-1(x) } multiply by window function w (x) respectively, be p ₀Rank fraction Fourier conversion, wherein p ₀=-2arc cot (μ ₀)/π obtains p ₀Rank fractional order Fourier domain data { A ₀(ω), A ₁(ω) ..., A _K-1(ω); B ₀(ω), B ₁(ω) ..., B _K-1(ω) };

(6) to 2k data segment { A ₀(ω), A ₁(ω) ..., A _K-1(ω); B ₀(ω), B ₁(ω) ..., B _K-1(ω) }, ask the mould value respectively, calculate the adaptive threshold T=θ+K σ of each data segment, wherein T is a threshold value, and θ is an average, and σ is a variance, and K is a regulatory factor, and the data that surpass thresholding T in the data segment are changed to threshold T, suppresses the frequency sweep interference signal;

(7) with the result of step (6), promptly the data segment of the 2k after the threshold processing carries out p ₀Rank contrary fraction Fourier conversion, wherein p ₀=-2arccot (μ ₀)/π, obtain time domain data a ' ₀(ω), a ' ₁(ω) ..., a ' _K-1(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' _K-1(ω) };

(8) to 2k data segment a ' ₀(ω), a ' ₁(ω) ..., a ' _K-1(ω); B ' ₀(ω), b ' ₁(ω) ..., b ' _K-1(ω) } go overlapping processing, at first 2k data segment is arranged as a ' ₀(ω), b ' ₀(ω), a ' ₁(ω), b ' ₁(ω) ..., a ' _K-1(ω), b ' _K-1(ω) }, each data segment, length is M, and 2k data segment total length is 2kM=2N; M/4 data of preceding M/4 that removes each data segment again and back, obtain a new 2k data segment a " ₀(ω), b " ₀(ω), a " ₁(ω), b " ₁(ω) ..., a " _K-1(ω), b " _K-1(ω) }, be designated as f ' (x), each data segment, length becomes M/2, and 2k data segment total length is kM=N, and f ' is (x) consistent with the length of handling preceding f (x) signal;

(9) if exist a plurality of frequency sweeps to disturb, repeating step (2)-(8), the conversion exponent number in the step each time (5) is: p _i=-2arccot (μ _i)/π, wherein μ _i∈ { μ ₀, μ ₁..., μ _M-1.

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