Anti-interference Beidou navigation signal receiving method

Abstract

The invention discloses an anti-interference Beidou navigation signal receiving method, which comprises the following steps of: firstly, receiving a Beidou navigation signal by a radio frequency antenna array, then carrying out pre-filtering, frequency mixing and low-pass filtering processing on the Beidou navigation signal by a radio frequency front-end circuit to obtain an analog intermediate-frequency signal, carrying out analog-to-digital conversion on the analog intermediate-frequency signal to obtain a digital intermediate-frequency signal, and sending the digital intermediate-frequency signal to a receiver; and finally, the digital intermediate frequency signal enters the field programmable logic gate array for digital down-conversion processing. The signals output after digital down-conversion processing enter the self-adaptive anti-interference processing module for anti-interference processing; and finally, the signal subjected to anti-interference processing is recovered into an intermediate-frequency signal after digital up-conversion processing, and the intermediate-frequency signal is captured by the tracking and capturing module and finally sent to the navigation processing module for processing to obtain navigation positioning information. According to the method, the implementation complexity is low, the capture result is accurate, and the amplitude of the output signal is obviously reduced.

Description

Technical Field

[0001] The invention relates to the field of satellite navigation, and in particular to an anti-interference Beidou navigation signal receiving method. Background Art

[0002] The guide star navigation system is mainly composed of three parts: the space segment, the operation and control segment, and the user segment. Theoretically, any of these segments may be attacked, and no matter which segment is attacked or affected, the performance of the navigation system will be reduced, and eventually the system will partially or completely stop working. It is not so easy to threaten the space segment and the operation and control segment of the navigation system, which requires quite high technology and resources. In general, the user segment is the most vulnerable. Because the navigation satellite is located in the space tens of thousands of kilometers above the earth's surface, the transmitted signal is extremely weak, and the spread spectrum technology is the mainstream technology used by the current major satellite navigation systems. The signal power for transmission is suppressed below the noise power, and then the transmitted satellite signal is restored at the receiving end through the despreading technology. Therefore, the power of the satellite signal received by the receiving equipment on the ground is very low.

[0003] When there are various interferences in the environment, ordinary receivers often cannot work properly, and the Beidou navigation system anti-interference receiver comes into being. There are two main types of interference received by navigation receivers: narrowband interference and broadband interference. The commonly used anti-interference methods of the current Beidou navigation system are: time domain filtering technology, frequency domain filtering technology, spatial domain filtering technology, and polarization anti-interference technology. Through the analysis of various interference forms and the principles of anti-interference technology, it can be seen that time domain and frequency domain adaptive anti-interference technology can only suppress multiple narrowband interferences, and is powerless against interference with a certain bandwidth. Spatial domain adaptive anti-interference technology based on adaptive array antenna can not only suppress narrowband interference but also achieve good suppression effect on broadband interference. Therefore, this technology is increasingly used in the field of navigation receiver anti-interference. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an anti-interference Beidou navigation signal receiving method, which has low implementation complexity, accurate capture results, and significantly reduced amplitude of the output signal.

[0005] The technical solution of the present invention is:

[0006] A method for receiving an anti-interference Beidou navigation signal comprises the following steps:

[0007] (1) The RF antenna array receives the Beidou navigation signal, which is then processed by the RF front-end circuit for pre-filtering, mixing, and low-pass filtering to obtain an analog intermediate frequency signal. The analog intermediate frequency signal is then converted into a digital intermediate frequency signal through analog-to-digital conversion. Finally, the digital intermediate frequency signal enters the field-editable logic gate array for digital down-conversion processing;

[0008] (2) The output signal after digital down-conversion processing enters the adaptive anti-interference processing module for anti-interference processing;

[0009] (3) The signal after anti-interference processing is restored to an intermediate frequency signal after digital up-conversion processing. The intermediate frequency signal is then captured by the tracking and capture module and finally sent to the navigation processing module for processing to obtain navigation positioning information.

[0010] The radio frequency front-end circuit comprises a pre-filter and a phase-locked loop connected in sequence. The pre-filter filters out interference signals distributed outside the signal bandwidth, and then mixes and low-pass filters the signals through the phase-locked loop to generate analog intermediate frequency signals.

[0011] The center frequency of the pre-filter at 1dB bandwidth is 1268.52±10.23MHz, and the center frequency at 50dB bandwidth is 1268.52±30MHz; the frequency of the local oscillator signal generated by the crystal voltage-controlled oscillator of the phase-locked loop is 1222MHz.

[0012] The digital down-conversion is composed of a digital controlled oscillator, a digital mixer and a low-pass filter. The digital mixer mixes the digital intermediate frequency signal and the carrier signal generated by the digital controlled oscillator. The mixed signal is filtered by the low-pass filter to output the down-converted I-channel and Q-channel orthogonal digital baseband signals.

[0013] The adaptive anti-interference processing module adopts an adaptive sidelobe cancellation algorithm to suppress interference signals and determine the number of auxiliary antennas so that the number M of interference sources is not greater than the number N of auxiliary antenna channels, thereby eliminating interference signals from different directions in the main antenna channel.

[0014] Advantages of the present invention:

[0015] The present invention has low implementation complexity and accurate capture results, and is particularly suitable for B1C signal capture in large dynamic scenes. The satellite navigation signal with interference signals is passed through an adaptive sidelobe cancellation system, so that the amplitude of the output signal is significantly reduced, thereby effectively suppressing the interference signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] See Figure 1 , a method for receiving an anti-interference Beidou navigation signal, specifically comprising the following steps:

[0019] (1) The RF antenna array 1 (4-element circular array) receives the Beidou navigation signal, and then the pre-filter of the RF front-end circuit 2 filters out the interference signal distributed outside the signal bandwidth. Then, the signal at the B3 frequency point of 1268.52±10.23MHz is modulated into an analog intermediate frequency signal with a center frequency of 46.52±10.23MHz through the phase-locked loop mixing and low-pass filtering of the RF front-end circuit 2. The analog intermediate frequency signal is then sampled by the A / D sampling module 3 in a bandpass sampling mode with a sampling frequency of 61.38MHz. It is a four-channel digital intermediate frequency signal, and the signal spectrum is concentrated between -30.69MHz and 30.69MHz. Finally, the four-channel digital intermediate frequency signals enter the field editable logic gate array for four-channel digital down-conversion processing. Each digital down-conversion 4 is composed of a digitally controlled oscillator, a digital mixer and a low-pass filter. The digital mixer mixes the digital intermediate frequency signal and the carrier signal generated by the digitally controlled oscillator. The mixed signal is filtered by the low-pass filter and outputs the down-converted I-channel and Q-channel orthogonal digital baseband signals;

[0020] The center frequency of the pre-filter at 1 dB bandwidth is 1268.52 ± 10.23 MHz, and the center frequency at 50 dB bandwidth is 1268.52 ± 30 MHz; the frequency of the local oscillator signal generated by the crystal voltage-controlled oscillator of the phase-locked loop is 1222 MHz;

[0021] (2) The baseband signal output after the digital down-conversion 4 is processed enters the adaptive anti-interference processing module 5 for anti-interference processing and then combined;

[0022] (3) The combined signal is processed by the digital up-conversion module 6 to restore the intermediate frequency signal, which is then captured by the tracking and capturing module 7 and finally sent to the navigation processing module 8 for processing to obtain the navigation positioning information.

[0023] Among them, the digital down-conversion 4, the adaptive anti-interference processing module 5, and the digital up-conversion 6 are all processed by the field-editable logic gate array FPGA.

[0024] The adaptive anti-interference processing module uses an adaptive sidelobe cancellation algorithm to suppress interference signals. First, the number of auxiliary antennas is determined. The RF antenna array is set to have one main antenna channel, N auxiliary antenna channels, and be interfered by M interference sources.

[0025] The M interference sources are represented as

[0026] The interference signal entering the main antenna channel is D, as shown in the following formula (1):

[0027]

[0028] In formula (1), j represents the index number of the interference source; represents the phase of the Mth interference source; t represents time; represents the interference signal generated by the Mth interference source at time t and entering the main antenna channel; n0(t) represents the system noise in the main antenna channel, which is related to time t; the set of interference signals generated by M interference sources at time t and entering the main antenna channel is A, as shown in the following formula (2):

[0029]

[0030] The interference signal received by the N auxiliary antenna channels is expressed as follows (3):

[0031]

[0032] In formula (3), n i (t) is the system noise in the uncorrelated auxiliary antenna channels; φ ij is the phase difference generated by the jth interference signal when it reaches the i-th auxiliary antenna channel, i = 1, 2, ..., N, j = 1, 2, ..., M;

[0033] The signal in the N auxiliary antenna channels is expressed as follows (4):

[0034]

[0035] Formula (4) can be simplified as formula (5):

[0036] X N =E φ A+n (5);

[0037] Then set the adaptive optimal weight W opt =[w1,w2,…,w N ] T , the weighted sum of the signals in the N auxiliary antenna channels is S(t) = W opt TE φ A + W opt T n; where S(t) represents the variation of the signal sent from the satellite to the receiver with time t, and D(t) represents the variation of the interference signal entering the main antenna channel with time t;

[0038] When the thermal noise in the auxiliary antenna channel is not considered, then interference cancellation, i.e., S(t) = D(t), gives the following equation (6);

[0039]

[0040] From this, the solution for W opt only depends on φ ij , that is, the phase difference generated when the interference signal arrives at the auxiliary antenna channel;

[0041] The differences regarding the number M of interference sources and the number N of auxiliary antenna channels are divided into the following three cases:

[0042] When N = M, E φ is a full - rank matrix, and its value after modulo operation is not zero. W opt has a unique solution:

[0043]

[0044] E φ has an inverse matrix, and according to Cramer's rule, the following equation (7) can be obtained:

[0045]

[0046] In equation (7), W opt T represents the transpose of the optimal weight vector, which is used to weight the signals in the auxiliary antenna channel to achieve the purpose of interference cancellation; E φ represents the matrix composed of the phase differences generated when the interference signal arrives at the main antenna channel and the auxiliary antenna channel;

[0047] When N > M, E φ is not a full - rank matrix, and its value after modulo operation on E φ is zero. The optimal weight W opt T has no solution, that is, the weight does not exist; when there is noise, the inverse matrix of E φ exists, and W opt T has a solution, but there will be cancellation residues;

[0048] When N < M, the cancellation performance is very poor because the auxiliary antenna channel cannot generate enough nulls to cancel the interference signals from different directions;

[0049] Therefore, the number M of interference sources is required to be less than or equal to the number N of auxiliary antenna channels in order to eliminate interference signals from different directions in the main antenna channel.

[0050] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for receiving Beidou navigation signals with anti-interference, characterized in that: The specific steps include: (1) The RF antenna array receives the Beidou navigation signal, which is then processed by the RF front-end circuit for pre-filtering, mixing, and low-pass filtering to obtain an analog intermediate frequency signal. The analog intermediate frequency signal is then converted into a digital intermediate frequency signal through analog-to-digital conversion. Finally, the digital intermediate frequency signal enters the field-editable logic gate array for digital down-conversion processing; (2) The output signal after digital down-conversion processing enters the adaptive anti-interference processing module for anti-interference processing; (3) The signal after anti-interference processing is restored to an intermediate frequency signal after digital up-conversion processing. The intermediate frequency signal is then captured by the tracking and capture module and finally sent to the navigation processing module for processing to obtain navigation positioning information.

2. The method for receiving an anti-interference Beidou navigation signal according to claim 1, characterized in that: The radio frequency front-end circuit comprises a pre-filter and a phase-locked loop connected in sequence. The pre-filter filters out interference signals distributed outside the signal bandwidth, and then mixes and low-pass filters the signals through the phase-locked loop to generate analog intermediate frequency signals.

3. The anti-interference Beidou navigation signal receiving method according to claim 2, characterized in that: The center frequency of the pre-filter at 1dB bandwidth is 1268.52±10.23MHz, and the center frequency at 50dB bandwidth is 1268.52±30MHz; the frequency of the local oscillator signal generated by the crystal voltage-controlled oscillator of the phase-locked loop is 1222MHz.

4. The anti-interference Beidou navigation signal receiving method according to claim 1, characterized in that: The digital down-conversion is composed of a digital controlled oscillator, a digital mixer and a low-pass filter. The digital mixer mixes the digital intermediate frequency signal and the carrier signal generated by the digital controlled oscillator. The mixed signal is filtered by the low-pass filter to output the down-converted I-channel and Q-channel orthogonal digital baseband signals.

5. The anti-interference Beidou navigation signal receiving method according to claim 1, characterized in that: The adaptive anti-interference processing module adopts an adaptive sidelobe cancellation algorithm to suppress interference signals and determine the number of auxiliary antennas so that the number M of interference sources is not greater than the number N of auxiliary antenna channels, thereby eliminating interference signals from different directions in the main antenna channel.

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