CN102680988B - High-sensitivity navigation satellite signal nonlinear acquiring method and device - Google Patents

Abstract

The invention aims to provide a high-sensitivity navigation satellite signal nonlinear acquiring method and device. Relevant power loss is reduced by using a DBZP (Double Block Zero Padding) technology in the method and device; the time for relevant calculation is shortened by using an FFT (Fast Fourier Transform Algorithm); the signal to noise ratio for system output is increased by utilizing the characteristic of a nonlinear bistable stochastic resonance system; and an MTM (Maximum to Mean) threshold detection method is introduced in the acquiring process, so that the detecting accuracy is improved. By using the high-sensitivity navigation satellite signal nonlinear acquiring method and device, the GPS (Global Positioning System) signal acquiring sensitivity can be increased to the maximum extent; and the acquiring time can be greatly shortened to the great extent, so that the technical support is provided for the real-time and high-sensitivity acquisition of a weak GPS signal.

Description

The non-linear catching method of high-sensitivity navigational satellite signal and device

Technical field

A little less than the present invention is applicable to, the capturing navigation satellite signal field, be specifically related to the non-linear catching method of a kind of high-sensitivity navigational satellite signal and device.

Background technology

In recent years, GPS (Global Positioning System, GPS) has obtained using more and more widely.Along with deepening continuously of this location technology development, the user is also more and more higher to its request for utilization, and non-blind area, high sensitivity, real-time location and navigation become the direction of this technical development.Yet the overwhelming majority uses the user distributions of hand-held positioning equipment in the intensive urban area of high building, and the most of the time is in indoor.Because the phenomenons such as blocking of being subject to, multipath and interference are more serious, compare with conventional environment, gps signal is in indoor environment, energy has more weakening and decline, larger delay is arranged time of arrival, and received signal to noise ratio has deterioration greatly, so, its availability and bearing accuracy all can descend greatly, the overall performance severe exacerbation of GPS.Wait under the low signal-to-noise ratio environment indoor, to the working portion that the GPS receiver starts at first, namely the performance index of capturing function module are had higher requirement, and must the fast high-sensitive degree catch the signal under the low signal-to-noise ratio environment.But present GPS capture technique almost is difficult to satisfy this requirement, and existing GPS receiver is difficult to work indoor the grade under environment.The catching methods such as common coherent integration, non-coherent integration, differential coherence integration can improve sensitivity to a certain extent, but all require integration time longer, the requirement that can't satisfy indoor weak signal high sensitivity and catch in real time.If gps signal can not be captured by the fast high-sensitive degree, so follow-up all functions are all with influenced, such as tracking, navigation message extraction, location compute etc.

2011 04 month " systems engineering and electronic technology " the 33rd volume the 4th is interim has proposed a kind of " based on the high sensitivity GPS signal capture algorithm of accidental resonance ", at first this algorithm carries out the relevant pre-service of segmentation with the part matched filter to gps signal, then utilize accidental resonance to improve the signal to noise ratio (S/N ratio) of signal after pre-service, realize obtaining higher acquisition sensitivity in relatively short relevant accumulated time.Yet this algorithm is when large and integration time is longer at the gps signal Doppler shift, to cause spreading rate that larger variation occurs, thereby to code cycle generation considerable influence, when digital medium-frequency signal and local signal being done when relevant, can cause the correlation peak decay larger, thereby affect acquisition sensitivity; And the part matched filtering in above-mentioned algorithm is a bit ofly to do relevantly, causes preprocessing process consuming time larger, is difficult to reach the requirement that fast high-sensitive degree gps signal is caught.

Summary of the invention

Technical matters to be solved by this invention is to provide the non-linear catching method of a kind of high-sensitivity navigational satellite signal and device, and the method can effectively reduce with device the loss that large Doppler frequency causes related power in correlated process; Utilize the characteristic of nonlinear system-bi-stable stochastic resonance theory system, namely under certain condition, the characteristic that noise energy can shift to signal energy improve the gps signal acquisition sensitivity to greatest extent; And can reduce to the utmost capture time, catching for the real-time high sensitivity of weak gps signal provides technical support.

For addressing the above problem, the present invention is achieved by the following scheme:

The non-linear catching method of a kind of high-sensitivity navigational satellite signal of the present invention comprises the steps:

Step 1: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling, and set suitable Doppler shift variable initial value and maximal value, namely set the Doppler shift hunting zone, set simultaneously the ratio of Doppler shift scouting interval, MTM(maximum related value and relevant average) detection threshold, bi-stable stochastic resonance theory systematic parameter, defend asterisk variable initial value and defend the asterisk maximal value;

Step 2: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift;

Step 3: respectively the satellite-signal after sampling and local pseudo-code satellite-signal are carried out two pieces zero expansions;

Step 4: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and local pseudo-code satellite-signal after expanding through two pieces zero;

Step 5: correlated results is processed, and preserved the solid part signal of correlated results;

Step 6: the solid part signal to correlated results carries out the double sampling accidental resonance;

Step 7: the signal of exporting in step 6 is done Fourier transform and delivery;

Step 8: to each satellite, the maximal value after delivery in the searching step 7 on frequency direction and code time-delay direction; Namely to each satellite, at first seek the maximal value after delivery and preservation in step 7 corresponding to original frequency; Then return to step 2 and find out the maximal value after delivery and preservation in step 7 corresponding to next Doppler frequency; Until preserve the maximal value after delivery in step 7 corresponding to all frequencies of this satellite; The last maximal value of a maximal value after as this satellite delivery of finding out from the maximal value after delivery corresponding to above-mentioned all frequencies again;

Afterwards, maximal value after this satellite delivery is compared with the detection threshold of setting in step 1, if this maximal value is greater than the detection threshold of setting in step 1, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass the detection threshold of setting in step 1, repeating step two next satellite of search, until searched for all satellites, withdraw from and catch, and this moment, expression was caught unsuccessful.

The described double sampling accidental resonance of above-mentioned steps six step comprises double sampling and accidental resonance step, namely at first the solid part signal of the correlated results preserved is carried out double sampling, makes the frequency of signal after sampling meet the requirement of small parameter accidental resonance; Then allow the signal after sampling enter bi-stable stochastic resonance theory system and the output of resonating.

Above-mentioned Doppler shift hunting zone is preferably-10KHz～10KHz.

The above-mentioned Doppler shift scouting interval is preferably 5000Hz, so only need search can search for 4 times 1 gps satellite-10KHz～10KHz Doppler shift scope, thereby greatly shortened search time, improved capture rate.

Above-mentioned detection threshold is preferably between 3～7.

Above-mentioned bi-stable stochastic resonance theory systematic parameter is a=1, b=1.

The above-mentioned initial value of defending the asterisk variable is 1, and maximal value is 30.

The non-linear acquisition equipment of a kind of high-sensitivity navigational satellite signal of the present invention comprises as lower module:

The frequency-change sampling module: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling;

Local pseudo-code generator: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift;

The zero module of expanding of two pieces: respectively two pieces zero expansions are carried out in the local pseudo-code satellite-signal of the satellite-signal after the frequency-change sampling module samples and local pseudo-code generator generation;

Fast Fourier Transform (FFT) cyclic convolution correlation module: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and the local pseudo-code satellite-signal of expanding module output through two pieces zero;

Get the real part module: correlated results is processed, and preserved the solid part signal of correlated results;

Double sampling accidental resonance module: the solid part signal of getting the correlated results that the real part module preserves is carried out double sampling, make it pass through bi-stable stochastic resonance theory system and the output of resonating;

Fourier transform and delivery module: the signal to the output of double sampling accidental resonance module is done Fourier transform and delivery;

The ratio of MTM(maximum related value and relevant average) threshold test module: to every satellite, seek the maximal value of Fourier transform and the output of delivery module on frequency direction and code time-delay direction, namely to each satellite, at first seek the maximal value after delivery corresponding to original frequency and preserve; Then repeat to return maximal value and preservation after local pseudo-code generator is found out delivery corresponding to next Doppler frequency, until preserve the maximal value after delivery corresponding to all frequencies of this satellite; The last maximal value of a maximal value after as this satellite delivery of finding out from the maximal value after delivery corresponding to above-mentioned all frequencies again;

If the maximal value after this satellite delivery is greater than predefined detection threshold, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass predefined detection threshold, return to local pseudo-code generator and search for next satellite, until searched for all satellites, withdraw from and catch, at this moment, expression is caught unsuccessful.

Above-mentioned double sampling accidental resonance module preferably includes secondary sampling unit and accidental resonance unit, wherein, secondary sampling unit carries out double sampling to the solid part signal of the correlated results getting the real part module and preserve, makes the frequency of signal after double sampling meet the small parameter semaphore request of bi-stable stochastic resonance theory; The output of resonating of the signal of accidental resonance unit after to double sampling.

Compared with prior art, the present invention has improved the gps signal acquisition sensitivity to greatest extent within the short time of trying one's best.This invention adopts the DBZP technology to reduce the related power loss; Reduced with the FFT technology and done relevant required time; Utilizing the characteristic of non-linear bi-stable stochastic resonance theory system---the signal function under very noisy disturbs is when the bi-stable stochastic resonance theory nonlinear system, signal and noise are under the synergy of nonlinear system, noise energy can occur to the transfer of signal energy, generation is similar to the resonance output in mechanics, thereby greatly improves system's output signal-to-noise ratio; Introduced MTM(maximum related value and relevant average ratio in acquisition procedure) threshold detection method, improved correct verification and measurement ratio.

Description of drawings

Fig. 1 is a kind of high-sensitivity navigational satellite signal acquisition system schematic diagram.

Embodiment

A kind of high-sensitivity navigational satellite signal acquisition methods as shown in Figure 1, comprises the steps:

Step 1: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling, and set suitable Doppler shift variable initial value and maximal value, namely set the Doppler shift hunting zone, set simultaneously the ratio of Doppler shift scouting interval, MTM(maximum related value and relevant average) detection threshold, bi-stable stochastic resonance theory systematic parameter, defend asterisk variable initial value and defend the asterisk maximal value.

In the present invention, described Doppler shift hunting zone is-10KHz～10KHz.The scouting interval of described Doppler shift is 5000Hz.Described detection threshold refers to the detection threshold of MTM, and wherein MTM represents the ratio of maximum related value and relevant average, if calculate gained MTM value over detection threshold B _T, think that namely signal is accurately caught, in the present invention, described detection threshold B _TBe set as between 3～7.Described bi-stable stochastic resonance theory systematic parameter a=1, b=1.According to the number of present gps satellite, in the present invention, the described initial value design of defending the asterisk variable is 1, and maximal value is set as 30.

From the L1 frequency range GPS simulating signal down coversion of satellite launch and the digital medium-frequency signal after sampling be

$r\left(t_j\right)=\mathrm{Ad}\left(t_j\right)C\left((t_j-\mathrm{\τ})(1+\frac{f_d}{f_{L1}})\right)\cos (2\mathrm{\π}\·(f_{\mathrm{IF}}+f_d)t_j+\mathrm{\φ})+n\left(t_j\right)---\left(1\right)$

In formula, A is signal amplitude, and d (t) is navigation data information, and C (t) is the C/A code, f _dBe Doppler shift, f _L1Be high frequent carrier frequency, f _IFBe the intermediate frequency carrier frequency, φ is initial phase, and n (t) is additive white Gaussian noise, t _jBe j sampling instant, τ is the time delay that signal arrives receiver.

Step 2: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift.

K the local pseudo-code signal model that produces of time period is

$s_k\left(t_i\right)=C\left((t_i-\widehat{\mathrm{\τ}})(1+\frac{{\hat{f}}_d}{f_{L1}})\right)\exp \left(j2\mathrm{\π}(f_{\mathrm{IF}}+{\hat{f}}_d)t_i\right)---\left(2\right)$

In formula, s _k(i) k local pseudo-code signal that produces of time period, C (t) is the C/A code,

Be Doppler frequency estimation value, f _L1Be high frequent carrier frequency, f _IFBe intermediate frequency carrier frequency, t _i=(kN+i) T _sBe i sampling instant,

Estimated value for time delay.

Step 3: respectively the satellite-signal after sampling and local pseudo-code satellite-signal are carried out two pieces zero expansions.

Because Doppler shift to the factor of influence of code phase is

When large and integration time is longer when Doppler shift, cause spreading rate that larger variation occurs, thereby to code cycle generation considerable influence, directly do relevant to digital medium-frequency signal and local signal and carry out difference and add up, can cause the correlation peak decay larger, thereby affect acquisition sensitivity, the DBZP technology can be improved in correlated process and cause that by large Doppler shift spreading rate changes the related power loss that causes.

If sampling gps signal after expansion and the local pseudo-code GPS signals that produces are expressed as respectively

$r_k^{\&prime;}\left(i\right)=\left\{\begin{array}{cc}{r}_k\left(i\right)& 0\&le;i<N\\ r_{k+1}(i-N)& N\&le;i<2N\end{array}\right.---\left(3\right)$

$s_k^{\&prime;}\left(i\right)=\left\{\begin{array}{cc}{s}_k\left(i\right)& 0\&le;i<N\\ 0& N\&le;i<2N\end{array}\right.---\left(4\right)$

In formula, r _k(i) be k coherence time section digital medium-frequency signal; s _k(i) k local pseudo-code signal that produces of time period.

Step 4: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and local pseudo-code satellite-signal after expanding through two pieces zero.

Step 5: correlated results is processed, and preserved the solid part signal of correlated results.

Utilize the FFT cyclic convolution to carry out related operation the corresponding blocks in formula (4), (5), have

$g(k,\widehat{\mathrm{\&tau;}})=\mathrm{Re}\left[\mathrm{IFFT}(\mathrm{FFT}\left(r_k^{\&prime;}\left(i\right)\right)\mathrm{FFT}\left(s_k^{\&prime;}\left(i\right)\right))*)\right]$

$=\frac{1}{2}\mathrm{Ad}\left(k\right)R_c\left(\mathrm{\&Delta;\&tau;}\right)T_a{S}_a\left(\mathrm{\&pi;\&Delta;}{f}_d{T}_a\right)\cos ((2k-1)\mathrm{\&pi;\&Delta;}{f}_d{T}_a+\mathrm{\&theta;})+n\left(k\right)---\left(6\right)$

In formula

For

Under the correlated results of different code time delays, R _c(△ τ) is C/A code cyclic convolution correlation,

Be residual doppler frequencies deviation, S _a(x)=sin (x)/x, n (k) is the noise item after integration, its variance is

Rewriting formula (6) has

$g(t_k,\widehat{\mathrm{\&tau;}})=A^{\&prime;}\cos (2\mathrm{\&pi;}{\mathrm{ft}}_k+\mathrm{\&theta;})+n\left(k\right)---\left(7\right)$

In formula,

For processing rear signal amplitude, f=△ f _dBe the residual doppler frequencies deviation that will search for, It is k section time series.

Step 6: the solid part signal to correlated results carries out the double sampling accidental resonance.In the present invention, described double sampling accidental resonance step comprises double sampling and accidental resonance step, namely at first, solid part signal to the correlated results preserved carries out double sampling, make signal frequency after sampling meet the requirement of small parameter accidental resonance, then, allow the signal after sampling enter bi-stable stochastic resonance theory system and the output of resonating.

The Langevin equation model of continuous bistable-state random resonance one-dimensional flow mechanical system is

dx/dt=ax-bx ³+Acos(2πf ₀t)+n(t) （8）

In formula, A is detected weak periodic signal amplitude, f ₀Be signal frequency, n (t) is that intensity is that D, average are 0, variance is 1 white noise, and a, b are systematic parameter, and x (t) is system output signal, and the barrier height of bistable system is △ U=a ²/ 4b.

Driving frequency f due to the bi-stable stochastic resonance theory system requirements ₀Very low, be limited in small parameter (frequency, amplitude, noise intensity are all much smaller than 1) scope.And the frequency f of signal=△ f in formula (7) _dLarger, be generally [10KHz-+10KHz], head and shoulders above the small parameter scope.

Adopt the double sampling Stochastic Resonance Theory that the f in formula (7) is transformed in the small parameter scope, establishing frequency input signal is f, and sample frequency is f _s, the double sampling frequency is f _sr, after double sampling, signal frequency is f _r, definition f _r/ f _sr=f ' ₀/ f _s, f _r=(f/f _s) f _sr, f wherein _rThe order of magnitude should be controlled in the small parameter scope of adiabatic approximation theory.After double sampling, (7) formula can be written as

$g(t_k,\widehat{\mathrm{\&tau;}})=A^{\&prime;}\cos (2\mathrm{\&pi;}{f}_r{t}_k+\mathrm{\&theta;})+n\left(k\right)---\left(9\right)$

In formula (9)

For the represented bistable-state random resonance system of input signal entry type (8), have

$\mathrm{dx}(t_k,\widehat{\mathrm{\&tau;}})/\mathrm{dt}=\mathrm{ax}(t_k,\widehat{\mathrm{\&tau;}})-b{x}^3(t_k,\widehat{\mathrm{\&tau;}})+g(t_k,\widehat{\mathrm{\&tau;}})---\left(10\right)$

And utilize fourth order Runge-Kutta way solving equation (10), namely

$x(t_{k+1},\widehat{\mathrm{\&tau;}})=x(t_i,\widehat{\mathrm{\&tau;}})+(k_1+{2k}_2+{2k}_3+k_4)/6---\left(11\right)$

$k_1=h\&lsqb;\mathrm{ax}(t_k,\widehat{\mathrm{\&tau;}})-b{x}^3(t_k,\widehat{\mathrm{\&tau;}})+g(t_k,\widehat{\mathrm{\&tau;}})\&rsqb;---\left(12\right)$

$k_2=h\left\{a\right[x(t_k,\widehat{\mathrm{\&tau;}})+k_1/2]-b{[x(t_k,\widehat{\mathrm{\&tau;}})+k_1/2]}^3+g(t_k,\widehat{\mathrm{\&tau;}})\}---\left(13\right)$

$k_3=h\left\{a\right[x(t_k,\widehat{\mathrm{\&tau;}})+k_2/2]-b{[x(t_k,\widehat{\mathrm{\&tau;}})+k_2/2]}^3+g(t_{k+1},\widehat{\mathrm{\&tau;}})\}---\left(14\right)$

$k_4=h\left\{a\right[x(t_k,\widehat{\mathrm{\&tau;}})+k_3]-b{[x(t_k,\widehat{\mathrm{\&tau;}})+k_3]}^3+g(t_{k+1},\widehat{\mathrm{\&tau;}})\}---\left(15\right)$

H=1/f wherein _srBe time step.

Step 7: the signal of exporting in step 6 is done Fourier transform and delivery.

Fourier transform and delivery are done in output to bi-stable stochastic resonance theory, have

$Y(u,\widehat{\mathrm{\&tau;}})=\left|\mathrm{FFT}\left(x(t_k,\widehat{\mathrm{\&tau;}})\right)\right|,$ u＝0，1…N-1 (16)

In formula, u is the sequence number of numerical frequency,

Be the code time-delay.

Step 8: to each satellite, the maximal value after delivery in the searching step 7 frequency direction is delayed time direction with code on: namely to each satellite, at first seek the maximal value after delivery and preservation in step 7 corresponding to original frequency; Then return to step 2 and find out the maximal value after delivery and preservation in step 7 corresponding to next Doppler frequency; Until preserve the maximal value after delivery in step 7 corresponding to all frequencies of this satellite; The last maximal value of a maximal value after as this satellite delivery of finding out from the maximal value after delivery corresponding to above-mentioned all frequencies again.

Afterwards, maximal value after this satellite delivery is compared with the detection threshold of setting in step 1, if this maximal value is greater than the detection threshold of setting in step 1, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass the detection threshold of setting in step 1, repeating step two next satellite of search, until searched for all satellites, withdraw from and catch, and this moment, expression was caught unsuccessful.

Said process is namely, at u and

In the upper searching formula of direction (16)

Maximal value

If this value is greater than the detection threshold of setting in step 1, u reaches

Be Doppler frequency and the code time-delay that to catch.

Adopt the designed non-linear acquisition equipment of high-sensitivity navigational satellite signal of said method, as shown in Figure 1, comprise that frequency-change sampling module, local pseudo-code generator, two piece zero expand module, Fast Fourier Transform (FFT) cyclic convolution correlation module, get the ratio of real part module, double sampling accidental resonance module, Fourier transform and delivery module and MTM(maximum related value and relevant average) the threshold test module.Wherein

The frequency-change sampling module: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling.

Local pseudo-code generator: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift.

The zero module of expanding of two pieces: respectively the local pseudo-code satellite-signal of the satellite-signal after the frequency-change sampling module samples and local pseudo-code generator generation carried out two pieces zero expansions.

Fast Fourier Transform (FFT) cyclic convolution correlation module: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and the local pseudo-code satellite-signal of expanding module output through two pieces zero.

Get the real part module: correlated results is processed, and kept the solid part signal of correlated results.

Double sampling accidental resonance module: the solid part signal of getting the correlated results that the real part module preserves is carried out double sampling, make it pass through bi-stable stochastic resonance theory system and the output of resonating.The accidental resonance of double sampling described in the present invention module comprises secondary sampling unit and accidental resonance unit, wherein secondary sampling unit carries out double sampling to the solid part signal of the correlated results getting the real part module and preserve, and makes signal frequency after sampling meet the requirement of bi-stable stochastic resonance theory small parameter signal; The output of resonating of the signal of accidental resonance unit after to double sampling.

Fourier transform and delivery module: the signal to the output of double sampling accidental resonance module is done Fourier transform and delivery.

The ratio of MTM(maximum related value and relevant average) threshold test module: to every satellite, seek the maximal value of Fourier transform and the output of delivery module on frequency direction and code time-delay direction, namely to each satellite, at first seek the maximal value after delivery corresponding to original frequency and preserve; Then repeat to return maximal value and preservation after local pseudo-code generator is found out delivery corresponding to next Doppler frequency, until preserve the maximal value after delivery corresponding to all frequencies of this satellite; The last maximal value of a maximal value after as this satellite delivery of finding out from the maximal value after delivery corresponding to above-mentioned all frequencies again.If the maximal value after this satellite delivery is greater than predefined detection threshold, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass predefined detection threshold, return to local pseudo-code generator and search for next satellite, until searched for all satellites, withdraw from and catch, at this moment, expression is caught unsuccessful.

Claims (9)

1. the non-linear catching method of high-sensitivity navigational satellite signal, is characterized in that comprising the steps:

Step 1: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling, and set suitable Doppler shift variable initial value and maximal value, namely set the Doppler shift hunting zone, set simultaneously Doppler shift scouting interval, maximum related value and the ratio of relevant average detection threshold, bi-stable stochastic resonance theory systematic parameter, defend asterisk variable initial value and defend the asterisk maximal value;

Step 2: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift;

Step 3: respectively the satellite-signal after sampling and local pseudo-code satellite-signal are carried out two pieces zero expansions;

Step 4: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and local pseudo-code satellite-signal after expanding through two pieces zero;

Step 5: correlated results is processed, and kept the solid part signal of correlated results;

Step 6: the solid part signal to the correlated results preserved carries out the double sampling accidental resonance;

Step 7: the signal of exporting in step 6 is done Fourier transform and delivery;

Step 8: to each satellite, the maximal value after delivery in the searching step 7 on frequency direction and code time-delay direction; Namely to each satellite, at first seek the maximal value after delivery and preservation in step 7 corresponding to original frequency; Then return to step 2 and find out the maximal value after delivery and preservation in step 7 corresponding to next Doppler frequency; Until preserve the maximal value after delivery in step 7 corresponding to all frequencies of this satellite; The last maximal value of a maximal value after as this satellite delivery of finding out from the maximal value after delivery corresponding to above-mentioned all frequencies again;

Afterwards, maximal value after this satellite delivery is compared with the detection threshold of setting in step 1, if this maximal value is greater than the detection threshold of setting in step 1, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass the detection threshold of setting in step 1, repeating step two next satellite of search, until searched for all satellites, withdraw from and catch, and this moment, expression was caught unsuccessful.

2. the non-linear catching method of high-sensitivity navigational satellite signal according to claim 1 is characterized in that:

The described double sampling accidental resonance of step 6 step comprises double sampling step and accidental resonance step, namely at first, solid part signal to the correlated results preserved carries out double sampling, make signal frequency after sampling meet the requirement of small parameter accidental resonance, then, allow the signal after sampling enter the bi-stable stochastic resonance theory system, and carry out accidental resonance.

3. the non-linear catching method of described high-sensitivity navigational satellite signal according to claim 1 and 2 is characterized in that: described Doppler shift hunting zone is-10KHz～10KHz.

4. the non-linear catching method of high-sensitivity navigational satellite signal according to claim 3, it is characterized in that: the described Doppler shift scouting interval is 5000Hz.

5. the non-linear catching method of described high-sensitivity navigational satellite signal according to claim 1 and 2, is characterized in that, described detection threshold is between 3～7.

6. the non-linear catching method of described high-sensitivity navigational satellite signal according to claim 1 and 2, it is characterized in that: bi-stable stochastic resonance theory systematic parameter initial value is a=1, b=1.

7. the non-linear catching method of described high-sensitivity navigational satellite signal according to claim 1 and 2, it is characterized in that: the initial value of defending the asterisk variable is 1, maximal value is 30.

8. the non-linear acquisition equipment of high-sensitivity navigational satellite signal is characterized in that comprising as lower module:

The frequency-change sampling module: the Satellite Simulation signal to the Navsat emission carries out down coversion and sampling;

Local pseudo-code generator: produce local pseudo-code satellite-signal according to Navsat to be searched number and Doppler shift;

The zero module of expanding of two pieces: respectively two pieces zero expansions are carried out in the local pseudo-code satellite-signal of the satellite-signal after the frequency-change sampling module samples and local pseudo-code generator generation;

Fast Fourier Transform (FFT) cyclic convolution correlation module: utilize the Fast Fourier Transform (FFT) cyclic convolution to carry out related operation to satellite-signal and the local pseudo-code satellite-signal of expanding module output through two pieces zero;

Get the real part module: correlated results is processed, and kept the solid part signal of correlated results;

Double sampling accidental resonance module: the solid part signal of getting the correlated results that the real part module preserves is carried out double sampling, make it pass through bi-stable stochastic resonance theory system and the output of resonating;

Fourier transform and delivery module: the signal to the output of double sampling accidental resonance module is done Fourier transform and delivery;

The ratio threshold test module of maximum related value and relevant average: to every satellite, seek the maximal value of Fourier transform and the output of delivery module on frequency direction and code time-delay direction; If the maximal value after this satellite delivery is greater than predefined detection threshold, the corresponding frequency of this maximal value and code time-delay are Doppler frequency and the code time-delay that will catch; If this maximal value does not surpass predefined detection threshold, return to local pseudo-code generator and search for next satellite, until searched for all satellites, withdraw from and catch, at this moment, expression is caught unsuccessful.

9. the non-linear acquisition equipment of high-sensitivity navigational satellite signal according to claim 8 is characterized in that: described double sampling accidental resonance module comprises secondary sampling unit and accidental resonance unit, wherein

Secondary sampling unit carries out double sampling to the solid part signal of getting the correlated results that the real part module preserves, makes signal frequency after sampling meet the requirement of bi-stable stochastic resonance theory small parameter signal;

The accidental resonance unit is to the output of resonating of the signal after double sampling.

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