CN109088838A - Pseudo-code-Doppler's quick capturing method of direct expansion dpsk signal under a kind of high dynamic - Google Patents

Abstract

Translated fromChinese

本发明公开了一种高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，包括以下步骤：首先通过载波对接收到的中频直扩DPSK信号进行下变频处理；之后利用非线性变换联合FFT捕获多普勒频偏；再利用多普勒频偏值对载波进行修正；之后用修正后的载波对直扩DPSK信号进行下变频处理；最后通过码相位压缩相关器对多路连续相位本地伪码与多普勒补偿后的中频直扩DPSK信号进行的搜索，获取伪码估计值。本发明能够实现高动态下直扩DPSK信号的捕获，完成伪码相位和多普勒频偏的联合估计，具有较小的多普勒频偏估计误差性能，且具有很好的伪码相位捕获性能，捕获时间短，从而保证接收信号在进入信号跟踪处理模块之前即已得到较好的粗同步，复杂度较低，具有较强的实用价值。

The invention discloses a pseudo-code-Doppler rapid acquisition method of high dynamic down-direct spread DPSK signal, which comprises the following steps: first, the received intermediate-frequency direct-spread DPSK signal is subjected to down-conversion processing through a carrier wave; Combine FFT to capture Doppler frequency offset; then use the Doppler frequency offset value to correct the carrier; then use the corrected carrier to down-convert the direct spread DPSK signal; finally use the code phase compression correlator to perform multiple continuous phase The local pseudo code is searched with the Doppler-compensated intermediate frequency direct spread DPSK signal to obtain the estimated value of the pseudo code. The present invention can realize the acquisition of direct spread DPSK signals under high dynamics, complete the joint estimation of pseudocode phase and Doppler frequency offset, has smaller Doppler frequency offset estimation error performance, and has good pseudocode phase capture High performance, short capture time, so as to ensure that the received signal has been coarsely synchronized before entering the signal tracking processing module, the complexity is low, and it has strong practical value.

Description

Pseudo-code-Doppler's quick capturing method of direct expansion dpsk signal under a kind of high dynamic

Technical field

The invention belongs to direct sequence signal receiver processing technology field, direct expansion dpsk signal under especially a kind of high dynamicPseudo-code-Doppler's quick capturing method.

Background technique

The final goal of direct expansion dpsk signal receiver processing is that despread-and-demodulation goes out to send data, pseudo-code phase and carrier frequencyThe capture of rate is the precondition of correct despread-and-demodulation, and previous receiver is become under the direct expansion dpsk signal received mostlyFrequency carries out pseudo-code phase capture and carrier doppler capturing frequency deviation respectively after handling.Traditional method for acquiring pseudo code has sliding relatedMethod and matching matrix, there are contradictions between acquisition speed and implementation complexity.Simultaneously under high dynamic environment, receiver withUsually there is very high radial velocity between transmitter, this makes reception signal, and there are tens the kHz even Doppler of several hundred kHzFrequency displacement has a huge impact the capture and tracking of spreading code.It then becomes necessary to carrier Doppler frequency carry out capture andCompensation, this is also referred to as carrier wave intercepting and capturing.Then the capture of pseudo-code signal, which becomes, catches pseudo-code phase and carrier doppler frequency deviationIt obtains, this capture time for just needing to grow very much.So being accurately rapidly performed by under high dynamic environment and being captured as technology hardly possiblePoint.

G.J.R.Povey et al. first proposed based on numerical portion matched filter and FFT combination algorithm (PMF-FFT Capturing Models), although this method alleviates influence of the Doppler shift to detection threshold to a certain extent, andThe two dimension capture of pseudo-code phase and carrier wave frequency deviation is realized, but the capture range of this method Doppler shift is smaller, height is dynamicIt is still not applicable under state environment.Thus, how accurately and rapidly to be completed under high dynamic environment spread-spectrum signal pseudo-code phase andDoppler shift capture, becomes the key technology of direct expansion dpsk signal all-digital receiver.And there is no in the prior art can be veryIt adapts to high dynamic environment well and reaches the method for more excellent capture effect, so that the performance of direct expansion dpsk signal all-digital receiver is notIt is good.

Summary of the invention

Technical problem to be solved by the present invention lies in provide a kind of to realize quickly catching for direct expansion dpsk signal under high dynamicThe method obtained completes the Combined estimator of pseudo-code phase and Doppler shift.

The technical solution for realizing the aim of the invention is as follows: pseudo-code-Doppler of direct expansion dpsk signal under a kind of high dynamicQuick capturing method, comprising the following steps:

Step 1 passes through carrier wave f_cDown-converted is carried out to the intermediate frequency direct expansion dpsk signal received；

Step 2 is chosen nonlinear transformation coefficient L and FFT points, and is become using nonlinear transformation joint FFT is lower to step 1Dpsk signal after frequency carries out Doppler shift estimation, obtains Doppler shift value

Step 3 utilizes Doppler shift valueTo carrier wave f_cIt is modified, obtains revised carrier wave f_c'；

Step 4 passes through revised carrier wave f_c' down-converted is carried out to the intermediate frequency direct expansion dpsk signal received, it obtainsObtain the compensated intermediate frequency direct expansion dpsk signal of Doppler；

Step 5 carries out the intermediate frequency direct expansion dpsk signal after multichannel continuous phase local pseudo-code and step 4 Doppler effect correctionSearch obtains pseudo-code estimated valueTo complete pseudo-code-Doppler's fast Acquisition.

Compared with prior art, the present invention its remarkable advantage are as follows: 1) the method for the present invention is simple, it is easy to accomplish, it may be implementedThe fast Acquisition of direct expansion dpsk signal under high dynamic completes the Combined estimator of pseudo-code phase and Doppler shift；2) present invention is logicalNonlinear transformation joint FFT method estimating Doppler frequency deviation is crossed, there is lesser Doppler shift evaluated error performance；3) this hairIt is bright that fast search is carried out to code phase by code phase compressor, reduce total search number, greatly reduces capture time, energyIt is preferably thick synchronous to guarantee that reception signal has just obtained before entering signal tracking (essence is synchronous) processing module.

Present invention is further described in detail with reference to the accompanying drawing.

Detailed description of the invention

Fig. 1 is pseudo-code-Doppler's quick capturing method flow chart of direct expansion dpsk signal under high dynamic of the invention.

Fig. 2 is that the present invention is based on the functional block diagrams of nonlinear transformation-FFT Nonlinear Transformation in Frequency Offset Estimation.

Fig. 3 is that code phase of the present invention compresses relevant functional block diagram.

Fig. 4 is the 3-D graphic schematic diagram that pseudo-code of the embodiment of the present invention-Doppler captures result.

Fig. 5 be the embodiment of the present invention detection probability and false-alarm probability with input signal-to-noise ratio change curve schematic diagram.

Specific embodiment

In conjunction with Fig. 1, pseudo-code-Doppler's quick capturing method of dpsk signal under a kind of high dynamic of the present invention, including it is followingStep:

Step 1 passes through carrier wave f_cDown-converted carried out to the intermediate frequency direct expansion dpsk signal that receives, after down-convertedDpsk signal are as follows:

In formula, ρ (n)=∑ γ_kR₁(-iT_c),For the signal after spread spectrum, N is spreading code period, d_kTo passTransmission of data, c_kFor spreading code, d_k/NTo press spreading code periodic sampling to transmission data, | * |_NFor the modulo-N arithmetic of " * "；R₁(*) is to holdThe continuous time is T_cBase band pulse shape；The centre frequency of BPSK modulator is f₁=f_c-1/(4T_c), f_cFor carrier frequency, T_cForSpreading code chip width；τ is pseudo- code error；f_dFor Doppler shift；For initial phase, it will be assumed that be 0；R_cFor spreading code speedRate；N (n) is white Gaussian noise.

Step 2 chooses nonlinear transformation coefficient L and FFT points, and using nonlinear transformation and FFT to step 1 down coversionDpsk signal afterwards carries out Doppler shift estimation, obtains Doppler shift valueBased on nonlinear transformation-FFT DopplerThe principle of offset estimation is as shown in Fig. 2, core concept is to carry out Doppler shift estimation using nonlinear transformation joint FFT.

After carrying out L nonlinear transformation to the direct expansion dpsk signal y (n) after down coversion, available y'(n) are as follows:

In formula, L is nonlinear transformation coefficient, N'(n) be

In formula, N_L-1,…N₀For the coefficient of each secondary item of noise expansion.

Known ρ (n) ≈ ± 1, therefore when L is taken as even number, spread spectrum data do not influence the estimation of carrier wave frequency deviation, and frequency deviation value meetingBecome original L times.To y'(n) FFT operation is carried out, it will appear peak value on frequency spectrum, and the position of peak value is that Doppler estimatesEvaluation

In formula, R_cFor spread-spectrum code rate；K_maxFor spectrum peak position；N_FFTFor FFT points；L is nonlinear transformationCoefficient.

By the minimal error of formula (4) available offset estimation are as follows:

Frequency offset estimation range are as follows:

Preferably, nonlinear transformation coefficient L takes 4, FFT points to take 2048.

Step 3 utilizes Doppler shift valueTo carrier wave f_cIt is modified, obtains revised carrier wave f_c', formula usedAre as follows:

Step 4 passes through revised carrier wave f_c' down-converted is carried out to the intermediate frequency direct expansion dpsk signal received, it obtainsObtain the compensated intermediate frequency direct expansion dpsk signal of Doppler.

Step 5, access code phase-compression COEFFICIENT K_l, correlator is compressed to multichannel continuous phase local pseudo-code by code phaseIt is scanned for the intermediate frequency direct expansion dpsk signal after step 4 Doppler effect correction, obtains pseudo-code estimated valueTo complete pseudo-code-Doppler's fast Acquisition.

When carrying out code phase search, will also occur correlation peak when pseudo-code phase is near received signal code phase, becauseThis can compress adjacent unit, reduce total search unit number, substantially reduce the thick capture time of signal.

It is as shown in Figure 3 that code phase compresses relevant principle.If the pseudo-code phase compressed coefficient is K_l, then locally compressed code is K_lRoad differs the sub- pseudo-code sequence summation an of code phase each other are as follows:

In formula, c (*) is local pseudo code sequence.Enable locally compressed code phaseI=0,1 ... SN/K_l- 1, whereinN is PN code length, and total number of phases is SN, i.e., pseudo-code phase is divided into SN/K_lA section, is denoted as H.The then resident sheet of i-thGround compressed code are as follows:

δ τ is enabled to indicate to receive the difference of code phase and locally compressed code phase: δ τ=τ-τ_c.If receiving code phaseThen thinkFor optimal compression code phase, it is denoted asτ withDifference be denoted asOptimal compressionPhase intervalIt is denoted as H₁, other compression sections are denoted as H₀.If taking correlation intergal length is entire PN-code captureSN, locally compressed code phase areWhen, while ignoring initial phaseAnd noise contribution n (i), compression correlation function can be with tableIt is shown as:

When its auto-correlation function may be expressed as: pseudo-code after over-sampling

Such as when S=2, only there are correlations on these three code phases.For formula (11), only whenWhenThere are significant correlation energy values, therefore can be by the value interval of m from [0 K_c- 1] it narrows down toFollowing analysis considers a kind of optimal cases, and all 2S-1 there are the phase points of correlation to be entirely located in optimal compression code phase areaBetweenIt is interior, i.e.,AndAt this point, compression correlationIt can indicateIt is as follows:

Section 2 in above formula braces is approximately zero after integrating in a PN-code capture due to the presence of phase difference,Formula (12) can abbreviation are as follows:

By above formula (13b) as can be seen that f_dInfluence to correlation is mainly reflected in ∑ exp (the j2 π f of formula (13a)_dn/R_c), show as Sinc functional form, correlation bandwidth B_c=2R_c/L.Work as f_dBeyond B_cWhen can cause serious decline, influence correctCapture.

Preferably, code phase compressed coefficient K_lChoose 4.

Below with reference to embodiment, present invention is further described in detail.

Embodiment

Simulation parameter is arranged in the present embodiment are as follows: spreading code uses Gold sequence, code length N=1023；Sample frequency f_s=245.52MHz；Carrier frequency f_c=76.725MHz, spread-spectrum code rate R_c=20.46Mchip/s, data rate R_b=20kbps.Code phase error τ=200, Doppler shift f_d=201250Hz, nonlinear transformation coefficient L=4, FFT points are2048 points, pseudo-code compressed coefficient K_l=4, Signal to Noise Ratio (SNR)=- 10dB.

In conjunction with Fig. 4 three-dimensional figure it is found that simulation result pseudo-code differ estimated value1chip is differed with preset value；Doppler shift is estimated as250Hz is differed with preset value, is in teachings, calculation is thus demonstratedMethod has preferable accuracy.

Fig. 5 is Signal to Noise Ratio (SNR) uniform value, Doppler shift f in [- 30dB, 0dB] range_d=80kHz, false-alarm are generalRate P_fThe detection probability of 5000 Monte Carlo simulations and the change curve of false-alarm probability are carried out when=0.001.In Fig. 5, due toCFAR detection thresholding is set, and the constant approach of false-alarm probability is 0；And when SNR >=-21dB, thus detection probability 1 proves to calculateMethod has preferable working performance under low signal-to-noise ratio environment.

The method of the present invention is simple, it is easy to accomplish, fast search is carried out to code phase by code phase compressor, is reduced totalSearch number, greatly reduce capture time, and have that algorithm complexity is small, be completed at the same time pseudo-code phase and Doppler shift is caughtObtain, evaluated error is small, expands the advantages such as processing gain, suitable for the application environment of high dynamic, there is stronger practical value.

Claims (7)

Translated fromChinese

1.一种高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，包括以下步骤：1. a kind of pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under a kind of high dynamics, it is characterized in that, may further comprise the steps:步骤1、通过载波f_c对接收到的中频直扩DPSK信号进行下变频处理；Step 1, carry out down-conversion processing to the received intermediate frequency direct spread DPSK signal by carrier_fc ;步骤2、选取非线性变换系数L与FFT点数，并利用非线性变换联合FFT对步骤1下变频后的DPSK信号进行多普勒频偏估计，获得多普勒频偏值Step 2. Select the nonlinear transformation coefficient L and the number of FFT points, and use the nonlinear transformation combined with FFT to estimate the Doppler frequency offset of the down-converted DPSK signal in step 1, and obtain the Doppler frequency offset value步骤3、利用多普勒频偏值对载波f_c进行修正，获得修正后的载波f_c'；Step 3, using the Doppler frequency offset value Correct the carrier f_c to obtain the corrected carrier f_c ';步骤4、通过修正后的载波f_c'对接收到的中频直扩DPSK信号进行下变频处理，获得多普勒补偿后的中频直扩DPSK信号；Step 4, carry out down-conversion processing to the received intermediate frequency direct spread DPSK signal by the corrected carrier f_c ', and obtain the intermediate frequency direct spread DPSK signal after Doppler compensation;步骤5、对多路连续相位本地伪码与步骤4多普勒补偿后的中频直扩DPSK信号进行搜索，获取伪码估计值从而完成伪码—多普勒快速捕获。Step 5. Search the multi-channel continuous phase local pseudo code and the intermediate frequency direct spread DPSK signal after Doppler compensation in step 4 to obtain the estimated value of the pseudo code In order to complete the pseudo-code-Doppler fast capture.2.根据权利要求1所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，步骤1中下变频处理后的DPSK信号为：2. the pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under high dynamics according to claim 1, it is characterized in that, the DPSK signal after down-conversion processing in the step 1 is:式中，ρ(n)＝∑γ_kR₁(-iT_c)，为扩频后的信号，N为扩频码周期，d_k为传输数据，c_k为扩频码，d_k/N为对传输数据按扩频码周期采样，|*|_N为“*”的模N运算；R₁(*)为持续时间为T_c的基带脉冲波形；BPSK调制器的中心频率为f₁＝f_c-1/(4T_c)，f_c为载波频率，T_c为扩频码码片宽度；τ为伪码误差；f_d为多普勒频偏；为初始相位；R_c为扩频码速率；N(n)为高斯白噪声。In the formula, ρ(n)=∑γ_k R₁ (-iT_c ), is the signal after spreading, N is the spreading code period, d_k is the transmission data, c_k is the spreading code, d_k/N is sampling the transmission data according to the spreading code period, |*|_N is "*" The modulo N operation of ; R₁ (*) is the baseband pulse waveform whose duration is T_c ; the center frequency of the BPSK modulator is f₁ =f_c -1/(4T_c ), f_c is the carrier frequency, and T_c is The chip width of the spreading code; τ is the pseudo-code error; f_d is the Doppler frequency offset; is the initial phase; R_c is the spreading code rate; N(n) is Gaussian white noise.3.根据权利要求2所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，步骤2所述利用非线性变换联合FFT对步骤1下变频后的DPSK信号进行多普勒频偏估计，获得多普勒频偏值所用公式为：3. the pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under high dynamics according to claim 2, it is characterized in that, the DPSK signal after the step 1 down-conversion is utilized in step 2 using nonlinear transformation joint FFT Perform Doppler frequency offset estimation and obtain Doppler frequency offset value The formula used is:式中，R_c为扩频码速率；K_max为频谱峰值所在位置；N_FFT为FFT点数；L为非线性变换系数；y'(n)为L次非线性变换后的直扩DPSK信号。In the formula, R_c is the spreading code rate; K_max is the position of the spectrum peak; N_FFT is the number of FFT points; L is the nonlinear transformation coefficient; y'(n) is the direct spread DPSK signal after L times of nonlinear transformation.4.根据权利要求1所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，步骤2中所述非线性变换系数L取4，FFT点数取2048。4. the pseudo-code-Doppler rapid acquisition method of direct spread DPSK signal under high dynamics according to claim 1, is characterized in that, described in step 2, nonlinear transformation coefficient L gets 4, and FFT point number gets 2048.5.根据权利要求1所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，步骤3所述利用多普勒频偏值对载波f_c进行修正，获得修正后的载波f_c'，所用公式为：5. the pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under high dynamics according to claim 1, is characterized in that, the described step 3 utilizes Doppler frequency offset value Correct the carrier f_c to obtain the corrected carrier f_c ', the formula used is:6.根据权利要求1所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，步骤5所述对多路连续相位本地伪码与步骤4多普勒补偿后的中频直扩DPSK信号进行搜索，获取伪码估计值具体为：6. the pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under high dynamics according to claim 1, is characterized in that, described in step 5 to multi-channel continuous phase local pseudo-code and step 4 Doppler compensation After the intermediate frequency direct spread DPSK signal is searched to obtain the estimated value of the pseudo code Specifically:选取码相位压缩系数K_l，通过码相位压缩相关器对多路连续相位本地伪码与步骤4多普勒补偿后的中频直扩DPSK信号进行搜索，获取伪码估计值Select the code phase compression coefficient K_l , and use the code phase compression correlator to search the multi-channel continuous phase local pseudo code and the intermediate frequency direct spread DPSK signal after Doppler compensation in step 4 to obtain the estimated value of the pseudo code7.根据权利要求6所述的高动态下直扩DPSK信号的伪码—多普勒快速捕获方法，其特征在于，所述码相位压缩系数K_l选取4。7. the pseudo-code-Doppler fast acquisition method of direct spread DPSK signal under high dynamics according to claim 6, is characterized in that, described code phase compression factor K₁ is chosen 4.