CN108508460B

CN108508460B - GNSS signal carrier tracking method and device

Info

Publication number: CN108508460B
Application number: CN201710109579.9A
Authority: CN
Inventors: 吴骏
Original assignee: Sanechips Technology Co Ltd
Current assignee: Sanechips Technology Co Ltd
Priority date: 2017-02-27
Filing date: 2017-02-27
Publication date: 2020-06-09
Anticipated expiration: 2037-02-27
Also published as: CN108508460A; WO2018153083A1

Abstract

The invention discloses a GNSS signal carrier tracking method, which comprises the following steps: carrying out first coherent accumulation operation on the despread complex signal to obtain a first coherent accumulation result, and carrying out second coherent accumulation operation to obtain a second coherent accumulation result; the first coherent accumulation operation comprises: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: rotating the last second coherent accumulation result according to a second phase interval before coherent accumulation; when the times of the first coherent accumulation operation and the times of the second coherent accumulation operation reach a first preset value, setting the first coherent accumulation result as a first target coherent accumulation result, and setting the second coherent accumulation result as a second target coherent accumulation result; and adjusting the frequency of the reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result. The invention also discloses a GNSS signal carrier tracking device.

Description

GNSS signal carrier tracking method and device

Technical Field

The present invention relates to the field of Satellite-based Navigation technologies, and in particular, to a method and an apparatus for tracking a Global Navigation Satellite System (GNSS) signal carrier.

Background

Currently, in most GNSS signal receivers, a GNSS signal carrier Frequency and Phase tracking device recorded in the GNSS textbook entitled "GPS principle and application" (second edition, Elliott d. kaplan) is used, which uses a Phase Locked Loop (PLL) and a Frequency Locked Loop (FLL) to perform carrier tracking, as shown in fig. 1, and the tracking sensitivity is about-158 dBm.

Essentially, an effective means for improving the sensitivity of the GNSS receiver to receive signals, especially the carrier tracking sensitivity, is a maximum likelihood function of signal frequency offset estimation based on Binary Phase Shift Keying (BPSK). In the working state of the GNSS receiver, the receiver can only acquire the center frequency of the satellite emission signal, the spreading code phase and rate, and the code rate of the modulation data, so the maximum likelihood function of the signal frequency offset estimation used in the GNSS receiver is the maximum likelihood function basically following the content of the unknown modulation data.

Currently, there are three main frequency offset estimation methods used as follows:

the first mode is as follows: in terms of time domain, the result of the maximum likelihood function is equivalent to that when the frequency sweeping operation is performed on a continuous time domain until a certain frequency point has the maximum value of energy gain, the frequency point is the frequency deviation estimated value. The fundamental reasons for this change in gain magnitude are: within a specific integration time, a relation of singe (sinc) function attenuation exists between carrier frequency offset and integral energy gain. In practical use, in order to perform stable loop tracking, it is impossible to perform frequency sweep operation to check attenuation of the sinc function, so that three sets of Numerically Controlled Oscillators (NCO) are introduced to perform frequency offset estimation, and the principles of sinc attenuation of carrier frequency offset and gain of GNSS signals and left-right frequency offset clamp tracking are shown in fig. 2. Fig. 3 is a schematic diagram of a device for performing GNSS signal frequency tracking by using a three-way frequency converter (i.e., three sets of NCO), and as shown in fig. 3, taking 20ms coherent integration time as an example, the frequency setting numbers of the three sets of NCO are respectively set as a center frequency fs and a center frequency offset to the left of 10 Hz: f. of_{Left side of}Fs-10Hz, and center frequency right offset 10 Hz: f. of_{Right side}Fs +10 Hz. When the output frequency of NCO is completely aligned with the actually input carrier frequency, the gain difference value of the left and right frequency offsets is 0, namely A_{f left}-A _{f right side}0; when the output frequency of the NCO is greater than the actually input carrier frequency, the gain difference value of the left and right frequency offsets is greater than 0, namely A_{f left}-A_{f right side}Is greater than 0; when the output frequency of the NCO is less than the actually input carrier frequency, the gain difference value of the left and right frequency offsets is less than 0, namely A_{f left}-A_{f right side}If the frequency deviation is less than 0, the gain difference value of the left frequency deviation and the right frequency deviation is sent to a loop filter to be used as a frequency discrimination signal, and then frequency tracking can be completed.

The second way is: from the frequency domain, the estimation of the carrier frequency offset is equivalent to the frequency point represented by the maximum gain value after Fast Fourier Transform (FFT) is performed on the input signal, but because the FFT may bring ambiguity of frequency estimation, two frequency points on the left and right of the frequency point represented by the maximum gain value also need to be taken after the FFT, and the gain difference of the left and right frequency offsets is calculated; fig. 4 is a schematic diagram of an apparatus for performing GNSS signal frequency tracking by using an FFT method, and as shown in fig. 4, 8-point FFT operation is performed on 20ms coherent data, so that the frequency offset range covered by each FFT result is ± 25Hz, and a gain difference value of left and right frequency offsets is sent to a loop filter as a frequency discrimination signal, thereby completing frequency tracking.

The third mode is as follows: similarly, considering from the frequency domain, if the carrier phase inversion compensation brought by the modulation data can be performed by the backend data processing, the maximum coherent integration length can break through the limit of 20ms, and at this time, the carrier frequency offset can be obtained by a simple long-integration FFT operation.

The three frequency offset estimation modes have certain defects, the implementation of the first mode needs to rely on three sets of NCO to carry out frequency offset estimation, and in the implementation of a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), the scale of a digital Circuit is increased, and the Circuit structure is complex; the implementation of the second method needs to introduce additional FFT operation, which also increases the circuit scale; the third mode depends on the cooperation of a back-end data processing program to eliminate phase reversal caused by data modulation, so that the coupling degree of the system is increased, and the structure is complex.

Disclosure of Invention

In order to solve the problems in the prior art, embodiments of the present invention are expected to provide a GNSS signal carrier tracking method and apparatus, which can reduce complexity of GNSS signal carrier tracking, thereby reducing digital circuit scale.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the embodiment of the invention provides a GNSS signal carrier tracking method, which comprises the following steps:

carrying out first coherent accumulation operation on the obtained de-spread complex signal to obtain a first coherent accumulation result, and carrying out second coherent accumulation operation to obtain a second coherent accumulation result; the first coherent accumulation operation comprises: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: rotating a previous second coherent accumulation result according to a second phase interval before coherent accumulation, wherein the first phase interval and the second phase interval are opposite numbers; the de-spread complex signal is a GNSS signal after down-conversion and de-spread;

when the times of performing the first coherent accumulation operation reach a first preset value and the times of performing the second coherent accumulation operation reach the first preset value, setting the first coherent accumulation result as a first target coherent accumulation result and setting the second coherent accumulation result as a second target coherent accumulation result;

and adjusting the frequency of a reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result, wherein the reference frequency complex signal is used for performing down-conversion on the GNSS signal.

In the foregoing solution, the performing a first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result includes:

when obtaining the despread complex signal, calculating a current first coherent accumulation result B according to a previous first coherent accumulation result B1, the currently obtained despread complex signal a, and the first phase interval ∈ Ts, the current first coherent accumulation result satisfying: b + B1 me^-j2πεTs(ii) a When the number of times of performing the first coherent accumulation operation is 1, the last first coherent accumulation result is 0;

wherein Ts is a time interval of the last first coherent accumulation result delay, epsilon is an angle phase of the last first coherent accumulation result rotation, and j is an imaginary unit.

In the foregoing scheme, the performing a second coherent accumulation operation on the obtained despread complex signal to obtain a second coherent accumulation result includes:

when the despread complex signal is obtained, a current second coherent accumulation result C is calculated on the basis of a previous second coherent accumulation result B2, the currently obtained despread complex signal A and the second phase interval- ε -Ts,the current second coherent accumulation result satisfies: c + B2 × e^j2πεTs(ii) a When the number of times of performing the second coherence accumulation operation is 1, the last second coherence accumulation result is 0;

wherein Ts is a time interval of delay of the previous second coherent accumulation result, -e is an angular phase of rotation of the previous second coherent accumulation result, and j is an imaginary unit.

In the above scheme, the method further comprises:

and executing the first coherent accumulation operation on the obtained de-spread complex signal to obtain a first coherent accumulation result and executing the second coherent accumulation operation to obtain a second coherent accumulation result when the frequency of the first coherent accumulation operation does not reach the first preset value and the frequency of the second coherent accumulation operation does not reach the first preset value.

In the foregoing solution, the adjusting the frequency of the reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result includes:

performing a modulo operation on the first target coherent accumulation result to obtain a modulo first target coherent accumulation result; performing a modulus operation on the second target coherent accumulation result to obtain a modulus-solved second target coherent accumulation result;

subtracting the modulo first target coherent accumulation result and the modulo second target coherent accumulation result to obtain a frequency error identification result, wherein the frequency error identification result is used for identifying the frequency error between the GNSS signal carrier and the reference frequency complex signal;

and generating frequency adjustment information according to the frequency error identification result so as to adjust the frequency of the reference frequency complex signal.

In the foregoing solution, the generating frequency adjustment information according to the frequency error identification result includes:

performing incoherent accumulation on the frequency error discrimination result to obtain a first incoherent accumulation result;

judging whether the frequency of the non-coherent accumulation of the frequency error discrimination result is less than a second preset value;

if yes, executing the step of carrying out first coherent accumulation operation on the obtained de-spread complex signal to obtain a first coherent accumulation result, and carrying out second coherent accumulation operation to obtain a second coherent accumulation result; and if not, generating frequency adjustment information according to the first incoherent accumulation result.

In the foregoing scheme, after obtaining the despread complex signal, the method further includes:

carrying out coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result;

judging whether the times of coherent accumulation is less than the first preset value;

if yes, executing the step of carrying out coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result; if not, setting the third coherent accumulation result as a third target coherent accumulation result;

calculating a phase error discrimination result according to the third target coherent accumulation result, wherein the phase error discrimination result is used for discriminating a phase error between the GNSS signal carrier and the reference frequency complex signal;

and generating phase adjustment information according to the phase error identification result so as to adjust the phase of the reference frequency complex signal.

In the foregoing solution, the generating phase adjustment information according to the phase error discrimination result includes:

performing incoherent accumulation on the phase error discrimination result to obtain a second incoherent accumulation result;

judging whether the number of times of performing incoherent accumulation on the phase error identification result is less than a third preset value;

if yes, executing the step of carrying out coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result; and if not, generating phase adjustment information according to the second incoherent accumulation result.

The embodiment of the invention also provides a GNSS signal carrier tracking device, which comprises: the device comprises a first coherent accumulation module, a setting module and a frequency adjustment module; wherein the content of the first and second substances,

the first coherent accumulation module is used for carrying out first coherent accumulation operation on the obtained de-spread complex signal to obtain a first coherent accumulation result and carrying out second coherent accumulation operation to obtain a second coherent accumulation result; the first coherent accumulation operation comprises: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: rotating a previous second coherent accumulation result according to a second phase interval before coherent accumulation, wherein the first phase interval and the second phase interval are opposite numbers; the de-spread complex signal is a GNSS signal after down-conversion and de-spread;

the setting module is used for setting the first coherent accumulation result as a first target coherent accumulation result and setting the second coherent accumulation result as a second target coherent accumulation result when the times of performing the first coherent accumulation operation and the times of performing the second coherent accumulation operation reach a first preset value;

the frequency adjustment module is configured to adjust a frequency of a reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result, where the reference frequency complex signal is used to perform down-conversion on the GNSS signal.

In the foregoing solution, the first coherent accumulation module is specifically configured to, when the despread complex signal is obtained, calculate a current first coherent accumulation result B according to a previous first coherent accumulation result B1, a currently obtained despread complex signal a, and the first phase interval ∈ Ts, where the current first coherent accumulation result satisfies: b + B1 me^-j2πεTs(ii) a When the number of times of performing the first coherent accumulation operation is 1, the previous first coherent accumulation result is 0, Ts is a time interval during which the previous first coherent accumulation result is delayed, epsilon is an angular phase of rotation of the previous first coherent accumulation result, and j is an imaginary unit.

In the foregoing solution, the first coherent accumulation module is further configured to perform the following stepsWhen the despread complex signal is obtained, calculating a current second coherent accumulation result C according to a previous second coherent accumulation result B2, the despread complex signal A obtained currently and the second phase interval- ε -Ts, wherein the current second coherent accumulation result satisfies: c + B2 × e^j2πεTs(ii) a When the number of times of performing the second coherence accumulation operation is 1, the previous second coherence accumulation result is 0, Ts is a time interval during which the previous second coherence accumulation result is delayed, -epsilon is an angle phase at which the previous second coherence accumulation result rotates, and j is an imaginary number unit.

In the above scheme, the apparatus further comprises:

and the first processing module is used for triggering the first coherent accumulation module when the frequency of performing the first coherent accumulation operation does not reach the first preset value and the frequency of performing the second coherent accumulation operation does not reach the first preset value.

In the foregoing solution, the frequency adjustment module includes: a modulo arithmetic unit, a subtraction unit and a generation unit; wherein the content of the first and second substances,

the modulus calculation unit is used for performing modulus calculation on the first target coherent accumulation result to obtain a modulus-calculated first target coherent accumulation result; performing a modulus operation on the second target coherent accumulation result to obtain a modulus-solved second target coherent accumulation result;

the subtraction unit is configured to subtract the first target coherent accumulation result after the modulus from the second target coherent accumulation result after the modulus to obtain a frequency error identification result, where the frequency error identification result is used to identify a frequency error between the GNSS signal carrier and the reference frequency complex signal;

and the generating unit is used for generating frequency adjustment information according to the frequency error identification result so as to adjust the frequency of the reference frequency complex signal.

In the foregoing solution, the generating unit includes: the device comprises a noncoherent accumulation subunit, a judgment subunit and a processing subunit; wherein the content of the first and second substances,

the incoherent accumulation subunit is configured to perform incoherent accumulation on the frequency error identification result to obtain a first incoherent accumulation result;

the judging subunit is configured to judge whether the number of times of performing incoherent accumulation on the frequency error identification result is smaller than a second preset value;

the processing subunit is configured to trigger the first coherent accumulation module when the number of times of performing incoherent accumulation is smaller than the second preset value; and when the number of times of incoherent accumulation reaches the second preset value, generating frequency adjustment information according to the first incoherent accumulation result.

In the above scheme, the apparatus further comprises: the device comprises a second coherent accumulation module, a judgment module, a second processing module, a calculation module and a generation module; wherein the content of the first and second substances,

the second coherent accumulation module is used for performing coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result;

the judging module is used for judging whether the times of coherent accumulation is smaller than the first preset value;

the second processing module triggers the second coherent accumulation module when the number of coherent accumulation is smaller than the first preset value; when the times of coherent accumulation reach the first preset value, setting the third coherent accumulation result as a third target coherent accumulation result;

the calculating module is configured to calculate a phase error discrimination result according to the third target coherent accumulation result, where the phase error discrimination result is used to discriminate a phase error between the GNSS signal carrier and the reference frequency complex signal;

and the generating module is used for generating phase adjustment information according to the phase error identification result so as to adjust the phase of the reference frequency complex signal.

In the foregoing solution, the generating module includes: the device comprises a noncoherent accumulation unit, a judgment unit and a processing unit; wherein the content of the first and second substances,

the incoherent accumulation unit is used for carrying out incoherent accumulation on the phase error discrimination result to obtain a second incoherent accumulation result;

the judging unit is used for judging whether the number of times of performing incoherent accumulation on the phase error identification result is less than a third preset value;

the processing unit is used for triggering the second coherent accumulation module when the number of times of non-coherent accumulation is smaller than the third preset value; and when the number of times of incoherent accumulation reaches the third preset value, generating phase adjustment information according to the second incoherent accumulation result.

Therefore, the embodiment of the invention performs the first coherent accumulation operation and the second coherent accumulation operation on the despread complex signal, namely the GNSS signal after down-conversion and despreading circularly and repeatedly to obtain the first target coherent accumulation result and the second target coherent accumulation result; adjusting the frequency of a reference frequency complex signal according to the first target coherent accumulation result and a second target coherent accumulation result, wherein the reference frequency complex signal is used for performing down-conversion on the GNSS signal; since the first coherent accumulation operation includes: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: before coherent accumulation, rotating a last second coherent accumulation result according to a second phase interval, wherein the first phase interval and the second phase interval are opposite numbers, frequency conversion of frequency right deviation of the de-spread complex signal can be realized through the rotating operation of the first phase interval which reciprocates circularly, and frequency conversion of frequency left deviation of the de-spread complex signal can be realized through the rotating operation of the second phase interval which reciprocates circularly; therefore, the embodiment of the invention replaces the generation of two local reference frequencies and the frequency conversion operation by the rotation operation of the first phase interval and the second phase interval, thereby effectively reducing the GNSS signal frequency tracking complexity and reducing the operation amount and the circuit implementation scale.

Drawings

FIG. 1 is a schematic diagram of a GNSS signal carrier frequency and phase tracking device in textbook GPS principle and application;

FIG. 2 is a schematic diagram of clamp tracking of sinc attenuation and left-right frequency offset of carrier frequency offset and gain of GNSS signals;

FIG. 3 is a schematic diagram of an apparatus for GNSS signal frequency tracking using a three-way converter;

FIG. 4 is a schematic diagram of an apparatus for GNSS signal frequency tracking using FFT;

FIG. 5 is a flowchart illustrating a first implementation of a GNSS signal carrier tracking method according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of the signal composition structure of B1I;

fig. 7 is a schematic diagram of a detailed flow of adjusting the frequency of the reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result in the implementation flow shown in fig. 5;

FIG. 8 is a schematic diagram of a loop filter in a second order carrier frequency tracking loop;

FIG. 9 is a flowchart illustrating a second implementation of a GNSS signal carrier tracking method according to a second embodiment of the present invention;

FIG. 10 is a schematic diagram of a loop filter in a second order carrier frequency and phase joint tracking loop;

FIG. 11 is a schematic view of an application scenario of a GNSS signal carrier tracking method according to a third embodiment of the present invention;

FIG. 12 is a second schematic view of an application scenario of a third GNSS signal carrier tracking method according to the present invention;

FIG. 13 is a schematic diagram illustrating a first exemplary embodiment of a GNSS signal carrier tracking apparatus;

FIG. 14 is a schematic diagram of a detailed structure of a frequency adjustment module in the apparatus shown in FIG. 13;

FIG. 15 is a schematic diagram of a detailed structure of a generating unit in the apparatus shown in FIG. 14;

FIG. 16 is a schematic structural diagram illustrating a second exemplary embodiment of a GNSS signal carrier tracking apparatus of the present invention;

fig. 17 is a schematic diagram of a detailed structure of a generating module in the apparatus shown in fig. 16.

Detailed Description

The GNSS signal carrier tracking method provided by the embodiment of the invention is mainly applied to a receiver system, and a first target coherent accumulation result and a second target coherent accumulation result are obtained by circularly and repeatedly carrying out a first coherent accumulation operation and a second coherent accumulation operation on a de-spread complex signal, namely, a GNSS signal which is subjected to down-conversion and de-spread; adjusting the frequency of a reference frequency complex signal according to the first target coherent accumulation result and a second target coherent accumulation result, wherein the reference frequency complex signal is used for performing down-conversion on the GNSS signal; since the first coherent accumulation operation includes: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: before coherent accumulation, rotating a last second coherent accumulation result according to a second phase interval, wherein the first phase interval and the second phase interval are opposite numbers, frequency conversion of frequency right deviation of the de-spread complex signal can be realized through the rotating operation of the first phase interval which reciprocates circularly, and frequency conversion of frequency left deviation of the de-spread complex signal can be realized through the rotating operation of the second phase interval which reciprocates circularly; therefore, the embodiment of the invention replaces the generation of two local reference frequencies and the frequency conversion operation by the rotation operation of the first phase interval and the second phase interval, thereby effectively reducing the GNSS signal frequency tracking complexity and reducing the operation amount and the circuit implementation scale.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 5 is a schematic flow chart illustrating an implementation of a GNSS signal carrier tracking method according to a first embodiment of the present invention, and referring to fig. 5, the GNSS signal carrier tracking method according to the present embodiment includes the following steps:

step 101, performing a first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result, and performing a second coherent accumulation operation to obtain a second coherent accumulation result; the first coherent accumulation operation comprises: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: rotating a previous second coherent accumulation result according to a second phase interval before coherent accumulation, wherein the first phase interval and the second phase interval are opposite numbers; the de-spread complex signal is a GNSS signal after down-conversion and de-spread;

here, the GNSS signal may be a GPS signal or a beidou signal, and in the following embodiment, the GNSS signal is described in detail by taking a B1I signal of a beidou non-GEO satellite as an example; specifically, the B1I signal is a digital signal output by the receiver at radio frequency, and the digital signal is an intermediate frequency carrier signal with residual frequency difference, and contains digitally modulated spreading codes and navigation information; fig. 6 is a schematic diagram of a signal composition structure of B1I, and referring to fig. 6, the length of the spreading code is 2046chips, the period of the spreading code is 1ms, a Niemann Huffman (NH) code is modulated on the spreading code in a two-level code form, and the symbol bit width of the navigation information is 20 ms.

The GNSS signal carrier tracking method in the embodiment is mainly applied to a GNSS signal carrier tracking device and used for tracking a GNSS signal carrier frequency. The apparatus includes a local carrier generator capable of generating a reference frequency complex signal comprising a co-directional branch (i.e., path I) signal and a quadrature branch (i.e., path Q) signal to counteract a residual frequency bias in the GNSS signal.

It should be noted that the type of the GNSS signal may be a single I-path real signal, a single Q-path real signal, or a complex signal synthesized by an I-path and a Q-path, and the down-conversion of the acquired GNSS signal requires corresponding processing according to the type of the GNSS signal; specifically, if the GNSS signal is a single I-path or single Q-path real signal, performing real multiplication on the GNSS signal and an I-path signal and a Q-path signal generated by a local carrier generator, respectively, to obtain an initial complex signal with a frequency offset removed, where the initial complex signal is synthesized from an I-path signal after down-conversion and a Q-path signal after down-conversion; and if the GNSS signal is a complex signal synthesized by an I path and a Q path, performing complex multiplication operation on the GNSS signal and the I path signal and the Q path signal generated by the local carrier generator to obtain an initial complex signal with frequency deviation stripped, wherein the initial complex signal is synthesized by the I path signal after down-conversion and the Q path signal after down-conversion.

It should be appreciated that since Pseudo Random Noise (PRN) spreading codes in the GNSS signal have strong auto-correlation and weak cross-correlation, only the PRN spreading codes are stripped and the despread complex signal can be coherently accumulated subsequently.

Here, first, after down-converting the GNSS signal, an initial complex signal may be obtained, where the initial complex signal includes a down-converted I-path signal and a down-converted Q-path signal. And then stripping the spreading code in the initial complex signal to obtain a despread complex signal, wherein the despread complex signal comprises a despread I path signal and a despread Q path signal.

Specifically, when the despread complex signal is obtained, performing a first coherent accumulation operation on the obtained despread I-path signal, and performing a first coherent accumulation operation on the obtained despread Q-path signal; specifically, when a despread I-path signal is obtained, first, a previous first coherent accumulation result is delayed by a first time interval Ts before coherent accumulation, and the previous first coherent accumulation result is synthesized from a previous first coherent accumulation result of the despread I-path signal and a previous first coherent accumulation result of the despread Q-path signal; then, the delayed last first coherent accumulation result is rotated by the epsilon angle phase, i.e. the last first coherent accumulation result and e^-j2πεTsMultiplying; and finally, adding the multiplied last first coherent accumulation result with the current despread I path signal and the current despread Q path signal respectively to obtain a current first coherent accumulation result.

In this embodiment, the current despread complex signal is denoted by a, where a is I₁+jQ₁Wherein, I₁For the current de-spread I-path signal, Q₁The current de-spread Q path signal is obtained; the last first coherent accumulation result is denoted by B1, B1 ═ I_B1+jQ_B1Wherein, I_B1For the last first coherent accumulation result, Q, of the despread I-path signal_B1After despreadingThe last first coherent accumulation result of the Q-path signal; delaying the previous first coherent accumulation result and then performing phase rotation, wherein the first phase interval of the rotation is represented by epsilon Ts; according to I_B＝I₁+I_B1*e^-j2πεTs、Q_B＝Q₁+Q_B1*e^-j2πεTsAnd B ═ I_B+jQ_BA current first coherent accumulation result B may be calculated.

Meanwhile, when the despreading complex signal is obtained, second coherent accumulation operation is carried out on the obtained despreading I path signal, and second coherent accumulation operation is carried out on the obtained despreading Q path signal; specifically, when a despread I-path signal is obtained, first, a previous second coherent accumulation result is delayed by a first time interval Ts before coherent accumulation, and the previous second coherent accumulation result is synthesized by a previous second coherent accumulation result of the despread I-path signal and a previous second coherent accumulation result of the despread Q-path signal; then, the delayed last second coherent accumulation result is rotated by an angle phase of-epsilon, namely the last second coherent accumulation result and e^j2πεTsMultiplying; and finally, adding the multiplied last second coherent accumulation result with the current despread I path signal and the current despread Q path signal respectively to obtain the current second coherent accumulation result.

In this embodiment, the current despread complex signal is denoted by a, where a is I₁+jQ₁In which I₁For the current de-spread I-path signal, Q₁The current de-spread Q path signal is obtained; the last second coherent accumulation result is represented by B2, B2 ═ I_B2+jQ_B2In which I_B2For the last second coherent accumulation result, Q, of the despread I-path signal_B2The second coherent accumulation result is the last second coherent accumulation result of the despread Q-path signal; delaying the last second coherent accumulation result and then performing phase rotation, wherein a second phase interval of the rotation is represented by-epsilon-Ts; according to I_C＝I₁+I_B2*e^j2πεTs、Q_C＝Q₁+Q_B2*e^j2πεTsAnd C ═ I_C+jQ_CThe current second coherent accumulation result C may be calculated.

Furthermore, the epsilon can be set according to actual needs, and the specific setting needs to refer to the characteristics of the GNSS signal; in this embodiment, the epsilon can be described in detail by taking 12.5Hz as an example according to the characteristics of the B1I signal. The Ts can be set according to actual needs, and the specific setting needs to refer to the characteristics of the GNSS signals; in this embodiment, according to the characteristic of NH code modulation in the B1I signal, the Ts may be described in detail by taking a sampling interval of 1ms as an example. According to the set values of epsilon and Ts, the first phase interval is 0.0125, and correspondingly, the first phase rotation angle 2 pi epsilon Ts is 0.07854 radians; the second phase interval is-0.0125, and correspondingly, the second phase rotation angle-2 pi epsilon Ts is-0.07854 radians.

Step 102, when determining that the number of times of performing a first coherent accumulation operation reaches a first preset value and the number of times of performing a second coherent accumulation operation reaches the first preset value, setting the first coherent accumulation result as a first target coherent accumulation result, and setting the second coherent accumulation result as a second target coherent accumulation result;

here, the first preset value may be set according to actual needs, and specifically set a sign bit width of navigation information in the GNSS signal to be referred to; in this embodiment, since the sign bit width of the navigation information in the B1I signal is 20ms, and the sign bit width of each NH code is 1ms, the first preset value can be set to 20.

It should be noted that, the despread complex signal is a digital signal, in this embodiment, the symbol bit width of the digital signal is 1ms, that is, the despread complex signal obtained each time is different when the first coherent accumulation operation and the second coherent accumulation operation are performed, so when it is determined that the number of times of performing the first coherent accumulation operation does not reach the first preset value and the number of times of performing the second coherent accumulation operation does not reach the first preset value, the step of performing the first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result and performing the second coherent accumulation operation to obtain a second coherent accumulation result is performed in a loop; and, when the number of times of performing the first coherent accumulation operation is 1, the previous first coherent accumulation result is 0, and when the number of times of performing the second coherent accumulation operation is 1, the previous second coherent accumulation result is 0.

It should be noted that after the first coherent accumulation result is set as a first target coherent accumulation result and the second coherent accumulation result is set as a second target coherent accumulation result, the first coherent accumulation result and the second coherent accumulation result need to be cleared; after the zero clearing, the number of times of performing the first coherent accumulation operation and the second coherent accumulation operation is counted again from 1.

It will be appreciated that by performing a first coherent accumulation operation on the obtained despread complex signal, a rotation of the previous first coherent accumulation result by a first phase interval ε Ts, i.e. e, can be performed cyclically^-j2πεTsPhase operation, so that frequency conversion operation of epsilon frequency can be carried out on the de-spread complex signal; by performing the second coherent accumulation operation on the obtained despread complex signal, the rotation of the previous second coherent accumulation result by the second phase interval-epsilon-Ts, i.e. e^j2πεTsPhase operation, so that frequency conversion operation of-epsilon frequency to the despread complex signal can be realized.

Step 103, adjusting the frequency of a reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result, where the reference frequency complex signal is used for performing down-conversion on the GNSS signal.

Fig. 7 is a schematic diagram of a refined flow of adjusting the frequency of the reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result in the implementation flow shown in fig. 5, and referring to fig. 7, step 103 specifically includes the following steps:

step 1031, performing modulo operation on the first target coherent accumulation result to obtain a modulo first coherent accumulation result; performing a modulus operation on the second target coherent accumulation result to obtain a modulus-solved second target coherent accumulation result;

in this example, according to

Performing modulo calculation on the first target coherent accumulation result to obtain a modulo-calculated first target coherent accumulation result; according to

And performing modulus calculation on the second target coherent accumulation result to obtain a second target coherent accumulation result after the modulus calculation.

Step 1032, subtracting the modulo first target coherent accumulation result from the modulo second target coherent accumulation result to obtain a frequency error identification result, where the frequency error identification result is used to identify a frequency error between the GNSS signal carrier and the reference frequency complex signal;

in this example, according to

Calculating the frequency error discrimination result.

Step 1033, performing incoherent accumulation on the frequency error discrimination result to obtain a first incoherent accumulation result;

here, a non-coherent accumulation gain may be obtained by non-coherently accumulating the frequency error discrimination signal to improve carrier tracking sensitivity of the GNSS signal.

1034, judging whether the frequency of the non-coherent accumulation of the frequency error discrimination result is less than a second preset value;

generally, the more the number of times of accumulation, the larger the incoherent accumulation gain, but because the incoherent accumulation has square loss, in a weak signal frequency tracking scene, there is a limit state of the accumulated gain, that is, no matter how many times of incoherent accumulation, the accumulated gain cannot be increased without limit.

It should be noted that the second preset value may be set according to actual needs, and the specific setting needs to be according to GNSS signal characteristics; according to the B1I signal characteristics, the second preset value can be set to any integer value greater than 1 in principle, however, the second preset value cannot be set to infinity due to the square loss of the incoherent accumulation and due to the consideration of time, and therefore, in this embodiment, the second preset value can be described in detail by taking 10 as an example.

Step 1035, when the number of times of performing incoherent accumulation is smaller than the second preset value, performing a first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result, and performing a second coherent accumulation operation to obtain a second coherent accumulation result; and when the number of times of incoherent accumulation reaches the second preset value, generating frequency adjustment information according to the first incoherent accumulation result.

Here, in order to form a closed carrier frequency tracking loop to adjust the frequencies of the I-path signal and the Q-path signal generated by the local carrier generator, the GNSS signal carrier tracking apparatus further includes a loop filter that may generate frequency adjustment information based on the first incoherent accumulation result.

In this embodiment, according to the characteristics of the B1I signal, a closed second-order carrier frequency tracking loop may be formed by using a loop filter structure as shown in fig. 8, and the second-order carrier frequency tracking loop may effectively resist frequency deviation generated by acceleration during the motion of the receiver, so as to increase the robustness of frequency tracking. Referring to fig. 8, the loop filter inputs the first non-coherent accumulation result and outputs a first NCO frequency control word fed back to the local carrier generator, where the first NCO frequency control word includes frequency adjustment information, where tnocoh is an update time interval of the first non-coherent accumulation result. Because the loop filter firstly multiplies the obtained first incoherent accumulation result by the parameters a and b, different frequency tracking loop gains and loop bandwidths can be obtained by setting the parameter values a and b so as to meet the trade-off and balance between the tracking sensitivity and the motion state of the receiver.

Specifically, the acquired B1I signal is multiplied by the I path signal and the Q path signal generated by the local carrier generator to down-convert the B1I signal, and obtain an initial complex signal with frequency offset removed;

stripping a spreading code in the initial complex signal to obtain a de-spread complex signal;

when obtaining said despread complex signal A, wherein A ═ I₁+jQ₁The last first coherent accumulation results B1 and e^-j2πεTsMultiplication, wherein B1 ═ I_B1+jQ_B1Obtaining the result B1 × e after B1 rotates for the first phase interval^-j2πεTsAnd according to I_B＝I₁+I_B1*e^-j2πεTs、Q_B＝Q₁+Q_B1*e^-j2πεTsAnd B ═ I_B+jQ_BCalculating a current first coherent accumulation result B; at the same time, the last second coherent accumulation result B2 is equal to I_B2+jQ_B2And e^j2πεTsMultiplying to obtain the result B2 × e after B2 rotates by a second phase interval^j2πεTsAnd according to I_C＝I₁+I_B2*e^j2πεTs、Q_C＝Q₁+Q_B2*e^j2πεTsAnd C ═ I_C+jQ_CCalculating a current second coherent accumulation result C;

judging whether the frequency of coherent accumulation operation reaches 20;

when the number of times of coherent accumulation operation reaches 20, setting the first coherent accumulation result as a first target coherent accumulation result, and setting the second coherent accumulation result as a second target coherent accumulation result;

clearing the first coherent accumulation result and the second coherent accumulation result;

according to

Performing modulo calculation on the first target coherent accumulation result to obtain a modulo-calculated first target coherent accumulation result; and according to

Performing modulo calculation on the second target coherent accumulation result to obtain a modulo second target coherent accumulation result;

according to

Calculating the frequency error discrimination result;

judging whether the number of times of performing incoherent accumulation on the frequency error identification result reaches 10;

and when the number of times of incoherent accumulation reaches 10, inputting the first incoherent accumulation result into a loop filter, and outputting a first NCO frequency control word fed back to a local carrier generator by the loop filter so as to adjust the frequency of an I path signal and a Q path signal generated by the local carrier generator.

It can be understood that by performing the first coherent accumulation operation and the second coherent accumulation operation on the obtained despread complex signals, the GNSS signal frequency tracking complexity can be effectively reduced because: in one aspect, the first coherent accumulation operation comprises: before coherent accumulation, the last first coherent accumulation result is rotated according to a first phase interval, and the last first coherent accumulation result is circularly and repeatedly rotated by a first phase interval epsilon Ts, namely e^-j2πεTsThe phase operation can realize the frequency conversion operation of epsilon frequency on the de-spread complex signal; in another aspect, the second coherent accumulation operation comprises: before coherent accumulation, the last second coherent accumulation result is rotated according to second phase interval, and the second phase interval-epsilon-Ts rotation is carried out on the last second coherent accumulation result in a cyclic reciprocating manner, namely e is carried out^j2πεTsAnd performing phase operation to realize frequency conversion operation of-epsilon frequency on the despread complex signal. Therefore, the frequency conversion of epsilon frequency of the de-spread complex signal can be realized through the simple rotation operation of the first phase interval epsilon Ts, and the frequency conversion of epsilon frequency of the de-spread complex signal can be realized through the simple rotation operation of the second phase interval epsilon Ts, so that the generation and frequency conversion operation of two local reference frequencies can be replaced, the frequency tracking complexity of the GNSS signal can be effectively reduced, and the operation amount and the circuit implementation scale can be reduced.

Furthermore, in an application scenario where a carrier phase of a GNSS signal needs to be obtained, the carrier phase of the GNSS signal needs to be tracked, so that a carrier tracking effect capable of locking both frequency and phase is obtained.

Fig. 9 is a schematic flow chart illustrating an implementation of a second GNSS signal carrier tracking method according to the present invention, and referring to fig. 9, in the step 101 of the first method embodiment, the GNSS signal carrier tracking method of the present embodiment further includes:

104, performing coherent accumulation on the obtained despread complex signals to obtain a third coherent accumulation result;

here, while the first coherent accumulation operation and the second coherent accumulation operation are performed on the despread complex signals, coherent accumulation is performed on the obtained despread complex signals to obtain a third coherent accumulation result.

Step 105, judging whether the times of coherent accumulation is less than the first preset value;

106, when the times of coherent accumulation is smaller than the first preset value, executing the step of coherent accumulation on the obtained despread complex signal to obtain a third coherent accumulation result; when the times of coherent accumulation reach the first preset value, setting the third coherent accumulation result as a third target coherent accumulation result;

specifically, when the number of times of coherent accumulation reaches 20, the third coherent accumulation result may be sent to a subsequent module for data demodulation, and may be used to calculate a phase error discrimination result.

Step 107, calculating a phase error discrimination result according to the third target coherent accumulation result, where the phase error discrimination result is used to discriminate a phase error between the GNSS signal carrier and the reference frequency complex signal;

here, the third target coherent accumulation result is represented by D, where the third target coherent accumulation result is a complex number, and D ═ I_D+jQ_DRepresents; in this embodiment, can be according to

Or

And calculating a phase error discrimination result.

Step 108, performing incoherent accumulation on the phase error discrimination result to obtain a second incoherent accumulation result;

step 109, judging whether the number of times of performing incoherent accumulation on the phase error identification result is less than a third preset value;

here, the third preset value may be set according to actual needs, and the specific setting needs to be according to GNSS signal characteristics; according to the B1I signal characteristics, the third preset value can be set to any integer value greater than 1 in principle, however, based on the reason that the square loss exists in the non-coherent accumulation and based on the time consideration, the third preset value cannot be set to infinity, and in order to achieve the synchronization of frequency locking and phase locking, therefore, in this embodiment, the third preset value can be set to 10.

Step 1010, when the number of times of performing incoherent accumulation is smaller than the third preset value, performing coherent accumulation on the obtained despread complex signal to obtain a third coherent accumulation result; and when the number of times of non-coherent accumulation reaches the third preset value, generating phase adjustment information according to the second non-coherent accumulation result so as to adjust the phase of the reference frequency complex signal.

In this embodiment, according to the signal characteristics of B1I, a closed second-order carrier frequency and phase joint tracking loop can be formed by using a loop filter structure as shown in fig. 10, and the loop filter can internally fuse the first incoherent accumulation result and the second incoherent accumulation result. Referring to fig. 10, the loop filter inputs the first incoherent accumulation result and the second incoherent accumulation result, and outputs a second NCO frequency control word fed back to the local carrier generator, where the second NCO frequency control word includes both frequency adjustment information and phase adjustment information, where tnocoh is an update time interval of the incoherent accumulation result, and multiplication factors a, b, and c together form a tracking loop gain and a loop bandwidth.

In the third embodiment of the GNSS signal carrier tracking method of the present invention, in order to explain the practical application of the GNSS signal carrier tracking method of the present invention, the GNSS signal carrier tracking method of the present invention is explained in detail by combining an application scene graph.

Fig. 11 is a schematic diagram of an application scenario of a third GNSS signal carrier tracking method according to an embodiment of the present invention, configured to track a carrier frequency of a GNSS signal, and is shown in fig. 11, where the application scenario includes a local carrier generator, a frequency converter, a spreading code despreader, a first accumulator/clearer, a first delay, a first phase rotator, a first modulo operation unit, a second accumulator/clearer, a second delay, a second phase rotator, a second modulo operation unit, a third accumulator/clearer, a subtractor, a first incoherent accumulator/clearer, and a loop filter, where the loop filter is a frequency discrimination loop filter.

The GNSS signal carrier tracking method of the present invention will be described in detail below with reference to fig. 11.

The frequency converter carries out residual frequency stripping operation on the acquired GNSS signal according to the I path signal and the Q path signal generated by the local carrier generator, and outputs an initial complex signal of stripping frequency deviation;

a spread spectrum code despreader peels off the spread spectrum code in the initial complex signal and outputs a despread complex signal with the spread spectrum code peeled off;

the first accumulation/zero clearing device adds the de-spread complex signal obtained currently and the last first coherent accumulation result after the phase rotation of the first phase rotator to obtain the current first coherent accumulation result; the first delayer delays the last first coherent accumulation result by one sampling interval Ts; the first phase rotator rotates the last first coherent accumulation result of the delay by epsilon angle phase, i.e. e is carried out^-j2πεTsOperating; the first accumulation/zero clearing device outputs a current first coherent accumulation result every 20ms and clears the first coherent accumulation result;

at the same time, the second accumulation/zero clearing device phase-compares the despread complex signal obtained currently with the phase signal passed through the second phase rotatorAdding the previous second coherent accumulation results of the bit rotation to obtain the current second coherent accumulation result; the second time delay device delays the last second coherent accumulation result by a sampling interval Ts; the second phase rotator rotates the delayed last second coherent accumulation result by an angle of-epsilon phase, i.e. e^j2πεTsOperating; the second accumulation/zero clearing device outputs the current second coherent accumulation result every 20ms and clears the second coherent accumulation result;

meanwhile, the third accumulation/zero clearing device performs coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result; outputting the third trunk accumulation result every 20ms, resetting the third trunk accumulation result, and sending the output third trunk accumulation result to a rear-stage module for data demodulation;

the first modulus calculation unit calculates the modulus of the first coherent accumulation result and outputs the first coherent accumulation result after the modulus calculation; the second modulus calculation unit calculates the modulus of the second coherent accumulation result and outputs the second coherent accumulation result after modulus calculation;

the subtracter subtracts the second coherent accumulation result after the modulus from the first coherent accumulation result after the modulus calculation, and outputs a frequency error identification result;

the first incoherent accumulation/zero clearing device carries out incoherent accumulation on the frequency error identification result, and when the frequency of the incoherent accumulation on the frequency error identification result reaches 10, a first incoherent accumulation result is output;

and the frequency discrimination loop filter outputs a first NCO frequency control word according to the first incoherent accumulation result, wherein the first NCO frequency control word comprises frequency adjustment information so as to adjust the frequency of the I path signal and the Q path signal generated by the local carrier generator.

Further, fig. 12 is a second schematic view of an application scenario of a third GNSS signal carrier tracking method according to the present invention, configured to perform joint tracking on a carrier frequency and a phase of a GNSS signal, and is shown in fig. 12, where the application scenario includes a local carrier generator, a frequency converter, a spreading code despreader, a first accumulation/zero clearing unit, a first delay unit, a first phase rotator, a first modulo operation unit, a second accumulation/zero clearing unit, a second delay unit, a second phase rotator, a second modulo operation unit, a third accumulation/zero clearing unit, a subtractor, a phase discriminator, a first incoherent accumulation/zero clearing unit, a second incoherent accumulation/zero clearing unit, and a loop filter, where the loop filter is a frequency discrimination/phase discrimination loop filter.

The GNSS signal carrier tracking method of the present invention will be described in detail below with reference to fig. 12.

meanwhile, the second accumulation/zero clearing device adds the currently obtained despread complex signal with the last second coherent accumulation result subjected to phase rotation by the second phase rotator to obtain a current second coherent accumulation result; the second time delay device delays the last second coherent accumulation result by a sampling interval Ts; the second phase rotator rotates the delayed last second coherent accumulation result by an angle of-epsilon phase, i.e. e^j2πεTsOperating; the second accumulation/zero clearing device outputs the current second coherent accumulation result every 20ms and clears the second coherent accumulation result;

meanwhile, the third accumulation/zero clearing device performs coherent accumulation on the obtained de-spread complex signals to obtain a third coherent accumulation result; outputting the third phase trunk accumulation result every 20ms, clearing the third phase trunk accumulation result, and sending the output third phase trunk accumulation result to a post-stage module for data demodulation on one hand and a phase discriminator on the other hand;

the subtracter subtracts the second coherent accumulation result after the modulus from the first coherent accumulation result after the modulus calculation, and outputs a frequency error identification result; phase detector based on

Or

Calculating a phase error discrimination result;

the first incoherent accumulation/zero clearing device carries out incoherent accumulation on the frequency error identification result, and when the frequency of the incoherent accumulation on the frequency error identification result reaches 10, a first incoherent accumulation result is output; the second incoherent accumulation/zero clearing device carries out incoherent accumulation on the phase error identification result, and when the number of times of the incoherent accumulation on the phase error identification result reaches 10, a second incoherent accumulation result is output;

and the frequency discrimination/phase discrimination loop filter outputs a second NCO frequency control word according to the first incoherent accumulation result and the second incoherent accumulation result, wherein the second NCO frequency control word comprises frequency adjustment information and phase adjustment information so as to adjust the frequency and the phase of the I path signal and the Q path signal generated by the local carrier generator.

The invention also provides a GNSS signal carrier tracking device, which is used for realizing the specific details of the GNSS signal carrier tracking method of the invention and achieving the same effect.

Fig. 13 is a schematic structural diagram of a GNSS signal carrier tracking apparatus according to a first embodiment of the present invention, and referring to fig. 13, the GNSS signal carrier tracking apparatus of the present embodiment includes: a first coherent accumulation module 21, a setting module 22 and a frequency adjustment module 23; wherein the content of the first and second substances,

the first coherent accumulation module 21 is configured to perform a first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result, and perform a second coherent accumulation operation to obtain a second coherent accumulation result; the first coherent accumulation operation comprises: rotating a last first coherent accumulation result by a first phase interval prior to coherent accumulation, the second coherent accumulation operation comprising: rotating a previous second coherent accumulation result according to a second phase interval before coherent accumulation, wherein the first phase interval and the second phase interval are opposite numbers; the de-spread complex signal is a GNSS signal after down-conversion and de-spread;

the setting module 22 is configured to set the first coherent accumulation result as a first target coherent accumulation result and set the second coherent accumulation result as a second target coherent accumulation result when determining that the number of times of performing the first coherent accumulation operation reaches a first preset value and the number of times of performing the second coherent accumulation operation reaches the first preset value;

the frequency adjustment module 23 is configured to adjust a frequency of a reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result, where the reference frequency complex signal is used to perform down-conversion on the GNSS signal.

Optionally, the GNSS signal carrier tracking apparatus of this embodiment further includes: the first processing module 24 is configured to trigger the first coherent accumulation module 21 when determining that the number of times of performing the first coherent accumulation operation does not reach the first preset value and the number of times of performing the second coherent accumulation operation does not reach the first preset value.

Optionally, the first coherent accumulation module 21 is specifically configured to, when obtaining the despread complex signal, calculate a current first coherent accumulation result B according to a previous first coherent accumulation result B1, a currently obtained despread complex signal a, and the first phase interval ∈ Ts, where the current first phase is a first phaseThe dry accumulation result satisfies: b + B1 me^-j2πεTs(ii) a When the number of times of performing the first coherent accumulation operation is 1, the previous first coherent accumulation result is 0, Ts is a time interval during which the previous first coherent accumulation result is delayed, epsilon is an angular phase of rotation of the previous first coherent accumulation result, and j is an imaginary unit.

Optionally, the first coherent accumulation module 21 is further configured to, when obtaining the despread complex signal, calculate a current second coherent accumulation result C according to a previous second coherent accumulation result B2, the currently obtained despread complex signal a, and the second phase interval-epsilon _ Ts, where the current second coherent accumulation result satisfies: c + B2 × e^j2πεTs(ii) a When the number of times of performing the second coherence accumulation operation is 1, the previous second coherence accumulation result is 0, Ts is a time interval during which the previous second coherence accumulation result is delayed, -epsilon is an angle phase at which the previous second coherence accumulation result rotates, and j is an imaginary number unit.

Fig. 14 is a schematic diagram of a detailed structure of a frequency adjustment module in the apparatus shown in fig. 13, and referring to fig. 14, the frequency adjustment module 23 includes: a modulo operation unit 231, a subtraction unit 232, and a generation unit 233; wherein the content of the first and second substances,

the modulo operation unit 231 is configured to perform modulo operation on the first target coherent accumulation result to obtain a modulo first target coherent accumulation result; performing a modulus operation on the second target coherent accumulation result to obtain a modulus-solved second target coherent accumulation result;

the subtracting unit 232 is configured to subtract the first target coherent accumulation result after the modulus from the second target coherent accumulation result after the modulus to obtain a frequency error identification result, where the frequency error identification result is used to identify a frequency error between the GNSS signal carrier and the reference frequency complex signal;

the generating unit 233 is configured to generate frequency adjustment information according to the frequency error identification result, so as to adjust the frequency of the reference frequency complex signal.

Fig. 15 is a schematic diagram of a detailed structure of a generating unit in the apparatus shown in fig. 14, and referring to fig. 15, the generating unit 233 includes: a non-coherent accumulation sub-unit 2331, a judgment sub-unit 2332, and a processing sub-unit 2333; wherein the content of the first and second substances,

the incoherent accumulation subunit 2331 is configured to perform incoherent accumulation on the frequency error identification result to obtain a first incoherent accumulation result;

the determining subunit 2332 is configured to determine whether the number of times of performing incoherent accumulation on the frequency error identification result is less than a second preset value;

the processing sub-unit 2333 is configured to trigger the first coherent accumulation module 21 when the number of times of performing incoherent accumulation is smaller than the second preset value; and when the number of times of incoherent accumulation reaches the second preset value, generating frequency adjustment information according to the first incoherent accumulation result.

Fig. 16 is a schematic structural diagram of a second embodiment of the GNSS signal carrier tracking apparatus of the present invention, and referring to fig. 16, the GNSS signal carrier tracking apparatus of the present embodiment further includes, on the basis of the first embodiment of the apparatus: a second coherent accumulation module 25, a judgment module 26, a second processing module 27, a calculation module 28 and a generation module 29; wherein the content of the first and second substances,

the second coherent accumulation module 25 is configured to perform coherent accumulation on the obtained despread complex signal to obtain a third coherent accumulation result;

the judging module 26 is configured to judge whether the number of times of performing coherent accumulation is smaller than the first preset value;

the second processing module 27 triggers the second coherent accumulation module 25 when the number of coherent accumulation is smaller than the first preset value; when the number of times of coherent accumulation reaches the first preset value, setting the third coherent accumulation result as a third target coherent accumulation result, and resetting the third coherent accumulation result and the number of times of coherent accumulation;

the calculating module 28 is configured to calculate a phase error identification result according to the third target coherent accumulation result, where the phase error identification result is used to identify a phase error between the GNSS signal carrier and the reference frequency complex signal;

the generating module 29 is configured to generate phase adjustment information according to the phase error identification result, so as to adjust the phase of the reference frequency complex signal;

fig. 17 is a schematic diagram of a detailed structure of a generating module in the apparatus shown in fig. 16, and referring to fig. 17, the generating module 29 includes: an incoherent accumulation unit 291, a judgment unit 292, and a processing unit 293; wherein the content of the first and second substances,

the incoherent accumulation unit 291 is configured to perform incoherent accumulation on the phase error identification result to obtain a second incoherent accumulation result;

the determining unit 292 is configured to determine whether the number of times of performing incoherent accumulation on the phase error identification result is smaller than a third preset value;

the processing unit 293 is configured to trigger the second coherent accumulation module 25 when the number of times of performing incoherent accumulation is smaller than the third preset value; and when the number of times of incoherent accumulation reaches the third preset value, generating phase adjustment information according to the second incoherent accumulation result.

In practical applications, the first coherent accumulation module 21, the setting module 22, the frequency adjustment module 23, the first Processing module 24, the second coherent accumulation module 25, the determination module 26, the second Processing module 27, the calculation module 28, the generation module 29, the modulo operation Unit 231, the subtraction Unit 232, the generation Unit 233, the incoherent accumulation Unit 291, the determination Unit 292, the Processing Unit 293, the incoherent accumulation subunit 2331, the determination subunit 2332, and the Processing subunit 2333 may be implemented by a Central Processing Unit (CPU), a MicroProcessor Unit (MPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), or the like located in a mobile terminal.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and scope of the present invention are included in the protection scope of the present invention.

Claims

1. A GNSS signal carrier tracking method, the method comprising:

adjusting the frequency of a reference frequency complex signal according to the first target coherent accumulation result and a second target coherent accumulation result, wherein the reference frequency complex signal is used for performing down-conversion on the GNSS signal;

wherein the performing a first coherent accumulation operation on the obtained despread complex signal to obtain a first coherent accumulation result comprises:

2. The method of claim 1, wherein performing the second coherent accumulation operation on the obtained despread complex signal to obtain a second coherent accumulation result comprises:

when the despread complex signal is obtained, calculating a current second coherent accumulation result C according to a previous second coherent accumulation result B2, the currently obtained despread complex signal a, and the second phase interval-epsilon _ Ts, where the current second coherent accumulation result satisfies: c + B2 × e^j2πεTs(ii) a When the number of times of performing the second coherence accumulation operation is 1, the last second coherence accumulation result is 0;

3. The method of claim 1, further comprising:

4. The method of claim 1, wherein adjusting the frequency of the reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result comprises:

5. The method of claim 4, wherein generating frequency adjustment information based on the frequency error discrimination comprises:

6. The method of claim 1, wherein after obtaining the despread complex signal, the method further comprises:

7. The method of claim 6, wherein generating phase adjustment information based on the phase error discrimination comprises:

8. A GNSS signal carrier tracking apparatus, the apparatus comprising: the device comprises a first coherent accumulation module, a setting module and a frequency adjustment module; wherein the content of the first and second substances,

the frequency adjusting module is configured to adjust a frequency of a reference frequency complex signal according to the first target coherent accumulation result and the second target coherent accumulation result, where the reference frequency complex signal is used to perform down-conversion on the GNSS signal;

the first coherent accumulation module is specifically configured to, when the despread complex signal is obtained, calculate a current first coherent accumulation result B according to a previous first coherent accumulation result B1, the currently obtained despread complex signal a, and the first phase interval ∈ Ts, where the current first coherent accumulation result satisfies: b + B1 me^-j2πεTs(ii) a When the number of times of performing the first coherent accumulation operation is 1, the previous first coherent accumulation result is 0, Ts is a time interval during which the previous first coherent accumulation result is delayed, epsilon is an angular phase of rotation of the previous first coherent accumulation result, and j is an imaginary unit.

9. The apparatus of claim 8, wherein the first coherent accumulation module is further configured to, when obtaining the despread complex signal, calculate a current second coherent accumulation result C according to a previous second coherent accumulation result B2, a currently obtained despread complex signal a, and the second phase interval-s _ Ts, wherein the current second coherent accumulation result satisfies: c + B2 × e^j2πεTs(ii) a When the number of times of performing the second coherence accumulation operation is 1, the previous second coherence accumulation result is 0, Ts is a time interval during which the previous second coherence accumulation result is delayed, -epsilon is an angle phase at which the previous second coherence accumulation result rotates, and j is an imaginary number unit.

10. The apparatus of claim 8, further comprising:

11. The apparatus of claim 10, wherein the frequency adjustment module comprises: a modulo arithmetic unit, a subtraction unit and a generation unit; wherein the content of the first and second substances,

12. The apparatus of claim 11, wherein the generating unit comprises: the device comprises a noncoherent accumulation subunit, a judgment subunit and a processing subunit; wherein the content of the first and second substances,

13. The apparatus of claim 8, further comprising: the device comprises a second coherent accumulation module, a judgment module, a second processing module, a calculation module and a generation module; wherein the content of the first and second substances,

14. The apparatus of claim 13, wherein the generating module comprises: the device comprises a noncoherent accumulation unit, a judgment unit and a processing unit; wherein the content of the first and second substances,