CN105277955A - Baseband signal processing method used for GPS satellite navigation - Google Patents
Baseband signal processing method used for GPS satellite navigation Download PDFInfo
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- CN105277955A CN105277955A CN201410840021.4A CN201410840021A CN105277955A CN 105277955 A CN105277955 A CN 105277955A CN 201410840021 A CN201410840021 A CN 201410840021A CN 105277955 A CN105277955 A CN 105277955A
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Abstract
The present invention discloses a baseband signal processing method used for GPS satellite navigation. The method comprises rapidly capturing a selected satellite by using a method based on matched filtering and an FFT, thus to obtain code phase and Doppler information under large range uncertainty; confirming the code phase and Doppler information of the captured satellite by adopting a method based on fine capture; carrying out dynamic range traction on a code phase and a carrier frequency by adopting a code loop and a frequency-locked loop; tracking the code phase and the carrier frequency by adopting the code loop and the frequency-locked loop of proper bandwidths; and carrying out bit synchronization and frame synchronization, and carrying out navigation message decoding after success, thus to obtain satellite position and speed informaton and parameters used by navigational positioning calculation. With adoption of the baseband signal processing method used for GPS satellite navigation, high-quality raw observed quantities of a pseudorange and a carrier phase can be output, the precision of the pseudorange and the carrier phase is raised, and the reliability is also raised.
Description
Technical field
The present invention relates to gps satellite signal process field, particularly relate to a kind of method for processing baseband signal for gps satellite navigation.
Background technology
Satellite navigation receiver is each visible satellite-signal of code acquisition from the satellite-signal received, obtain the rough code phase values of institute's capturing satellite signal and carrier doppler value, then caught satellite is admitted to the tracking that idle tracking channel carries out satellite-signal.Only guestimate can be carried out to carrier doppler value and code phase parameter value owing to catching, the object of following the tracks of is exactly the estimated value of these parameters of becoming more meticulous, and keep the tracking to these parameters, then from the satellite-signal traced into, navigation message is demodulated, and extract raw pseudo range measured value from code tracking loop, extract raw carrier phase measured value from carrier phase-locked loop.Traditional if adopted serial search methods carried out to pseudo-random code catch, and to each Doppler frequently lattice to search for, search time certainly will be caused very long, and calculated amount is very large, very high to the requirement of hardware resource.The code phase that captures and Doppler frequency are just determined in the search carrying out merely a pseudo-random code and Doppler lattice frequently, must make lower detection probability and higher false-alarm probability.The trapped state of common receiver terminate to enter tracking mode until tracking mode to reach convergence stable, can export raw pseudo range and carrier-phase measurement, the time that tracking loop enters steady state (SS) is longer, and the precision of original observed quantity is not high yet.
For common navigation receiver, the original measurement value precision obtained from track loop is not high enough, and pseudo-range measurements precision is decimetre rank, and carrier-phase measurement precision is a centimetre rank.But high precision navigation neceiver is owing to being widely used in the fields such as mobile mapping, CORS system, precision agriculture, intelligent transportation, marine prods, receiver needs to obtain centimetre-sized pseudo-range measurements, millimetre-sized carrier-phase measurement from track loop, and require reliably to export these measured values, just can make the carrying out that follow-up positioning calculation is reliable and stable, therefore with to the arrangement of method for processing baseband signal, higher requirement be proposed to choosing of track loop parameter.
Summary of the invention
In view of current gps satellite signal process field above shortcomings, the invention provides a kind of method for processing baseband signal for gps satellite navigation, can the pseudorange of outputting high quality and the original observed quantity of carrier phase, make pseudorange accuracy higher, carrier phase precision is also higher, and improves reliability.
For achieving the above object, embodiments of the invention adopt following technical scheme:
For a method for processing baseband signal for gps satellite navigation, the described method for processing baseband signal for gps satellite navigation comprises the following steps:
Obtain correlation from baseband signal and select the visible satellite meeting certain altitude angular threshold;
Selected satellite is adopted and catches fast based on the mode of matched filtering and FFT, to obtain code phase under uncertainty on a large scale and doppler information;
If acquisition success, then the method for catching based on essence is adopted to confirm to the code phase of the satellite captured and Doppler;
If smart acquisition success, then code ring and FLL is adopted to carry out dynamic range traction to code phase and carrier frequency;
If draw successfully, then the mode adopting code ring to be combined with FLL carries out more meticulous code phase and the estimation of carrier doppler;
If successfully carry out PGC demodulation and Frequency Locking, then the code ring of appropriate bandwidth and phaselocked loop is adopted to carry out the tracking of code phase and carrier frequency;
Carry out bit synchronous and frame synchronization, carry out navigation message decoding after success and resolve satellite position used, satellite velocities information and parameter to obtain navigator fix.
According to one aspect of the present invention, describedly obtain correlation from baseband signal and select the visible satellite meeting certain altitude angular threshold and comprise: according to the ephemeris preserved before navigation neceiver shutdown and receiver location information, calculate the visible satellite in present receiving machine start moment, select the visible satellite of satisfied certain satellite elevation angle thresholding.
According to one aspect of the present invention, described to selected satellite adopt be specially with the mode that the mode of FFT catches middle FFT fast based on matched filtering: when local pseudo-code and Received signal strength pseudo-code phase consistent time, after local pseudo-code is multiplied with Received signal strength, result is remaining residual carrier wave only
fFT analysis of spectrum is done to it, just can obtain Doppler shift f
d.
According to one aspect of the present invention, the code phase of described certain satellite to capturing and Doppler adopt the method for catching based on essence to carry out confirmation to comprise: be provided with M I, Q value, threshold value is set to A (A span 6--12), initial value is set to B (B span such as 1--2), and K=B; Obtain I, Q quadratic sum; Parallel M relevant envelope value carries out thresholding judgement; If I totalizer did not have thresholding, then judged whether the K in I totalizer (K=K+1) equals A, otherwise judged whether the K in I totalizer (K=K-1) equals 0; If the K in I totalizer (K=K+1) equals A, then confirm as smart acquisition success, become by the branch road of K=A and be positioned at middle correlator, essence is caught complete, and state transfer mark change state moving cursor points to NextState; If the K in I totalizer (K=K-1) equals 0, then unsuccessful for catching, arrange subsequently K=B move to a lower M code phase proceed thresholding judge, if moved, all chips are also unsuccessful catches, then value of frequency point is adjusted and move from initial phase and catch, frequency moves complete throwing away and does not catch, then confirm as and catch unsuccessfully.
According to one aspect of the present invention, the described code phase to certain satellite and Doppler catch and adopt the method for catching based on essence to be confirmed to be executed in parallel to the code phase of certain satellite captured and Doppler.
According to one aspect of the present invention, described employing code ring and FLL can be the embodiment that code phase and carrier frequency carry out dynamic range traction: adopt code ring and FLL to carry out twice dynamic range traction to code phase and carrier frequency.
According to one aspect of the present invention, described employing code ring and FLL are carried out twice dynamic range traction to code phase and carrier frequency and specifically be can be: first time adopts the code ring of large bandwidth and FLL to carry out great dynamic range traction to code phase and carrier frequency, wherein carrier wave frequency locking ring wave filter bandwidth gets 100Hz, and Loop filter bandwidth gets 10 ~ 99Hz; Second time adopts the wide code ring of smaller strip and FLL to carry out smaller dynamic range traction to code phase and carrier frequency, and wherein, carrier wave frequency locking ring wave filter bandwidth gets 10 ~ 99Hz, and Loop filter bandwidth gets 0 ~ 9Hz.
According to one aspect of the present invention, the tracking that the code ring of described employing appropriate bandwidth and phaselocked loop carry out code phase and carrier frequency specifically can be: if PGC demodulation and Frequency Locking, then loop enters good state, otherwise loop returns trapped state, under good state, adopt the code ring of appropriate bandwidth and phaselocked loop to carry out the tracking of code phase and carrier frequency, wherein, Loop filter bandwidth and phase locked loop filter bandwidth adopt the value through theory calculate.
According to one aspect of the present invention, described in carry out bit synchronous and frame synchronization comprises: under phase frequency locks effective good state, start bit synchronous, demodulate telegraph text data bit stream, synchronously success, thus transfer frame synchronization to.
According to one aspect of the present invention, carry out after described success that navigation message decoding resolves satellite position used to obtain navigator fix, satellite velocities information specifically can be: after frame synchronization, carry out navigation message decoding, obtain ephemeris, almanac information, obtain navigator fix from ephemeris almanac and resolve satellite position used, satellite velocities information and parameter.
Advantage of the invention process: the method for processing baseband signal for gps satellite navigation of the present invention is caught based on the mode of matched filtering and FFT fast by adopting selected satellite, to obtain code phase under uncertainty on a large scale and doppler information, the method of catching based on essence is adopted to confirm again, code ring and FLL is adopted to carry out dynamic range traction to code phase and carrier frequency after confirming, the code ring of appropriate bandwidth and phaselocked loop is adopted to carry out the tracking of code phase and carrier frequency after success locking phase and frequency, finally carry out bit synchronous and frame synchronization, and after success, carry out navigation message decoding resolve satellite position used to obtain navigator fix, satellite velocities information and parameter, the mode of matched filtering+FFT is adopted to carry out fast Acquisition, once can carry out serial search to multiple code phase, and try to achieve the value of all Doppler's frequency lattice of corresponding each code phase simultaneously, search for code phase and Doppler frequency can walk abreast and carry out, accelerate acquisition speed, smart acquisition mode is adopted to confirm the code phase captured and Doppler frequency after catching, improve the detection probability of the satellite-signal detected and reduce false-alarm probability, improve the reliability of signal capture and the accuracy to Signal parameter estimation, subsequently, first FLL and code ring is adopted to draw, to accelerate the speed of convergence of track loop, the form of phaselocked loop and code ring is finally adopted to carry out tenacious tracking, with the original observed quantity of the pseudorange and carrier phase that ensure track loop outputting high quality, make the pseudorange accuracy of GPS higher, carrier phase precision is higher, and improve the reliability of track loop.
Accompanying drawing explanation
In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, be briefly described to the accompanying drawing used required in embodiment below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is a kind of method for processing baseband signal schematic diagram for gps satellite navigation of the present invention;
Fig. 2 is the bit synchronous process flow diagram of a kind of method for processing baseband signal for gps satellite navigation of the present invention;
Fig. 3 is that the essence of a kind of method for processing baseband signal for gps satellite navigation of the present invention catches process flow diagram;
Fig. 4 is smoothing filter schematic diagram of the present invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
As shown in Figure 1, Figure 2 and Figure 3, a kind of method for processing baseband signal for gps satellite navigation, the described method for processing baseband signal for gps satellite navigation comprises the following steps:
Step S1: obtain correlation from baseband signal and select the visible satellite meeting certain altitude angular threshold;
Described step S1 obtains correlation and the embodiment selecting the visible satellite meeting certain altitude angular threshold can be from baseband signal: after obtaining correlation from baseband signal, first selecting-star algorithm is adopted, so-called selecting-star algorithm, the ephemeris according to preserving before navigation neceiver shutdown and receiver location information, calculate the visible satellite in present receiving machine start moment, select the visible satellite of the visible satellite namely certain satellite elevation angle thresholding meeting certain altitude angular threshold.
In actual applications, the elevation angle threshold value of described certain satellite elevation angle thresholding is generally chosen between 5 ° to 10 °.
Step S2: adopt selected satellite and catch fast based on the mode of matched filtering and FFT, to obtain code phase under uncertainty on a large scale and doppler information;
Described step S2 adopts selected satellite and catches fast based on the mode of matched filtering and FFT, can be with the embodiment obtaining code phase under uncertainty on a large scale and doppler information: adopt the mode based on matched filtering and FFT to catch fast to selected usable satellite, this mode can be caught N number of chip simultaneously, accelerate acquisition speed and save hardware resource, catch unsuccessfully, catch the visible satellite that next satisfies condition; Obtain the code phase under uncertainty on a large scale and doppler information after acquisition success, proceed to acknowledgement state.
In actual applications, described FFT mode specifically can be: when local pseudo-code is consistent with Received signal strength pseudo-code phase, after local pseudo-code is multiplied with Received signal strength, and result is remaining residual carrier wave only
fFT analysis of spectrum is done to it, just can obtain Doppler shift f
d.
In actual applications, the value of N is chosen according to actual hardware resource and required acquisition speed, and the value of N is generally a hundreds of chip, and have employed technology and fast Acquisition algorithm based on selecting star, make the cold start-up time be less than 50s, the warm start time is less than 35s.In order to improve acquisition sensitivity, fast Acquisition adopts the non-coherent accumulation of many milliseconds, makes receiver can be less than the navigation signal of-133dBm by lock-on signal power.
Step S3: if acquisition success, then adopt the method for catching based on essence to confirm to the code phase of the satellite captured and Doppler;
If described step S3 acquisition success, then the embodiment that code phase and the Doppler of the satellite captured adopt the method for catching based on essence to confirm be can be: to code phase and the Doppler of certain satellite captured, the method of catching based on essence is adopted to confirm, improve the detection probability of the satellite-signal detected and reduce false-alarm probability, improve the reliability of signal capture and the accuracy to Signal parameter estimation.If catch unsuccessfully, then continue to perform step S2 and catch.
In actual applications, described employing is carried out confirmation based on the method that essence is caught and is comprised and be provided with M I, Q value, and threshold value is set to A (A span 6--12), and initial value is set to B (B span such as 1--2), and K=B; Obtain I, Q quadratic sum; Parallel M relevant envelope value carries out thresholding judgement; If I totalizer did not have thresholding, then judged whether the K in I totalizer (K=K+1) equals A, otherwise judged whether the K in I totalizer (K=K-1) equals 0; If the K in I totalizer (K=K+1) equals A, then confirm as smart acquisition success, become by the branch road of K=A and be positioned at middle correlator, essence is caught complete, and state transfer mark change state moving cursor points to NextState; If the K in I totalizer (K=K-1) equals 0, then unsuccessful for catching, arrange subsequently K=B move to a lower M code phase proceed thresholding judge, if moved, all chips are also unsuccessful catches, then value of frequency point is adjusted and move from initial phase and catch, frequency moves complete throwing away and does not catch, then confirm as and catch unsuccessfully.
Wherein, described A and B chooses according to practical experience, in general, and A=10, B=2.
In actual applications, A and the B parameter of described smart catching method also can be arranged according to environment residing for receiver is different.
In actual applications, described in the present embodiment, the code phase of certain satellite and Doppler caught and adopt the method for catching based on essence to be confirmed to be executed in parallel to the code phase of certain satellite captured and Doppler, accelerating acquisition speed.
Step S4: if smart acquisition success, then adopt code ring and FLL to carry out dynamic range traction to code phase and carrier frequency;
If the smart acquisition success of described step S4, code ring and FLL is then adopted to can be the embodiment that code phase and carrier frequency carry out dynamic range traction: if smart acquisition success, then illustrate and confirmed acquisition success, adopt code ring and FLL to carry out dynamic range traction to code phase and carrier frequency subsequently.If essence is caught unsuccessfully, then continue to perform from step S2 catches, then confirm.
In actual applications, because follow-up track loop can export raw pseudo range for locating and raw carrier phase measured value, the time of reception of satellite-signal is wherein obtained by the C/A code phase measuring value of code ring, satellite-signal launch time is obtained by navigation message, (satellite-signal launch time-satellite signal receiving time) * c=raw pseudo range, wherein c=3*10^8 is the light velocity, therefore the code phase measuring precision of code ring directly determines raw pseudo range precision, at track loop coherent integration time, satellite-signal carrier-to-noise ratio, when front and back correlator spacing is certain, code ring measuring accuracy is just directly determined by the loop bandwidth of Loop filter.Carrier phase measurement precision directly determines the precision of raw carrier phase measured value, and when track loop coherent integration time, satellite-signal carrier-to-noise ratio are certain, carrier phase measurement precision is just directly determined by the loop bandwidth of carrier phase-locked loop.Because the code phase after catching is half-chip, frequency is hundreds of hertz, therefore, can adopt twice traction during traction.
Described twice traction is as follows: first time adopts the code ring of large bandwidth and FLL to carry out great dynamic range traction to code phase and carrier frequency, and wherein carrier wave frequency locking ring wave filter bandwidth gets 100Hz, and Loop filter bandwidth gets 10 ~ 99Hz; Second time adopts the wide code ring of smaller strip and FLL to carry out smaller dynamic range traction to code phase and carrier frequency, and wherein, carrier wave frequency locking ring wave filter bandwidth gets 10 ~ 99Hz, and Loop filter bandwidth gets 0 ~ 9Hz.The bandwidth of the loop filter of FLL and code ring reduces gradually, to accelerate the speed of convergence of track loop.
Step S5: if draw successfully, then the mode adopting code ring to be combined with FLL carries out more meticulous code phase and the estimation of carrier doppler;
If described step S5 draws successfully, the estimation that the mode then adopting code ring to be combined with FLL carries out more meticulous code phase and carrier doppler is specially: drawing successfully, and the mode adopting code ring to be combined with FLL is carried out the estimation of more meticulous code phase and carrier doppler thus carries out PGC demodulation and Frequency Locking.
Step S6: if successfully carry out PGC demodulation and Frequency Locking, then adopt the code ring of appropriate bandwidth and phaselocked loop to carry out the tracking of code phase and carrier frequency;
If described step S6 successfully carries out PGC demodulation and Frequency Locking, the embodiment then adopting the code ring of appropriate bandwidth and phaselocked loop to carry out the tracking of code phase and carrier frequency can be: if PGC demodulation and Frequency Locking, then loop enters good state, otherwise loop returns trapped state, under good state, the code ring of appropriate bandwidth and phaselocked loop is adopted to carry out the tracking of code phase and carrier frequency.The form of phaselocked loop and code ring is adopted to carry out tenacious tracking, with the original observed quantity of the pseudorange and carrier phase that ensure track loop outputting high quality, the pseudorange accuracy of GPSL1 (RMS) is made to be less than 30cm, carrier phase precision (RMS) is less than 1mm, and improves the reliability of track loop.
In actual applications, described FLL FLL selects: arctan (point intersects) phase detector, this frequency discriminator represents one frequency discrimination method the most accurately, and the amplitude of their frequency discrimination result and signal has nothing to do, and but calculated amount is lower.Phase-locked loop pll selects two quadrant arctan function phase detector: arctan (Q/I) phase detector, when actual phase difference dystopy is within the scope of-90 ° to 90 °, the work of this phase detector keeps linear, and its identified result exported and signal amplitude have nothing to do, the most a kind of in various Cohan tower phaselocked loop phase detector, wherein Q is the signal of code tracking loop quadrature branch, and I is the signal of code tracking loop in-phase branch.Code ring DLL selects: noncoherently subtract delayed envelope in advance.
In actual applications, PGC demodulation is carried out and the mode of Frequency Locking can be as follows:
Locking decision is divided into Frequency Locking and PGC demodulation.Wherein Frequency Locking uses:
Wherein: I
kthe signal of the instant branch road of homophase in k moment, I
k-1it is the signal of the instant branch road of homophase in k-1 moment.Q
kthe signal of the orthogonal instant branch road in k moment, Q
k-1it is the signal of the orthogonal instant branch road in k-1 moment.Sign (x) is sign function, and it returns the sign of x, namely obtains-1 when x is less than 0, otherwise obtains 1.L
fit is Frequency Locking judgment variables.
Frequency Locking judgment variables L afterwards
fthrough a smoothing filter, as shown in Figure 4:
Wherein: α is filter coefficient, and value is between 0-1.L
fn () is the Frequency Locking judgment variables in n moment, Out (n) is the filtering output variable in n moment, Out (n-1) is the filtering output variable in the n-1 moment after a unit delay, filtering Output rusults variable Out (n) and a threshold value in n moment carry out judging (such as 0.75), judge that loop is the need of switching state, namely judge frequency-locked loop whether losing lock.
In actual applications, wherein PGC demodulation uses:
I (n) is the signal of the instant branch road of homophase in n moment, and Q (n) is the signal of the orthogonal instant branch road in n moment, and M is cumulative number of times.
If it is good that its result C2 Φ is greater than 0.9 tracking effect, if be less than 0.75, then judge phase-locked loop losing lock.
In actual applications, in order to export high-precision pseudorange and carrier-phase measurement, wherein, Loop filter bandwidth and phase locked loop filter bandwidth adopt the value through theory calculate.Thus the satellite-signal captured can be followed the tracks of faster, and the raw pseudo range measured value of energy outputting high quality and raw carrier phase measured value.
Step S7: carry out bit synchronous and frame synchronization, carries out navigation message decoding after success and resolves satellite position used, satellite velocities information and parameter to obtain navigator fix;
Described step S7 carries out bit synchronous and frame synchronization, carry out navigation message decoding after success to can be with the embodiment obtaining navigator fix and resolve satellite position used, satellite velocities information and parameter: under phase frequency locks effective good state, start bit synchronous, demodulate telegraph text data bit stream, synchronous success, thus transfer frame synchronization to, navigation message decoding is carried out after frame synchronization, obtain ephemeris, almanac information, obtain navigator fix from ephemeris almanac and resolve satellite position used, satellite velocities information and parameter.
In actual applications, the principle of described bit synchronous can be as follows:
Arrange the bit synchronous timing statistics of Ts (Ts such as gets 20ms or its integral multiple), determine thresholding N1 (N1 such as gets 25), N2 (N2 such as gets 15), the 1-20 bit number of demarcation is each constructs counter.1ms data judge to overturn with 1ms before, as overturn the totalizer+1 of corresponding label, judge whether the counter >=N1 only having a Nogata label, if it is bit synchronous success is judged, every 20ms adds up and is averaging and carries out demodulation judgement, if bit value >=0.9 demodulated or≤-0.9, then judge demodulation success, composition bit stream.If bit value≤0.9 demodulated or >=-0.9, then judge demodulation failure, tolerance counting+1.Judge afterwards unsuccessfully to tolerate counting >N (N value such as 2--5), if otherwise bit synchronous success, if and timing statistics more than after MTs (M value such as 6--10), still unsuccessful synchronization failure, returns and recaptures.If the counter < N1 of a Nogata label, then judge whether 2 and above Nogata label < N1 but >=N2, if it is synchronization failure, counter O reset adds up Ts again, timing statistics is more than after MTs, still unsuccessful then synchronization failure, returns and recaptures.
In actual applications, after bit synchronous, the coherent accumulation time-switching of tracking loop is the coherent accumulation of many milliseconds, increase signal energy, further raising is to the tracking of weak signal, and the original observed quantity quality of data, navigation message decoding is carried out after frame synchronization, obtain ephemeris, almanac information, obtain navigator fix from ephemeris almanac and resolve satellite position used, satellite velocities information, and Ionospheric Parameters, clock correction parameter etc., these parameters pass to further part together with raw pseudo range measured value, raw carrier phase measured value.
Advantage of the invention process: the method for processing baseband signal for gps satellite navigation of the present invention by catching fast based on the mode of matched filtering and FFT the employing of selected satellite, to obtain code phase under uncertainty on a large scale and doppler information.The method of catching based on essence is adopted to confirm again, adopt code ring and FLL to carry out dynamic range traction to code phase and carrier frequency after confirming, after successful locking phase and frequency, adopt the code ring of appropriate bandwidth and phaselocked loop to carry out the tracking of code phase and carrier frequency.Finally carry out bit synchronous and frame synchronization, and after success, carry out navigation message decoding resolve satellite position used, satellite velocities information and parameter to obtain navigator fix.The mode of matched filtering+FFT is adopted to carry out fast Acquisition, once can carry out serial search to multiple code phase, and the value of all Doppler simultaneously trying to achieve corresponding each code phase lattice frequently, the search for code phase and Doppler frequency can walk abreast and carry out, and accelerates acquisition speed.Adopt smart acquisition mode to confirm the code phase captured and Doppler frequency after catching, improve the detection probability of the satellite-signal detected and reduce false-alarm probability, improve the reliability of signal capture and the accuracy to Signal parameter estimation.Subsequently, first FLL and code ring is adopted to draw, to accelerate the speed of convergence of track loop, the form of phaselocked loop and code ring is finally adopted to carry out tenacious tracking, with the original observed quantity of the pseudorange and carrier phase that ensure track loop outputting high quality, make the pseudorange accuracy of GPS higher, carrier phase precision is higher, and improves the reliability of track loop.
The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, the technician of any skilled is in technical scope disclosed by the invention; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of described claim.
Claims (10)
1. for a method for processing baseband signal for gps satellite navigation, it is characterized in that, the described method for processing baseband signal for gps satellite navigation comprises the following steps:
Obtain correlation from baseband signal and select the visible satellite meeting certain altitude angular threshold;
Selected satellite is adopted and catches fast based on the mode of matched filtering and FFT, to obtain code phase under uncertainty on a large scale and doppler information;
If acquisition success, then the method for catching based on essence is adopted to confirm to the code phase of the satellite captured and Doppler;
If smart acquisition success, then code ring and FLL is adopted to carry out dynamic range traction to code phase and carrier frequency;
If draw successfully, then the mode adopting code ring to be combined with FLL carries out more meticulous code phase and the estimation of carrier doppler;
If successfully carry out PGC demodulation and Frequency Locking, then the code ring of appropriate bandwidth and phaselocked loop is adopted to carry out the tracking of code phase and carrier frequency;
Carry out bit synchronous and frame synchronization, carry out navigation message decoding after success and resolve satellite position used, satellite velocities information and parameter to obtain navigator fix.
2. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, describedly obtain correlation from baseband signal and select the visible satellite meeting certain altitude angular threshold and comprise: according to the ephemeris preserved before navigation neceiver shutdown and receiver location information, calculate the visible satellite in present receiving machine start moment, select the visible satellite of satisfied certain satellite elevation angle thresholding.
3. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, described to selected satellite adopt be specially with the mode that the mode of FFT catches middle FFT fast based on matched filtering: when local pseudo-code and Received signal strength pseudo-code phase consistent time, after local pseudo-code is multiplied with Received signal strength, result is remaining residual carrier wave only
fFT analysis of spectrum is done to it, just can obtain Doppler shift f
d.
4. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, the code phase of described certain satellite to capturing and Doppler adopt the method for catching based on essence to carry out confirmation to comprise: be provided with M I, Q value, threshold value is set to A (A span 6--12), initial value is set to B (B span such as 1--2), and K=B; Obtain I, Q quadratic sum; Parallel M relevant envelope value carries out thresholding judgement; If I totalizer did not have thresholding, then judged whether the K in I totalizer (K=K+1) equals A, otherwise judged whether the K in I totalizer (K=K-1) equals 0; If the K in I totalizer (K=K+1) equals A, then confirm as smart acquisition success, become by the branch road of K=A and be positioned at middle correlator, essence is caught complete, and state transfer mark change state moving cursor points to NextState; If the K in I totalizer (K=K-1) equals 0, then unsuccessful for catching, arrange subsequently K=B move to a lower M code phase proceed thresholding judge, if moved, all chips are also unsuccessful catches, then value of frequency point is adjusted and move from initial phase and catch, frequency moves complete throwing away and does not catch, then confirm as and catch unsuccessfully.
5. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, the described code phase to certain satellite and Doppler catch and adopt the method for catching based on essence to be confirmed to be executed in parallel to the code phase of certain satellite captured and Doppler.
6. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, described employing code ring and FLL can be the embodiment that code phase and carrier frequency carry out dynamic range traction: adopt code ring and FLL to carry out twice dynamic range traction to code phase and carrier frequency.
7. the method for processing baseband signal for gps satellite navigation according to claim 6, it is characterized in that, described employing code ring and FLL are carried out twice dynamic range traction to code phase and carrier frequency and specifically be can be: first time adopts the code ring of large bandwidth and FLL to carry out great dynamic range traction to code phase and carrier frequency, wherein carrier wave frequency locking ring wave filter bandwidth gets 100Hz, and Loop filter bandwidth gets 10 ~ 99Hz; Second time adopts the wide code ring of smaller strip and FLL to carry out smaller dynamic range traction to code phase and carrier frequency, and wherein, carrier wave frequency locking ring wave filter bandwidth gets 10 ~ 99Hz, and Loop filter bandwidth gets 0 ~ 9Hz.
8. the method for processing baseband signal for gps satellite navigation according to claim 1, it is characterized in that, the tracking that the code ring of described employing appropriate bandwidth and phaselocked loop carry out code phase and carrier frequency specifically can be: if PGC demodulation and Frequency Locking, then loop enters good state, otherwise loop returns trapped state, under good state, the code ring of appropriate bandwidth and phaselocked loop is adopted to carry out the tracking of code phase and carrier frequency, wherein, Loop filter bandwidth and phase locked loop filter bandwidth adopt the value through theory calculate.
9. according to the method for processing baseband signal for gps satellite navigation one of claim 1 to 8 Suo Shu, it is characterized in that, describedly carry out bit synchronous and frame synchronization comprises: under phase frequency locks effective good state, start bit synchronous, demodulate telegraph text data bit stream, bit synchronous success, thus transfer frame synchronization to.
10. the method for processing baseband signal for gps satellite navigation according to claim 9, it is characterized in that, carry out after described success that navigation message decoding resolves satellite position used to obtain navigator fix, satellite velocities information specifically can be: after frame synchronization, carry out navigation message decoding, obtain ephemeris, almanac information, obtain navigator fix from ephemeris almanac and resolve satellite position used, satellite velocities information and parameter.
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| CN106411807A (en) * | 2016-08-31 | 2017-02-15 | 北京钧威科技有限公司 | High-speed railway vehicle-ground communication system-based modulation and demodulation method and system |
| CN107037457A (en) * | 2017-03-28 | 2017-08-11 | 上海双微导航技术有限公司 | A kind of satellite-based enhancing receiver based on Inmarsat systems |
| CN107884787A (en) * | 2017-11-23 | 2018-04-06 | 深圳开阳电子股份有限公司 | A kind of method, apparatus and satellite navigation receiver of the demodulation of GNSS texts |
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| CN111399006B (en) * | 2020-04-07 | 2020-11-24 | 北京理工大学 | High-sensitivity GNSS carrier tracking loop optimization method |
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