CN109407121B - Configurable navigation signal compatible capturing and tracking device - Google Patents

Configurable navigation signal compatible capturing and tracking device Download PDF

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CN109407121B
CN109407121B CN201811358195.1A CN201811358195A CN109407121B CN 109407121 B CN109407121 B CN 109407121B CN 201811358195 A CN201811358195 A CN 201811358195A CN 109407121 B CN109407121 B CN 109407121B
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CN109407121A (en
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张前南
陶磊岩
杨春景
尚佳栋
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Beijing Institute of Remote Sensing Equipment
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related

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Abstract

The invention discloses a configurable compatible capturing and tracking device for navigation signals, wherein in an initial state, the navigation signals enter a correlation module after passing through an orthogonal frequency deviation removal module, the correlation module performs correlation de-spreading processing on the navigation signals and then sends the navigation signals to an FFT (fast Fourier transform) judgment module, the FFT judgment module outputs a capturing success mark under the condition of successful judgment, the capturing process is ended, and tracking is started; under the capture failure, the step adjustment module selects different search steps according to the type of the navigation signal input by the system, and the adjusting code generation module carries out the next capture process; after the tracking is started, the early, middle and late correlators output multi-path correlation values, a peak value jumping module is triggered to perform secondary peak locking judgment, if the multi-path correlation values are locked on a secondary peak, a stepping adjusting module is prompted to perform 1/2-chip phase jumping, meanwhile, a code loop phase discriminator and a filter realize real-time tracking of pseudo codes, and a carrier loop phase discriminator and the filter finish real-time tracking of carriers. The device has the advantages of low processing difficulty, good compatibility and channel consistency and the like.

Description

Configurable navigation signal compatible capturing and tracking device
Technical Field
The invention relates to the field of navigation signal acquisition and tracking, in particular to a configurable navigation signal compatible acquisition and tracking device which is mainly used for acquiring and tracking new and old system satellite navigation signals.
Background
With the rapid development of Global Navigation Satellite System (GNSS), on the basis of the original direct sequence spread spectrum (DSSS-BPSK), people have developed a Binary Offset Carrier (BOC) modulation mode, which effectively realizes frequency band public and spectrum separation, and brings the advantages of better anti-interference and high-precision measurement.
The design and implementation of the GNSS navigation signal endow a plurality of systems with the capability of mutual compatible operation, and the multi-system compatible operation mainly comprises the signal and information processing compatibility of three navigation systems of GPS, Beidou (BDS) and Galileo (Galileo). Wherein signals of L1C of GPS, E1 of Galileo and B1C of BDS share the L1 frequency point of the original GPS, namely 1575.42MHz, the modulation mode of data components is BOC (1,1), and pilot components are TMBOC (6,1,4/33), CBOC (6,1,1/11) and QMBOC (6,1, 4/33); the GPS L5, Galileo E5a, and BDS B2a signals are modulated using the GPS L5 frequency point, 1176.45MHz, using or equivalent to BPSK (10). In the acquisition tracking channel hardware implementation of the multi-system navigation receiver, the design of the acquisition tracking channel with configurable parameters has great flexibility and universality, and especially under the condition that three navigation systems are not upgraded and transformed, the compatibility of the navigation signal algorithm modulated by the original BPSK is particularly important.
Disclosure of Invention
The invention aims to provide a navigation signal compatible capturing and tracking device with configurable channels, which solves the problems of rapid capturing and accurate tracking of navigation signals of new and old systems. Specifically, the device mainly aims at BOC (1,1) modulation of a new system navigation signal L1C/E1/B1C, BPSK (10) modulation of L5/E5a/B2a and BPSK (1)/BPSK (2) modulation of an old system navigation signal, and provides a capturing and tracking device with configurable parameters to flexibly adapt to different signal types, achieve integrated capturing and tracking processing of the navigation signals, and improve channel consistency.
The invention provides a configurable navigation signal compatible capturing and tracking device, which comprises: the device comprises an orthogonal frequency deviation removing module, a correlation module, an FFT (fast Fourier transform) judgment module, a stepping adjustment module, a code generation module, a morning, noon and evening correlator, a peak value hopping module, a code loop phase discriminator, a carrier loop phase discriminator, a code loop filter and a carrier loop filter.
The orthogonal frequency deviation removing module has the function of removing the carrier residual frequency deviation of the navigation signal according to the frequency word obtained by capturing and tracking;
the function of the correlation module is to perform correlation de-spread of the navigation signal according to the length of the capture time;
the FFT judging module has the functions of carrying out FFT operation according to the related despreading result of the related module and judging whether the capturing is successful or not;
The step adjusting module has the function of outputting a chip step control word according to the type of the navigation signal and the judgment information given by the acquisition and tracking;
the code generation module has the function of controlling the stepping of the spread spectrum code according to the chip stepping control word given by the stepping adjustment module to generate a pseudo-random sequence of the corresponding code rate;
the early, middle and late correlator has the functions of de-spreading the navigation signal and outputting a plurality of paths of correlation values which can be used by the code loop phase discriminator and the carrier loop phase discriminator;
the peak value jumping module has the function of solving the problem of secondary peak false lock in the acquisition process of the BOC (1,1) signal;
the code loop phase discriminator has the function of outputting the offset of the pseudo code according to the correlation values of the early, middle and late correlators;
the carrier loop phase discriminator has the function of outputting carrier offset according to the correlation values of the early, middle and late correlators;
the function of the code loop filter is to filter high-frequency noise in the pseudo code offset;
the function of the carrier loop filter is to filter out high frequency noise in the carrier offset.
The device adopts direct acquisition processing of navigation signals, solves the problem of BOC (1,1) acquisition phase ambiguity by using a peak value jump technology in the tracking process, can be effectively suitable for processing GPS L1C/Galileo E1/BDS B1C signals and GPS L5/Galileo E5a/BDS B2a signals on the basis of being compatible with the traditional BPSK acquisition tracking algorithm, and has the unique difference that a peak value jump module is added in a tracking part, a stepping adjustment module is changed into a configurable parameter, and a code generation module simultaneously supports a spread spectrum code and a BOC local code. The device realizes smooth upgrade of a navigation signal processing algorithm, has lower algorithm complexity and better channel consistency, and has higher capturing and tracking performance because the BOC signal is received by double side bands.
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FIG. 1 is a schematic diagram of a configurable navigation signal compatible acquisition tracking architecture of the present invention;
FIG. 2 is a schematic diagram of a configurable navigation signal compatible acquisition tracking flow of the present invention;
FIG. 3 shows a three-peak structure of the autocorrelation function of the BOC (1,1) signal of the present invention.
1. Orthogonal frequency deviation removing module 2, correlation module 3, FFT decision module 4, step adjusting module 5, code generating module 6, early, middle and late correlators 7, peak value hopping module 8, code loop phase discriminator 9, carrier loop phase discriminator 10, code loop filter 11, carrier loop filter
Detailed Description
The following describes the embodiments of the present invention in detail.
The method for compatibly acquiring and tracking the configurable navigation signal comprises the following specific steps of:
the first step is as follows: constructing a configurable navigation signal compatible acquisition tracking structure, the structure comprising: the system comprises an orthogonal frequency deviation removing module 1, a correlation module 2, an FFT decision module 3, a stepping adjustment module 4, a code generation module 5, a morning, noon and evening correlator 6, a peak value hopping module 7, a code loop phase discriminator 8, a carrier loop phase discriminator 9, a code loop filter 10 and a carrier loop filter 11.
The orthogonal frequency deviation removing module 1 has the function of removing the carrier residual frequency deviation of the navigation signal according to the frequency word obtained by capturing and tracking;
The function of the correlation module 2 is to perform correlation de-spread of the navigation signal according to the length of the capture time;
the FFT decision module 3 has the functions of carrying out FFT operation according to the related despreading result of the related module 2 and deciding whether the capturing is successful;
the step adjusting module 4 has the function of outputting a chip step control word according to the type of the navigation signal and the judgment information given by the acquisition and tracking;
the code generation module 5 has the function of controlling the stepping of the spread spectrum code according to the chip stepping control word given by the stepping adjustment module 4 to generate a pseudo-random sequence of the corresponding code rate;
the early, middle and late correlator 6 has the function of despreading the navigation signal and outputting a plurality of paths of correlation values which can be used by the code loop phase discriminator 8 and the carrier loop phase discriminator 9;
the peak value jumping module 7 has the function of solving the problem of secondary peak false lock in the acquisition process of the BOC (1,1) signal;
the code loop phase discriminator 8 has the function of outputting the pseudo code offset according to the correlation value of the early, middle and late correlators 6;
the carrier loop phase discriminator 9 has the function of outputting carrier offset according to the correlation value of the early, middle and late correlators 6;
the function of the code loop filter 10 is to filter out high-frequency noise in the pseudo code offset;
the function of the carrier loop filter 11 is to filter out high frequency noise in the carrier offset.
The second step: the orthogonal frequency deviation removing module 1 adopts a digital carrier NCO and frequency mixing mode, firstly, the carrier NCO generates sine and cosine signals with corresponding frequencies according to frequency words output by the FFT judging module 3 and the carrier loop filter 11; and secondly, sending the sine and cosine signal and an input baseband digital signal into a digital mixer to complete complex multiplication, thereby realizing the function of removing frequency deviation.
The third step: the correlation module 2 sends the navigation signal after stripping the carrier wave to 11 paths of parallel correlators, and simultaneously sends 11 paths of local code sequences to the parallel correlators, and the correlators carry out integration-zero clearing operation according to given time to complete coherent de-spreading processing to obtain 11 paths of coherent integral quantity.
The fourth step: the FFT decision module 3 integrates 11 paths of coherent integration values output by the correlation module 2 into 256 groups by using a segmented correlation combined with a zero filling FFT technology, sends the 256 zeros to a 512-point Fast Fourier Transform (FFT) after the coherent value of each path is filled with the 256 zeros, adopts a pipeline working mode for FFT operation, sequentially completes FFT operation of 11 groups of 11 multiplied by 512 coherent values of different phases and result modular square taking, completes maximum value search, takes the searched maximum value as a capturing decision quantity, and detects whether the decision quantity exceeds a threshold or not. If not, adjusting the local code phase to restart the search of the next phase, otherwise ending the acquisition process and starting the tracking.
The fifth step: the step adjustment module 4 synthesizes the decision result of the FFT decision module 3, the jump enable of the peak jump module 7, and the tracking frequency word output chip step adjustment control word of the code loop filter 10, and sends them to the code generation module 5. Specifically, in the acquisition stage, the step adjustment module 4 provides different chip search step lengths according to the modulation system type of the signal to be acquired, where the search step of the BOC (1,1) signal is 1/6 chips, and the search steps of BPSK (1)/BPSK (2)/BPSK (10) are all 1/2 chips; after the acquisition is successfully shifted to tracking, whether front-to-back 1/2 chip hopping is carried out or not is determined according to hopping enabling given by the peak value hopping module 7; in the stable tracking process, the real-time tracking frequency word of the code loop filter 10 is synthesized to output the final control word.
And a sixth step: the code generation module 5 generates a local spread spectrum code sequence or a BOC code sequence with the same code rate as the navigation signal in a mode of generating a polynomial or a lookup table according to the chip stepping control word under the driving of a high-frequency clock. According to the design, the code generation module 5 equally divides the pseudo code into 11 paths, outputs the 11 paths in parallel to capture the required pseudo code, and simultaneously outputs 5 paths of pseudo code sequences of time path, advance 1/2 chips, advance 1/6 chips, retard 1/6 chips and retard 1/2 chips for subsequent tracking.
The seventh step: the early, middle and late correlators 6 implement coherent despreading of the navigation signals and output 5 paths of correlation values which can be used by the code loop phase detector 8 and the carrier loop phase detector 9. The amplitudes of the correlation results of 5 branches without time-path advance, 1/2 chips advance, 1/6 chips advance, 1/6 chips retard and 1/2 chips retard are respectively marked as P0、E-1/2、E-1/6、L+1/6、L+1/2And the I, Q branch correlation result of the clock-time path is IP、QP。
Eighth step: the peak value jumping module 7 makes a size decision on the amplitude of the correlation result of 5 branches output by the early, middle and late correlators 6, rewrites the formula (1) and the formula (2) to obtain the following formula (6) and formula (7),
Figure BDA0001866640160000061
Figure BDA0001866640160000062
starting a comparison result counter Lcount and Rcount, if the formula (6) is satisfied, the Lcount is automatically decreased by 1, and the Rcount is automatically increased by 1; if formula (7) is satisfied, Lcount is added by 1, Rcount is subtracted by 1; if the values are not satisfied, the values of Lcount and Rcount are kept unchanged. And when the Lcount is larger than 15, the current phase tracking is locked on the left side secondary peak, when the Rcount is larger than 15, the current phase tracking is locked on the right side secondary peak, the peak value hopping module outputs a corresponding hopping enable in the opposite direction, the driving code generation module 5 skips 1/2 chips, then zero clearing of the counter Lcount and the Rcount is completed, and next peak value hopping detection is started.
The ninth step: the code loop phase detector 8 calculates the two paths of correlation amplitudes of the lead 1/6 chips and the lag 1/6 chips given by the early, middle and late correlators 6 according to the formula (3) to output the pseudo code offset delta cp。
The tenth step: the carrier loop phase detector 9 calculates the output carrier offset phi according to the equation (4) for the correlation value of the immediate path I, Q given by the early, middle and late correlators 6e。
The eleventh step: the code loop filter 10 performs digital domain discretization on a second-order filter shown in formula (5), performs high-frequency noise filtering on the input pseudo code offset, and obtains a code tracking frequency word, wherein the loop characteristic circular frequency omegan1rad/s was chosen.
A twelfth step: the carrier loop filter 11 performs high-frequency noise filtering on the input carrier offset according to a second-order filter shown in formula (5) to obtain a carrier tracking frequency word, wherein the loop characteristic circle frequency ω isn16rad/s were chosen.
Thus, configurable navigation signal compatible acquisition tracking is completed.
Specifically, the device mainly aims at BOC (1,1) modulation of a new system navigation signal L1C/E1/B1C, BPSK (10) modulation of L5/E5a/B2a and BPSK (1)/BPSK (2) modulation of an old system navigation signal, and provides a parameter-configurable capturing and tracking device to flexibly adapt to different signal types, achieve integrated capturing and tracking processing of the navigation signals, and improve channel consistency.
The invention provides a configurable navigation signal compatible capturing and tracking device, which comprises: the system comprises an orthogonal frequency deviation removing module 1, a correlation module 2, an FFT (fast Fourier transform) judging module 3, a stepping adjusting module 4, a code generating module 5, a morning, noon and evening correlator 6, a peak value jumping module 7, a code loop phase discriminator 8, a carrier loop phase discriminator 9, a code loop filter 10 and a carrier loop filter 11.
The orthogonal frequency deviation removing module 1 has the function of removing the carrier residual frequency deviation of the navigation signal according to the frequency word obtained by capturing and tracking;
the function of the correlation module 2 is to perform correlation despreading of the navigation signal according to the length of the capture time;
the FFT judging module 3 has the functions of carrying out FFT operation according to the related despreading result of the related module 2 and judging whether the capturing is successful or not;
the step adjusting module 4 has the function of outputting chip step control words according to the type of the navigation signal and the judgment information given by the acquisition tracking;
the code generation module 5 has the function of controlling the stepping of the spread spectrum code according to the chip stepping control word given by the stepping adjustment module to generate a pseudo-random sequence of the corresponding code rate;
the early, middle and late correlator 6 has the functions of despreading the navigation signal and outputting a plurality of paths of correlation values which can be used by a code loop phase discriminator and a carrier loop phase discriminator;
the peak value jumping module 7 has the function of solving the problem of secondary peak false lock in the acquisition process of the BOC (1,1) signal;
the code loop phase discriminator 8 has the function of outputting the pseudo code offset according to the correlation value of the early, middle and late correlators;
the carrier loop phase discriminator 9 has the function of outputting carrier offset according to the correlation values of the early, middle and late correlators;
the function of the code loop filter 10 is to filter out high frequency noise in the pseudo code offset;
The function of the carrier loop filter 11 is to filter out high frequency noise in the carrier offset.
Preferably, the quadrature frequency-offset removal module 1 uses a digital mixing method to achieve the purpose of removing carrier frequency offset from the baseband digital signal by using a given frequency word. The orthogonal frequency deviation removing module comprises a digital frequency mixing part and a carrier digital oscillator (NCO), wherein the carrier NCO generates sine and cosine signals with corresponding frequencies according to captured and tracked input frequency words, and the digital frequency mixing part performs complex multiplication on the signals and input baseband digital signals to realize the frequency deviation removing function.
Preferably, the correlation module 2 completes the correlation integration of the navigation signal after the carrier wave is stripped according to a given integration time, and obtains the coherent integration quantity through despreading processing. Considering different signal types and different pseudo code period lengths, the device uses a frequency domain parallel search capture technology, in order to accelerate the chip linear search rate, a correlation module 2 adopts 11 paths of parallel correlators to complete parallel de-spread integration of signals, and outputs 11 paths of correlation values.
Preferably, the FFT decision module 3 integrates 11 channels of coherent integration quantities output by the correlation module 2 into a plurality of groups by using a piecewise correlation in combination with a zero-padding FFT technique, then performs Fast Fourier Transform (FFT) by padding appropriate zeros in sequence, the FFT operation adopts a pipeline working mode, sequentially completes FFT operations of 11 groups of different phase correlation values and a result modulo square, then completes maximum value search, uses the searched maximum value as a capture decision quantity Z, and detects whether the decision quantity exceeds a threshold θ. If not, adjusting the local code phase to restart the search of the next phase, otherwise ending the acquisition process and starting the tracking.
Preferably, the step adjustment module 4 synthesizes the decision result of the FFT decision module, the jump enable of the peak jump module, and the tracking frequency word output chip step adjustment control word of the code loop, and sends them to the code generation module. As one of the core modules with configurable parameters, in particular, in the acquisition stage, different chip search step lengths are given according to the modulation system type of the signal to be acquired, where the search step of the BOC (1,1) signal is 1/6 chips, and the search steps of BPSK (1)/BPSK (2)/BPSK (10) are all 1/2 chips; after the acquisition is successfully shifted to the tracking, whether the front 1/2 chip hopping and the back 1/2 chip hopping are carried out is determined according to the hopping enabling given by the peak value hopping module 7; in the stable tracking process, the final control word is output by integrating the real-time tracking frequency word of the code ring.
Preferably, the code generating module 5 generates a local spreading code sequence or a BOC code sequence at the same code rate as the navigation signal in a generator polynomial or a lookup table manner according to the chip stepping control word under the driving of the high-frequency clock. According to the requirement, the code generation module 5 equally divides the pseudo code into 11 paths, parallelly outputs 11 paths to capture the required pseudo code, and simultaneously outputs 5 paths of pseudo code sequences, namely time path, advance 1/2 chips, advance 1/6 chips, lag 1/6 chips and lag 1/2 chips for subsequent tracking.
Preferably, the early, middle and late correlators 6 function to coherently despread the pilot signal while outputting 5-way correlation values that are available to the code loop phase detector and the carrier loop phase detector.
Preferably, the function of the peak value jumping module 7 is to solve the problem of phase ambiguity of the BOC (1,1) signal during the capturing process, that is, a possible secondary peak false-lock phenomenon. As shown in fig. 3, relative to the single peak structure of BPSK, the autocorrelation function of the BOC (1,1) signal has a trimodal structure, with a relatively narrower main peak and two secondary peaks at positions ± 1/2 chips.
The amplitudes of the correlation results of 5 branches without time-path advance, 1/2 chips advance, 1/6 chips advance, 1/6 chips retard and 1/2 chips retard are respectively marked as P0、E-1/2、E-1/6、L+1/6、L+1/2. If the current code tracking loop is locked on the right side secondary peak, then there is the following relationship:
Figure BDA0001866640160000101
on the contrary, if locking on the left side secondary peak, there is the following relationship:
Figure BDA0001866640160000102
if the peak locking state is not met, the current locking state is indicated to be locked on the main peak, and adjustment is not needed. In order to further reduce noise influence and realize stable tracking, the 5 groups of correlation values need to be continuously judged for a plurality of times, when the relation of the magnitude satisfying the formula (1) or the formula (2) is accumulated for a certain number of times, the correlation values are considered to be locked on the secondary peak, the peak value jumping module outputs jumping enable, and 1/2 chips are jumped towards the corresponding reverse direction.
Preferably, the code loop phase detector 8 functions to output the pseudo code offset according to the correlation value of the early, middle and late correlators, and the phase detector adopts a noncoherent early minus late amplitude calculation formula, that is
Figure BDA0001866640160000103
Wherein, deltacpAnd the pseudo code offset output by the phase discriminator.
Preferably, the function of the carrier loop phase detector 9 is to output the carrier offset according to the correlation value of the early, middle and late correlators, and the calculation formula adopted by the phase detector is
φe＝sign(IP)·QP (4)
Wherein, IPRepresenting the coherent integral value, Q, of the I path of the instantaneous pathPRepresenting the instantaneous Q-way coherent integration value. sign (x) is a sign taking function, returning the sign of x, phieIs the carrier phase offset output by the phase detector.
Preferably, the function of the code loop filter 10 is to filter out high-frequency noise in the pseudo code offset output by the code loop phase detector, and specifically, the code loop uses a second-order filter, where the laplacian domain of the filter transfer function h(s) is expressed as
Figure BDA0001866640160000111
Wherein, ω isnIs the characteristic circle frequency of the loop, s is the laplacian.
Preferably, the function of the carrier loop filter 11 is to filter out high frequency noise in the carrier offset, wherein the filter is a second order filter in accordance with the code loop.
The device adopts direct acquisition processing of navigation signals, solves the problem of BOC (1,1) acquisition phase ambiguity by using a peak jump technology in the tracking process, can be effectively suitable for processing GPS L1C/Galileo E1/BDS B1C signals and GPS L5/Galileo E5a/BDS B2a signals on the basis of being compatible with the traditional BPSK acquisition tracking algorithm, and has the unique difference that a peak jump module is added in a tracking part, a stepping adjustment module is changed into a parameter configurable module, and a code generation module simultaneously supports spread spectrum codes and BOC local codes. The device realizes smooth upgrade of a navigation signal processing algorithm, has lower algorithm complexity and better channel consistency, and has higher acquisition and tracking performance because BOC signals are received by double sidebands.

Claims (13)

1. A configurable navigation signal compatible acquisition tracking device, the device comprising: the device comprises an orthogonal frequency deviation removing module (1), a correlation module (2), an FFT (fast Fourier transform) judging module (3), a stepping adjusting module (4), a code generating module (5), a morning, noon and evening correlator (6), a peak value hopping module (7), a code ring phase discriminator (8), a carrier ring phase discriminator (9), a code ring filter (10) and a carrier ring filter (11);
the orthogonal frequency deviation removing module (1) removes the carrier residual frequency deviation of the navigation signal according to the frequency word obtained by capturing and tracking;
the correlation module (2) performs correlation de-spread of the navigation signal according to the length of the capturing time;
the FFT decision module (3) carries out FFT operation according to the related despreading result of the related module (2) and decides whether the acquisition is successful;
the stepping adjustment module (4) outputs a chip stepping control word according to the type of the navigation signal and the judgment information given by the acquisition tracking;
the code generation module (5) controls the stepping of the spread spectrum code according to the chip stepping control word given by the stepping adjustment module (4) to generate a pseudo-random sequence of a corresponding code rate;
the early, middle and late correlator (6) despreads the navigation signal and outputs a plurality of paths of correlation values which can be used by a code loop phase discriminator (8) and a carrier loop phase discriminator (9);
The peak value jumping module (7) solves the problem of secondary peak false lock in the acquisition process of the BOC (1,1) signal;
the code loop phase discriminator (8) outputs the offset of the pseudo code according to the correlation value of the early, middle and late correlators (6);
the carrier loop phase discriminator (9) outputs carrier offset according to the correlation value of the early, middle and late correlators (6);
the code loop filter (10) filters high-frequency noise in the pseudo code offset;
a carrier loop filter (11) filters out high frequency noise in the carrier offset.
2. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the quadrature de-frequency deviation module (1) employs a digital carrier NCO and frequency mixing manner, and firstly the carrier NCO generates sine and cosine signals of corresponding frequencies according to frequency words output by the FFT decision module (3) and the carrier loop filter (11); and secondly, sending the sine and cosine signal and an input baseband digital signal into a digital mixer to complete complex multiplication, thereby realizing the function of removing frequency deviation.
3. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the correlation module (2) sends the navigation signal after stripping the carrier to 11 parallel correlators, and simultaneously sends 11 local code sequences to the parallel correlators, and the correlators perform integration-zero clearing operation according to a given time to complete coherent despreading processing to obtain 11 coherent integration quantities.
4. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the FFT decision module (3) integrates 11 paths of coherent integral quantities output by the correlation module (2) into 256 groups by using a piecewise correlation in combination with a zero-padding FFT technique, feeds the coherent value of each path into a 512-point fast fourier transform FFT after padding 256 zeros, and performs FFT operation in a pipeline mode to sequentially perform FFT operation and result modulo square of 11 × 512 coherent values of 11 groups of different phases and perform maximum value search, and detects whether the decision quantity exceeds a threshold by using a searched maximum value as a capturing decision quantity; if not, adjusting the local code phase to restart the search of the next phase, otherwise ending the acquisition process and starting the tracking.
5. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the step adjustment module (4) integrates the decision result of the FFT decision module (3), the jump enable of the peak jump module (7), and the tracking frequency word output chip step adjustment control word of the code loop filter (10) into the code generation module (5).
6. The configurable navigation signal compatible acquisition tracking device according to claim 5, wherein in the acquisition phase, the step adjustment module (4) provides different chip search step lengths according to the modulation system type of the signal to be acquired, wherein the search step of the BOC (1,1) signal is 1/6 chips, and the search steps of BPSK (1)/BPSK (2)/BPSK (10) are 1/2 chips; after the acquisition is successfully shifted into tracking, whether front and back 1/2 chip hopping is carried out is determined according to hopping enabling given by a peak value hopping module (7); in the stable tracking process, the real-time tracking frequency word of the code loop filter (10) is synthesized to output a final control word.
7. The configurable apparatus for compatible acquisition and tracking of navigation signals according to claim 1, wherein the code generation module (5) generates a local spreading code sequence or a BOC code sequence at the same code rate as the navigation signals according to a chip step control word under the driving of a high frequency clock, and the code generation module (5) equally divides the pseudo code into 11 channels, and outputs 11 channels in parallel to acquire the required pseudo code, and outputs 5 channels of pseudo code sequences, i.e. time channel, advanced 1/2 chips, advanced 1/6 chips, retarded 1/6 chips and retarded 1/2 chips for subsequent tracking.
8. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the early, middle and late correlator (6) implements coherent despreading of the navigation signal, outputs 5 paths of correlation values for the code loop phase detector (8) and the carrier loop phase detector (9), and records the amplitudes of the correlation results of 5 paths of the immediate path, the early 1/2 chips, the early 1/6 chips, the late 1/6 chips and the late 1/2 chips as P0、E-1/2、E-1/6、L+1/6、L+1/2And the correlation result of I, Q branch of the clock-as-you-go path is IP、QP。
9. The configurable navigation signal compatible capturing and tracking device according to claim 8, wherein the peak skipping module (7) decides the correlation result amplitude of 5 branches outputted from the early, middle and late correlators 6 according to the magnitudes of the equations (1) and (2),
Figure FDA0001866640150000031
Figure FDA0001866640150000032
Starting a comparison result counter Lcount and Rcount, if the formula (1) is satisfied, the Lcount is automatically decreased by 1, and the Rcount is automatically increased by 1; if the formula (2) is satisfied, Lcount is self-added with 1, Rcount is self-subtracted with 1; if the Lcount and the Rcount are not satisfied, the Lcount and the Rcount values are kept unchanged; and when the Lcount is greater than 15, the current phase tracking is considered to be locked on the left side secondary peak, when the Rcount is greater than 15, the current phase tracking is considered to be locked on the right side secondary peak, the peak value jumping module outputs corresponding jumping enable in the opposite direction, the driving code generation module (5) jumps 1/2 chips, then zero clearing of the counter Lcount and the Rcount is completed, and next peak value jumping detection is started.
10. The configurable navigation signal compatible acquisition tracking device according to claim 9, wherein the code loop phase detector (8) calculates the pseudo code offset δ according to equation (3) for the two-way correlation amplitude of the early 1/6 chips and the late 1/6 chips given by the early, middle and late correlators (6)cp。
Figure FDA0001866640150000041
11. The configurable navigation signal compatible capturing and tracking device according to claim 1, wherein the carrier loop phase detector (9) calculates an output carrier offset φ according to equation (4) for the instantaneous I, Q correlation value provided by the early, middle and late correlators (6)eWherein sign (x) is a sign-taking function, returning the sign of x-
φe＝sign(IP)·QP(4)。
12. According to the rightThe configurable compatible capturing and tracking device for navigation signals as claimed in claim 1, wherein the code loop filter (10) performs digital domain discretization on a second-order filter shown in formula (5), performs high-frequency noise filtering on an input pseudo code offset to obtain a code tracking frequency word, wherein the loop characteristic circular frequency ω is a frequency of the code tracking frequency wordnThe selection is made at 1rad/s,
Figure FDA0001866640150000042
ωnis the characteristic circle frequency of the loop, and s is the laplacian.
13. The configurable navigation signal compatible capturing and tracking device according to claim 12, wherein the carrier loop filter (11) performs high frequency noise filtering on the input carrier offset according to a second order filter shown in formula (5) to obtain a carrier tracking frequency word, wherein the loop characteristic circle frequency ω is a frequency of the carrier tracking frequency wordn16rad/s were chosen.
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