CN108196269B - Method for detecting weak harmonic interference signal in satellite navigation anti-interference antenna system - Google Patents

Method for detecting weak harmonic interference signal in satellite navigation anti-interference antenna system Download PDF

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CN108196269B
CN108196269B CN201711467672.3A CN201711467672A CN108196269B CN 108196269 B CN108196269 B CN 108196269B CN 201711467672 A CN201711467672 A CN 201711467672A CN 108196269 B CN108196269 B CN 108196269B
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王晓宇
张铁峰
张骅
董正芳
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/21—Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/35—Constructional details or hardware or software details of the signal processing chain
    • G01S19/37—Hardware or software details of the signal processing chain

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Abstract

The invention provides a method for detecting weak harmonic interference signals in a satellite navigation anti-interference antenna system, which adopts coherent accumulation of frequency spectrum energy as a check quantity and adaptively calculates a decision threshold to detect the weak harmonic interference signals in the satellite navigation anti-interference antenna system. Compared with a manual detection and identification method, the method has the characteristics that the detection threshold is determined in a self-adaptive mode on the basis of the sampling data by carrying out automatic detection processing on the original digital signals sampled by each channel in the system, and the detection probability of weak harmonic signals in the system can be effectively improved.

Description

Method for detecting weak harmonic interference signal in satellite navigation anti-interference antenna system
Technical Field
The invention belongs to the field of satellite navigation anti-interference, and relates to a method for detecting weak harmonic interference signals in a satellite navigation anti-interference antenna system.
Background
At present, a satellite navigation anti-interference antenna system is a key device for protecting a satellite navigation receiver from working normally in a complex electromagnetic environment. In order to enable the performance of the satellite navigation anti-interference antenna system to reach the designed optimal value, factors influencing the system performance inside the system need to be accurately detected and eliminated in the process of system design, production and debugging.
The satellite navigation anti-interference antenna system mainly comprises a receiving array antenna, a low noise amplifier, a multi-channel radio frequency assembly and a digital signal processing assembly. Due to the processing technology, the working characteristics of analog components and the like, weak harmonic interference signals with different degrees exist in each channel in the satellite navigation anti-interference antenna system. The satellite navigation anti-interference algorithm enables weak harmonic interference signals in the system to be equivalent to external interference signals incident from a certain direction or multiple directions for suppression processing, so that part of processing freedom of the anti-interference algorithm is consumed, and the maximum anti-interference number and the maximum interference suppression capability of the anti-interference algorithm are influenced.
At present, the detection of weak harmonic interference in the satellite navigation anti-interference antenna system is mainly to observe and analyze output signals of each module such as a low noise amplifier and a multi-channel radio frequency assembly by using instrument tools such as a spectrum analyzer in the debugging process. And (3) the engineers use the real-time observation or the maximum holding function of the spectrum analyzer to manually observe the frequency spectrum of the output signal of each module, and detect and identify the weak harmonic interference signal in the system. For weak harmonic interference signals with power close to or weaker than system noise, detection omission is easily caused by manual detection and identification.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for detecting weak harmonic interference signals in a satellite navigation anti-interference antenna system, which adopts coherent accumulation of frequency spectrum energy as a check quantity and adaptively calculates a decision threshold to detect the weak harmonic interference signals in the satellite navigation anti-interference antenna system, and can effectively improve the detection probability of the weak harmonic signals in the system.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
the method comprises the steps of firstly, collecting and storing digital signals output by an analog-to-digital converter of a satellite navigation anti-interference antenna with a set time length of T milliseconds under the condition of no external electromagnetic interference, and storing the number L of data points in each corresponding channel as T multiplied by Fs×103Wherein F issSampling frequency for the analog-to-digital converter;
assuming that the satellite navigation anti-interference antenna system comprises M channels, the acquired and stored data form a matrix with dimension L multiplied by M, and the ith column of data of the matrix is marked as x (i) ([ x)0,x1,…,xL-1]T；
Secondly, dividing the data vector x (i) into sub-data segments which are mutually overlapped, wherein the length of each sub-data block is N, the value of N is set to be the positive integer power of 2, the overlapping rate between two adjacent sub-data blocks is set to be 50%, and the total number of the sub-data blocks is
Figure BDA0001531420210000021
The kth (K ═ 1,2, … K) sub-data block is denoted xk(i)；
Thirdly, constructing a vector y with the size of Nx 1 dimension, and initializing each element in y to be 0, wherein y is represented as0＝0；
Fourthly, sequentially sub-data blocks xkPerforming fast Fourier transform, setting the number of fast Fourier transform points to be N, and recording the result of the fast Fourier transform as Xk，XkIs a vector of dimension Nx 1; calculating XkThe nth element X in the vectorkThe squares of the modulus values of (n) are summed up in the nth element of the vector y, yk(n)＝yk-1(n)+|Xk(n)|2，n＝1,2,...,N；
Fifthly, dividing the vector y into S sub-bands according to the effective working bandwidth B of the satellite navigation system,
Figure BDA0001531420210000022
Fsfor sampling frequency, use ysThe S-th subband data block, S-1, 2, …, S, representing vector y;
sixthly, the sub-band data block y is searched in sequencesMaximum value of dsThe maximum values in the S subbands are combined into a vector d ═ d of size S × 11,d2,…,dS]T；
Seventhly, searching the minimum value d in the vector dminLet the noise mean power value PnoiseAnd initialized to 0, a counter J is designed and initialized to 0; sequentially judging whether each element y (n) of the vector y is smaller than dminIf it is less than dminThen y (n) is added to PnoiseAnd (4) performing middle accumulation, adding 1 to the count of the counter J, and calculating P after judging all N elementsnoiseA combination of J and PnoiseUpdating the value;
eighth step with PnoiseIs twice as the decision threshold value ytCarrying out weak harmonic interference detection, and sequentially judging whether each element y (n) of the vector y is larger than ytIf y (n) > ytThen the decision is on-frequencyDot
Figure BDA0001531420210000023
There is interference and f (n) is output.
The invention has the beneficial effects that: through coherent accumulation of the spectrum capability of a plurality of data blocks, the energy of a weak harmonic interference signal in the satellite navigation anti-interference antenna system is subjected to coherent accumulation gain, and the signal-to-noise ratio of the weak harmonic interference signal relative to the thermal noise of the system is improved. Meanwhile, compared with a fixed judgment threshold, the judgment threshold is calculated based on the sampling data in a self-adaptive mode, so that the detection probability of weak harmonic interference under the condition of different anti-interference antenna system state differences can be further improved. The method is suitable for early optimal performance debugging of the satellite navigation anti-interference antenna system, system state self-checking report and the like.
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FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of mutually overlapping sub-data block partitions.
Detailed Description
The present invention will be further described with reference to the following drawings and examples, which include, but are not limited to, the following examples.
The method comprises the following steps:
the first step is as follows: under the condition of no external electromagnetic interference, acquiring and storing a digital signal output by an anti-interference satellite navigation antenna analog-to-digital converter (A/D) with the time length of T milliseconds (T is more than or equal to 1), wherein the number of corresponding data points of each channel is L, the length of the storage time T (the dimension is millisecond and is recorded as ms), and the sampling frequency F of the analog-to-digital converter (A/D)sThe calculation relationship between (dimension is megahertz, noted MHz) is:
L＝T×Fs×103 (1)
assuming that the satellite navigation anti-interference antenna system comprises M channels, the acquired and stored data form a matrix with dimension L multiplied by M. The ith (i ═ 1,2, …, M) column data of the data matrix is denoted as x (i) ═ x0,x1,…,xL-1]TThe superscript T is the transpose operator.
The second step is that: dividing a data vector x (i) (i ═ 1,2, …, M) into sub data segments which are overlapped with each other, setting the length of each sub data block to be N (the value of N is set to be the positive integer power of 2, usually to be 1024 or 2048), setting the overlapping rate between two adjacent sub data blocks to be 50%, and setting the total number of the sub data blocks to be K. Under the condition of 50% data overlap rate, the relationship between K and N and L is as follows;
Figure BDA0001531420210000031
wherein the content of the first and second substances,
Figure BDA0001531420210000032
the rounding-down operator. The kth (K ═ 1,2, … K) sub-data block is denoted xk(i)。
The third step: constructing a vector with dimension Nx 1, and recording as y, initializing each element in y to 0, and expressing as:
y0＝0 (3)
where the subscript 0 denotes the initial state and the 0 on the right side of the equation denotes a column vector containing N0 elements.
The fourth step: in turn, a sub-data block xk(K is 1,2, … K) performing Fast Fourier Transform (FFT), setting the number of FFT points to N, and recording the result of the FFT as Xk，XkIs a vector of dimension N × 1. Calculating XkThe N-th (N-1, 2.., N) element X in the vectorkThe square of the modulus value of (n) is added to the nth element in the vector y, and the calculation expression is:
yk(n)＝yk-1(n)+|Xk(n)|2 (4)
the fifth step: dividing the vector y into S sub-bands according to the effective working bandwidth B (dimension is megahertz) of the satellite navigation system, dividing the number S of the sub-bands, the effective working bandwidth B and the sampling frequency FsThe calculated relationship between them is as follows:
Figure BDA0001531420210000041
wherein the content of the first and second substances,
Figure BDA0001531420210000042
the rounding-down operator. By ys(S-1, 2, …, S) denotes the S-th subband data block of the vector y.
And a sixth step: searching sub-band data block y in turnsMaximum value d in (S-1, 2, …, S)sThe search algorithm adopts a bubble sorting method, and the maximum value in S sub-bands is formed into a vector d with the size of S multiplied by 1:
d＝[d1,d2,…,dS]T (6)
the seventh step: searching for minimum value d in vector d by adopting bubble sorting methodminLet the noise mean power value PnoiseAnd initialized to 0, a counter J is designed and initialized to 0. Sequentially determining whether each element y (N) (1, 2., N) of the vector y is less than dminIf it is less than dminThen y (n) is added to PnoiseAnd (4) performing middle accumulation, adding 1 to the count of the counter J, and calculating P after judging all N elementsnoiseA combination of J and PnoiseAnd updating the value.
Eighth step: with PnoiseIs twice as the decision threshold value ytAnd carrying out weak harmonic interference detection, and sequentially judging whether each element y (N) (N is 1,2, and N) of the vector y is larger than ytIf y (n) > ytIf so, it is determined that there is interference at the frequency point f (n), and f (n) is output, where f (n) is calculated as follows:
Figure BDA0001531420210000043
the method is suitable for detecting the weak harmonic interference signals in the satellite navigation anti-interference antenna systems such as GPS, BDS and GLONASS. The embodiment of the invention is illustrated by taking the detection of weak harmonic interference signals in a 4-unit BD2-B3 frequency point anti-interference antenna system as an example.
Step 1: under the condition of no external electromagnetic interference, the device is turned onThe digital signal processing module of the satellite navigation anti-interference antenna system collects and stores the received signals of all 4 channels, and the sampling frequency FsThe sampling time is 2.1141ms when the frequency is set to be 62MHz, and the number L of signal points collected and stored in each channel can be calculated to be 131072 according to the formula (1). Finally, the 4 channels of stored data form a matrix with dimensions 131072 × 4.
Step 2: dividing the ith (i ═ 1,2, …,4) column vector x (i) of the data matrix into mutually overlapped sub data blocks, setting the length of each sub data block to be 2048, and setting the overlap ratio between two adjacent sub data blocks to be 50%, then calculating the total number of the sub data blocks to be 127 according to the formula (2). The kth (k ═ 1,2, … 127) sub-data block is denoted as xk(i) In that respect FIG. 2 is a schematic diagram of a sub-data block partitioning process overlapping with each other.
And step 3: a vector of 2048 x 1 dimensions is constructed, denoted as y, and each element in y is initialized to 0.
And 4, step 4: in turn, a sub-data block xk(i) (k is 1,2, … 127) performing Fast Fourier Transform (FFT), setting the number of FFT points to 2048, and recording the result of the FFT as Xk，XkIs a vector of 2048 × 1 dimensions. Calculating X according to equation (5)kThe n-th (n-1, 2.., 2048) element X in the vectorkThe modulus value of (n) is squared and accumulated in the nth element of the vector y.
And 5: the effective working bandwidth B of the BD2-B3 frequency point satellite navigation signal is 20.46MHz, the vector y can be divided into 30 sub-bands according to the calculation of the formula (5), and y is usedm(m-1, 2, …,30) denotes the mth subband data block of the vector y.
Step 6: searching sub-band data block y in turnmMaximum value d in (1, 2, …,30)mThe searching algorithm adopts a 'bubbling' sorting method, and the maximum value in 30 sub-bands is formed into a vector d [ [ d ] with dimension size of 30 multiplied by 1 [ [ d ]1,d2,…,d30]TThe superscript T is the transpose operator.
And 7: searching for minimum value d in vector d by adopting bubble sorting methodminLet the noise mean power value PnoiseAnd initialized to 0, a counter J is designed and initialized to 0. It is determined in turn whether each element y (n) (1, 2., 2048) of the vector y is less than dminIf it is less than dminThen y (n) is added to PnoiseAnd (4) performing middle accumulation, adding 1 to the count of the counter J, and calculating P after all 2048 elements are judgednoiseJ and update PnoiseThe value is obtained.
And 8: with PnoiseIs twice as the decision threshold value ytCarrying out weak harmonic interference detection, and sequentially judging whether each element y (n) (n is 1,2, 2048) of the vector y is larger than ytIf y (n) > ytIf so, the interference exists on the frequency point f (n), and the weak interference harmonic frequency f (n) is calculated according to the formula (8) and output. To this end, detection of weak harmonic interference in the ith channel.
And (5) completing the detection of weak harmonic interference in all channels according to the steps 2 to 8 in sequence.

Claims (1)

1. A method for detecting weak harmonic interference signals in a satellite navigation anti-interference antenna system is characterized by comprising the following steps:
the method comprises the steps of firstly, collecting and storing digital signals output by an analog-to-digital converter of a satellite navigation anti-interference antenna with a set time length of T milliseconds under the condition of no external electromagnetic interference, and storing the number L of data points in each corresponding channel as T multiplied by Fs×103Wherein F issSampling frequency for the analog-to-digital converter;
assuming that the satellite navigation anti-interference antenna system comprises M channels, the acquired and stored data form a matrix with dimension L multiplied by M, and the ith column of data of the matrix is marked as x (i) ([ x)0,x1,…,xL-1]T；
Secondly, dividing the data vector x (i) into sub-data blocks which are overlapped with each other, wherein the length of each sub-data block is N, the value of N is set to be the positive integer power of 2, the overlapping rate between two adjacent sub-data blocks is set to be 50%, and the total number of the sub-data blocks is
Figure FDA0001531420200000011
K (k is 1, 2)… K) sub-data blocks denoted xk(i)；
Thirdly, constructing a vector y with the size of Nx 1 dimension, and initializing each element in y to be 0, wherein y is represented as0＝0；
Fourthly, sequentially sub-data blocks xkPerforming fast Fourier transform, setting the number of fast Fourier transform points to be N, and recording the result of the fast Fourier transform as Xk，XkIs a vector of dimension Nx 1; calculating XkThe nth element X in the vectorkThe squares of the modulus values of (n) are summed up in the nth element of the vector y, yk(n)＝yk-1(n)+|Xk(n)|2，n＝1,2,...,N；
Fifthly, dividing the vector y into S sub-bands according to the effective working bandwidth B of the satellite navigation system,
Figure FDA0001531420200000012
Fsfor sampling frequency, use ysThe S-th subband data block, S-1, 2, …, S, representing vector y;
sixthly, the sub-band data block y is searched in sequencesMaximum value of dsThe maximum values in the S subbands are combined into a vector d ═ d of size S × 11,d2,…,dS]T；
Seventhly, searching the minimum value d in the vector dminLet the noise mean power value PnoiseAnd initialized to 0, a counter J is designed and initialized to 0; sequentially judging whether each element y (n) of the vector y is smaller than dminIf it is less than dminThen y (n) is added to PnoiseAnd (4) performing middle accumulation, adding 1 to the count of the counter J, and calculating P after judging all N elementsnoiseA combination of J and PnoiseUpdating the value;
eighth step with PnoiseIs twice as the decision threshold value ytCarrying out weak harmonic interference detection, and sequentially judging whether each element y (n) of the vector y is larger than ytIf y (n) > ytIf yes, the decision is at the frequency point
Figure FDA0001531420200000021
There is interference and f (n) is output.
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CN109217913A (en) * 2018-09-07 2019-01-15 中国卫通集团股份有限公司 Examining system is searched on a kind of satellite interference source ground
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