A satellite navigation weak interference adaptive detection method and system based on training sequence

Abstract

The present invention discloses a satellite navigation weak interference adaptive detection method based on training sequence, comprising the following steps: Step 1: According to the characteristics of satellite navigation signal and interference signal, the training sequence library module traverses and outputs the training sequence; Step 2: The correlator module is responsible for performing correlation operation on the processed received signal and the training sequence outputted in Step 1; Step 3: The integrator module performs integral modulus operation on the correlation value; Step 4: After performing correlation capture judgment on parameters of all dimensions, the judgment result is outputted. The method and system disclosed by the present invention can effectively detect weak interference signals mixed in the satellite navigation receiving signal, thereby improving the working ability of the navigation receiver in a complex electromagnetic environment and improving the reliability of the navigation system.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite navigation, and in particular relates to a satellite navigation weak interference adaptive detection method and system based on a training sequence in the field. Background Art

[0002] Beidou Navigation Satellite System (BDS) is a global active satellite positioning and communication system (GNSS) independently developed and built by my country. The successful launch of the third-generation Beidou satellite in a "two-satellite-in-one-launch" manner marks the official entry of the Beidou system into the global networking stage. At present, the Beidou navigation system has been widely used in various fields such as shipping, aerospace, agriculture, electromechanical, transportation and surveying and mapping in my country, and has become an important support for China's national defense and economic construction. However, affected by the complex electromagnetic interference environment in space, the Beidou navigation system faces huge challenges in terms of availability and reliability. In the GPS system, there have been many incidents of unreliable navigation caused by interference. For example, Chengdu Shuangliu Airport, Harbin Taiping International Airport and other airports have caused satellite navigation signals to be lost on many flights due to some illegally installed satellite navigation jammers. Many similar incidents have shown the destructiveness of space interference to the navigation system. Therefore, it is a hot topic for navigation workers to study satellite navigation anti-interference technology and interference monitoring technology, improve the working ability of navigation receivers in complex electromagnetic environments, and improve the reliability of navigation systems. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a satellite navigation weak interference adaptive detection method and system based on training sequence.

[0004] The present invention adopts the following technical solution:

[0005] A satellite navigation weak interference adaptive detection method based on a training sequence, the improvement of which is that it comprises the following steps:

[0006] Step 1: According to the characteristics of the satellite navigation signal and the interference signal, different parameters of the signal sequence are set in different dimensions to form a training sequence library module. When the receiver receives the signal, the training sequence library module traverses and outputs the training sequence;

[0007] Step 2: The correlator module is responsible for correlating the processed received signal with the training sequence output in step 1, and outputting the correlation value to the integrator module; each correlator module is composed of four parts: FFT transform processor, multiplier, IFFT transform and random access memory;

[0008] Step 3: The integrator module performs integral modulo operation on the relevant value, the adaptive decision module is responsible for detecting and judging the integral modulo operation result, and the output display module updates the state of interference signal detection in real time;

[0009] Step 4: After relevant capture and judgment of parameters in all dimensions, the judgment results are output to complete the detection of weak interference to satellite navigation.

[0010] Furthermore, the step 1 is specifically as follows:

[0011] The frequency bands of the training sequence library module include L1, L2, and L5 bands of GPS, B1, B2, and B3 bands of BDS, and L1, L2, and L3 bands of GLONASS;

[0012] The modulation modes of the training sequence library module include BPSK modulation, QPSK modulation and BOC modulation;

[0013] The bandwidth of satellite navigation interference signal is set to 2~24MHz;

[0014] According to this setting, the parameters of the three dimensions are traversed and combined to form a weak interference signal library, which is the training sequence library module. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of the other dimension.

[0015] Furthermore, the step 2 is specifically as follows:

[0016] The FFT transform processor in the correlator module processes the received signal y RF (n) and training sequence j'(n) are processed by FFT respectively:

[0017] y RF (n)→Y RF (jω)

[0018] j'(n)→J'(jω)

[0019] The transformed signal is temporarily stored in the random access memory. After both signals are processed, the two signals are multiplied by the multiplier:

[0020] V(jω)=Y RF (jω)×J'(jω)

[0021] The result obtained by the multiplication operation is processed by IFFT transformation to obtain the correlation value;

[0022] V(jω)→v(n)

[0023] Output the correlation value to the integrator block.

[0024] Furthermore, the step 3 is specifically as follows:

[0025] The integrator module performs an integral modulo operation on the relevant value:

[0026] ∫v(n)dn

[0027] The value obtained by the integral modulo operation is transmitted to the adaptive decision module for comparison and decision;

[0028] The adaptive threshold decision value is set by using the correlation value of N reference chip units around the detected chip unit, where V is the integral value of the detected chip unit, N is the number of reference chip units around the detected chip unit, and X 1 ,X 2 ,…X N is the integral value of the N reference chip units around the detected chip unit, Thr is the threshold value proportional factor, and the power estimate Z is expressed as:

[0029]

[0030] According to the false alarm probability function P of the adaptive threshold decision FA for:

[0031]

[0032] After the adaptive threshold decision value is calculated according to the input signal, the integral value obtained by the integrator module is compared with the adaptive threshold decision value. When the integral value is greater than the adaptive threshold decision value, it is determined that the characteristic parameters of a certain signal in the training sequence library have a high correlation with the characteristic parameters of the weak interference signal in the received signal. When the integral value is less than the adaptive threshold decision value, it means that the detection is unsuccessful. The signal form is changed by changing the parameters and characteristics of the signal in the training sequence library, and then the above steps are repeated;

[0033] After all characteristic parameters in the training sequence library are subjected to ergodic correlation operations with the received signal, a rough parameter estimation of the weak interference signal in the received signal is obtained, and the form of the weak interference signal is determined.

[0034] A satellite navigation weak interference adaptive detection system based on training sequence, the improvement of which is that it includes a training sequence library module, a correlator module, an integrator module, an adaptive decision module and an output display module;

[0035] The training sequence library module sets different parameters of the signal sequence in different dimensions to form a training sequence. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of another dimension.

[0036] The correlator module is responsible for correlating the processed received signal with the training sequence, and using the correlator module to traverse and search for training sequences with different bandwidth settings; the correlation value obtained by the correlator module is input into the integrator module, and the integrator module integrates and modulos the correlation value to obtain the decision value;

[0037] The decision value is compared with the adaptive threshold decision value calculated according to the received signal in the adaptive decision module; the training sequence bandwidth whose decision value is greater than the adaptive threshold decision value is obtained through traversal comparison; the form of the weak interference signal is determined according to the three-dimensional parameters, and the weak interference mixed in the signal is detected;

[0038] The output display module updates the status of interference signal detection in real time.

[0039] The beneficial effects of the present invention are:

[0040] The method and system disclosed in the present invention can effectively detect weak interference signals mixed in satellite navigation reception signals, thereby improving the working ability of the navigation receiver in a complex electromagnetic environment and improving the reliability of the navigation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic flow diagram of the method of the present invention;

[0042] Figure 2 It is the implementation schematic diagram of the correlator module;

[0043] Figure 3 It is the implementation principle diagram of the adaptive decision module;

[0044] Figure 4 It is a block diagram of the system disclosed in the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] In the presence of weak interference (-150dBm / Hz to -160dBm / Hz), the receiver can capture the signal when the satellite signal landing power is greater than -130dBm, providing an opportunity for weak interference detection based on the receiver measuring 10dB. When interference occurs, weak interference detection of satellite navigation can be achieved by using the parameters in the intermediate frequency, capture and tracking stages of the satellite navigation receiver.

[0047] The processes of correlation, capture, and judgment are the basic procedures for capturing weak satellite navigation signals. The received signal is correlated with the local signal. When the correlation value exceeds the set capture threshold, the signal is determined to exist, and the capture of the navigation signal is completed. Similarly, when detecting weak interference in satellite navigation, the capture algorithm can also be used to detect and identify weak interference signals mixed in the received signal.

[0048] Embodiment 1, this embodiment discloses a satellite navigation weak interference adaptive detection method based on training sequence, such as Figure 1 As shown, the following steps are included:

[0049] Step 1: According to the characteristics of satellite navigation signals and common interference signals, for example, a weak interference signal sequence similar to the characteristics is set, and different parameters of the signal sequence are set in different dimensions to form a training sequence library module. When the receiver receives the signal, the training sequence library module traverses and outputs the training sequence;

[0050] The establishment of the training sequence library module is mainly defined from three parameter characteristics:

[0051] From the characteristics of satellite navigation interference signals, we can know that the frequency bands of weak interference signals include various common frequency bands such as L1, L2, L5 bands of GPS, B1, B2, B3 bands of BDS, L1, L2, L3 bands of GLONASS, etc. Therefore, the frequency band of the training sequence library signal can be set accordingly;

[0052] The modulation modes of the training sequence library module include BPSK modulation, QPSK modulation and BOC modulation;

[0053] The common bandwidth of satellite navigation interference signals can be set to 2 to 24 MHz;

[0054] According to this setting, the parameters of the three dimensions are traversed and combined to form a weak interference signal library, which is the training sequence library module. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of the other dimension.

[0055] Step 2: The correlator module is responsible for performing correlation operation on the processed received signal and the training sequence outputted in step 1, and outputting the correlation value to the integrator module; in this embodiment, the frequency, bandwidth and modulation mode of the interference signal are jointly searched, and each correlator module is composed of four parts: an FFT transform processor, a multiplier, an IFFT transform and a random access memory;

[0056] like Figure 2As shown in the figure, the working process of the correlator module is as follows: the received signal is correlated and then transmitted to the correlator module. In this module, the signal after sampling and processing is correlated with the training sequence output by the training sequence library module. Assume that the received signal model is where r i (n) represents the signal received from the i-th satellite, j(n) represents the interference signal, and q(n) represents other noise signals. The specific representation of j(n) varies depending on the type of interference. The training sequence is represented by j'(n).

[0057] The FFT transform processor in the correlator module processes the received signal y RF (n) and training sequence j'(n) are processed by FFT respectively:

[0058] y RF (n)→Y RF (jω)

[0059] j'(n)→J'(jω)

[0060] The transformed signal is temporarily stored in the random access memory. After both signals are processed, the two signals are multiplied by the multiplier:

[0061] V(jω)=Y RF (jω)×J'(jω)

[0062] The result obtained by the multiplication operation is processed by IFFT transformation to obtain the correlation value;

[0063] V(jω)→v(n)

[0064] Output the correlation value to the integrator block.

[0065] Step 3: The integrator module performs integral modulo operation on the correlation value (the complex result obtained by the correlator module), and the adaptive decision module is responsible for detecting and judging the integral modulo operation result, and the output display module updates the state of interference signal detection (capture) in real time;

[0066] The integrator module performs an integral modulo operation on the relevant value:

[0067] ∫v(n)dn

[0068] The value obtained by the integral modulo operation is transmitted to the adaptive decision module for comparison and decision;

[0069] Reasonable selection of capture threshold V nThe size of the threshold is a key step in achieving good performance in weak interference detection. On the one hand, a threshold value that is too small can easily cause a false alarm (FA), that is, a certain satellite navigation weak interference signal does not actually exist but the detection system declares that the signal has been detected; on the other hand, a threshold value that is too large can easily cause a missed alarm (MD), that is, the detection system fails to detect the actual weak interference signal. The threshold value of the traditional fixed threshold decision method is obtained by solving a function of the signal noise variance and the false alarm probability. The threshold value of this method is independent of the input power of the signal, but because the power of the weak interference signal is small, its signal detection success rate is low. To solve this problem, this embodiment adopts an adaptive decision module. The adaptive decision module can reduce the impact of changes in the input signal on the detection decision results. Its principle is as follows Figure 3 shown.

[0070] The adaptive threshold decision value is set by using the correlation value of N reference chip units around the detected chip unit, where V is the integral value of the detected chip unit, N is the number of reference chip units around the detected chip unit, and X 1 ,X 2 ,…X N is the integral value of the N reference chip units around the detected chip unit, Thr is the threshold value proportional factor, which is related to the false alarm probability, and the power estimation value Z is expressed as:

[0071]

[0072] According to the false alarm probability function P of the adaptive threshold decision FA for:

[0073]

[0074] Therefore, when the false alarm probability value and the number of reference units are known, the adaptive threshold value of weak interference under constant false alarm probability can be obtained.

[0075] After the adaptive threshold decision value is calculated based on the input signal, the integral value obtained by the integrator module is compared with the adaptive threshold decision value. When the integral value is greater than the adaptive threshold decision value, it is determined that the characteristic parameter of a signal in the training sequence library has a high correlation with the characteristic parameter of the weak interference signal in the received signal, thereby roughly determining the approximate range of this characteristic parameter. When the integral value is less than the adaptive threshold decision value, it means that the detection is unsuccessful, and the signal form is changed by changing the parameters and characteristics of the signal in the training sequence library, and then repeating the above steps;

[0076] After all characteristic parameters in the training sequence library are subjected to ergodic correlation operations with the received signal, a rough parameter estimation of the weak interference signal in the received signal is obtained, and the form of the weak interference signal is determined.

[0077] Step 4: After relevant capture and judgment of parameters in all dimensions, the judgment results are output to complete the detection of weak interference to satellite navigation.

[0078] like Figure 4 As shown, this embodiment also discloses a satellite navigation weak interference adaptive detection system based on training sequence, including a training sequence library module, a correlator module, an integrator module, an adaptive decision module and an output display module;

[0079] Assume that the frequency of the weak interference signal mixed in the satellite navigation signal received by the receiver is the GPS L1 frequency, the signal modulation method is BPSK modulation, and the interference signal bandwidth is 16Hz.

[0080] The training sequence library module sets different parameters of the signal sequence in different dimensions according to the characteristics of the satellite navigation signal and the common interference signal to form a training sequence. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of the other dimension.

[0081] The GPS L1 frequency point can be selected as the frequency point of the training sequence, the signal modulation mode is determined to be BPSK modulation, and the signal bandwidth selection is traversed in the range of 2 to 24 MHz.

[0082] The correlator module is responsible for correlating the processed received signal with the training sequence, and using the correlator module to traverse and search for training sequences with different bandwidth settings; the correlation value obtained by the correlator module is input into the integrator module, and the integrator module integrates and modulos the correlation value to obtain the decision value;

[0083] The decision value is compared with the adaptive threshold decision value calculated according to the received signal in the adaptive decision module; the training sequence bandwidth whose decision value is greater than the adaptive threshold decision value is obtained through traversal comparison; the form of the weak interference signal is determined according to the three-dimensional parameters, and the weak interference mixed in the signal is detected;

[0084] The output display module updates the status of interference signal detection in real time.

[0085] If the BDS B1 frequency point is selected as the frequency point of the training sequence, the signal modulation mode is determined to be BOC modulation, and the signal bandwidth selection is traversed in the range of 2 to 24 MHz.

[0086] The correlation value obtained by the correlator module is input into the integrator module, and the correlation value is integrated and modulo-ed to obtain the decision value.

[0087] The decision value is compared with the adaptive threshold decision value calculated according to the received signal in the adaptive decision module. Through traversal comparison, no training sequence with a decision value greater than the adaptive threshold decision value is obtained. At this time, it is necessary to change the parameters of the other two dimensions and use the same method to traverse and search until the decision value is greater than the adaptive threshold decision value, then it can be determined that the weak interference signal is detected successfully.

Claims

1. A satellite navigation weak interference adaptive detection method based on training sequence, characterized in that: The steps include: Step 1: According to the characteristics of the satellite navigation signal and the interference signal, different parameters of the signal sequence are set in different dimensions to form a training sequence library module. When the receiver receives the signal, the training sequence library module traverses and outputs the training sequence; The step 1 is specifically as follows: The frequency bands of the training sequence library module include L1, L2, and L5 bands of GPS, B1, B2, and B3 bands of BDS, and L1, L2, and L3 bands of GLONASS; The modulation modes of the training sequence library module include BPSK modulation, QPSK modulation and BOC modulation; The bandwidth of satellite navigation interference signal is set to 2~24MHz; According to this setting, the parameters of the three dimensions are traversed and combined to form a weak interference signal library, which is the training sequence library module. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of the other dimension; Step 2: The correlator module is responsible for correlating the processed received signal with the training sequence output in step 1, and outputting the correlation value to the integrator module; each correlator module is composed of four parts: FFT transform processor, multiplier, IFFT transform and random access memory; Step 3: The integrator module performs integral modulo operation on the relevant value, the adaptive decision module is responsible for detecting and judging the integral modulo operation result, and the output display module updates the state of interference signal detection in real time; Step 4: After relevant capture and judgment of parameters in all dimensions, the judgment results are output to complete the detection of weak interference to satellite navigation.

2. The method for adaptively detecting weak interference in satellite navigation based on training sequence according to claim 1, characterized in that: The step 2 is specifically as follows: The FFT transform processor in the correlator module processes the received signal y RF (n) and training sequence j'(n) are processed by FFT respectively: y RF (n)→Y RF (jω) j'(n)→J'(jω) The transformed signal is temporarily stored in the random access memory. After both signals are processed, the two signals are multiplied by the multiplier: V(jω)=Y RF (jω)×J’(jω) The result obtained by the multiplication operation is processed by IFFT transformation to obtain the correlation value; V(jω)→v(n) Output the correlation value to the integrator block.

3. The method for adaptively detecting weak interference in satellite navigation based on training sequence according to claim 2, characterized in that: The step 3 is specifically as follows: The integrator module performs an integral modulo operation on the relevant value: ∫v(n)dn The value obtained by the integral modulo operation is transmitted to the adaptive decision module for comparison and decision; The adaptive threshold decision value is set by using the correlation values ​​of N reference chip units around the detected chip unit, where V is the integral value of the detected chip unit, N is the number of reference chip units around the detected chip unit, X1, X2, ... X N is the integral value of the N reference chip units around the detected chip unit, Thr is the threshold value proportional factor, According to the false alarm probability function P of the adaptive threshold decision FA for: After the adaptive threshold decision value is calculated according to the input signal, the integral value obtained by the integrator module is compared with the adaptive threshold decision value. When the integral value is greater than the adaptive threshold decision value, it is determined that the characteristic parameters of a signal in the training sequence library have a high correlation with the characteristic parameters of the weak interference signal in the received signal. When the integral value is less than the adaptive threshold decision value, it means that the detection is unsuccessful. The signal form is changed by changing the parameters and characteristics of the signal in the training sequence library, and then the above steps are repeated; After all characteristic parameters in the training sequence library are subjected to ergodic correlation operations with the received signal, a rough parameter estimation of the weak interference signal in the received signal is obtained, and the form of the weak interference signal is determined.

4. A satellite navigation weak interference adaptive detection system based on training sequence, characterized by: It includes a training sequence library module, a correlator module, an integrator module, an adaptive decision module and an output display module; The training sequence library module sets different parameters of the signal sequence in different dimensions to form a training sequence. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of another dimension. The frequency bands of the training sequence library module include L1, L2, and L5 bands of GPS, B1, B2, and B3 bands of BDS, and L1, L2, and L3 bands of GLONASS; The modulation modes of the training sequence library module include BPSK modulation, QPSK modulation and BOC modulation; The bandwidth of satellite navigation interference signal is set to 2~24MHz; According to this setting, the parameters of the three dimensions are traversed and combined to form a weak interference signal library, which is the training sequence library module. When the receiver receives the signal, the training sequence library module generates a training sequence by fixing the parameters of two dimensions and traversing the parameter selection of the other dimension; The correlator module is responsible for correlating the processed received signal with the training sequence, and using the correlator module to traverse and search for training sequences with different bandwidth settings; the correlation value obtained by the correlator module is input into the integrator module, and the integrator module integrates and modulos the correlation value to obtain the integral value; The integral value is compared with the adaptive threshold decision value calculated according to the received signal in the adaptive decision module; the training sequence bandwidth whose integral value is greater than the adaptive threshold decision value is obtained by traversal comparison; Determine the form of weak interference signals based on three-dimensional parameters and detect weak interference mixed in the signal; The output display module updates the status of interference signal detection in real time.

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