CN102680988A - 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

High-sensitivity navigational satellite signal non-linear catching method and device

Technical field

The present invention is applicable to weak capturing navigation satellite signal field, is specifically related to a kind of high-sensitivity navigational satellite signal non-linear catching method and device.

Background technology

In recent years, (Global Positioning System GPS) has obtained more and more widely application to GPS.Along with deepening continuously of this location technology development, the user is also increasingly high to its request for utilization, and non-blind area, high sensitivity, real-time positioning 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 phenomenons such as blocking of receiving, multipath and interference are more serious, compare with conventional environment, gps signal is in indoor environment; Energy has more weakening and decline; Bigger 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, promptly the performance index of capturing function module are had higher requirement, and must catch the signal under the low signal-to-noise ratio environment by the fast high-sensitive degree.But present GPS capture technique almost is difficult to satisfy this requirement, the very difficult work under indoor environment such as grade of existing GPS receiver.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, can't satisfy the requirement of indoor weak signal high sensitivity and captured 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 to have proposed a kind of " based on the high sensitivity GPS signal capture algorithm of accidental resonance "; This algorithm at first carries out the relevant pre-service of segmentation with the part matched filter to gps signal; Utilize accidental resonance to improve the signal to noise ratio (S/N ratio) of signal after the pre-service then, be implemented in and obtain higher acquisition sensitivity in the relatively short relevant accumulated time.Yet this algorithm is when big and integration time is longer at the gps signal Doppler shift; To cause spreading rate that bigger variation takes place; Thereby to sign indicating number cycle generation considerable influence; When digital medium-frequency signal and local signal being done when relevant, can cause the correlation peak decay bigger, thereby influence acquisition sensitivity; And the part matched filtering in the above-mentioned algorithm is a bit ofly to do relevantly, causes preprocessing process consuming time bigger, 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 provides a kind of high-sensitivity navigational satellite signal non-linear catching method and device, and this method and apparatus can effectively reduce the loss that big Doppler frequency causes related power in the correlated process; Utilize the characteristic of NLS-bistable stochastic resonance system, promptly under certain condition, noise energy can improve the gps signal acquisition sensitivity to greatest extent to the signal energy transfer character; And can reduce capture time to the utmost, catching for the real-time high sensitivity of weak gps signal provides technical support.

For addressing the above problem, the present invention realizes through following scheme:

A kind of high-sensitivity navigational satellite signal non-linear of the present invention catching method 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; Promptly set the Doppler shift hunting zone, set simultaneously Doppler shift scouting interval, the MTM ratio of relevant average (maximum related value with) detection threshold, bistable stochastic resonance system parameter, defend asterisk variable initial value and defend the asterisk maximal value;

Step 2: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating;

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

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

Step 5: correlated results is handled, 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 the step 6 is done Fourier transform and delivery;

Step 8:, frequency direction is delayed time direction with sign indicating number on, seek the maximal value behind the delivery in the step 7 to each satellite; Promptly, at first seek maximal value behind the delivery and preservation in the corresponding step 7 of original frequency to each satellite; Repeating step two is found out maximal value behind the delivery and preservation in the corresponding step 7 of next Doppler frequency then, the maximal value in the corresponding step 7 of all frequencies of preserving this satellite behind the delivery; The last maximal value of a maximal value after of from the maximal value behind the corresponding delivery of above-mentioned all frequencies, finding out again as this satellite delivery;

Afterwards; Maximal value behind this satellite delivery is compared with the detection threshold of setting in the step 1; If this maximal value is greater than the detection threshold of setting in the step 1, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass the detection threshold of setting in the step 1, then repeating step two next satellite of search up to having searched for all satellites, then withdraw from and catch, and this moment, expression was caught unsuccessful.

Above-mentioned steps six said double sampling accidental resonance steps comprise double sampling and accidental resonance step, promptly at first the solid part signal of the correlated results preserved are carried out double sampling, make the frequency of sampling back signal meet the requirement of small parameter accidental resonance; Let the signal after sampling get into the bistable stochastic resonance system then, 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 shortened search time greatly, improved capture rate.

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

Above-mentioned bistable stochastic resonance system parameter is a=1, b=1.

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

A kind of high-sensitivity navigational satellite signal non-linear of the present invention acquisition equipment comprises like 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: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating;

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

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

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

Double sampling accidental resonance module: the solid part signal to getting the correlated results that the real part module preserves carries out double sampling, makes it through the bistable stochastic resonance 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 MTM ratio of relevant average (maximum related value with) threshold test module: to every satellite;, frequency direction seeks the maximal value of Fourier transform and the output of delivery module delaying time direction with sign indicating number on; Promptly to each satellite, at first seek the maximal value behind the corresponding delivery of original frequency and preserve; Repeat to return maximal value and preservation after local pseudo-code generator is found out the corresponding delivery of next Doppler frequency then, the maximal value behind the corresponding delivery of all frequencies of preserving this satellite; The last maximal value of a maximal value after of from the maximal value behind the corresponding delivery of above-mentioned all frequencies, finding out again as this satellite delivery;

If the maximal value behind this satellite delivery is greater than predefined detection threshold, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass predefined detection threshold, then return local pseudo-next satellite of code generator search, up to having searched for all satellites, then 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 the double sampling meet the small parameter semaphore request of bistable accidental resonance; 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 in the short as far as possible time.This invention adopts the DBZP technology to reduce the related power loss; Reduced with the FFT technology and to have done relevant required time; Utilize the characteristic of non-linear bistable stochastic resonance system---when signal under very noisy disturbs acts on bistable accidental resonance NLS; Signal and noise are under the synergy of NLS; The transfer of noise energy to signal energy can take place; Generation is similar to the resonance output in the mechanics, thereby greatly improves system's output signal-to-noise ratio; Introduce MTM (maximum related value and relevant average ratio) threshold detection method in the acquisition procedure, 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, comprise 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; Promptly set the Doppler shift hunting zone, set simultaneously Doppler shift scouting interval, the MTM ratio of relevant average (maximum related value with) detection threshold, bistable stochastic resonance system parameter, defend asterisk variable initial value and defend the asterisk maximal value.

In the present invention, said Doppler shift hunting zone is-10KHz～10KHz.The scouting interval of said Doppler shift is 5000Hz.Said detection threshold is meant the detection threshold of MTM, and wherein MTM representes the ratio of maximum related value and relevant average, if calculate gained MTM value above detection threshold B _T, think that promptly signal is accurately caught, in the present invention, said detection threshold B _TBe set between 3～7.Said bistable stochastic resonance system parameter a=1, b=1.According to the number of present gps satellite, in the present invention, the said initial value design of defending the asterisk variable is 1, and maximal value is set at 30.

From the L1 frequency range GPS simulating signal down coversion of satellites transmits and the digital medium-frequency signal after the sampling do

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

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

Step 2: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating.

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

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

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

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

Estimated value for time delay.

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

Since Doppler shift to code phase factor of influence be

when Doppler shift greatly and integration time when longer; Cause spreading rate that bigger variation takes place; Thereby to sign indicating number cycle generation considerable influence; Directly do relevant and carry out difference and add up digital medium-frequency signal and local signal; Can cause the correlation peak decay bigger; Thereby influence acquisition sensitivity, the DBZP technology can be improved in the correlated process and cause that by big Doppler shift spreading rate changes the related power loss that causes.

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

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

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

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

Step 5: correlated results is handled, 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

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

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

In the formula

For

Under the correlated results of different sign indicating number time delays, R _c(Δ τ) is C/A sign indicating number cyclic convolution correlation,

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

Rewriting formula (6) has

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

In the formula,

For handling back signal amplitude, f=Δ 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; Said double sampling accidental resonance step comprises double sampling and accidental resonance step, promptly at first, the solid part signal of the correlated results preserved is carried out double sampling; Make signal frequency after the sampling meet the requirement of small parameter accidental resonance; Then, let the signal after sampling get into the bistable stochastic resonance system, and the output of resonating.

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

dx/dt=ax-bx ³+Acos(2πf ₀t)+n(t) （8）

A is a weak periodic signal amplitude to be detected in the formula, 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 a system output signal, and the barrier height of bistable system is Δ U=a ²/ 4b.

Because the driving frequency f that the bistable stochastic resonance system requires ₀Very low, be limited in small parameter (frequency, amplitude, noise intensity are all much smaller than the 1) scope.And the frequency f=Δ f of signal in the formula (7) _dBigger, be generally [10KHz-+10KHz], head and shoulders above the small parameter scope.

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

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

With

in the formula (9) is that input signal gets into the represented bistable-state random resonance system of formula (8), has

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

And utilize quadravalence Runge-Kutta method solving equation (10), promptly

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

$k_1=h[\mathrm{ax}(t_k,\widehat{\mathrm{\&tau;}})-{\mathrm{bx}}^3(t_k,\widehat{\mathrm{\&tau;}})+g(t_k,\widehat{\mathrm{\&tau;}})]---\left(12\right)$

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

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

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

H=1/f wherein _SrBe time step.

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

Fourier transform and delivery are done in output to the bistable accidental resonance, have

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

In the formula; U is the sequence number of numerical frequency, be the sign indicating number time-delay.

Step 8:, on frequency direction and yard time-delay direction, seek the maximal value behind the delivery in the step 7:, at first seek also preservation of the maximal value behind the delivery in the corresponding step 7 of original frequency promptly to each satellite to each satellite; Repeating step two is found out maximal value behind the delivery and preservation in the corresponding step 7 of next Doppler frequency then, the maximal value in the corresponding step 7 of all frequencies of preserving this satellite behind the delivery; The last maximal value of a maximal value after of from the maximal value behind the corresponding delivery of above-mentioned all frequencies, finding out again as this satellite delivery.

Afterwards; Maximal value behind this satellite delivery is compared with the detection threshold of setting in the step 1; If this maximal value is greater than the detection threshold of setting in the step 1, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass the detection threshold of setting in the step 1, then repeating step two next satellite of search up to having searched for all satellites, then withdraw from and catch, and this moment, expression was caught unsuccessful.

Said process promptly is; In on u and direction in the searching formula (16) maximal value

of

if the detection threshold that this value is set in greater than step 1, then u and

are the Doppler frequency that will catch and yard delay time.

Adopt the high-sensitivity navigational satellite signal non-linear acquisition equipment that said method designed; 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 real part module, double sampling accidental resonance module, Fourier transform and delivery module and MTM the ratio of relevant average (maximum related value with) 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: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating.

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

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

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

Double sampling accidental resonance module: the solid part signal to getting the correlated results that the real part module preserves carries out double sampling, makes it through the bistable stochastic resonance 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 sampling back signal frequency meet the requirement of bistable accidental resonance 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 MTM ratio of relevant average (maximum related value with) threshold test module: to every satellite;, frequency direction seeks the maximal value of Fourier transform and the output of delivery module delaying time direction with sign indicating number on; Promptly to each satellite, at first seek the maximal value behind the corresponding delivery of original frequency and preserve; Repeat to return maximal value and preservation after local pseudo-code generator is found out the corresponding delivery of next Doppler frequency then, the maximal value behind the corresponding delivery of all frequencies of preserving this satellite; The last maximal value of a maximal value after of from the maximal value behind the corresponding delivery of above-mentioned all frequencies, finding out again as this satellite delivery.If the maximal value behind this satellite delivery is greater than predefined detection threshold, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass predefined detection threshold, then return local pseudo-next satellite of code generator search, up to having searched for all satellites, then withdraw from and catch, at this moment, expression is caught unsuccessful.

Claims (9)

1. high-sensitivity navigational satellite signal non-linear catching method 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; Promptly set the Doppler shift hunting zone, set simultaneously Doppler shift scouting interval, maximum related value and the ratio of relevant average detection threshold, bistable stochastic resonance system parameter, defend asterisk variable initial value and defend the asterisk maximal value;

Step 2: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating;

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

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

Step 5: correlated results is handled, 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 the step 6 is done Fourier transform and delivery;

Step 8:, frequency direction is delayed time direction with sign indicating number on, seek the maximal value behind the delivery in the step 7 to each satellite; Promptly, at first seek maximal value behind the delivery and preservation in the corresponding step 7 of original frequency to each satellite; Repeating step two is found out maximal value behind the delivery and preservation in the corresponding step 7 of next Doppler frequency then, the maximal value in the corresponding step 7 of all frequencies of preserving this satellite behind the delivery; The last maximal value of a maximal value after of from the maximal value behind the corresponding delivery of above-mentioned all frequencies, finding out again as this satellite delivery;

Afterwards; Maximal value behind this satellite delivery is compared with the detection threshold of setting in the step 1; If this maximal value is greater than the detection threshold of setting in the step 1, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass the detection threshold of setting in the step 1, then repeating step two next satellite of search up to having searched for all satellites, then withdraw from and catch, and this moment, expression was caught unsuccessful.

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

The said double sampling accidental resonance of step 6 step comprises double sampling step and accidental resonance step; Promptly at first; Solid part signal to the correlated results preserved carries out double sampling, makes signal frequency after the sampling meet the requirement of small parameter accidental resonance, then; Let the signal after sampling get into the bistable stochastic resonance system, and carry out accidental resonance.

3. according to claim 1 or 2 said high-sensitivity navigational satellite signal non-linear catching methods, it is characterized in that: said Doppler shift hunting zone is-10KHz～10KHz.

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

5. according to claim 1 or 2 said high-sensitivity navigational satellite signal non-linear catching methods, it is characterized in that said detection threshold is between 3～7.

6. according to claim 1 or 2 said high-sensitivity navigational satellite signal non-linear catching methods, it is characterized in that: bistable stochastic resonance system parameter initial value is a=1, b=1.

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

8. high-sensitivity navigational satellite signal non-linear acquisition equipment is characterized in that comprising like 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: according to Navsat to be searched number and the local pseudo-code satellite-signal of Doppler frequency offset generating;

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

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

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

Double sampling accidental resonance module: the solid part signal to getting the correlated results that the real part module preserves carries out double sampling, makes it through the bistable stochastic resonance 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:, on frequency direction and sign indicating number time-delay direction, seek the maximal value of Fourier transform and the output of delivery module to every satellite; If the maximal value behind this satellite delivery is greater than predefined detection threshold, then time-delay is the Doppler frequency and sign indicating number time-delay that will catch to the pairing frequency of this maximal value with sign indicating number; If this maximal value does not surpass predefined detection threshold, then return local pseudo-next satellite of code generator search, up to having searched for all satellites, then withdraw from and catch, at this moment, expression is caught unsuccessful.

9. high-sensitivity navigational satellite signal non-linear acquisition equipment according to claim 8 is characterized in that: said secondary 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 sampling back signal frequency meet the requirement of bistable accidental resonance small parameter signal;

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

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