Pseudo code capturing method and device, equipment and storage medium

Abstract

The invention discloses a pseudo code capturing method, device and equipment and a storage medium, relates to the technical field of satellite navigation, is applied to a satellite navigation receiver, and comprises the following steps: performing down-conversion on a navigation signal transmitted by a satellite to obtain two paths of IQ signals with aliasing; the navigation signal is a multi-period time domain signal; performing down-sampling on the I-path signal and the Q-path signal in the IQ-path signal to obtain an I-path down-sampling signal and a Q-path down-sampling signal; performing matched filtering on the I-path down-sampling signal and the Q-path down-sampling signal by using a partial matched filter based on a local pseudo code to obtain an I-path filtering row vector and a Q-path filtering row vector; and respectively carrying out fast Fourier transform on the I-path filtering row vector and the Q-path filtering row vector to obtain a target capture result comprising a code phase and Doppler frequency offset. According to the invention, the inlet signal-to-noise ratio of the receiver can be improved, the effect of improving the capture performance, especially the capture sensitivity, is achieved, and the anti-interference performance of the receiver is improved.

Description

Technical Field

[0001] The present application relates to the technical field of satellite navigation, and particularly to a method, device, equipment and storage medium for pseudo-code acquisition. Background Art

[0002] Currently, when a navigation receiver acquires the pseudo-code (i.e., PRN, Pseudo Random Noise code) of a direct sequence spread spectrum (DSSS, Direct Sequence Spread Spectrum) system, it usually captures the code phase and Doppler frequency offset separately in parallel or serial mode according to the specific application scenario, so as to obtain an optimal balance point between the acquisition time and hardware resources. Currently, the mainstream pseudo-code acquisition methods include serial phase search acquisition method, sequential estimation fast acquisition method, matched filter method, sliding correlation acquisition method, etc. Among them, the matched filter method is different from other acquisition search methods. This method improves the search speed by reducing the single-period integration time and is a fast acquisition method.

[0003] However, due to the limitations of the GNSS (Global Navigation Satellite System) itself, the power of the signal to the ground is low and it is easily affected by various unintentional interference signals and human hostile signals. As a result, when the satellite navigation receiver performs the first acquisition through the above methods, the sensitivity of the received signal is generally low and it is difficult to improve. Moreover, too low signal-to-noise ratio at the input of the satellite navigation receiver will lead to a decrease in sensitivity.

[0004] In summary, how to acquire the pseudo-code of satellite navigation signals is still an issue to be further solved in this field. Summary of the Invention

[0005] In view of this, the purpose of the present application is to provide a method, device, equipment and storage medium for pseudo-code acquisition, which can improve the signal-to-noise ratio at the input of the receiver, achieve the effect of improving the acquisition performance, especially the acquisition sensitivity, and enhance the anti-interference performance of the receiver. The specific solutions are as follows:

[0006] In a first aspect, the present application discloses a pseudo-code acquisition method applied to a satellite navigation receiver, including:

[0007] When receiving a navigation signal transmitted by a satellite, perform down-conversion on the navigation signal to obtain two IQ signals with aliasing; the navigation signal is a multi-period time-domain signal;

[0008] Perform down-sampling on the I signal and Q signal in the two IQ signals respectively to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal;

[0009] Perform matched filtering on the I-channel decimated signal and the Q-channel decimated signal respectively based on the local pseudo-code and using a partial match filter to obtain an I-channel filtered row vector and a Q-channel filtered row vector;

[0010] Perform fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target acquisition result including code phase and Doppler frequency offset.

[0011] Optionally, the pseudo-code acquisition method further includes:

[0012] Initialize the sampling frequency of the baseband signal, pseudo-code rate, pseudo-code period, pseudo-random noise code number, multi-period integration length, decimation factor, number of points for fast Fourier transform, number of signal segments, number of points per signal segment, and acquisition threshold; wherein, the number of signal segments is less than or equal to the number of points for fast Fourier transform.

[0013] Optionally, the step of respectively decimating the I-channel signal and the Q-channel signal in the IQ two-channel signals to obtain an I-channel decimated signal and a Q-channel decimated signal includes:

[0014] Perform low-pass filtering on the I-channel signal and the Q-channel signal in the IQ two-channel signals respectively to obtain an I-channel low-pass filtered signal and a Q-channel low-pass filtered signal;

[0015] Decimate the I-channel low-pass filtered signal and the Q-channel low-pass filtered signal respectively according to the decimation factor to obtain an I-channel decimated signal and a Q-channel decimated signal.

[0016] Optionally, the step of performing matched filtering on the I-channel decimated signal and the Q-channel decimated signal respectively based on the local pseudo-code and using a partial match filter to obtain an I-channel filtered row vector and a Q-channel filtered row vector includes:

[0017] Determine the local pseudo-code corresponding to the pseudo-random noise code number, and sample the local pseudo-code based on the sampling frequency and using a partial match filter according to a preset number of repetition periods to obtain a sampled pseudo-code;

[0018] Multiply the I-channel decimated signal and the Q-channel decimated signal with the sampled pseudo-code respectively to obtain an I-channel row vector and a Q-channel row vector;

[0019] Segment the I-channel row vector and the Q-channel row vector respectively to obtain an I-channel segmented row vector and a Q-channel segmented row vector;

[0020] Accumulate the sampling points included in each segment of the I-channel segmented row vector and the Q-channel segmented row vector respectively to obtain an I-channel filtered row vector and a Q-channel filtered row vector.

[0021] Optionally, after respectively accumulating the sampling points included in each segment of the I-channel segmented post-row vector and the Q-channel segmented post-row vector to obtain the I-channel filtered row vector and the Q-channel filtered row vector, the following steps are further included:

[0022] Save the I-channel filtered row vector and the Q-channel filtered row vector into a random access memory.

[0023] Optionally, the steps of respectively performing a fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector to obtain a target acquisition result including a code phase and a Doppler frequency offset include:

[0024] Read the I-channel filtered row vector and the Q-channel filtered row vector in the random access memory, and perform a fast Fourier transform on the read I-channel filtered row vector and Q-channel filtered row vector to obtain a plurality of I-channel transformation results and a plurality of Q-channel transformation results;

[0025] Respectively combine the I-channel transformation results and the corresponding Q-channel transformation results to obtain a plurality of combined transformation results, and perform modulo operation on each of the combined transformation results to obtain a plurality of modulus values;

[0026] Construct a matrix based on all the modulus values to obtain a modulus value matrix, and determine the peak value in the modulus value matrix;

[0027] Judge whether the peak value is greater than the acquisition threshold. If so, calculate the code phase based on the pseudo-code rate and the sampling frequency, and calculate the Doppler frequency offset based on the number of signal segments, the multi-period integration length, the number of points of the fast Fourier transform, and the decimation frequency to obtain a target acquisition result including the code phase and the Doppler frequency offset.

[0028] Optionally, the step of down-converting the navigation signal to obtain aliased I and Q signals includes:

[0029] Generate a local oscillator frequency through a local oscillator, and mix the navigation signal based on the local oscillator frequency to obtain a mixed signal;

[0030] Perform down-conversion on the mixed signal to obtain aliased I and Q signals.

[0031] In a second aspect, the present application discloses a pseudo-code acquisition device applied to a satellite navigation receiver, including:

[0032] A signal down-conversion module, configured to down-convert the navigation signal to obtain aliased I and Q signals when receiving the navigation signal transmitted by a satellite; the navigation signal is a multi-period time-domain signal;

[0033] A downsampling module, configured to perform downsampling on the in-phase (I) signal and the quadrature (Q) signal in the I / Q two-path signals respectively, to obtain an I-path downsampled signal and a Q-path downsampled signal;

[0034] A matched filtering module, configured to perform matched filtering on the I-path downsampled signal and the Q-path downsampled signal respectively based on a local pseudo-code and by using a partial matched filter, to obtain an I-path filtered row vector and a Q-path filtered row vector; the local pseudo-code is a multi-period pseudo-code;

[0035] A Fourier transform module, configured to perform fast Fourier transform on the I-path filtered row vector and the Q-path filtered row vector respectively, to obtain a target acquisition result including a code phase and a Doppler frequency offset.

[0036] In a third aspect, the present application discloses an electronic device, including a processor and a memory; wherein, when the processor executes a computer program stored in the memory, the foregoing pseudo-code acquisition method is implemented.

[0037] In a fourth aspect, the present application discloses a computer-readable storage medium, configured to store a computer program; wherein, when the computer program is executed by a processor, the foregoing pseudo-code acquisition method is implemented.

[0038] It can be seen that the present application is applied to a satellite navigation receiver. When receiving a navigation signal transmitted by a satellite, first perform down-conversion on the navigation signal to obtain aliased I / Q two-path signals; the navigation signal is a multi-period time-domain signal; then perform downsampling on the I signal and the Q signal in the I / Q two-path signals respectively to obtain an I-path downsampled signal and a Q-path downsampled signal, and then perform matched filtering on the I-path downsampled signal and the Q-path downsampled signal respectively based on a local pseudo-code and by using a partial matched filter to obtain an I-path filtered row vector and a Q-path filtered row vector; the local pseudo-code is a multi-period pseudo-code; then perform fast Fourier transform on the I-path filtered row vector and the Q-path filtered row vector respectively, so as to obtain a target acquisition result including a code phase and a Doppler frequency offset. By combining a partial matched filter (PMF) and a fast Fourier transform (FFT), and using the multi-period characteristic of the received signal in the time domain, the present application can improve the input signal-to-noise ratio of the receiver, achieve the effect of improving the acquisition performance, especially the acquisition sensitivity, and improve the anti-interference performance of the receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0040] Figure 1 Flow chart of a pseudo - code acquisition method disclosed in this application;

[0041] Figure 2 Schematic diagram of a specific result matrix structure disclosed in this application;

[0042] Figure 3 Flow chart of a specific pseudo - code acquisition method disclosed in this application;

[0043] Figure 4 Flow block diagram of a specific pseudo - code acquisition method disclosed in this application;

[0044] Figure 5 Schematic diagram of the structure of a pseudo - code acquisition device disclosed in this application;

[0045] Figure 6 Structural diagram of an electronic device disclosed in this application. Specific embodiments

[0046] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0047] The embodiments of this application disclose a pseudo - code acquisition method, which is applied to a satellite navigation receiver. Refer to Figure 1 as shown, the method includes:

[0048] Step S11: When receiving the navigation signal transmitted by a satellite, perform down - conversion on the navigation signal to obtain two I and Q signals with aliasing; the navigation signal is a multi - period time - domain signal.

[0049] The pseudo - code acquisition scheme proposed in this application is applied to a satellite navigation receiver. When the satellite navigation receiver receives the navigation signal transmitted by a satellite, first perform down - conversion processing on the above - mentioned navigation signal to obtain two I and Q signals with aliasing, specifically including an I (In - Phase) path signal and a Q (Quadrature) path signal; among them, the navigation signal is a multi - period time - domain signal. For example, when receiving a multi - period time - domain navigation signal s L1 (t) with a length of T as shown in the following formula, first perform down - conversion on the multi - period time - domain navigation signal s L1 (t) to obtain two I and Q signals including s I (t) and s Q (t).

[0050]

[0051] Among them, A is the signal strength, f LO is the output frequency of the RF chip, t is the time, T d is the code phase, f d is the Doppler frequency offset. Both the code phase and the Doppler frequency offset are the results required for pseudo-code acquisition.

[0052] After down-converting the received multi-period time-domain navigation signal s L1 (t), the I and Q signals s I (t), s Q (t) with spectral aliasing are obtained as follows:

[0053] s I (t) = s L1 (t) * cos(2πf LO t);

[0054] s Q (t) = s L1 (t) * sin(2πf LO t).

[0055] It should be noted that before pseudo-code acquisition by the satellite navigation receiver, it specifically further includes: initializing the sampling frequency of the baseband signal, pseudo-code rate, pseudo-code period, pseudo-random noise code number, multi-period integration length, downsampling multiple, number of points of the fast Fourier transform, number of signal segments, number of points per signal segment, and acquisition threshold; among them, the number of signal segments is less than or equal to the number of points of the fast Fourier transform. In this embodiment, it is necessary to perform initialization settings on the parameters related to pseudo-code acquisition preset, specifically including the sampling frequency fs of the baseband signal, pseudo-code rate Rc, pseudo-code period Tcode, pseudo-random noise code number (i.e., PRN number), multi-period integration length T (T = N * Tcode, where N is the number of repetition periods), downsampling multiple d, number of points NFFT of the fast Fourier transform (FFT, Fast Fourier Transform), number of signal segments (i.e., number of groups of matched filters) K, acquisition threshold Th, and number of points per signal segment L (L = M / K), where K ≤ NFFT, M = fs * Tcode, M is the number of sampling points in N periods, and both L and M are integers.

[0056] Step S12: Respectively perform downsampling on the I-channel signal and the Q-channel signal in the IQ two-channel signals to obtain an I-channel downsampled signal and a Q-channel downsampled signal.

[0057] In this embodiment, after down-converting the navigation signal to obtain the aliased I and Q signals, further, downsampling operations are respectively performed on the I signal and the Q signal in the above I and Q signals, so as to obtain the downsampled I signal and the downsampled Q signal.

[0058] Specifically, the downsampling of the I signal and the Q signal in the I and Q signals to obtain the downsampled I signal and the downsampled Q signal may include: respectively performing low-pass filtering on the I signal and the Q signal in the I and Q signals to obtain the low-pass filtered I signal and the low-pass filtered Q signal; respectively downsampling the low-pass filtered I signal and the low-pass filtered Q signal according to the downsampling factor to obtain the downsampled I signal and the downsampled Q signal. For example, after down-converting the navigation signal to obtain the aliased I and Q signals, first perform low-pass filtering on the two signals in the I and Q signals respectively through a low-pass filter to obtain the low-pass filtered I signal and the low-pass filtered Q signal, and then respectively downsample the above low-pass filtered I signal and the above low-pass filtered Q signal according to the downsampling factor d at initialization to obtain the downsampled I signal and the downsampled Q signal.

[0059] Step S13: Based on the local pseudo-code and using a partial matched filter, respectively perform matched filtering on the downsampled I signal and the downsampled Q signal to obtain the filtered I row vector and the filtered Q row vector.

[0060] In this embodiment, after downsampling to obtain the downsampled I signal and the downsampled Q signal, a partial matched filter (PMF, Partial Matched Filters) can be used and based on the local pseudo-code, respectively perform matched filtering on the above downsampled I signal and the above downsampled Q signal, and then obtain the filtered I row vector and the filtered Q row vector.

[0061] Specifically, the matched filtering of the I-channel downsampled signal and the Q-channel downsampled signal respectively using the local pseudo-code and the partial match filter to obtain the I-channel filtered row vector and the Q-channel filtered row vector may include: determining the local pseudo-code corresponding to the pseudo-random noise code number, sampling the local pseudo-code based on the sampling frequency according to a preset number of repetition periods using the partial match filter to obtain the sampled pseudo-code; multiplying the I-channel downsampled signal and the Q-channel downsampled signal by the sampled pseudo-code respectively to obtain the I-channel row vector and the Q-channel row vector; segmenting the I-channel row vector and the Q-channel row vector respectively to obtain the segmented I-channel row vector and the segmented Q-channel row vector; accumulating the sampling points included in each segment of the segmented I-channel row vector and the segmented Q-channel row vector respectively to obtain the I-channel filtered row vector and the Q-channel filtered row vector. For example, after downsampling to obtain the I-channel downsampled signal and the Q-channel downsampled signal, the partial match filter is used to first sample the local pseudo-code according to fs and repeat it N times to obtain the sampled pseudo-code of N periods, and then multiply the I-channel downsampled signal and the Q-channel downsampled signal by the sampled pseudo-code of N periods to obtain 2 row vectors of size 1xM. Then, the above row vectors are respectively divided into K segments, and each segment has L points. Then, accumulate once for every L sampling points to obtain 1 point. Finally, the K-segment row vectors can obtain row vectors of size 1xK, that is, after the two-channel signals are processed by matched filtering, two corresponding row vectors of size 1xK, namely y, can be obtained. m , that is, the I-channel filtered row vector and the Q-channel filtered row vector. It should be noted that the local pseudo-code corresponds to the pseudo-random noise code number (i.e., PRN number) during initialization, and the code phase of the local pseudo-code can be set to 1.

[0062] Further, after accumulating the sampling points included in each segment of the segmented I-channel row vector and the segmented Q-channel row vector respectively to obtain the I-channel filtered row vector and the Q-channel filtered row vector, it may further include: saving the I-channel filtered row vector and the Q-channel filtered row vector to a random access memory. That is, save the two-channel filtered row vectors to a random access memory (RAM).

[0063] Step S14: Perform fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain the target capture result including the code phase and the Doppler frequency offset.

[0064] In this embodiment, after performing matched filtering on the I-channel downsampled signal and the Q-channel downsampled signal to obtain the I-channel filtered row vector and the Q-channel filtered row vector, perform fast Fourier transform (FFT, Fast Fourier Transform) on the above I-channel filtered row vector and the above Q-channel filtered row vector respectively, so as to obtain the target capture result including the code phase and the Doppler frequency offset.

[0065] Specifically, the step of respectively performing fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector to obtain a target capture result including code phase and Doppler frequency offset may include: reading the I-channel filtered row vector and the Q-channel filtered row vector in the random access memory, and performing fast Fourier transform on the read I-channel filtered row vector and Q-channel filtered row vector to obtain a plurality of I-channel transform results and a plurality of Q-channel transform results; respectively combining the I-channel transform results and the corresponding Q-channel transform results to obtain a plurality of combined transform results, and taking the modulus of each of the combined transform results to obtain a plurality of modulus values; constructing a matrix based on all the modulus values to obtain a modulus matrix, and determining the peak value in the modulus matrix; determining whether the peak value is greater than the capture threshold. If so, calculating the code phase based on the pseudo-code rate and the sampling frequency, and calculating the Doppler frequency offset based on the number of signal segments, the multi-period integration length, the number of points of the fast Fourier transform, and the decimation frequency, so as to obtain a target capture result including code phase and Doppler frequency offset. In this embodiment, first, the I-channel filtered row vector and the Q-channel filtered row vector in the random access memory (i.e., RAM) are read, then the read I-channel filtered row vector and the Q-channel filtered row vector are subjected to fast Fourier transform with NFFT points to obtain two row vectors of size 1xNFFT. Then, the two row vectors are added and the modulus is taken to obtain a row vector of size 1xNFFT (i.e., the modulus value). Then, by changing the code phase and traversing 1-M, a plurality of row vectors of size 1xNFFT are obtained. After combining all the obtained row vectors, a result matrix of size MxNFFT (i.e., the modulus matrix) can be obtained. As shown in Figure 2 After fast Fourier transform, a result matrix with M rows and NFFT columns can be obtained, and each row contains the coherent integration result of a phase point. Further, determine the peak value max of the result matrix, as well as the row i and column k where the peak value is located, and determine whether the peak value max is greater than the capture threshold Th. If the peak value max > capture threshold Th, the capture success flag can be set, and the code phase can be calculated based on the pseudo-code rate Rc and the sampling frequency fs, and the Doppler frequency offset can be calculated based on the number of signal segments K, the multi-period integration length T, the number of points of the fast Fourier transform NFFT, and the decimation frequency f down to calculate the Doppler frequency offset, so as to obtain a target capture result including code phase and Doppler frequency offset.

[0066] Among them, the calculation formula of the code phase (i.e., code phase frequency offset) is:

[0067]

[0068] The calculation formula of the Doppler frequency offset is:

[0069]

[0070] It should be noted that if max < TH, the next PRN number can be used to restart the pseudo-code acquisition operation. By utilizing the strong correlation between adjacent two-period signals, the multi-period characteristic of the received signal in the time domain, and the multi-signal cycle matched filtering in the time domain, the gain of the result matrix can be improved, thereby enhancing the signal-to-noise ratio and achieving the effect of improving the acquisition performance, especially the acquisition sensitivity.

[0071] It can be seen that the embodiment of the present application is applied to a satellite navigation receiver. When receiving a navigation signal transmitted by a satellite, the navigation signal is first down-converted to obtain two IQ signals with aliasing; the navigation signal is a multi-period time-domain signal; then the I-channel signal and the Q-channel signal in the two IQ signals are respectively down-sampled to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal, and then based on a local pseudo-code and using a partial match filter, the I-channel down-sampled signal and the Q-channel down-sampled signal are respectively subjected to match filtering to obtain an I-channel filtered row vector and a Q-channel filtered row vector; the local pseudo-code is a multi-period pseudo-code; then the I-channel filtered row vector and the Q-channel filtered row vector are respectively subjected to a fast Fourier transform to obtain a target acquisition result including a code phase and a Doppler frequency offset. The embodiment of the present application combines a partial match filter (PMF) and a fast Fourier transform (FFT), and utilizes the multi-period characteristic of the received signal in the time domain, which can improve the input signal-to-noise ratio of the receiver, achieve the effect of improving the acquisition performance, especially the acquisition sensitivity, and enhance the anti-interference performance of the receiver.

[0072] The embodiment of the present application discloses a specific pseudo-code acquisition method, which is applied to a satellite navigation receiver. Refer to Figure 3 as shown, the method includes:

[0073] Step S21: Initialize the sampling frequency of the baseband signal, the pseudo-code rate, the pseudo-code period, the pseudo-random noise code number, the multi-period integration length, the down-sampling multiple, the number of points of the fast Fourier transform, the number of signal segments, the number of points of each signal segment, and the acquisition threshold; wherein, the number of signal segments is less than or equal to the number of points of the fast Fourier transform.

[0074] In this embodiment, first, the sampling frequency of the baseband signal \(f_s = 6.2\ MHz\), the pseudo-code rate \(R_c = 1.023\ MHz\), the pseudo-code period \(T_{code}=1\ ms\), the pseudo-random noise code number (i.e., PRN number), the multi-period integration length \(T\) (\(T = N\times T_{code}=1023\), where \(N = 5\) is the number of repetition periods), the downsampling factor \(d = 10\), the number of points of the fast Fourier transform \(N_{FFT}=128\), the number of signal segments (i.e., the number of matched filter groups) \(K\), the acquisition threshold \(Th = 64\), and the number of points in each signal segment \(L\) (\(L = M / K)=775\), where \(K\leq N_{FFT}\), \(M = f_s\times T_{code}\) are initialized.

[0075] Step S22: When receiving the navigation signal transmitted by the satellite, generate a local oscillator frequency through a local oscillator, and mix the navigation signal based on the local oscillator frequency to obtain a mixed signal; the navigation signal is a multi-period time-domain signal.

[0076] In this embodiment, when receiving a 5-ms long GPS L1 signal transmitted by the satellite, refer to Figure 4 As shown, first generate a local oscillator frequency through a local oscillator, and then mix the local oscillator frequency with the frequency of the above GPS L1 signal to obtain a mixed signal; among them, the navigation signal is a multi-period time-domain signal.

[0077] Step S23: Down-convert the mixed signal to obtain two IQ signals with aliasing.

[0078] In this embodiment, refer to Figure 4 As shown, after mixing the above GPS L1 signal, down-convert the mixed signal to obtain two IQ signals including an I signal and a Q signal.

[0079] Step S24: Perform low-pass filtering on the I signal and the Q signal in the two IQ signals respectively to obtain an I low-pass filtered signal and a Q low-pass filtered signal.

[0080] Step S25: Downsample the I low-pass filtered signal and the Q low-pass filtered signal respectively according to the downsampling factor to obtain an I downsampled signal and a Q downsampled signal.

[0081] In this embodiment, downsample the above I low-pass filtered signal and the above Q low-pass filtered signal respectively according to the downsampling factor \(d = 10\), so that the above GPS L1 signal is divided into two paths and the sampling frequency is reduced from 62 MHz to 6.2 MHz, thereby obtaining an I downsampled signal and a Q downsampled signal.

[0082] Step S26: Based on the local pseudo-code and using a partial match filter, perform match filtering on the I-channel downsampled signal and the Q-channel downsampled signal respectively to obtain an I-channel filtered row vector and a Q-channel filtered row vector.

[0083] In this embodiment, the above I-channel downsampled signal and the above Q-channel downsampled signal are respectively divided into K = 40 segments by using a partial match filter, and each segment contains L = 775 numbers. The local pseudo-code, such as the local CA (Conditional Access) code, is sampled at a sampling frequency of 6.2 MHz, and match filtering is performed on the two IQ signals respectively.

[0084] Specifically, multi-channel parallel match filtering can be performed by using match filters with different numbers of channels. For each match filtering in the parallel channels, two row vectors of size 1x40 can be obtained. Then, by traversing the code phase from 1 to M (M = 6.2M * Tcode = 6200), multiple I-channel filtered row vectors and Q-channel filtered row vectors can be obtained.

[0085] Step S27: Perform fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target capture result including the code phase and the Doppler frequency offset.

[0086] Furthermore, perform fast Fourier transform (FFT) on the above I-channel filtered row vector and the above Q-channel filtered row vector respectively. The number of points of the fast Fourier transform is NFFT = 128. It should be noted that since each row vector has only 40 points, in order to complete the 128-point FFT, zero-padding operations need to be performed on the row vectors. Specifically, 88 zeros need to be padded. After the two signals pass through match filtering and FFT, two 128-point row vectors can be obtained. Then, add the two 128-point row vectors and take the modulus. After 6200 offsets of the local CA code, 6200 groups of results can be obtained, that is, the amplitudes of 6200 phase points; all the results can form a result matrix. If the peak value in the result matrix is greater than the capture threshold Th, the code phase offset and the Doppler frequency offset corresponding to the peak value are the target capture results. The corresponding target capture results can be obtained through the corresponding Doppler frequency offset and code phase offset calculation formulas. Specifically, the code phase offset is:

[0087]

[0088] The Doppler frequency offset is:

[0089]

[0090] Among them, for the more specific processing process of the above step S24, reference can be made to the corresponding content disclosed in the foregoing embodiments, and details will not be elaborated here.

[0091] It can be seen that the embodiment of the present application combines a partial match filter (PMF) and a fast Fourier transform (FFT), and uses the multi-period characteristic of the received signal in the time domain and the strong correlation between two adjacent period signals to capture the pseudo-code, which can improve the input signal-to-noise ratio of the receiver, achieve the effect of improving the capture performance, especially the capture sensitivity, and improve the anti-interference performance of the receiver.

[0092] Correspondingly, the embodiment of the present application also discloses a pseudo-code capture device applied to a satellite navigation receiver. Refer to Figure 5 As shown, the device includes:

[0093] A signal down-conversion module 11, configured to perform down-conversion on the navigation signal when receiving the navigation signal transmitted by the satellite to obtain two I / Q signals with aliasing; the navigation signal is a multi-period time-domain signal;

[0094] A down-sampling module 12, configured to perform down-sampling on the I signal and the Q signal in the two I / Q signals respectively to obtain a down-sampled I signal and a down-sampled Q signal;

[0095] A matched filtering module 13, configured to perform matched filtering on the down-sampled I signal and the down-sampled Q signal respectively based on the local pseudo-code by using a partial match filter to obtain an I-channel filtered row vector and a Q-channel filtered row vector; the local pseudo-code is a multi-period pseudo-code;

[0096] A Fourier transform module 14, configured to perform fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target capture result including a code phase and a Doppler frequency offset.

[0097] Among them, the specific working processes of the above-mentioned various modules can refer to the corresponding content disclosed in the foregoing embodiments, and will not be elaborated herein.

[0098] It can be seen that the embodiment of the present application is applied to a satellite navigation receiver. When receiving a navigation signal transmitted by a satellite, first, the navigation signal is down-converted to obtain two I / Q signals with aliasing; the navigation signal is a multi-period time-domain signal; then, the I-channel signal and the Q-channel signal in the two I / Q signals are respectively down-sampled to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal, and then, based on a local pseudo-code and using a partial match filter, the I-channel down-sampled signal and the Q-channel down-sampled signal are respectively subjected to match filtering to obtain an I-channel filtered row vector and a Q-channel filtered row vector; the local pseudo-code is a multi-period pseudo-code; then, the fast Fourier transform is respectively performed on the I-channel filtered row vector and the Q-channel filtered row vector, so as to obtain a target acquisition result including a code phase and a Doppler frequency offset. The embodiment of the present application combines a partial match filter (PMF) and a fast Fourier transform (FFT), and utilizes the multi-period characteristic of the received signal in the time domain, which can improve the input signal-to-noise ratio of the receiver, achieve the effect of improving the acquisition performance, especially the acquisition sensitivity, and improve the anti-interference performance of the receiver.

[0099] In some specific embodiments, the pseudo-code acquisition device may further include:

[0100] An initialization unit, configured to initialize the sampling frequency of the baseband signal, the pseudo-code rate, the pseudo-code period, the pseudo-random noise code number, the multi-period integration length, the down-sampling multiple, the number of points of the fast Fourier transform, the number of signal segments, the number of points of each signal segment, and the acquisition threshold; wherein, the number of signal segments is less than or equal to the number of points of the fast Fourier transform.

[0101] In some specific embodiments, the down-sampling module 12 may specifically include:

[0102] A low-pass filtering unit, configured to respectively perform low-pass filtering on the I-channel signal and the Q-channel signal in the two I / Q signals to obtain an I-channel low-pass filtered signal and a Q-channel low-pass filtered signal;

[0103] A down-sampling unit, configured to respectively down-sample the I-channel low-pass filtered signal and the Q-channel low-pass filtered signal according to the down-sampling multiple to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal.

[0104] In some specific embodiments, the match filtering module 13 may specifically include:

[0105] A determination unit, configured to determine a local pseudo-code corresponding to the pseudo-random noise code number;

[0106] A sampling unit, configured to sample the local pseudo-code according to a preset number of repetition periods based on the sampling frequency and using a partial match filter to obtain a sampled pseudo-code;

[0107] A multiplication calculation unit for multiplying the I-channel decimated signal and the Q-channel decimated signal with the sampled pseudo-code respectively to obtain an I-channel row vector and a Q-channel row vector;

[0108] A segmentation unit for segmenting the I-channel row vector and the Q-channel row vector respectively to obtain a segmented I-channel row vector and a segmented Q-channel row vector;

[0109] An accumulation calculation unit for accumulating the sampling points included in each segment of the segmented I-channel row vector and the segmented Q-channel row vector respectively to obtain an I-channel filtered row vector and a Q-channel filtered row vector.

[0110] In some specific embodiments, after the accumulation calculation unit, the following may further be included:

[0111] A storage unit for storing the I-channel filtered row vector and the Q-channel filtered row vector in a random access memory.

[0112] In some specific embodiments, the Fourier transform module 14 may specifically include:

[0113] A reading unit for reading the I-channel filtered row vector and the Q-channel filtered row vector in the random access memory;

[0114] A Fourier transform unit for performing a fast Fourier transform on the read I-channel filtered row vector and Q-channel filtered row vector to obtain a plurality of I-channel transform results and a plurality of Q-channel transform results;

[0115] A transform result merging unit for merging the I-channel transform results and the corresponding Q-channel transform results respectively to obtain a plurality of merged transform results;

[0116] A modulus calculation unit for taking the modulus of each of the merged transform results to obtain a plurality of moduli;

[0117] A unit for constructing a matrix based on all the moduli to obtain a modulus matrix and determining the peak value in the modulus matrix;

[0118] A judgment unit for judging whether the peak value is greater than the capture threshold;

[0119] A capture result calculation unit, if the peak value is greater than the capture threshold, then calculating the code phase based on the pseudo-code rate and the sampling frequency, and calculating the Doppler frequency offset based on the number of signal segments, the multi-period integration length, the number of points of the fast Fourier transform, and the decimation frequency to obtain a target capture result including the code phase and the Doppler frequency offset.

[0120] In some specific embodiments, the signal down-conversion module 11 may specifically include:

[0121] A local oscillator frequency generation unit for generating a local oscillator frequency through a local oscillator;

[0122] A mixing unit for mixing the navigation signal based on the local oscillator frequency to obtain a mixed signal;

[0123] A down-conversion unit for down-converting the mixed signal to obtain an IQ two-channel signal with aliasing.

[0124] Furthermore, an embodiment of the present application also discloses an electronic device. Figure 6 It is a structural diagram of an electronic device 20 shown according to an exemplary embodiment. The content in the figure should not be considered as any limitation to the scope of use of the present application.

[0125] Figure 6 It is a schematic structural diagram of an electronic device 20 provided by an embodiment of the present application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. Among them, the memory 22 is used to store a computer program, and the computer program is loaded and executed by the processor 21 to implement the relevant steps in the pseudo-code acquisition method disclosed in any of the foregoing embodiments. In addition, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0126] In this embodiment, the power supply 23 is used to provide a working voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows is any communication protocol applicable to the technical solution of the present application, and no specific limitation is imposed on it here; the input / output interface 25 is used to obtain external input data or output data to the outside, and its specific interface type can be selected according to specific application needs, and no specific limitation is made here.

[0127] In addition, as a carrier for resource storage, the memory 22 may be a read-only memory, a random access memory, a disk, or an optical disc, etc. The resources stored thereon may include an operating system 221, a computer program 222, etc., and the storage method may be temporary storage or permanent storage.

[0128] Among them, the operating system 221 is used to manage and control each hardware device and the computer program 222 on the electronic device 20, and it may be Windows Server, Netware, Unix, Linux, etc. In addition to the computer program that can be used to complete the pseudo-code acquisition method executed by the electronic device 20 disclosed in any of the foregoing embodiments, the computer program 222 may further include a computer program that can be used to complete other specific tasks.

[0129] Furthermore, the present application also discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, the foregoing disclosed pseudo-code capture method is implemented. For the specific steps of this method, reference may be made to the corresponding content disclosed in the foregoing embodiments, and details will not be elaborated herein.

[0130] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and reference may be made to the description of the method part for related parts.

[0131] Those skilled in the art can further realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components and steps of the examples have been generally described according to their functions in the foregoing description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0132] The steps of the methods or algorithms described in combination with the embodiments disclosed herein can be directly implemented by hardware, software modules executed by a processor, or a combination of the two. The software modules can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0133] Finally, it should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0134] The above has introduced in detail a method, apparatus, device, and storage medium for pseudo-code capture provided by the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present application.

Claims

1. A method for pseudo-code acquisition, characterized in that Applied to a satellite navigation receiver, including: When receiving a navigation signal transmitted by a satellite, down-converting the navigation signal to obtain two-channel IQ signals with aliasing; the navigation signal is a multi-period time-domain signal; Down-sampling the I-channel signal and the Q-channel signal in the two-channel IQ signals respectively to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal; Based on a local pseudo-code and using a partial match filter, respectively perform match filtering on the I-channel down-sampled signal and the Q-channel down-sampled signal to obtain an I-channel filtered row vector and a Q-channel filtered row vector; Perform fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target acquisition result including code phase and Doppler frequency offset.

2. The pseudo-code capture method according to claim 1, wherein It further includes: Initializing the sampling frequency, pseudo-code rate, pseudo-code period, pseudo-random noise code number, multi-period integration length, down-sampling multiple, fast Fourier transform number of points, signal segmentation number, number of points in each segment of the signal, and acquisition threshold of the baseband signal; wherein, the signal segmentation number is less than or equal to the fast Fourier transform number of points.

3. The pseudo-code capture method according to claim 2, wherein The down-sampling the I-channel signal and the Q-channel signal in the two-channel IQ signals respectively to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal includes: Performing low-pass filtering on the I-channel signal and the Q-channel signal in the two-channel IQ signals respectively to obtain an I-channel low-pass filtered signal and a Q-channel low-pass filtered signal; Down-sampling the I-channel low-pass filtered signal and the Q-channel low-pass filtered signal respectively according to the down-sampling multiple to obtain an I-channel down-sampled signal and a Q-channel down-sampled signal.

4. The pseudo-code capture method according to claim 2, wherein The performing match filtering on the I-channel down-sampled signal and the Q-channel down-sampled signal respectively based on a local pseudo-code and using a partial match filter to obtain an I-channel filtered row vector and a Q-channel filtered row vector includes: Determining a local pseudo-code corresponding to the pseudo-random noise code number, and sampling the local pseudo-code based on the sampling frequency and using a partial match filter according to a preset number of repetition periods to obtain a sampled pseudo-code; Multiplying the I-channel down-sampled signal and the Q-channel down-sampled signal with the sampled pseudo-code respectively to obtain an I-channel row vector and a Q-channel row vector; Segmenting the I-channel row vector and the Q-channel row vector respectively to obtain an I-channel segmented row vector and a Q-channel segmented row vector; Accumulating the sampling points included in each segment of the I-channel segmented row vector and the Q-channel segmented row vector respectively to obtain an I-channel filtered row vector and a Q-channel filtered row vector.

5. The pseudo-code capture method according to claim 4, wherein After the accumulating the sampling points included in each segment of the I-channel segmented row vector and the Q-channel segmented row vector respectively to obtain an I-channel filtered row vector and a Q-channel filtered row vector, it further includes: Saving the I-channel filtered row vector and the Q-channel filtered row vector to a random access memory.

6. The pseudo-code capture method according to claim 5, wherein The performing fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target acquisition result including code phase and Doppler frequency offset includes: Read the I-channel filtered row vector and the Q-channel filtered row vector in the random access memory, and perform fast Fourier transform on the read I-channel filtered row vector and Q-channel filtered row vector to obtain a plurality of I-channel transformation results and a plurality of Q-channel transformation results; Merge the I-channel transformation results and the corresponding Q-channel transformation results respectively to obtain a plurality of merged transformation results, and take the modulus of each of the merged transformation results to obtain a plurality of modulus values; Construct a matrix based on all the modulus values to obtain a modulus matrix, and determine the peak value in the modulus matrix; Judge whether the peak value is greater than the acquisition threshold. If so, calculate the code phase based on the pseudo-code rate and the sampling frequency, and calculate the Doppler frequency offset based on the number of signal segments, the multi-period integration length, the number of points of the fast Fourier transform, and the decimation frequency to obtain a target acquisition result including the code phase and the Doppler frequency offset.

7. The pseudo-code capture method according to any one of claims 1 to 6, characterized in that, The down-conversion of the navigation signal to obtain aliased I and Q channel signals includes: Generate a local oscillator frequency through a local oscillator, and mix the navigation signal based on the local oscillator frequency to obtain a mixed signal; Perform down-conversion on the mixed signal to obtain aliased I and Q channel signals.

8. A pseudo-code acquisition device, characterized in that Applied to a satellite navigation receiver, including: A signal down-conversion module for down-converting the navigation signal received from a satellite to obtain aliased I and Q channel signals when the navigation signal is received; the navigation signal is a multi-period time-domain signal; A decimation module for respectively decimating the I-channel signal and the Q-channel signal in the I and Q channel signals to obtain an I-channel decimated signal and a Q-channel decimated signal; A matched filtering module for performing matched filtering on the I-channel decimated signal and the Q-channel decimated signal respectively based on a local pseudo-code and using a partial matched filter to obtain an I-channel filtered row vector and a Q-channel filtered row vector; the local pseudo-code is a multi-period pseudo-code; A Fourier transform module for performing fast Fourier transform on the I-channel filtered row vector and the Q-channel filtered row vector respectively to obtain a target acquisition result including the code phase and the Doppler frequency offset.

9. An electronic device, characterized in that, Including a processor and a memory; wherein, when the processor executes the computer program stored in the memory, the pseudo-code acquisition method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that, For storing a computer program; wherein, when the computer program is executed by a processor, the pseudo-code acquisition method according to any one of claims 1 to 7 is implemented.

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