CN109884673B - New system satellite signal NH code stripping method - Google Patents
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Abstract
The invention belongs to a method for stripping NH codes of satellite signals of a new system. The acquisition is divided into two stages of pre-acquisition and full-bit acquisition, and in the pre-acquisition stage, a parallel frequency search algorithm is adopted to carry out a round of full-range search on the frequency and the code phase of a satellite navigation signal with the length of one pseudo code period; and then, in a full-bit acquisition stage, adjusting the phase of local cache data according to an accurate code phase acquisition result, performing correlation operation on every two adjacent pseudo code periods in the satellite navigation signal with the length of one NH code period, judging whether NH code element hopping exists between the pseudo code periods according to the correlation operation result, adding 1 to a count variable of a TONG detector of a corresponding code sequence if the judgment result is the same as the assumed NH code sequence hopping rule every time, and subtracting 1 from the count variable if the judgment result is different from the assumed NH code sequence hopping rule, wherein the NH code sequence hopping sequence corresponding to the TONG detector which firstly reaches the upper limit of the count is the hopping sequence of the NH code elements in the satellite navigation signal to be detected. The method has the advantages that through pre-capturing and full-bit capturing, the ambiguity of frequency capturing is eliminated, the rough synchronization of the NH code is realized, the problems that the satellite navigation signal is influenced by the NH code in the tracking stage, the pre-detection integral time which is longer than 1ms and a four-phase arc tangent phase discriminator cannot be adopted are solved, and the method is suitable for the tracking requirement of a high-sensitivity loop.
Description
Technical Field
The invention belongs to a signal processing method of a satellite navigation receiver, and particularly relates to a method for stripping NH codes of satellite signals of a new system.
Background
At present, a Beidou system adopts navigation messages, Neumann-Hoffman (NH) codes and pseudo codes to synchronously modulate at a frequency point B1I, the original bit rate of the satellite navigation messages is 50bit/s, the data bit rate after NH code modulation is 1000bit/s, and data bit inversion can occur in each pseudo code period. NH code modulation is also widely applied to new system satellite signals, and the improvement has advantages and disadvantages, on one hand, the addition of the NH code can improve the narrow-band interference resistance and improve the cross-correlation characteristic among satellite navigation signals; on the other hand, the existence of the NH code also causes ambiguity of frequency acquisition, and the tracking pre-detection integration time length is limited, thereby affecting the tracking accuracy.
In order to prolong the integral time of the pre-detection, a four-phase arc tangent phase discriminator sensitive to data bit reversal is adopted, the tracking precision and sensitivity are improved, the coarse synchronization of the NH code is considered to be completed in the capturing stage, and the influence of the NH code on a tracking loop is eliminated.
Disclosure of Invention
The invention aims to provide a method for realizing NH code stripping of a new system satellite signal in an acquisition stage.
The invention is realized in this way, a new system satellite signal NH code stripping method, including the following steps,
step 1, realizing full-range capture of a satellite navigation signal with the length of one pseudo code period by adopting a parallel frequency search algorithm;
step 2, adjusting the phase of local cache data according to the code phase capturing result;
step 3, realizing the small-range capture of the satellite navigation signals with the length of two pseudo code periods by adopting a parallel frequency search algorithm;
step 4, judging whether NH code element hopping exists between the two pseudo code periods according to the magnitude of the captured peak value;
step 5, comparing the hopping judgment result with the hopping rule of the corresponding code element in the supposed NH code sequence, and adjusting the counting variable of the TONG detector according to the comparison result;
and 6, repeating the steps 3 to 6, and traversing every two adjacent pseudo code periods in one NH code period.
And 7, comparing the maximum value of the count variables of all the TONG detectors with a preset upper limit, and if the maximum value exceeds the preset upper limit, the jump sequence of the NH code sequence corresponding to the maximum value is the jump sequence of the NH code elements in the detected satellite navigation signal.
The step 1 comprises the following operations:
assuming that the pseudo code period of a satellite signal of a new system is 1ms, the NH code period is 20ms, one NH code period comprises 20 code elements, and each code element corresponds to one pseudo code period;
the pre-capture stage adopts full-range capture, and the frequency search range is (f)min,fmax) Generally, 20kHz can be taken, and the code phase searching range is a pseudo code period;
after the satellite navigation signal is subjected to down-conversion by a hardware circuit, the full-range capture is completed in the FPGA, and the processing process is as follows:
buffering a received signal: caching a section of satellite intermediate frequency signal with the length of 21ms after front-end processing in the FPGA;
mixing: mixing the satellite intermediate frequency signal with a carrier signal output by a carrier NCO;
pseudo code correlation: sequentially delaying the pseudo code signal output by the pseudo code NCO by 0.5 chip in the FPGA to obtain NaWay parallel pseudo code, and then NaThe pseudo-codes are respectively related to the satellite intermediate frequency signals of the first 1ms after frequency mixing to obtain NaMixing the correlation results;
partial accumulation: n is a radical ofaRespectively carrying out 50us related accumulation on the branch to obtain MaA total of N accumulation resultsa×MaAn accumulated result;
FFT and modulus taking: n is a radical ofaM on a branchaRespectively performing L on the accumulated resultsa(La≥Ma) Point FFT, and taking module operation to real part and imaginary part of FFT result to obtain Na×LaAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
The step 2 comprises the following operations:
and resolving the fuzzy Doppler frequency shift corresponding to the capture peak value and the code phase with the resolution of 0.5 chip in the DSP, and then adjusting the phase of local cache data according to the code phase capture result to align the local pseudo code with the pseudo code in the received signal.
The step 3 comprises the following operations:
the full bit capturing stage adopts small-range capturing with a frequency search range of (f)m'in,fm'ax) Compared with (f)min,fmax) The selection of specific numerical values needs to consider the dynamic application environment, the jump of the NH code element is at least not less than 1kHz, the code phase searching range is 10 chips near the pre-capturing result, and the searching step length is 0.1 chip;
the process of full bit capture is as follows:
pseudo code correlation: pseudo code signal for outputting pseudo code NCO in FPGAThe number is delayed by 0.1 chip in sequence to obtain NbWay parallel pseudo code, and then NbThe road pseudo code is respectively related to the satellite intermediate frequency signal of the first 2ms of the whole pseudo code period after frequency mixing to obtain NbMixing the correlation results;
partial accumulation: n is a radical ofbThe branch lines are respectively subjected to Yus correlation accumulation to obtain MbA total of N accumulation resultsb×MbAn accumulated result;
FFT and modulus taking: n is a radical ofbM on a branchbRespectively performing L on the accumulated resultsb(Lb≥Mb) Point FFT, and taking module operation to real part and imaginary part of FFT result to obtain Nb×LbAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
The step 4 comprises the following operations:
resolving the unambiguous Doppler frequency shift corresponding to the captured peak value and the code phase with the resolution of 0.1 chip in the DSP; and comparing the captured peak value with a preset threshold, if the peak value is larger than the threshold, indicating that no data jump exists in the 2ms satellite navigation signal, and if the peak value is smaller than the threshold, indicating that the data jump exists.
The step 5 comprises the following operations:
one NH code period contains 20 code elements, 20 code sequences corresponding to different initial code elements, each code sequence corresponds to one TONG detector in the DSP, and the counting variables corresponding to the 20 TONG detectors are respectively K1、K2、…、K20All initial values are preset as B, the judgment result of the jump in the step 4 is compared with the jump rule between 1 st bit and 2 nd bit of 20 code sequences, if both jump or not, the corresponding K isi(i is more than or equal to 1 and less than or equal to 20) plus 1, if the two are jumped one by one and do not jump, the corresponding KiMinus 1.
The step 6 comprises the following operations:
after the acquisition of the intermediate frequency signals of the satellite of the first 2ms and the judgment of NH code element hopping are completed, the steps 3 to 6 are repeated, the acquisition judgment results of 2 to 3ms, 3 to 4ms, … and 20 to 21ms are sequentially compared with the hopping rules among the 2 nd bit, the 3 rd bit, the 4 th bit, the … th bit and the 1 st bit of the 20 code sequences respectively, and the counting variable of the TONG detector is adjusted according to the comparison result.
The step 7 comprises the following operations:
if the count variable K of a certain TONG detectori(i is more than or equal to 1 and less than or equal to 20) is reduced to 0, the matching fails, and the matching of the corresponding TONG detector is finished; after completion of the resolution of one NH code period, 20 TONG detectors are counted against variable KiMaximum value of and KmaxAnd comparing the threshold value A, if the threshold value A is exceeded, the matching is successful, the jump sequence of the NH code sequence corresponding to the threshold value A is the jump sequence of the NH code element in the detected satellite navigation signal, and the bit synchronization of the satellite navigation signal is realized in the acquisition stage.
In the step 3: the full bit capturing stage adopts small-range capturing;
in the steps 4-7: the NH code stripping treatment process is as follows: and performing correlation operation on every two adjacent pseudo code periods in the satellite navigation signal with the length of one NH code period, judging whether NH code element hopping exists between the two pseudo code periods according to the result of the correlation operation, if the judgment result of each time is the same as the assumed NH code sequence hopping rule, adding 1 to the count variable of the TONG detector of the corresponding code sequence, if the judgment result of each time is different from the assumed NH code sequence hopping rule, subtracting 1 from the corresponding count variable, and the NH code sequence hopping sequence corresponding to the TONG detector which reaches the upper limit of the count first is the hopping sequence of the NH code elements in the detected satellite navigation signal.
The method has the advantages that the method for realizing NH code synchronization in the acquisition stage is provided, the problems that the satellite navigation signal is influenced by the NH code in the tracking stage and the problem that the pre-detection integral time longer than 1ms and a four-phase arc tangent phase discriminator cannot be adopted are solved, and the method is suitable for the tracking requirement of a high-sensitivity loop; through two stages of pre-capture and full-bit capture, the problem of frequency ambiguity caused by NH code element hopping is solved, and accurate capture of Doppler frequency shift is realized; and a smaller search range and a finer search step length are adopted in the full-bit acquisition stage, so that the code phase acquisition result is more accurate, and the acquisition time is saved.
Drawings
Fig. 1 is a flowchart of a method for stripping NH codes of a new system satellite signal according to the present invention;
fig. 2 is a schematic diagram of capturing a parallel frequency search algorithm in an FPGA of the present invention.
Detailed Description
The invention is described in detail below with reference to the following figures and specific embodiments:
a new system satellite signal NH code strip method, will catch and divide into two stages of catching and catching all bit, catch stage in advance, adopt the search algorithm of parallel frequency to carry on a round of all ranges search for frequency and code phase of satellite navigation signal of a pseudo code period of length, because the jump existence of NH code element, can realize the accurate catch of the code phase, can only realize the rough catch of the frequency; then, in the all-bit capturing stage, adjusting the phase of local cache data according to an accurate code phase capturing result, performing correlation operation on every two adjacent pseudo code periods in the satellite navigation signal with the length of one NH code period, judging whether NH code element hopping exists between the pseudo code periods according to the correlation operation result, if the judgment result is the same as the assumed NH code sequence hopping rule, adding 1 to the count variable of a TONG detector of a corresponding code sequence, if the judgment result is different from the assumed NH code sequence hopping rule, subtracting 1 from the corresponding count variable, wherein the NH code sequence hopping sequence corresponding to the TONG detector which firstly reaches the upper limit of the count is the hopping sequence of the NH code elements in the detected satellite navigation signal, and the method comprises the following steps:
step 1, realizing full-range capture of a satellite navigation signal with the length of one pseudo code period by adopting a parallel frequency search algorithm; step 2, adjusting the phase of local cache data according to the code phase capturing result; step 3, realizing the small-range capture of the satellite navigation signals with the length of two pseudo code periods by adopting a parallel frequency search algorithm; step 4, judging whether NH code element hopping exists between the two pseudo code periods according to the magnitude of the captured peak value; step 5, comparing the hopping judgment result with the hopping rule of the corresponding code element in the supposed NH code sequence, and adjusting the counting variable of the TONG detector according to the comparison result; step 6, repeating the step 3 to the step 6, and traversing every two adjacent pseudo code periods in one NH code period; and 7, comparing the maximum value of the count variables of all the TONG detectors with a preset upper limit, and if the maximum value exceeds the preset upper limit, the jump sequence of the NH code sequence corresponding to the maximum value is the jump sequence of the NH code elements in the detected satellite navigation signal.
Step 1 comprises the following operations:
assuming that the pseudo code period of a satellite signal of a new system is 1ms, the NH code period is 20ms, one NH code period comprises 20 code elements, and each code element corresponds to one pseudo code period;
the pre-capture stage adopts full-range capture, and the frequency search range is (f)min,fmax) Generally, 20kHz can be taken, and the code phase searching range is a pseudo code period;
after the satellite navigation signal is subjected to down-conversion by a hardware circuit, the full-range capture is completed in the FPGA, and the processing process is as follows:
buffering a received signal: caching a section of satellite intermediate frequency signal with the length of 21ms after front-end processing in the FPGA;
mixing: mixing the satellite intermediate frequency signal with a carrier signal output by a carrier NCO;
pseudo code correlation: sequentially delaying the pseudo code signal output by the pseudo code NCO by 0.5 chip in the FPGA to obtain NaWay parallel pseudo code, and then NaThe pseudo-codes are respectively related to the satellite intermediate frequency signals of the first 1ms after frequency mixing to obtain NaMixing the correlation results;
partial accumulation: n is a radical ofaRespectively carrying out 50us related accumulation on the branch to obtain MaA total of N accumulation resultsa×MaAn accumulated result;
FFT and modulus taking: n is a radical ofaM on a branchaRespectively performing L on the accumulated resultsa(La≥Ma) Point FFT, and taking module operation to real part and imaginary part of FFT result to obtain Na×LaAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
Step 2 comprises the following operations:
and resolving the fuzzy Doppler frequency shift corresponding to the capture peak value and the code phase with the resolution of 0.5 chip in the DSP, and then adjusting the phase of local cache data according to the code phase capture result to align the local pseudo code with the pseudo code in the received signal.
Step 3 comprises the following operations:
the full bit capturing stage adopts small-range capturing with a frequency search range of (f)m'in,fm'ax) Compared with (f)min,fmax) The selection of specific numerical values needs to consider the dynamic application environment, the jump of the NH code element is at least not less than 1kHz, the code phase searching range is 10 chips near the pre-capturing result, and the searching step length is 0.1 chip;
the process of full bit capture is as follows:
pseudo code correlation: sequentially delaying the pseudo code signal output by the pseudo code NCO by 0.1 chip in the FPGA to obtain NbWay parallel pseudo code, and then NbThe road pseudo code is respectively related to the satellite intermediate frequency signal of the first 2ms of the whole pseudo code period after frequency mixing to obtain NbMixing the correlation results;
partial accumulation: n is a radical ofbThe branch lines are respectively subjected to Yus correlation accumulation to obtain MbA total of N accumulation resultsb×MbAn accumulated result;
FFT and modulus taking: n is a radical ofbM on a branchbRespectively performing L on the accumulated resultsb(Lb≥Mb) Point FFT, and taking module operation to real part and imaginary part of FFT result to obtain Nb×LbAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
Step 4 comprises the following operations:
resolving the unambiguous Doppler frequency shift corresponding to the captured peak value and the code phase with the resolution of 0.1 chip in the DSP; and comparing the captured peak value with a preset threshold, if the peak value is larger than the threshold, indicating that no data jump exists in the 2ms satellite navigation signal, and if the peak value is smaller than the threshold, indicating that the data jump exists.
Step 5 comprises the following operations:
one NH code period contains 20 code elements corresponding to different startsThe code element has 20 code sequences, each code sequence corresponds to a TONG detector in the DSP, and the counting variables corresponding to the 20 TONG detectors are respectively K1、K2、…、K20All initial values are preset as B, the judgment result of the jump in the step 4 is compared with the jump rule between 1 st bit and 2 nd bit of 20 code sequences, if both jump or not, the corresponding K isi(i is more than or equal to 1 and less than or equal to 20) plus 1, if the two are jumped one by one and do not jump, the corresponding KiMinus 1.
Step 6 comprises the following operations:
after the acquisition of the intermediate frequency signals of the satellite of the first 2ms and the judgment of NH code element hopping are completed, the steps 3 to 6 are repeated, the acquisition judgment results of 2 to 3ms, 3 to 4ms, … and 20 to 21ms are sequentially compared with the hopping rules among the 2 nd bit, the 3 rd bit, the 4 th bit, the … th bit and the 1 st bit of the 20 code sequences respectively, and the counting variable of the TONG detector is adjusted according to the comparison result.
Step 7 comprises the following operations:
if the count variable K of a certain TONG detectori(i is more than or equal to 1 and less than or equal to 20) is reduced to 0, the matching fails, and the matching of the corresponding TONG detector is finished; after completion of the resolution of one NH code period, 20 TONG detectors are counted against variable KiMaximum value of and KmaxAnd comparing the threshold value A, if the threshold value A is exceeded, the matching is successful, the jump sequence of the NH code sequence corresponding to the threshold value A is the jump sequence of the NH code element in the detected satellite navigation signal, and the bit synchronization of the satellite navigation signal is realized in the acquisition stage.
As a preferable scheme:
in the step 3: the full bit capturing stage adopts small-range capturing;
step 4-7: the NH code stripping treatment process is as follows: and performing correlation operation on every two adjacent pseudo code periods in the satellite navigation signal with the length of one NH code period, judging whether NH code element hopping exists between the two pseudo code periods according to the result of the correlation operation, if the judgment result of each time is the same as the assumed NH code sequence hopping rule, adding 1 to the count variable of the TONG detector of the corresponding code sequence, if the judgment result of each time is different from the assumed NH code sequence hopping rule, subtracting 1 from the corresponding count variable, and the NH code sequence hopping sequence corresponding to the TONG detector which reaches the upper limit of the count first is the hopping sequence of the NH code elements in the detected satellite navigation signal.
As a further preferred embodiment:
in the step 3: the full bit capturing stage adopts small-range capturing with a frequency search range of (f)m'in,fm'ax) Compared with (f)min,fmax) The selection of specific numerical values needs to consider the dynamic application environment, the jump of the NH code element is at least not less than 1kHz, the code phase searching range is 10 chips near the pre-capturing result, and the searching step length is 0.1 chip;
step 4-7: the NH code stripping treatment process is as follows:
comparing the captured peak value with a preset threshold in the DSP, if the peak value is larger than the threshold, indicating that no data jump exists in the 2ms satellite navigation signal, and if the peak value is smaller than the threshold, indicating that the data jump exists;
the 20 code sequences corresponding to different initial code elements respectively correspond to one TONG detector in the DSP, and the counting variables corresponding to the 20 TONG detectors are respectively K1、K2、…、K20The initial value is all preset as B, the judgment result of the jump is compared with the jump rule between 1 st bit and 2 nd bit of 20 code sequences, if both jump or not, the corresponding K isi(i is more than or equal to 1 and less than or equal to 20) plus 1, if the two are jumped one by one and do not jump, the corresponding KiSubtracting 1;
after the acquisition of the intermediate frequency signals of the satellite of the previous 2ms and the jump judgment of the NH code element are completed, the acquisition judgment results of 2-3 ms, 3-4 ms, … and 20-21 ms are compared with the jump rules among the 2 nd bit, the 3 rd bit, the 4 th bit and the 20 th bit and 1 st bit of 20 code sequences respectively according to the same method, and the counting variable of the TONG detector is adjusted according to the comparison result;
if the count variable K of a certain TONG detectori(i is more than or equal to 1 and less than or equal to 20) is reduced to 0, the matching fails, and the matching of the corresponding TONG detector is finished; after completion of the resolution of one NH code period, 20 TONG detectors are counted against variable KiMaximum value of and KmaxAnd comparing the threshold value A, if the threshold value A is exceeded, the matching is successful, the jump sequence of the NH code sequence corresponding to the threshold value A is the jump sequence of the NH code element in the detected satellite navigation signal, and the bit synchronization of the satellite navigation signal is realized in the acquisition stage.
Claims (9)
1. A new system satellite signal NH code stripping method is characterized in that: comprises the following steps of (a) carrying out,
step 1, realizing full-range capture of a satellite navigation signal with the length of one pseudo code period by adopting a parallel frequency search algorithm;
step 2, adjusting the phase of local cache data according to the code phase capturing result;
step 3, realizing the small-range capture of the satellite navigation signals with the length of two pseudo code periods by adopting a parallel frequency search algorithm;
step 4, judging whether NH code element hopping exists between the two pseudo code periods according to the magnitude of the captured peak value;
step 5, comparing the hopping judgment result with the hopping rule of the corresponding code element in the supposed NH code sequence, and adjusting the counting variable of the TONG detector according to the comparison result;
step 6, repeating the step 3 to the step 6, and traversing every two adjacent pseudo code periods in one NH code period;
and 7, comparing the maximum value of the count variables of all the TONG detectors with a preset upper limit, and if the maximum value exceeds the preset upper limit, the jump sequence of the NH code sequence corresponding to the maximum value is the jump sequence of the NH code elements in the detected satellite navigation signal.
2. The method as claimed in claim 1, wherein the method comprises: the step 1 comprises the following operations:
assuming that the pseudo code period of a satellite signal of a new system is 1ms, the NH code period is 20ms, one NH code period comprises 20 code elements, and each code element corresponds to one pseudo code period;
the pre-capture stage adopts full-range capture, and the frequency search range is (f)min,fmax) Taking 20kHz, code phaseThe search range is one pseudo code period;
after the satellite navigation signal is subjected to down-conversion by a hardware circuit, the full-range capture is completed in the FPGA, and the processing process is as follows: buffering a received signal: caching a section of satellite intermediate frequency signal with the length of 21ms after front-end processing in the FPGA;
mixing: mixing the satellite intermediate frequency signal with a carrier signal output by a carrier NCO;
pseudo code correlation: sequentially delaying the pseudo code signal output by the pseudo code NCO by 0.5 chip in the FPGA to obtain NaWay parallel pseudo code, and then NaThe pseudo-codes are respectively related to the satellite intermediate frequency signals of the first 1ms after frequency mixing to obtain NaMixing the correlation results;
partial accumulation: n is a radical ofaRespectively carrying out 50us related accumulation on the branch to obtain MaA total of N accumulation resultsa×MaAn accumulated result;
FFT and modulus taking: n is a radical ofaM on a branchaRespectively performing L on the accumulated resultsa，La≥MaPoint FFT, and taking module operation to real part and imaginary part of FFT result to obtain Na×LaAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
3. The method as claimed in claim 1, wherein the method comprises: the step 2 comprises the following operations:
and resolving the fuzzy Doppler frequency shift corresponding to the capture peak value and the code phase with the resolution of 0.5 chip in the DSP, and then adjusting the phase of local cache data according to the code phase capture result to align the local pseudo code with the pseudo code in the received signal.
4. The method as claimed in claim 1, wherein the method comprises: the step 3 comprises the following operations:
the full bit acquisition stage adopts small range acquisition, and the frequency search range is (f'min,f'max) Compared with (f)min,fmax) The selection of specific numerical values needs to consider the dynamic application environment, the jump of the NH code element is at least not less than 1kHz, the code phase searching range is 10 chips near the pre-capturing result, and the searching step length is 0.1 chip;
the process of full bit capture is as follows:
pseudo code correlation: sequentially delaying the pseudo code signal output by the pseudo code NCO by 0.1 chip in the FPGA to obtain NbWay parallel pseudo code, and then NbThe road pseudo code is respectively related to the satellite intermediate frequency signal of the first 2ms of the whole pseudo code period after frequency mixing to obtain NbMixing the correlation results;
partial accumulation: n is a radical ofbThe branch lines are respectively subjected to Yus correlation accumulation to obtain MbA total of N accumulation resultsb×MbAn accumulated result;
FFT and modulus taking: n is a radical ofbM on a branchbRespectively performing L on the accumulated resultsb，Lb≥MbPoint FFT, and taking module operation to real part and imaginary part of FFT result to obtain Nb×LbAnd detecting the matrix in order, and transmitting the maximum value and the address thereof in the matrix to the DSP.
5. The method as claimed in claim 1, wherein the method comprises: the step 4 comprises the following operations:
resolving the unambiguous Doppler frequency shift corresponding to the captured peak value and the code phase with the resolution of 0.1 chip in the DSP; and comparing the captured peak value with a preset threshold, if the peak value is larger than the threshold, indicating that no data jump exists in the 2ms satellite navigation signal, and if the peak value is smaller than the threshold, indicating that the data jump exists.
6. The method as claimed in claim 1, wherein the method comprises: the step 5 comprises the following operations:
one NH code period contains 20 symbols, and there are 20 code sequences corresponding to different starting symbols, each code sequence corresponding to a TONG detector in the DSP, 20 TONsThe counting variables corresponding to the G detectors are respectively K1、K2、…、K20All initial values are preset as B, the judgment result of the jump in the step 4 is compared with the jump rule between 1 st bit and 2 nd bit of 20 code sequences, if both jump or not, the corresponding K isiI is more than or equal to 1 and less than or equal to 20 and is added with 1, and if the two do not jump one by one, the corresponding K isiMinus 1.
7. The method as claimed in claim 1, wherein the method comprises: the step 6 comprises the following operations:
after the acquisition of the intermediate frequency signals of the satellite of the first 2ms and the judgment of NH code element hopping are completed, the steps 3 to 6 are repeated, the acquisition judgment results of 2 to 3ms, 3 to 4ms, … and 20 to 21ms are sequentially compared with the hopping rules among the 2 nd bit, the 3 rd bit, the 4 th bit, the … th bit and the 1 st bit of the 20 code sequences respectively, and the counting variable of the TONG detector is adjusted according to the comparison result.
8. The method as claimed in claim 1, wherein the method comprises: the step 7 comprises the following operations:
if the count variable K of a certain TONG detectoriI is more than or equal to 1 and less than or equal to 20, and is reduced to 0, the matching fails, and the matching of the corresponding TONG detector is finished; after completion of the resolution of one NH code period, 20 TONG detectors are counted against variable KiMaximum value of and KmaxAnd comparing the threshold value A, if the threshold value A is exceeded, the matching is successful, the jump sequence of the NH code sequence corresponding to the threshold value A is the jump sequence of the NH code element in the detected satellite navigation signal, and the bit synchronization of the satellite navigation signal is realized in the acquisition stage.
9. The method as claimed in claim 1, wherein the method comprises: in the steps 4-7: the NH code stripping treatment process is as follows: and performing correlation operation on every two adjacent pseudo code periods in the satellite navigation signal with the length of one NH code period, judging whether NH code element hopping exists between the two pseudo code periods according to the result of the correlation operation, if the judgment result of each time is the same as the assumed NH code sequence hopping rule, adding 1 to the count variable of the TONG detector of the corresponding code sequence, if the judgment result of each time is different from the assumed NH code sequence hopping rule, subtracting 1 from the corresponding count variable, and the NH code sequence hopping sequence corresponding to the TONG detector which reaches the upper limit of the count first is the hopping sequence of the NH code elements in the detected satellite navigation signal.
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| KR101564828B1 (en) * | 2014-01-20 | 2015-10-30 | 한국과학기술원 | Signal processing method for ultra-fast acquisition and tracking of severely attenuated spread spectrum signals with doppler frequency and apparatus thereof |
| CN104898136A (en) * | 2015-05-19 | 2015-09-09 | 厦门大学 | Capturing method of Beidou second-generation B1 signals and system thereof |
| CN105911569B (en) * | 2016-04-06 | 2019-06-14 | 东南大学 | The weak D1 signal acquisition methods of Beidou satellite navigation system B1 frequency band based on sequence of symhols estimation |
| CN106646541A (en) * | 2016-11-23 | 2017-05-10 | 南京航空航天大学 | Beidou weak signal capture method based on difference correlation integral |
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