CN101132191A - Baseband signal processing method for GNSS receiver - Google Patents
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Abstract
This invention discloses a baseband signal processing method for GNSS receivers, particularly for common ranging-code signal for GNSS receiver, completing: the baseband signal catching, the tracking processing within frequency domain, easily for realization in large scale integrated circuit. During the signal catching step, FFT and IFFT calculation method is used for grouped calculation to simplify the time-domain related calculation. During the code-tracking, thus obtained related peak positions are found, then precision est1 mate of code phase is fulfilled by utilizing curve-fitting method. During the carrier tracking, DFT values of these points is calculated by using sliding DFT method, after the DFT point values ranges are determined based on rough carrier frequency estimate, and then proceeding estimate of carrier frequency, data demodulation by using IFFT output result.
Description
Technical Field
The invention belongs to the field of communication, relates to a signal processing method, and particularly relates to a baseband signal processing method of a GNSS receiver.
Background
The navigation message of a modern satellite navigation system (GPS, beidou second generation, galileo and the like) adopting the spread spectrum ranging code modulates pseudo-random codes and carrier waves twice in a data form to form a radio wave which is then continuously emitted to the ground. The user captures the satellite signal in the view through the receiver to obtain the navigation positioning information, and the communication basis of the system is spread spectrum communication, namely the simple working principle of the modern satellite navigation system.
The signal structure of a satellite navigation system is determined by the design target of the system, the positioning accuracy requirement, and the like. The satellite signal includes three signal components: a pseudorandom noise sequence (i.e., a PRN sequence, also known as a ranging code or subcarrier), a data code, and a carrier. The system spreads the navigation message signal over the frequency domain using the ranging code.
The ranging codes include both normal ranging codes (coarse acquisition codes) and precise ranging codes. Two ranging codes adopted by the existing satellite belong to PRN codes. The data code is also called navigation message, and is a binary 0, 1 code, the data code rate of each satellite navigation system is mostly different, but far lower than the ranging code rate, and the low data code rate is adopted to obtain larger spread spectrum gain. The ranging code and data code of the satellite use BPSK or QPSK to modulate the carrier.
The baseband signal processing mainly comprises the work of capturing, tracking, decoding and the like of satellite signals, aims to extract each observed quantity, and completes the extraction of navigation message data through the decoding of satellite navigation messages, which is the basis of the subsequent navigation resolving work of a receiver.
Fig. 1 shows a typical structure of a GNSS receiver, in which a digital baseband signal processor is the core of the receiver. An antenna receives a GNSS signal, and intermediate frequency digital signals after frequency mixing are formed after pre-amplification, RF/IF conversion and A/D conversion and are input to a digital baseband signal processor; the output of the digital baseband signal processor mainly comprises parameters such as pseudo range, doppler frequency, local time and the like. The parameters are used by a subsequent navigation signal processor to calculate the information required by the user, such as position, speed and the like according to a corresponding positioning algorithm. The digital baseband processor mainly realizes the following functions: generating a local reference pseudo code; capturing a pseudo code; pseudo code and carrier tracking; data demodulation (navigation message demodulation); acquiring carrier Doppler frequency (range rate) and carrier phase (range variation); signal-to-noise ratio information and the like are extracted from each satellite signal.
There are many capturing schemes for satellite signals using spread spectrum ranging codes, and a more common design method is to separate pseudo code search and carrier search organically and capture the two separately. The process of searching the two items separately can be further divided into: a search strategy of pseudo code serial carrier serial; a pseudo code serial carrier parallel search strategy; a search strategy of pseudo code parallel carrier serial is adopted; and (3) a pseudo code parallel carrier parallel search strategy. The capturing time corresponding to various search strategies is different, the full parallel speed is fastest, and the largest software and hardware resources are consumed. Such a method of sequentially searching a plurality of two-dimensional signal elements is called a sequential search method. In addition, an FFT method can be adopted, and GNSS satellite signals can be directly captured in two dimensions.
After capturing the satellite signal, the signal can be tracked by utilizing a pseudo code tracking ring and a carrier tracking ring, so that the reproduction signal of the receiver is accurately synchronized with the input signal, the related output is always in the maximum state, and simultaneously, each observed quantity and the navigation message are extracted.
Since the frequency and phase of the carrier are not precisely known when pseudo code tracking is performed, the conventional architecture typically employs a lead-lag type incoherent Digital Delay Locked Loop (DDLL). The correlation operation of the tracking loop adopts two independent correlators: an early code (early code) correlator and a late code (late code) correlator. The input signal is divided into two paths: one path is related to the advanced local reference code; the other path is correlated with a late local reference code. And the correlation result is subjected to integration (or accumulation), square and addition and subtraction operation to complete phase discrimination.
The carrier tracking loop is used for demodulating an output signal of the code tracking loop to obtain navigation message data and simultaneously obtain carrier Doppler frequency shift observed quantity. At present, the methods applied to carrier tracking are many, and a square loop, a Phase Locked Loop (PLL), a Frequency Locked Loop (FLL), and the like are commonly used. PLL dynamics are relatively sensitive but produce the most accurate pseudorange rate of change observations. For a given signal power, the PLL can provide data demodulation at a lower bit error rate than the FLL. Therefore, the PLL is suitable for use in a steady state tracking mode of a GNSS receiver carrier tracking loop. In the initial acquisition of signals, it is easier to achieve frequency locking (FLL) than phase locking in a dynamic environment, so that there is also a method to combine two loops for carrier tracking. The commonly used FLL frequency discriminator algorithm includes a cross product automatic frequency tracking algorithm (CPAFC) and the like.
The traditional time domain acquisition tracking signal processing method has the advantages of limited signal acquisition speed, narrow tracking bandwidth and weak processing capability on weak signals, and is not suitable for signal processing in a high dynamic environment or an interference environment.
Disclosure of Invention
The invention provides a baseband signal processing method of a GNSS receiver. The method is mainly suitable for receiving common ranging code signals of GNSS receivers, and completes capture and tracking processing of baseband signals in a frequency domain. In the code tracking process, after a plurality of correlation peak positions are found, the accurate estimation of the code phase is completed by using a curve fitting method. In the carrier tracking process, the range of sampling points for DFT operation is determined, the DFT value is calculated, the carrier frequency is estimated, and then the carrier frequency in the tracking loop is updated. When the navigation message is recovered, the demodulation of data is completed by utilizing the output result of IFFT in the code tracking process. The method completely utilizes frequency domain processing, utilizes digital signal processing methods such as FFT, IFFT, DFT and the like, greatly improves the calculation efficiency and the spectral analysis precision of multi-branch correlation, achieves higher speed, and is beneficial to fast capturing and recapturing signals. The method still has stronger robustness in a complex environment and is easy to be realized by applying a large-scale integrated circuit.
The invention relates to a method for processing a baseband signal of a GNSS receiver, which is characterized by comprising the following steps:
step 1: the antenna receives GNSS signals, and intermediate frequency digital signals are formed after preamplification, RF/IF conversion and A/D conversion.
Step 2: the digital baseband processor receives the mixed intermediate frequency digital signals, captures the signals, and utilizes FFT and IFFT calculation methods to carry out grouping calculation according to the existing frequency domain rapid capturing method to simplify time domain correlation operation.
And 3, step 3: and inputting the captured signal into a tracking module for code tracking and carrier tracking.
And 4, step 4: and judging the turning of the navigation message data according to the carrier phase difference of the modulated navigation message. And judging the change of the navigation message data bit by judging the change condition of the real part of the IFFT operation at the maximum peak value in two adjacent code phase updating periods of the code tracking loop according to the output information of the tracking loop. Thereby demodulating the navigation message data. And simultaneously, feeding back the demodulated result to the tracking module.
In step 3, when tracking the ranging code, firstly, the FFT and IFFT operations are used to find out the positions of multiple correlation peaks, then the least square method is used to perform triangle fitting, and the accurate estimation of the theoretical maximum peak position is completed according to the position of the triangle peak, thereby completing the accurate estimation of the code phase.
In step 3, when carrier tracking is performed, firstly, a multi-point sliding DFT algorithm is adopted, fourier transform calculation results of carrier signal sampling points in a previous window are utilized to calculate Fourier transform values of the sampling points in the window, and then, an interpolation DFT algorithm is utilized to perform spectrum analysis, so that accurate estimation of carrier frequency is completed.
In step 3, when the multi-point sliding DFT algorithm is used to calculate the fourier transform values of the sampling points in the window, first, the frequency search step and the coarse carrier frequency estimation value are obtained by the capture loop, then the range of the DFT value points to be calculated is determined, and then the multi-point sliding DFT algorithm is used to calculate the DFT values of the points.
The GNSS receiver baseband signal processing method has the advantages that:
(1) In the description of the method, the GNSS signal capturing and tracking operation completely utilizes frequency domain processing, so that the multi-branch related calculation efficiency is greatly improved, the signal rapid capturing and recapturing are facilitated, and the method is very suitable for signal capturing and tracking in weak signal environments, interference environments and higher dynamic environments.
(2) In the description of the method of the present invention, the GNSS signal acquisition and code tracking sections are implemented by using FFT and IFFT. When the FFT and the IFFT are designed, a flow line modular cascade structure can be adopted, so that the operation speed is higher; and the design of an integrated circuit can be completed by adopting a mature IP core, and the large-scale integrated circuit is easy to realize.
(3) When the steps of the method described by the invention are applied to carrier tracking, firstly, the range of calculating DFT value points is narrowed according to the frequency searching step length during capturing and the obtained rough carrier frequency estimation value, and then, the Fourier transform amplitude value required during frequency estimation is calculated by using a sliding DFT algorithm, so that the calculation complexity is greatly reduced, and the method is favorable for realizing an integrated circuit.
Drawings
FIG. 1 is a system block diagram of a conventional GNSS receiver;
fig. 2 is a block diagram of a conventional GNSS receiver frequency domain acquisition module.
FIG. 3 is a flowchart illustrating a method for processing baseband signals of a GNSS receiver according to the present invention;
FIG. 4 is a flowchart illustrating an intermediate frequency ranging code tracking method of a GNSS receiver baseband signal processing method according to the present invention;
FIG. 5 is a schematic flowchart of an intermediate frequency signal carrier tracking method of a GNSS receiver baseband signal processing method according to the present invention;
FIG. 6 is a diagram illustrating a conventional multi-point sliding DFT method for a GNSS receiver baseband signal processing method according to the present invention;
FIG. 7 is a diagram illustrating a ranging code phase acquisition result of a GNSS receiver baseband signal processing method according to the present invention;
FIG. 8 is a diagram illustrating a result of ranging code estimation in a code tracking process of a method for processing a baseband signal of a GNSS receiver according to the present invention;
FIG. 9 is a diagram illustrating carrier tracking results within 20 navigation message periods of a GNSS receiver baseband signal processing method of the present invention;
FIG. 10 is a waveform diagram of a navigation message at a transmitting end according to a method for processing a baseband signal of a GNSS receiver of the present invention;
FIG. 11 is a waveform diagram of a navigation message at a receiving end according to a method for processing a baseband signal of a GNSS receiver.
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings.
The method is mainly suitable for receiving common ranging code signals of the GNSS receiver, and completes capture and tracking processing of baseband signals in a frequency domain. In the capturing process, the FFT and IFFT calculation method is used for carrying out grouping calculation to simplify the time domain correlation operation. In the code tracking process, firstly, FFT and IFFT operation is used for finding out the positions of a plurality of correlation peaks, and then, a curve fitting method is used for finishing accurate estimation of code phases. In the carrier tracking process, firstly, the range of DFT value points is determined and calculated according to the rough carrier frequency estimation value obtained in the capturing process, DFT values of the points are calculated by using a sliding DFT method, then, the carrier frequency is estimated by using an interpolation DFT method, and the carrier frequency in a tracking loop is updated. When the navigation message is recovered, the demodulation of data is completed by utilizing the output result of IFFT in the code tracking process.
As shown in fig. 3, the method comprises the following steps:
the method comprises the following steps: as shown in fig. 1, the antenna receives GNSS signals, and forms mixed intermediate frequency digital signals after passing through a preamplifier, an RF/IF converter, and an a/D converter.
The output digitized intermediate frequency signal is as follows:
s(n)＝AD(nt s -τ)C(nt s -τ)cos[2π(f IF +f d )nt s +φ 0 ]+N′(n)(1)
wherein, s (n) is the output value of the intermediate frequency signal at the nth sampling point. A. f. of IF And phi 0 Representing amplitude, frequency and initial phase of the carrier wave, respectively, f d Is Doppler frequency offset, t s Is the sampling interval and τ is the time delay. D (nt) s ) And C (nt) s ) Respectively, navigation message data (D code) and a general ranging code, and N' represents a noise signal.
Step two: the digital baseband processor receives the mixed intermediate frequency digital signal, captures the signal, and utilizes FFT and IFFT calculation methods to perform grouping calculation in a capture loop according to the existing frequency domain rapid capture method to simplify time domain correlation operation.
If the sampling frequency of the A/D converter is a fixed value, i.e. the sampling interval t s As constants, there are:
Z(m，f d )＝I+jQ＝IFFT{FFT{s(n)exp[-j2π(f IF +f d )nt s ]}FFT * [C(m)]}(2)
where n = (i-1) M + M, which represents the M-th sampling point of the i-th ranging code period, and M ∈ [1, 2., M ∈]And M is the number of sampling points in each ranging code period. C (m) represents a locally generated C/a code, * represents taking conjugation. Z (m, f) d ) Representing the correlation of the input signal with the locally reproduced signal.
Order to
Signal acquisition is detected by performing a two-dimensional search at code phase and doppler frequency. I Z (m, f) d ) If | exceeds the threshold value V th Then is captured intoAnd otherwise, the capture fails. Of course, the determination of | Z (m, f) can be used here d )| 2 To be implemented.
The above-described operation is performed by performing a grouping calculation using FFT and IFFT calculation methods. As shown in fig. 2, the complex signal is obtained by multiplying the input signal by two orthogonal I and Q carriers generated by the local carrier NCO: and x (n) = I (n) + jQ (n), wherein x (n) enters an FFT converter for FFT conversion. Meanwhile, a code sequence generated by a local common ranging code generator passes through an FFT converter and a conjugation processor, the result after FFT conversion and conjugation processing is multiplied by the result after FFT conversion of x (n) in a multiplier, and the correlation result of a time domain is obtained after IFFT conversion, so that the correlation peak value corresponding to each code phase is obtained. These correlation peaks are passed through a squaring converter, the peak of the squared result is the code phase of the input signal, and is input into a logic controller. The carrier frequency scanned at this time is the acquisition frequency.
Step three: and inputting the captured signal into a tracking module for code tracking and carrier tracking.
The flow of the code tracking method described in the present invention is shown in fig. 4. The signal flow of the data-dependent portion here is similar to the capture process described above. Except that the frequency update of the carrier NCO is controlled by the estimated frequency derived from the carrier tracking loop, while the carrier phase in each update period should be continuous, for reasons that will be described in detail in the analysis of the demodulation module.
After correlation, a plurality of correlation peak values corresponding to different code phases are obtained by the IFFT converter, where the number of code phases is related to the sampling frequency, and the higher the sampling frequency, the higher the time resolution. However, limited by the capacity of the data processor, the sampling frequency cannot be increased infinitely, and in order to further improve the code phase estimation accuracy under the limited sampling rate, the method adopts a curve fitting method to estimate the code phase accurately, and uses an exemplary triangular least square fitting method. First, the FFT/IFFT module performs grouping operation to obtain correlation peak values corresponding to code phases. And inputting the correlation result into a threshold decision device, if the maximum correlation peak reaches a decision threshold, continuing the tracking process, and if not, ending the tracking process and re-capturing. If the tracking process is continued, the magnitude of each correlation peak value | Z | is compared in a peak value comparator, the maximum peak value and the peak value point near the maximum peak value are searched and reserved, and the peak value information is input into a navigation message demodulation module. And then inputting the comparison result in the peak value comparator into a curve fitting device, dividing the reserved peak value points into two groups by using the maximum peak value point as a boundary point by the curve fitting device, fitting each group of data points into two straight lines by applying a least square method, and obtaining the abscissa of the intersection point of the two straight lines as the accurate estimated value of the code phase. And finally, the common ranging code generator generates a common ranging code according to the obtained code phase estimation value and feeds the common ranging code back to the tracking loop.
To keep 9 peak points z 1 (x 1 ，y 1 )，z 2 (x 2 ，y 2 )，…，z 9 (x 9 ，y 9 ) For example, the specific mathematical expression is described as follows:
let the peak point retained in the peak comparator be:
{z 1 (x 1 ，y 1 )，z 2 (x 2 ，y 2 )，…，z 9 (x 9 ，y 9 )}，(z 1 ≤z 2 ≤z 3 ≤z 4 ≤z 5 ，z 9 ≤z 8 ≤z 7 ≤z 6 ≤z 5 )(3)
two straight lines to be fitted in the curve fitter are:
from the linear empirical formula of the least squares method:
substituting (5) and (6) into (4) to obtain the intersection abscissa of the two straight lines as follows:
x 0 the value of (a) is an accurate estimate of the code phase.
The carrier tracking method described in the present invention is shown in the flowchart of fig. 5.
And (3) the solution result of the navigation message (D code) obtained by the demodulation and fed back to the tracking loop by the demodulation module is input into a multiplier to be multiplied with the input intermediate frequency digital signal, so that the D code modulation is removed. And multiplying the local common ranging code generated by the common ranging code generator and the intermediate-frequency digital signal after the D code modulation is removed by a multiplier to finish despreading. From the expression of s (n), the signal after demodulation and despreading is:
s′(n)＝Acos[2π(f IF +f d )nt s +φ 0 ]+N′(n)(8)
if the phase tracking of the common ranging code is accurate, the signal to be frequency estimated in the carrier tracking loop is similar to a single-frequency signal s' with noise.
And carrying out DFT operation on the data section of the obtained single-frequency signal through a DFT converter, and analyzing the frequency spectrum by a frequency estimator so as to complete frequency estimation. When carrier frequency estimation is performed in a tracking loop, if an N-point fourier transform value in a sliding window of a DFT converter is calculated by FFT, the calculation load is too large, and real-time processing is difficult. Even if the recursion formula of the multi-point sliding DFT algorithm is applied to calculate the fourier variation value of N points, the calculation amount is still huge. The interpolation DFT algorithm can know that only the maximum spectral line and a spectral line value near the maximum spectral line are needed during frequency estimation, so that the range of calculating DFT value points can be reduced by the captured frequency information in the DFT converter, and then the recursion formula of the multi-point sliding DFT algorithm is applied to calculate the fourier variation value of the N point.
Let the frequency obtained by the acquisition loop be f acq Step value of frequency search in acquisition loop is f step Then the carrier doppler frequency range should be:
f∈[f acq -f step ，f acq +f step ](9)
as can be seen from the basic DFT theory, when performing the N-point DFT, the index range corresponding to equation (9) is:
wherein int (·) represents rounding.
After the data point range is determined, the DFT transformer may calculate the DFT values of each point according to the multi-point sliding DFT algorithm in the existing literature. As shown in fig. 6, assuming that the interval between two windows is P, the sliding window length is N. The purpose of the multipoint sliding DFT algorithm is to calculate the DFT value in each window according to the recursion relation. Let the discrete value of sampling of the time domain signal waveform at time i be S' (n), and Fourier transform is performed to S i (k) Then, taking i + p as the initial position, the N-point fourier transform is:
unlike the FFT, which calculates the fourier transform values of all points at once, the application of equation (11) can directly calculate the fourier transform value of a single point, which enables direct calculation of the fourier transform value of a desired point in equation (10), thus greatly reducing the computational complexity of the DFT converter.
The purpose of carrier tracking is to obtain an accurate estimate of the carrier frequency, and fig. 5 shows that after the DFT value of the desired point is obtained, frequency estimation can be done by a frequency estimator according to the DFT interpolation algorithm in the existing literature.
Observing the signal of equation (8), s is corrected in the DFT converter i ' after DFT, the magnitude term of the spectrum is:
wherein T = Nt s Then, the expression of the estimated value of the carrier frequency is given as:
where N is the number of DFT points, k 0 Is the position of the DFT maximum spectral line of s' (n). r = ± 1, when | S (k) 0 +1)|≤|S(k 0 -1) |, r = -1; when | S (k) 0 +1)|≥|S(k 0 -1) |, r =1.
Therefore, in the frequency estimator, the DFT value of the data point obtained by the DFT transformer is substituted into expression (13), and an estimated value of the carrier frequency can be obtained. And inputting the obtained carrier frequency estimated value into a code tracking loop, if the maximum correlation peak value of the code tracking loop reaches a judgment threshold, reselecting a data segment, and continuing the tracking process, otherwise, ending the tracking process.
The frequency resolution of DFT is 1/T, T = Nt s For the integration time of the signal, the frequency resolution of the DFT is limited by the sliding window length N when Δ t is constant. If the frequency resolution is too low, it is difficult to improve the frequency estimation accuracy even by using the interpolation DFT method. Therefore, a certain length of the pure carrier data segment should be accumulated for spectral analysis. When the GNSS signal is extremely weak, the length of the sliding window should be increased appropriately, that is, the length of the accumulated data segment at each carrier frequency update is increased.
Step four: and judging the turning of the navigation message data according to the carrier phase difference of the modulated navigation message. In the navigation message demodulation module, according to the output information of the tracking loop, the change of the navigation message data bit is judged by judging the change condition of the real part of the operation result of the IFFT converter at the maximum peak value in the phase updating period of two adjacent codes of the code tracking loop. Thereby demodulating the navigation message data. And simultaneously, feeding back the demodulated result to a tracking loop.
The invention describes a frequency domain baseband signal processing method, so that the demodulation mode of data is different from the demodulation method in the traditional GNSS receiver. In the frequency domain carrier tracking process, only the frequency of the carrier is tracked, so that the phase of the carrier cannot be accurately estimated, and therefore the method judges the inversion of navigation message data according to the phase difference of the carrier of the modulated navigation message, and further completes demodulation. In the code tracking loop, the real part of the operation result of the IFFT converter at the maximum peak value reflects the bit height of the navigation data, so the navigation message demodulation module judges the change of the navigation message data bit by judging the change condition of the real part of the operation result of the IFFT converter at the maximum peak value in two adjacent updating periods. Since the inversion of the demodulated data is judged by judging the change of the phase, the carrier phase in each update period of the code tracking loop should be continuous. This demodulation may cause the data bit string to have opposite signs. Such multivalueness of the demodulated data can be solved in the frame synchronization process.
From equation (2), the signal term in the ith accumulation result of the I branch accumulator is summarized as:
in the formula A r Amplitude, T, of a local reference carrier generated by a carrier generator i For the accumulator accumulating the time length, N, by the time i i Number of sampling points, T, accumulated by time i i ＝N i t s ，Δf i The error is estimated for the frequency of the reference carrier at time i,
for the phase difference, Δ τ, of the received signal from the local reference carrier generated by the carrier generator at time i i The code phase estimation error is measured for time i. R (-) is a correlation function, sa (-)) Is a sampling function. When the code phase delay and carrier frequency estimates are sufficiently accurate,
I i ≈Kd i cos(Δφ i )(15)
wherein K is a proportionality coefficient.
And the phase of the local reference carrier generated by the carrier generator is continuous, delta phi i ≈Δφ i-1 Therefore, the temperature of the molten steel is controlled,
I i I i-1 ≈K 2 cos 2 (Δφ i )d i d i-1 ∝d i d i-1 (16)
therefore, the navigation message demodulation module judges the change of the navigation message data bit by judging the change condition of the real part of the operation result of the IFFT converter at the maximum peak value in two adjacent updating periods of the code tracking loop. This demodulation may cause the data bit string to have opposite signs. Such multivalueness of the demodulated data can be solved in the frame synchronization process.
The computer simulation program generates the L1 signal of the GPS, the signal is converted to the intermediate frequency of 1.25MHz by the RF, the sampling frequency of the receiving end is set to 5MHz, therefore, 5000 sampling points exist in each C/A code period of the GPS. The chip delay is set to 504 samples, the doppler shift is 1907Hz, and the signal-to-noise ratio of the intermediate frequency signal arriving at the receiver is-10 dB.
Fig. 7 is a diagram illustrating the phase acquisition result of the ranging code received in step two of the method, and it can be seen that if the position of the maximum correlation peak is around 500, the code phase delay estimate approaches the actual delay of 504 chips. As shown in fig. 8, the maximum peak and 8 related peak points near the maximum peak are retained for code tracking in step three of the method, and the accurate estimated value of the code phase is obtained by triangular least square estimation, and it can be seen from the figure that the abscissa of the estimated triangular vertex is 504 chips, which is consistent with the simulation set value. Fig. 9 shows the carrier tracking process within the 20 navigation message data segments. As shown in the figure, the carrier frequency obtained by capturing is 1252kHz, after carrier tracking processing, the carrier frequency converges to the vicinity of the actual carrier doppler frequency 1251.907kHz, the convergence speed from the capturing frequency to the tracking frequency is fast, the fluctuation amplitude of the frequency estimation in each update period is small, and accurate tracking can be achieved.
Fig. 10 and fig. 11 compare the results of the navigation message at the sending end and the message demodulated by the receiving end, and it can be seen that the demodulated output waveform is substantially consistent with the sending waveform at the sending end, and a correct demodulation result can be obtained, thereby verifying the correctness of the demodulation by using the method of the present invention.
The skilled person can perform the baseband general ranging code signal processing of the GNSS receiver according to the description of the present invention, and implement the method of the present invention by using a software or hardware platform, especially a large scale integrated circuit. Compared with the traditional time domain baseband signal processing method of the GNSS receiver, the method has the advantages that the acquisition speed, the tracking bandwidth and the dynamic range of the receiver are greatly improved.
Claims (4)
1. A GNSS receiver baseband signal processing method is characterized by comprising the following steps:
the method comprises the following steps: an antenna receives a GNSS signal, and intermediate frequency digital signals are formed after pre-amplification, RF/IF conversion and A/D conversion;
step two: the digital baseband processor receives the mixed intermediate frequency digital signals, performs signal capture, and performs grouping calculation by using FFT and IFFT calculation methods according to the existing frequency domain rapid capture method to simplify time domain correlation operation;
step three: inputting the captured signal into a tracking module for code tracking and carrier tracking;
step four: judging the turning of navigation message data according to the carrier phase difference of the modulated navigation message; judging the change of navigation message data bit by judging the change condition of the real part of IFFT operation at the maximum peak value in two adjacent code phase updating periods of the code tracking loop according to the output information of the tracking loop; so as to demodulate the navigation message data; and simultaneously, feeding back the demodulated result to the tracking module.
2. The method of claim 1, wherein the processing of the baseband signals of the GNSS receiver comprises: in the third step, when tracking the ranging code, firstly, the FFT and IFFT operation is used for finding out the positions of a plurality of relevant peaks, then the least square method is used for carrying out triangle fitting, the accurate estimation of the position of the theoretical maximum peak value is completed according to the position of the vertex of the triangle, and further the accurate estimation of the code phase is completed.
3. The GNSS receiver baseband signal processing method of claim 1, wherein: in the third step, when carrier tracking is carried out, firstly, a multi-point sliding DFT algorithm is adopted, fourier transform calculation results of signal sampling points in a previous window are utilized to calculate Fourier transform values of the sampling points in the window, and then, an interpolation DFT algorithm is utilized to carry out spectrum analysis, so that accurate estimation of carrier frequency is completed.
4. A GNSS receiver baseband signal processing method according to claims 1 and 3, characterized in that: in the third step, when the multi-point sliding DFT algorithm is adopted to calculate the Fourier transform value of the sampling point in the window, firstly, the frequency search step length and the rough carrier frequency estimation value are obtained by the capture loop, then the range of the DFT value point to be calculated is determined, and then the DFT value of the point is calculated by the multi-point sliding DFT algorithm.
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| CN101359044B (en) * | 2008-09-19 | 2010-04-14 | 太原科技大学 | Method for calculating and eliminating interfere of GNSS strong signal to weak signal |
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Family Cites Families (3)
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