CN103605141A - Fast capturing method for GNSS code - Google Patents
Fast capturing method for GNSS code Download PDFInfo
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- CN103605141A CN103605141A CN201310615930.3A CN201310615930A CN103605141A CN 103605141 A CN103605141 A CN 103605141A CN 201310615930 A CN201310615930 A CN 201310615930A CN 103605141 A CN103605141 A CN 103605141A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/256—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to timing, e.g. time of week, code phase, timing offset
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- Radar, Positioning & Navigation (AREA)
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
The invention discloses a fast capturing method for a GNSS code. The fast capturing method mainly includes the steps that a code phase shift threshold and a carrier shift threshold are set in advance, a GNSS long code in a satellite signal and local pseudo code signals with different code phase shifts are subject to relevant processing, relevant results are subject to one-dimensional searching by a receiver, a correlation value is compared with the code phase shift threshold to acquire a code phase shift, and existence of a satellite is determined; then, one-dimensional carrier frequency searching is carried out, the correlation value is compared with the carrier shift threshold to acquire a carrier shift, and fast signal capturing is finished. The fast capturing method for the GNSS long code overcomes frequency shift accumulation brought by local crystal oscillators in the long code capturing process, and both sensitivity and speed are given consideration to finish fast long-code signal capturing without needing a large number of hardware resources.
Description
Technical field
The present invention relates to the quick capturing method of satellite-signal, relate in particular to a kind of for GNSS(Global Navigation Satellite System) quick capturing method of long period pseudo-code in signal.
Background technology
The current focus round GPS modernization, the navigation signal newly increasing exactly.L2C is the civil navigation signal of first new construction after GPS modernization, has had at present 9 satellite in orbit, and by 2016, can realize the whole network operation.
L2C has different signal structures from L1 signal, and it is comprised of two kinds of long code CL and short code CM two signals, and wherein CL code is navigation channel code, do not modulate navigation message above, CM code is data channel code, above has modulation navigation message, is subject to the restriction of text bit saltus step.
CM code is comprised of 10230 chips, and CL code is comprised of 10230*75 chip, and the CM code cycle is 20ms, and the CL code cycle is 1.5s, so the increase of correlation time, and tracking sensitivity is improved a lot; The code check of CL/CM is 511.5KHz, is half of C/A code bit rate, owing to having adopted FEC(forward error correction) technology, bandwidth is also 2.046MHz, and CM code is identical with the emissive power of CL code, respectively accounts for 50% of general power.The structure of L2C signal is as Fig. 1.
Although the power of L2C signal is than the low 1.5dB of the power of L1C/A signal,, L2C signal or just cause researcher's concern at the beginning of occurring.On the one hand, L2C signal energy and L1C/A combined signal make the error causing for overcoming ionosphere; On the other hand, L2C signal has pilot signal channel, be applicable to long coherent accumulation and process, and the CM code that in data channel, the cycle is 20ms and navigation data bit upset synchronous.
The long code CL signal of L2C is to form by time division multiplex, and does not modulate text, is applicable to carrying out long coherent integration, and the signal structure that these are special makes the L2C can be indoor, and realizes and catching under the poor condition of signal environment.Under general condition, Direct Acquisition CL signal not, but first by catching CM signal, then utilize the phase relation between CM and CL, then catch CL signal.But at C/A signal, do not exist, or under cannot the condition of aided capture, need Direct Acquisition L2C signal, due to the code cycle of the shortest CM code 20ms, according to common C/A code acquisition algorithm, need a large amount of computing time and hardware resource.
Therefore, those skilled in the art is devoted to develop a kind of fast Acquisition algorithm for GNSS long code, to overcome long code when catching, and the frequency shift (FS) accumulative total that local crystal oscillator brings, and taken into account sensitivity and speed, and do not need a large amount of hardware resources.
Summary of the invention
Because the above-mentioned defect of prior art, the signal sending from satellite reaches ground through very long distance, and receiver receives sort signal, and parses data wherein, obtains pseudo-range measurements and time value for locating.In whole process, various pseudo-codes reduce noise and disturb the destruction to signal.Each satellite all can corresponding its unique pseudo-code sequence, and to prevent intersatellite interference each other, this interference is called the cross-correlation interference of code.And identical pseudo-code, only have when code phase is consistent with code frequency, there is best correlativity, utilize this characteristic, the invention provides a kind of quick capturing method for GNSS long code, make receiver can constantly receive satellite-signal, and in motion process, keep the synchronism with sort signal.
Meanwhile, intermediate-freuqncy signal, through carrier wave NCO mixing, is peeled off carrier wave, in the signal of output, with Doppler frequency deviation, comprises the unstable frequency deviation of bringing of local crystal oscillator.Then two kinds of pseudo-codes that signal and local code generation device produce carry out relevant after, carry out the integration accumulation process of a period of time, reduction noise.Because CM code the shortest in L2C code is 20 times of the GPS C/A code cycle, so in carrying out the process of correlation integral, need to consider the impact of the frequency deviation that local crystal oscillator brings.Therefore, quick capturing method of the present invention, after integration is cumulative, is done conjugate multiplication computing by two paths of signals, eliminates a part of frequency deviation, makes the frequency search groove of pre-coherent integration become large, and acquisition in frequency domain speed is accelerated.
For achieving the above object, the invention provides a kind of quick capturing method for GNSS long code, it is characterized in that, comprising:
Further, in described step 1, initialization related data also comprises: pseudo-code is set and defends asterisk, carrier frequency is set, sets the pseudo-code cycle, the coherent integration time is set, the number of times of irrelevant integration and the delay time of conjugate multiplication are set.
Further, in described step 2, comprising:
The local pseudo-code phase of step (101) is slided, and obtains having the described local pseudo-code of different code phase offset;
Step (102) related operation: comprise a plurality of related operation passages, related operation passage described in each, the phase place of described local pseudo-code all keeps fixing deviation; In described satellite-signal, GNSS long code is carried out related operation described in each in related operation passage;
Step (107) is relevant cumulative: comprise coherent integration and irrelevant integration;
Step (108) mutual deviation divides;
Step (109) non-coherent integration: relevant with described step (107) cumulative identical;
The described code phase offset of step (110) is judged: the correlation that step (109) calculates and described code phase offset thresholding compare, be greater than described code phase offset thresholding, current code phase offset value is described code phase offset value, and jumps in step 3; Be less than described code phase offset thresholding, redirect is returned in step (101) again, re-start the judgement of described code phase offset.
Further, the described related operation in described step (102) comprises: unload ripple computing, pseudo code correlation computing and conjugate multiplication computing.
Further, described in each, related operation passage is independent of one another, and parallel processing.
Further, described step 3, determines in the carrier wave frequency deviation of signal, comprising:
Step (111) carrier wave frequency deviation adjustment: in carrier wave, carrier frequency is adjusted to setting;
Step (116) related operation: comprise a plurality of related operation passages; Related channel program described in each, described carrier frequency all keeps fixing deviation; Different described related operation passages, is correlated with different described carrier frequencies, obtains the correlation in different frequency section;
The described carrier wave frequency deviation of step (117) is judged: the correlation obtaining in described step (116) and carrier wave frequency deviation thresholding are compared: correlation is less than described carrier wave frequency deviation thresholding, described step (111) is returned in redirect; Correlation is greater than described carrier wave frequency deviation thresholding, and current carrier frequency offset values is exactly described carrier wave frequency deviation.
Further, described in each, related operation passage is independent of one another, and parallel processing.
Further, described catching method also comprises GNSS long code in described satellite-signal is first carried out to burst reason, and then carries out fast Acquisition according to described step 1, described step 2 and described step 3.
In a preferred embodiment of the present invention, to the described combined treatment of GNSS long code in described satellite-signal, be folding processing.
A kind of quick capturing method for GNSS long code of the present invention, by the determining of code phase offset and carrier shift, to complete the fast Acquisition to long code signal.Use catching method of the present invention, satellite receiver, as long as correlated results is carried out to linear search, finds code phase.Then as long as determine after the existence of satellite, then the frequency search that carries out one dimension just completes two-dimensional search process, with respect to traditional two-dimensional search process, reduced search time greatly.In result, not containing navigation message bit, can carry out long coherent integration.Meanwhile, conjugate multiplication has been removed reception carrier and has been copied the frequency difference between carrier wave, has avoided the 3dB loss of introducing in traditional correlator.
A kind of fast Acquisition algorithm for GNSS long code of the present invention, when having overcome long code and catching, the frequency shift (FS) accumulative total that local crystal oscillator brings, takes into account the fast Acquisition that sensitivity and speed complete long code signal, and does not need a large amount of hardware resources.
Below with reference to accompanying drawing, the technique effect of design of the present invention, concrete structure and generation is described further, to understand fully object of the present invention, feature and effect.
Accompanying drawing explanation
Fig. 1 is the structural representation of GPS L2C signal;
Fig. 2 is the process flow diagram of the quick capturing method of a kind of GNSS long code of the present invention;
Fig. 3 is the structural drawing of definite code phase offset of the quick capturing method of a kind of GNSS long code of the present invention;
Fig. 4 is the structural drawing of the folded code of GNSS long code in satellite-signal.
Embodiment
Below in conjunction with accompanying drawing, embodiments of the invention are elaborated: the present embodiment is implemented under with technical solution of the present invention prerequisite, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
The fast Acquisition algorithm of a kind of GNSS long code of the present invention specifically as shown in Figure 2, comprising:
The local pseudo-code phase of step 101 is slided: in code phase search process, the code phase of the local pseudo-code of constantly sliding, guarantees the synchronism of GNSS long code in local pseudo-code signal and satellite-signal, thereby peels off pseudo-code modulation, obtains telegraph text data.
Fig. 3 has provided a structural drawing of definite code phase offset of quick capturing method of the present invention.As shown in Figure 3, intermediate-freuqncy signal IF301, through carrier wave digital oscillator NCO(numerical controlled oscillator) after 302 mixing, peel off carrier wave; Signal after peeling off has comprised pseudo-code signal, text bit, satellite and relative to receiver, has moved Doppler frequency deviation and the unstable frequency deviation of bringing of the crystal oscillator of receiver own of bringing.In order further to obtain text bit, need to carry out relevant treatment with the pseudo-code signal that code generator 303 produces.In order to improve gain, need to carry out the integration accumulation process of a period of time, reduce noise and bring impact, acquisition procedure is exactly pseudo-code while differentiating local signal pseudo-code and satellite launch to receiver section and the deviation between frequency, then synchronous two pseudo-codes, just can eliminate the pseudo-code modulation in GNSS signal, obtain telegraph text data.Because cycle of GNSS long code is tens times or even hundred times of common pseudo-code (such as the chip lengths of GPS C/A code is 1023 chips).When this long code signal is caught, can consume very many time.The present invention is directed to long code signal and adopted two-way coherent signal, in having more Yi road signal, short code signal has also been carried out to relevant treatment, can provide in the back can difference variate-value, also take full advantage of the energy of short code signal simultaneously, improved sensitivity.Two-way coherent signal, after chronotron 304,305 time delays, carry out conjugate multiplication 306,307 with coherent signal respectively, obtain from differential signal, through thinking a new pseudo-code from differentiated signal, and then carry out coherent integration 308,309, coherent integration can improve associated gain value, eliminates the noise that part difference is brought.Signal after coherent integration is conjugate multiplication 310 again, obtains the correlated results of new pseudo-code, has peeled off carrier wave and peel off the impact that frequency deviation is brought in correlated results.Finally carry out after irrelevant integration 311, just can obtain the correlated results in code phase territory, slip code phase, obtains the maximal value of correlation, just can determine code phase offset.
In order to catch the signal of satellite, only need to determine after the existence of satellite, then can determine frequency deviation value to just searching in frequency domain.
Fig. 1 has provided in GNSS signal, the code structure figure of the L2C code that pseudo-code length is longer.Its telegraph text data, be modulated on short code CM, short code CM has 10230 chips, long code CL code has 10230*75 chip, two kinds of codes are by time-multiplexed mode weave in, after having interweaved, the length of each chip is reduced into half, power also reduces half, be equivalent to the 3dBm that declined, the difference of the GNSS signal of it and other is only that its pseudo-code length has increased, therefore, acquisition speed is slack-off mainly to be appeared in yard territory, by combining two kinds of codes, and then according to above-mentioned step 1, step 2 and step 3 are carried out the fast Acquisition of GNSS long code in satellite-signal, so both can accelerate capture time, can make full use of signal power again, improve acquisition sensitivity.In the present embodiment, in order to accelerate the search speed of code phase, utilized folded code to reduce search time.As shown in Figure 4, the CM code of L2C of take in figure is example to the form of folded code, will after code doubling, form new coded signal, new coded signal, and length only has original half, can add acquisition speed fast again.
More than describe preferred embodiment of the present invention in detail.The ordinary skill that should be appreciated that this area just can design according to the present invention be made many modifications and variations without creative work.Therefore, all technician in the art, all should be in the determined protection domain by claims under this invention's idea on the basis of existing technology by the available technical scheme of logical analysis, reasoning, or a limited experiment.
Claims (9)
1. for a quick capturing method for GNSS long code, it is characterized in that, comprising:
Step 1, initialization related data: code phase offset thresholding and carrier wave frequency deviation thresholding are set;
Step 2, determine the code phase offset of GNSS long code in satellite-signal: by local pseudo-code signal is carried out to phase slip, local pseudo-code signal and described GNSS long code under different code phase deviations are processed, correlation and described code phase offset thresholding after processing are compared, and what be greater than described code phase offset thresholding is exactly described code phase offset;
Step 3, determines the carrier wave frequency deviation of described satellite-signal: carrier frequency is adjusted, with different carrier frequencies, carried out relevant treatment, correlation and the comparison of described carrier wave frequency deviation thresholding to after processing, obtain described carrier wave frequency deviation.
2. a kind of quick capturing method for GNSS long code as claimed in claim 1, wherein, in described step 1, initialization related data also comprises: pseudo-code is set and defends asterisk, carrier frequency is set, sets the pseudo-code cycle, the coherent integration time is set, the number of times of irrelevant integration and the delay time of conjugate multiplication are set.
3. a kind of quick capturing method for GNSS long code as claimed in claim 1, wherein, in described step 2, comprising:
The local pseudo-code phase of step (101) is slided, and obtains having the described local pseudo-code of different code phase offset;
Step (102) related operation: comprise a plurality of related operation passages, related operation passage described in each, the phase place of described local pseudo-code all keeps fixing deviation; In described satellite-signal, GNSS long code is carried out related operation described in each in related operation passage;
Step (107) is relevant cumulative: comprise coherent integration and irrelevant integration;
Step (108) mutual deviation divides;
Step (109) non-coherent integration: relevant with described step (107) cumulative identical;
The described code phase offset of step (110) is judged: the correlation that step (109) calculates and described code phase offset thresholding compare, be greater than described code phase offset thresholding, current code phase offset value is described code phase offset value, and jumps in step 3; Be less than described code phase offset thresholding, redirect is returned in step (101) again, re-start the judgement of described code phase offset.
4. a kind of quick capturing method for GNSS long code as claimed in claim 3, wherein, the described related operation in described step (102) comprises: unload ripple computing, pseudo code correlation computing and conjugate multiplication computing.
5. a kind of quick capturing method for GNSS long code as claimed in claim 3, wherein, described in each, related operation passage is independent of one another, and parallel processing.
6. a kind of quick capturing method for GNSS long code as claimed in claim 1, wherein, described step 3, determine and comprise the carrier wave frequency deviation of signal:
Step (111) carrier wave frequency deviation adjustment: in carrier wave, carrier frequency is adjusted to setting;
Step (116) related operation: comprise a plurality of related operation passages; Related channel program described in each, described carrier frequency all keeps fixing deviation; Different described related operation passages, is correlated with different described carrier frequencies, obtains the correlation in different frequency section;
The described carrier wave frequency deviation of step (117) is judged: the correlation obtaining in described step (116) and carrier wave frequency deviation thresholding are compared: correlation is less than described carrier wave frequency deviation thresholding, described step (111) is returned in redirect; Correlation is greater than described carrier wave frequency deviation thresholding, and current carrier frequency offset values is exactly described carrier wave frequency deviation.
7. a kind of quick capturing method for GNSS long code as claimed in claim 6, wherein, described in each, related operation passage is independent of one another, and parallel processing.
8. a kind of quick capturing method for GNSS long code as claimed in claim 1, wherein, described catching method also comprises GNSS long code in described satellite-signal is first carried out to combined treatment, and then carries out fast Acquisition according to described step 1, described step 2 and described step 3.
9. a kind of quick capturing method for GNSS long code as claimed in claim 8, wherein, is folding processing to the described combined treatment of GNSS long code in described satellite-signal.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536020A (en) * | 2015-01-05 | 2015-04-22 | 泰斗微电子科技有限公司 | GNSS signal capturing method |
| CN105549042A (en) * | 2016-01-05 | 2016-05-04 | 中国科学院嘉兴微电子与系统工程中心 | Multi-sensor auxiliary satellite signal capturing apparatus and method |
| CN105656511A (en) * | 2016-01-20 | 2016-06-08 | 上海物联网有限公司 | Differential correlation acquisition method applied to environment with frequency offset and low signal to noise ratio |
| CN108802772A (en) * | 2017-04-28 | 2018-11-13 | 展讯通信（上海）有限公司 | The catching method and device of GNSS satellite, storage medium, terminal |
| CN109765581A (en) * | 2019-01-17 | 2019-05-17 | 上海华测导航技术股份有限公司 | A kind of tracking and processing method of L2C signal |
| CN111756432A (en) * | 2019-03-28 | 2020-10-09 | 广州海格通信集团股份有限公司 | Frequency selection method, device, equipment and storage medium |
-
2013
- 2013-11-27 CN CN201310615930.3A patent/CN103605141A/en active Pending
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536020A (en) * | 2015-01-05 | 2015-04-22 | 泰斗微电子科技有限公司 | GNSS signal capturing method |
| CN105549042A (en) * | 2016-01-05 | 2016-05-04 | 中国科学院嘉兴微电子与系统工程中心 | Multi-sensor auxiliary satellite signal capturing apparatus and method |
| CN105549042B (en) * | 2016-01-05 | 2018-04-03 | 中国科学院嘉兴微电子与系统工程中心 | A kind of apparatus and method of multisensor secondary satellite signal capture |
| CN105656511A (en) * | 2016-01-20 | 2016-06-08 | 上海物联网有限公司 | Differential correlation acquisition method applied to environment with frequency offset and low signal to noise ratio |
| CN105656511B (en) * | 2016-01-20 | 2020-04-07 | 上海物联网有限公司 | Differential correlation acquisition method suitable for environment with frequency offset and low signal-to-noise ratio |
| CN108802772A (en) * | 2017-04-28 | 2018-11-13 | 展讯通信（上海）有限公司 | The catching method and device of GNSS satellite, storage medium, terminal |
| CN108802772B (en) * | 2017-04-28 | 2020-04-03 | 展讯通信（上海）有限公司 | GNSS satellite capturing method and device, storage medium and terminal |
| CN109765581A (en) * | 2019-01-17 | 2019-05-17 | 上海华测导航技术股份有限公司 | A kind of tracking and processing method of L2C signal |
| CN111756432A (en) * | 2019-03-28 | 2020-10-09 | 广州海格通信集团股份有限公司 | Frequency selection method, device, equipment and storage medium |
| CN111756432B (en) * | 2019-03-28 | 2022-03-11 | 广州海格通信集团股份有限公司 | Frequency selection method, device, equipment and storage medium |
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Application publication date: 20140226 |