CN103344968A - INS auxiliary Beidou signal capturing method - Google Patents

Abstract

The invention discloses an INS auxiliary Beidou signal capturing method. The method includes the steps that firstly Doppler frequency generated by movements of a carrier and a satellite is calculated; the Doppler frequency is transmitted to a capturing loop of a receiver, and a carrier NCO of the loop adjusts carrier frequency; frequency mixing is conducted on intermediate frequency signals and local carrier signals to acquire in-phase signals and orthogonal signals, and the in-phase signals and the orthogonal signals correlation operations with local signals conduct respectively; correlation values acquired by each operation are stored in a cache to acquire an M*N matrix; correlation values of the in-phase branch and the orthogonal branch form a plural matrix, and whether the signals enter a tracking module or the signals are recaptured is judged until the signals are captured. The advantage of combining time domain capture and frequency domain capture is fully exerted, and a matching filter set is adopted in the matching process, so that capturing time is saved, and rapid capture of the signals in a high dynamic environment can be rapidly achieved; the correlation values of the in-phase signals and the orthogonal signals are combined in the matrix to conduct FFT conversion, so that hardware resources are saved.

Description

The Big Dipper signal acquisition methods that a kind of INS is auxiliary

Technical field

The invention belongs to the satellite navigation field, relate in particular to the method for the auxiliary Big Dipper signal capture of a kind of INS.

Background technology

The hi-tech characteristics of modern war show, are that the precision guided weapon in core information source has become the leading of war with the navigator fix technology, and high performance-price ratio Navigation And Guidance module is one of gordian technique of precision guided weapon.

How catching satellite-signal under high dynamic environment is the difficult problem that navigation neceiver needs to be resolved hurrily.Because the high-speed motion between carrier and the satellite makes signal produce very big Doppler shift, signal capture time-frequency domain search bandwidth can become very big, makes the number of frequency domain search point increase, and catches for receiver fast and has brought very big difficulty.

Progressively foundation along with China's Big Dipper two generations satellite system, be that acquisition performance or acquisition speed have all had higher requirement to receiver, the method that traditional receiver adopts time domain to catch is carried out related operation to the input data, the threshold value of correlation and setting relatively, in case greater than then finish and catch, having adopted frequency domain to catch afterwards again is the method for FFT parallel capture, has accelerated the speed of catching.Realize that simply still acquisition speed is slow though time domain is caught, the acquisition speed that frequency domain is caught is fast, the implementation complexity height.And the method that adopts matched filter and Fast Fourier Transform (FFT) to combine, catch advantage with parallel capture though effectively combine serial, but under high dynamic environment, because Doppler's variation range is very big, this method can't realize catching fast of signal.

The velocity information that provides by inertial navigation system (INS) can be in real time for navigation neceiver provides Doppler frequency, weaken in addition eliminate carrier with respect to satellite dynamically, improve the anti-interference of receiver.Therefore the method by utilizing inertial navigation system to come auxiliary matched wave filter and Fast Fourier Transform (FFT) to combine can fully solve the problem of former method fast capturing signal under high dynamic environment.

Summary of the invention

The object of the present invention is to provide the method for the auxiliary Big Dipper fast capturing signal of a kind of INS, be intended to solve the problem of fast capturing signal under high dynamic environment.

The necessary technology scheme:

The present invention is achieved in that the method for the Big Dipper fast capturing signal that a kind of INS is auxiliary.

Step 1. calculate the Doppler frequency that carrier and satellite motion produce.

Step 2. Doppler frequency is passed to the Capture Circle of receiver, make the carrier wave NCO of loop adjust carrier frequency.

Step 3. with intermediate-freuqncy signal and local carrier signal mixing, obtain homophase and quadrature two paths of signals, and carry out related operation with local signal respectively.

Step 4. the correlation that obtains after the computing each time is stored in the buffer memory, obtains the matrix of a M * N.

Step 5. the correlation of homophase and quadrature branch is constituted a complex matrix, judge that it enters tracking module or catches again, till capturing.

Further, step 1. according to the speed of INS system, position and satellite parametric reduction calculate the Doppler frequency that carrier and satellite motion produce.Wherein to resolve be the speed that INS is provided to INS information, and information such as position are resolved and are the Doppler frequency information between carrier and the satellite, is used for auxiliary receiver to catch.

According to the speed of INS system, position and satellite parametric reduction, the Doppler frequency that can calculate the generation of carrier and satellite motion is:

$f_{\mathrm{dopp}}+f_s=\frac{1}{\text{\λ}}\·({\stackrel{\→}{V}}^{\mathrm{rec}}-{\stackrel{\→}{V}}^s)\·{\stackrel{\→}{e}}^d=\frac{1}{\mathrm{\λ}}\·{\stackrel{\→}{V}}^{\mathrm{rec}}\·{\stackrel{\→}{e}}^d-\frac{1}{\mathrm{\λ}}\·{\stackrel{\→}{V}}^s\·{\stackrel{\→}{e}}^d---\left(1\right)$

Wherein, λ is the wavelength of carrier wave,

Be the speed of carrier,

Be the speed of satellite,

Be the unit vector of satellite to user's line direction.And

Can be obtained by the satellite almanac,

Then can be provided by INS.Resolving at software section of this module realizes.

Further, step 2. the carrier that INS data and almanac are provided is passed to the Capture Circle of receiver with respect to the Doppler frequency of satellite, makes the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information.Wherein INS information aided capture is the carrier wave NCO that the Doppler frequency information that INS and satellite ephemeris provide is passed to local trapping module, and carrier wave NCO adjusts the carrier frequency of generation according to doppler information, is used for peeling off the carrier wave in the signal.What this process adopted is the method that the auxiliary matched filter of INS and quick FFT conversion combine, and the velocity information that inertial navigation system is obtained is converted to Doppler frequency, offers local carrier NCO.

The carrier that INS data and almanac are provided utilizes interface between the software and hardware to pass to the Capture Circle of receiver with respect to the Doppler frequency of satellite, make the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information, local homophase and the quadrature carrier signal that produces can be expressed as:

In following formula, f _IFBe the intermediate-freuqncy signal frequency,

Be the initial phase of carrier wave, f _Acq=f _Dopp+ f _sThe doppler information that obtains for carrier wave NCO.At this moment, INS information has been passed to the signal capture module.

The emulation experiment of wherein using is to carry out under the high dynamic environment of setting, and the carrier initial velocity is that 8km/s, acceleration are respectively 20g/s and 5g/s.IF-FRE is 4.23MHz, supposes that the Doppler frequency step-size in search is 150Hz.Under high current intelligence, the speed of carrier movement is very big, the Doppler frequency that produces is very big, Doppler effect considerably beyond the satellite motion generation, therefore calculate the Doppler frequency that the carrier high-speed motion produces by INS, thereby dwindle Doppler's hunting zone, reduce capture time, improve acquisition speed.Carry out emulation in the input signal signal to noise ratio (S/N ratio) for-10dB, the method that adopts the auxiliary matched filter of INS and FFT conversion to combine.

Further, step 3. intermediate-freuqncy signal and the local carrier signal mixing that will obtain through front-end processing, obtain homophase and quadrature two paths of signals through low-pass filter then, two paths of signals enters the matched filter (N is less than spreading code length) on local M (M is 2 integral number power) individual N rank respectively, carries out related operation with local signal.Adopt the matched filter on M N rank when wherein carrying out matched filtering, just can obtain M * N correlation through a matched filtering like this.Namely in hardware circuit, intermediate-freuqncy signal and local carrier signal are multiplied each other, through obtaining quadrature and homophase two paths of signals after the low-pass filter, two paths of signals enters local matched filter banks respectively, the number of wave filter is M, the exponent number of single matched filter is the N rank, carry out related operation with local signal afterwards, obtain M * N correlation.

Detailed process is achieved in that respectively there is the matched filter on M N rank on I road and Q road, and establishing and receiving signal is r (n), and local signal is x (n), and when the data that enter matched filter are r (n+1) during to r (n+N), tap coefficient is that x (n+1) is to x (n+N); When data that enter matched filter when being r (n+N+1) to r (n+2N), tap coefficient is that x (n+N+1) is to x (n+2N); When data that enter matched filter when being r (n+ (m-1) N+1) to r (n+mN), tap coefficient is that x (n+ (m-1) N+1) is to x (n+mN).

Further, step 4. the correlation that obtains after the computing each time is stored in the buffer memory, obtains the matrix of a M * N.And intermediate-freuqncy signal and local carrier signal multiplied each other obtain quadrature and two branch roads of homophase, enter M (M is 2 integral number power) individual N (N is less than the length of spreading code) rank matched filter banks and carry out matched filtering, generate the matrix of M * N.Namely at software section, the correlation of two paths of signals is stored in the buffer memory, obtain a matrix of being formed by I+Qi (I is the correlation of in-phase signal, and Q is the correlation of orthogonal signal).

Detailed process is achieved in that first row element that can be got M * N matrix by step 3, i.e. the output result of first matched filter:

$\mathrm{cor}\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+1)r(n+i+1)$

$\mathrm{cor}\left(\mathrm{1,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+1)r(n+i+2)$

……

$\mathrm{cor}(1,N)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+1)r(n+i+N)---\left(3\right)$

In like manner can try to achieve matrix second row element is:

$\mathrm{cor}\left(\mathrm{2,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+N+1)r(n+i+N+1)$

$\mathrm{cor}\left(\mathrm{2,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+N+1)r(n+i+N+2)$

……

$\mathrm{cor}(2,N)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}x(n+i+N+1)r(n+i+2\·N)---\left(4\right)$

Make a _1,1=cor (1,1), then cor (2,1) can be expressed as a _{N+1, N+1}, can obtain M * N matrix thus and be:

$\left(\begin{array}{cccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& ...& a_{1,N}\\ a_{N+1,N+1}& a_{N+1,N+2}& ...& a_{N+\mathrm{1,2}N}\\ ...& ...& ...& ...\\ a_{(M-1)N+1,(M-1)N+1}& a_{(M-1)N+1,(M-1)N+2}& ...& a_{(M-1)N+1,\mathrm{MN}}\end{array}\right)---\left(5\right)$

Then with the real part as plural number of the correlation of I branch road, with the correlation of the Q branch road imaginary part as plural number, constitute the matrix that element form is I+Qi

$\left(\begin{array}{cccc}{I}_{\mathrm{1,1}}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{\mathrm{1,1}}i& I_{\mathrm{1,2}}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{\mathrm{1,2}}i& ...& {\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">I</figure-callout>}}_{1,N}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{1,N}i\\ I_{N+1,N+1}+Q_{N+1,N+1}i& I_{N+1,N+2}+Q_{N+1,N+2}i& ...& I_{N+\mathrm{1,2}N}+Q_{N+\mathrm{1,2}N}i\\ ...& ...& ...& ...\\ I_{(M-1)N+1,(M-1)N+1}+Q_{(M-1)N+1,(M-1)N+1}i& I_{(M-1)N+1,(M-1)N+2}+Q_{(M-1)N+1,(M-1)N+2}i& ...& I_{(M-1)N+1,\mathrm{MN}}+Q_{(M-1)N+1,\mathrm{MN}}i\end{array}\right)---\left(6\right).$

Further, step 5. the correlation of homophase and quadrature branch is constituted a complex matrix, each row of above-mentioned matrix are M point FFT, delivery is searched maximal value then, obtains the peak value of signal, compares with preset threshold, then capture signal greater than threshold value, enter tracking module, then need to adjust carrier frequency and code frequency is caught again less than threshold value, till capturing signal.Wherein the correlation of homophase and quadrature two paths of signals is merged in the matrix and carry out FFT, the element in this matrix is plural form, and the correlation of in-phase signal is as the real part of plural number, and the correlation of orthogonal signal is as the imaginary part of plural number.

The present invention compares method that the present invention overcome matched filter and FFT conversion fast can't be finished signal capture under high dynamic environment shortcoming with traditional method, make it give full play to it and combine time domain and catch the advantage of catching with frequency domain.And in coupling, adopted matched filter banks, saved capture time, can under high dynamic environment, finish catching fast signal rapidly.The more important thing is that it merges to a matrix with the correlation of quadrature and homophase two paths of signals and carries out the FFT conversion, has saved hardware resource.

Description of drawings

Fig. 1 is the auxiliary Big Dipper signal capture block diagram of INS provided by the invention;

Fig. 2 is the process flow diagram that the software and hardware of the auxiliary Big Dipper signal capture of INS provided by the invention is realized;

Fig. 3 is the Doppler frequency analogous diagram that carrier provided by the invention produces when doing high-speed motion with respect to satellite;

Fig. 4 is the simulation result of the method that combines of the auxiliary matched filter of INS provided by the invention and FFT.

Embodiment

The present invention is achieved in that the method for the Big Dipper fast capturing signal that a kind of INS is auxiliary.Below in conjunction with accompanying drawing the inventive method is described in more detail.Fig. 2 is the process flow diagram that the software and hardware of the auxiliary Big Dipper signal capture of INS provided by the invention is realized, its concrete steps are as follows as can be known by Fig. 1 and Fig. 2:

Step 1. calculate the Doppler frequency that carrier and satellite motion produce.

Step 2. Doppler frequency is passed to the Capture Circle of receiver, make the carrier wave NCO of loop adjust carrier frequency.

Step 3. with intermediate-freuqncy signal and local carrier signal mixing, obtain homophase and quadrature two paths of signals, and carry out related operation with local signal respectively.

Step 4. the correlation that obtains after the computing each time is stored in the buffer memory, obtains the matrix of a M * N.

Step 5. the correlation of homophase and quadrature branch is constituted a complex matrix, judge that it enters tracking module or catches again, till capturing.

In the present invention, step 1. according to the speed of INS system, position and satellite parametric reduction calculate the Doppler frequency that carrier and satellite motion produce.Wherein to resolve be the speed that INS is provided to INS information, and information such as position are resolved and are the Doppler frequency information between carrier and the satellite, is used for auxiliary receiver to catch.

According to the speed of INS system, position and satellite parametric reduction, the Doppler frequency that can calculate the generation of carrier and satellite motion is:

$f_{\mathrm{dopp}}+f_s=\frac{1}{\text{\&lambda;}}\&CenterDot;({\stackrel{\&RightArrow;}{V}}^{\mathrm{rec}}-{\stackrel{\&RightArrow;}{V}}^s)\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d=\frac{1}{\mathrm{\&lambda;}}\&CenterDot;{\stackrel{\&RightArrow;}{V}}^{\mathrm{rec}}\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d-\frac{1}{\mathrm{\&lambda;}}\&CenterDot;{\stackrel{\&RightArrow;}{V}}^s\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d---\left(1\right)$

Wherein, λ is the wavelength of carrier wave,

Be the speed of carrier,

Be the speed of satellite,

Be the unit vector of satellite to user's line direction.And Can be obtained by the satellite almanac,

Then can be provided by INS.Resolving at software section of this module realizes.

In the present invention, step 2. the carrier that INS data and almanac are provided is passed to the Capture Circle of receiver with respect to the Doppler frequency of satellite, makes the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information.Wherein INS information aided capture is the carrier wave NCO that the Doppler frequency information that INS and satellite ephemeris provide is passed to local trapping module, and carrier wave NCO adjusts the carrier frequency of generation according to doppler information, is used for peeling off the carrier wave in the signal.What this process adopted is the method that the auxiliary matched filter of INS and quick FFT conversion combine, and the velocity information that inertial navigation system is obtained is converted to Doppler frequency, offers local carrier NCO.

The carrier that INS data and almanac are provided utilizes interface between the software and hardware to pass to the Capture Circle of receiver with respect to the Doppler frequency of satellite, make the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information, local homophase and the quadrature carrier signal that produces can be expressed as:

In following formula, f _IFBe the intermediate-freuqncy signal frequency,

Be the initial phase of carrier wave, f _Acq=f _Dopp+ f _sThe doppler information that obtains for carrier wave NCO.At this moment, INS information has been passed to the signal capture module.

The emulation experiment of wherein using is to carry out under the high dynamic environment of setting, and the carrier initial velocity is that 8km/s, acceleration are respectively 20g/s and 5g/s.IF-FRE is 4.23MHz, supposes that the Doppler frequency step-size in search is 150Hz.

The Doppler that the carrier high-speed motion produces is change curve such as Fig. 3 in time, as can be seen from the figure, under high current intelligence, the speed of carrier movement is very big, and the Doppler frequency of generation is very big, considerably beyond the Doppler effect of satellite motion generation, therefore calculate the Doppler frequency that the carrier high-speed motion produces by INS, thereby dwindle Doppler's hunting zone, reduce capture time, improve acquisition speed.

Carry out emulation in the input signal signal to noise ratio (S/N ratio) for-10dB, method simulation result such as Fig. 4 of adopting the auxiliary matched filter of INS and FFT conversion to combine, as can be seen, this method can be finished preferably and catch, and has good anti-interference.

In the present invention, step 3. intermediate-freuqncy signal and the local carrier signal mixing that will obtain through front-end processing, obtain homophase and quadrature two paths of signals through low-pass filter then, two paths of signals enters the matched filter (N is less than spreading code length) on local M (M is 2 integral number power) individual N rank respectively, carries out related operation with local signal.Adopt the matched filter on M N rank when wherein carrying out matched filtering, just can obtain M * N correlation through a matched filtering like this.Namely in hardware circuit, intermediate-freuqncy signal and local carrier signal are multiplied each other, through obtaining quadrature and homophase two paths of signals after the low-pass filter, two paths of signals enters local matched filter banks respectively, the number of wave filter is M, the exponent number of single matched filter is the N rank, carry out related operation with local signal afterwards, obtain M * N correlation.

Detailed process is achieved in that respectively there is the matched filter on M N rank on I road and Q road, and establishing and receiving signal is r (n), and local signal is x (n), and when the data that enter matched filter are r (n+1) during to r (n+N), tap coefficient is that x (n+1) is to x (n+N); When data that enter matched filter when being r (n+N+1) to r (n+2N), tap coefficient is that x (n+N+1) is to x (n+2N); When data that enter matched filter when being r (n+ (m-1) N+1) to r (n+mN), tap coefficient is that x (n+ (m-1) N+1) is to x (n+mN).

In the present invention, step 4. the correlation that obtains after the computing each time is stored in the buffer memory, obtains the matrix of a M * N.And intermediate-freuqncy signal and local carrier signal multiplied each other obtain quadrature and two branch roads of homophase, enter M (M is 2 integral number power) individual N (N is less than the length of spreading code) rank matched filter banks and carry out matched filtering, generate the matrix of M * N.Namely at software section, the correlation of two paths of signals is stored in the buffer memory, obtain a matrix of being formed by I+Qi (I is the correlation of in-phase signal, and Q is the correlation of orthogonal signal).

Detailed process is achieved in that in steps three can get first row element of M * N matrix, i.e. the output result of first matched filter:

$\mathrm{cor}\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+1)$

$\mathrm{cor}\left(\mathrm{1,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+2)$

……

$\mathrm{cor}(1,N)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+N)---\left(3\right)$

In like manner can try to achieve matrix second row element is:

$\mathrm{cor}\left(\mathrm{2,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+N+1)$

$\mathrm{cor}\left(\mathrm{2,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+N+2)$

……

$\mathrm{cor}(2,N)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+2\&CenterDot;N)---\left(4\right)$

Make a _1,1=cor (1,1), then cor (2,1) can be expressed as a _{N+1, N+1}, can obtain M * N matrix thus and be:

$\left(\begin{array}{cccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& ...& a_{1,N}\\ a_{N+1,N+1}& a_{N+1,N+2}& ...& a_{N+\mathrm{1,2}N}\\ ...& ...& ...& ...\\ a_{(M-1)N+1,(M-1)N+1}& a_{(M-1)N+1,(M-1)N+2}& ...& a_{(M-1)N+1,\mathrm{MN}}\end{array}\right)---\left(5\right)$

Then with the real part as plural number of the correlation of I branch road, with the correlation of the Q branch road imaginary part as plural number, constitute the matrix that element form is I+Qi

$\left(\begin{array}{cccc}{I}_{\mathrm{1,1}}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{\mathrm{1,1}}i& I_{\mathrm{1,2}}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{\mathrm{1,2}}i& ...& I_{1,N}+{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{1,N}i\\ I_{N+1,N+1}+{\mathrm{<figure-callout\; id="1"\; label="Q\; N\; +"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{N+}i& I_{N+1,N+2}+{\mathrm{<figure-callout\; id="1"\; label="Q\; N\; +"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{N+}i& ...& I_{N+\mathrm{1,2}N}+{\mathrm{<figure-callout\; id="1"\; label="Q\; N\; +"\; filenames="HSA00000911667600022.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{N+}i\\ ...& ...& ...& ...\\ I_{(M-1)N+1,(M-1)N+1}+Q_{(M-1)N+1,(M-1)N+1}i& I_{(M-1)N+1,(M-1)N+2}+Q_{(M-1)N+1,(M-1)N+2}i& ...& I_{(M-1)N+1,\mathrm{MN}}+Q_{(M-1)N+1,\mathrm{MN}}i\end{array}\right)---\left(6\right).$

In the present invention, step 5. the correlation of homophase and quadrature branch is constituted a complex matrix, each row of above-mentioned matrix are M point FFT, delivery is searched maximal value then, obtains the peak value of signal, compares with preset threshold, then capture signal greater than threshold value, enter tracking module, then need to adjust carrier frequency and code frequency is caught again less than threshold value, till capturing signal.Wherein the correlation of homophase and quadrature two paths of signals is merged in the matrix and carry out FFT, the element in this matrix is plural form, and the correlation of in-phase signal is as the real part of plural number, and the correlation of orthogonal signal is as the imaginary part of plural number.

The method of the Big Dipper satellite signal capture that INS provided by the invention is auxiliary.Under high dynamic environment, the real-time Doppler frequency that provides the carrier high-speed motion to produce of INS is provided, pre-estimate the frequency range of Big Dipper signal, reduce the number of frequency domain search point, thereby shorten the time of catching, improve the acquisition performance of receiver.Adopt matched filter banks when catching, saved the time, when carrying out the FFT computing at last, with quadrature and the unified processing of in-phase branch, saved hardware resource.

The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. the method for the auxiliary Big Dipper fast capturing signal of an INS is characterized in that this method may further comprise the steps:

Step 1. calculate the Doppler frequency that carrier and satellite motion produce;

Step 2. Doppler frequency is passed to the Capture Circle of receiver, make the carrier wave NCO of loop adjust carrier frequency;

Step 3. with intermediate-freuqncy signal and local carrier signal mixing, obtain homophase and quadrature two paths of signals, and carry out related operation with local signal respectively;

Step 5. the correlation of homophase and quadrature branch is constituted a complex matrix, judge that it enters tracking module or catches again, till capturing.

2. the method for the auxiliary Big Dipper fast capturing signal of INS as claimed in claim 1 is characterized in that according to the speed of INS system, position and satellite parametric reduction calculate the Doppler frequency that carrier and satellite motion produce; Wherein to resolve be the speed that INS is provided to INS information, and information such as position are resolved and are the Doppler frequency information between carrier and the satellite, is used for auxiliary receiver to catch;

According to the speed of INS system, position and satellite parametric reduction, the Doppler frequency that can calculate the generation of carrier and satellite motion is:

$f_{\mathrm{dopp}}+f_s=\frac{1}{\text{\&lambda;}}\&CenterDot;({\stackrel{\&RightArrow;}{V}}^{\mathrm{rec}}-{\stackrel{\&RightArrow;}{V}}^s)\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d=\frac{1}{\mathrm{\&lambda;}}\&CenterDot;{\stackrel{\&RightArrow;}{V}}^{\mathrm{rec}}\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d-\frac{1}{\mathrm{\&lambda;}}\&CenterDot;{\stackrel{\&RightArrow;}{V}}^s\&CenterDot;{\stackrel{\&RightArrow;}{e}}^d---\left(1\right)$

Wherein, λ is the wavelength of carrier wave, Be the speed of carrier,

Be the speed of satellite,

Be the unit vector of satellite to user's line direction.And

Can be obtained by the satellite almanac,

Then can be provided by INS.Resolving at software section of this module realizes.

3. the method for the auxiliary Big Dipper fast capturing signal of INS as claimed in claim 1, it is characterized in that, the carrier that INS data and almanac are provided is passed to the Capture Circle of receiver with respect to the Doppler frequency of satellite, makes the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information; Wherein INS information aided capture is the carrier wave NCO that the Doppler frequency information that INS and satellite ephemeris provide is passed to local trapping module, and carrier wave NCO adjusts the carrier frequency of generation according to doppler information, is used for peeling off the carrier wave in the signal.What this process adopted is the method that the auxiliary matched filter of INS and quick FFT conversion combine, and the velocity information that inertial navigation system is obtained is converted to Doppler frequency, offers local carrier NCO;

The carrier that INS data and almanac are provided utilizes interface between the software and hardware to pass to the Capture Circle of receiver with respect to the Doppler frequency of satellite, make the carrier wave NCO of loop constantly adjust carrier frequency according to doppler information, local homophase and the quadrature carrier signal that produces can be expressed as:

In following formula, f _IFBe the intermediate-freuqncy signal frequency,

Be the initial phase of carrier wave, f _Acq=f _Dopp+ f _sThe doppler information that obtains for carrier wave NCO.At this moment, INS information has been passed to the signal capture module;

The emulation experiment of wherein using is to carry out under the high dynamic environment of setting, and the carrier initial velocity is that 8km/s, acceleration are respectively 20g/s and 5g/s.IF-FRE is 4.23MHz, supposes that the Doppler frequency step-size in search is 150Hz.Under high current intelligence, the speed of carrier movement is very big, the Doppler frequency that produces is very big, Doppler effect considerably beyond the satellite motion generation, therefore calculate the Doppler frequency that the carrier high-speed motion produces by INS, thereby dwindle Doppler's hunting zone, reduce capture time, improve acquisition speed.Carry out emulation in the input signal signal to noise ratio (S/N ratio) for-10dB, the method that adopts the auxiliary matched filter of INS and FFT conversion to combine.

4. the method for the auxiliary Big Dipper fast capturing signal of INS as claimed in claim 1, it is characterized in that, with intermediate-freuqncy signal and the local carrier signal mixing that has obtained through front-end processing, obtain homophase and quadrature two paths of signals through low-pass filter then, two paths of signals enters the matched filter on local M N rank respectively, carries out related operation with local signal; Adopt the matched filter on M N rank when wherein carrying out matched filtering, just can obtain M * N correlation through a matched filtering like this; Namely in hardware circuit, intermediate-freuqncy signal and local carrier signal are multiplied each other, through obtaining quadrature and homophase two paths of signals after the low-pass filter, two paths of signals enters local matched filter banks respectively, the number of wave filter is M, the exponent number of single matched filter is the N rank, carry out related operation with local signal afterwards, obtain M * N correlation;

Detailed process is achieved in that respectively there is the matched filter on M N rank on I road and Q road, and establishing and receiving signal is r (n), and local signal is x (n), and when the data that enter matched filter are r (n+1) during to r (n+N), tap coefficient is that x (n+1) is to x (n+N); When data that enter matched filter when being r (n+N+1) to r (n+2N), tap coefficient is that x (n+N+1) is to x (n+2N); When data that enter matched filter when being r (n+ (m-1) N+1) to r (n+mN), tap coefficient is that x (n+ (m-1) N+1) is to x (n+mN).

5. the method for the auxiliary Big Dipper fast capturing signal of INS as claimed in claim 1 is characterized in that, the correlation that obtains after the computing each time is stored in the buffer memory, obtains the matrix of a M * N; And intermediate-freuqncy signal and local carrier signal multiplied each other obtain quadrature and two branch roads of homophase, enter M N rank matched filter banks and carry out matched filtering, the matrix of generation M * N; Namely at software section, the correlation of two paths of signals is stored in the buffer memory, obtain a matrix of being formed by I+Qi, I is the correlation of in-phase signal, Q is the correlation of orthogonal signal;

Detailed process is achieved in that first row element that can be got M * N matrix by step 3, i.e. the output result of first matched filter:

$\mathrm{cor}\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+1)$

$\mathrm{cor}\left(\mathrm{1,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+2)$

……

$\mathrm{cor}(1,N)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+1)r(n+i+N)---\left(3\right)$

In like manner can try to achieve matrix second row element is:

$\mathrm{cor}\left(\mathrm{2,1}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+N+1)$

$\mathrm{cor}\left(\mathrm{2,2}\right)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+N+2)$

……

$\mathrm{cor}(2,N)=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x(n+i+N+1)r(n+i+2\&CenterDot;N)---\left(4\right)$

Make a _1,1=cor (1,1), then cor (2,1) can be expressed as a _{N+1, N+1}, can obtain M * N matrix thus and be:

$\left(\begin{array}{cccc}{a}_{\mathrm{1,1}}& a_{\mathrm{1,2}}& ...& a_{1,N}\\ a_{N+1,N+1}& a_{N+1,N+2}& ...& a_{N+\mathrm{1,2}N}\\ ...& ...& ...& ...\\ a_{(M-1)N+1,(M-1)N+1}& a_{(M-1)N+1,(M-1)N+2}& ...& a_{(M-1)N+1,\mathrm{MN}}\end{array}\right)---\left(5\right)$

Then with the real part as plural number of the correlation of I branch road, with the correlation of the Q branch road imaginary part as plural number, constitute the matrix that element form is I+Qi

$\left(\begin{array}{cccc}{I}_{\mathrm{1,1}}+Q_{\mathrm{1,1}}i& I_{\mathrm{1,2}}+Q_{\mathrm{1,2}}i& ...& I_{1,N}+Q_{1,N}i\\ I_{N+1,N+1}+Q_{N+1,N+1}i& I_{N+1,N+2}+Q_{N+1,N+2}i& ...& I_{N+\mathrm{1,2}N}+Q_{N+\mathrm{1,2}N}i\\ ...& ...& ...& ...\\ I_{(M-1)N+1,(M-1)N+1}+Q_{(M-1)N+1,(M-1)N+1}i& I_{(M-1)N+1,(M-1)N+2}+Q_{(M-1)N+1,(M-1)N+2}i& ...& I_{(M-1)N+1,\mathrm{MN}}+Q_{(M-1)N+1,\mathrm{MN}}i\end{array}\right)---\left(6\right).$

6. the method for the auxiliary Big Dipper fast capturing signal of INS as claimed in claim 1, it is characterized in that, the correlation of homophase and quadrature branch is constituted a complex matrix, each row of above-mentioned matrix are M point FFT, delivery is searched maximal value then, obtain the peak value of signal, compare with preset threshold, then capture signal greater than threshold value, enter tracking module, then need to adjust carrier frequency and code frequency is caught again less than threshold value, till capturing signal; Wherein the correlation of homophase and quadrature two paths of signals is merged in the matrix and carry out FFT, the element in this matrix is plural form, and the correlation of in-phase signal is as the real part of plural number, and the correlation of orthogonal signal is as the imaginary part of plural number.

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