Complex electromagnetic environment direction finding method based on multi-mode accumulation phase difference method

Abstract

The invention discloses a complex electromagnetic environment direction finding method based on a multi-mode accumulated phase difference method, and belongs to the technical field of radio direction finding. According to the invention, a multi-mode accumulation phase difference method is adopted, the phase difference of each frequency point after FFT transformation is independently calculated, multi-target simultaneous direction finding in a complex electromagnetic environment is realized, the multi-target signal direction finding resolution is improved, thousands of target signals in an analysis bandwidth can be simultaneously subjected to direction finding, and the method is not limited by signal processing path resources of a traditional direction finding method; different characteristic signal types can be adapted through different accumulation modes, and the direction finding capability of complex communication signals is improved; and the direction finding precision and the direction finding sensitivity are improved through a multi-time direction finding result accumulation function.

Description

Technical Field

[0001] The invention belongs to the technical field of radio direction finding, and in particular relates to a complex electromagnetic environment direction finding method based on a multi-mode cumulative phase difference method. Background Art

[0002] With the continuous development of radio technology, new technologies such as high-speed frequency hopping, spread spectrum, time division multiplexing, and complex modulation are being used more and more widely. Various low-probability-of-interception signals such as short pulse signals and swept-frequency interference are increasing. Therefore, electronic reconnaissance equipment is required to be able to process broadband signals and narrowband signals that arrive simultaneously within the analysis bandwidth in a complex electromagnetic environment, and have high processing efficiency to meet the detection requirements of low-interception communication signals such as frequency hopping and burst, so that electronic reconnaissance equipment can quickly find the direction and locate enemy electronic equipment.

[0003] Radio direction finding technology, according to different direction finding principles, direction finding systems can be divided into amplitude method, phase method, Doppler method, time difference method and spatial spectrum estimation method. Among them, interferometer direction finding has the advantages of high direction finding sensitivity, high direction finding accuracy, fast direction finding speed, can measure the pitch angle, and is insensitive to the amplitude of the received signal. Broadband direction finding (i.e., direction finding for signals of different frequencies simultaneously within a relatively wide frequency range) is often implemented using the FFT (Fast Fourier Transformation) interferometer system. The direction finding technology implemented by the FFT interferometer solves the problem of broadband multi-frequency simultaneous direction finding within the real-time bandwidth, and the direction finding frequency can be expanded through the sweep frequency direction finding control method.

[0004] 2. Existing implementation scheme of complex electromagnetic environment signal direction finding system:

[0005] Low-complexity direction finding scheme for adaptive wide- and narrow-band signals (CN 116430302 A)

[0006] The sampled signals are distinguished to determine broadband signals and narrowband signals, the signals are down-converted to obtain baseband signals, and the baseband signals are extracted and filtered. The filtered signals are calibrated using pre-stored antenna amplitude and phase calibration parameters, the covariance matrix of the signals is calculated based on the calibrated signals, the eigenvalues ​​and eigenvectors of the covariance matrix are extracted, the signal subspace and noise subspace are constructed based on the eigenvalues ​​and eigenvectors, and the azimuth angle of the received signal is estimated based on the signal subspace and the noise subspace, which can realize the automatic sorting, transmission and direction finding of wide-band and narrow-band signals.

[0007] Signal detection scheme based on shortwave direction finder broadband spectrum and direction finding data (CN 115529081 A)

[0008] The scanning direction finding function of the shortwave direction finder is used to collect broadband spectrum and direction finding data. The spectrum data is smoothed in the time domain in the form of a sliding window. The direction finding data is accumulated according to the sliding window size. The data after time domain smoothing is smoothed in the frequency domain in the form of a sliding window. The accumulated data is adaptively estimated in the form of a sliding window to obtain the noise floor curve. The data after frequency domain smoothing is raised by NdB based on the empirical value as the adaptive threshold for flexible decision. Signal detection is completed based on the adaptive threshold, spectrum data, and direction finding data. The multi-frame detection results are fused and processed to output a signal list.

[0009] Disadvantages of existing multi-target signal direction finding methods in complex electromagnetic signal environments:

[0010] 1. Low-complexity direction finding scheme for adaptive wide- and narrow-band signals

[0011] It is necessary to sort and distinguish wide-band and narrow-band signals, and process wide and narrow signals in separate channels. The processing method is complicated and there is a possibility of misjudgment of wide and narrow signals. When the number of signals is large, the target signal data may be lost due to the limitation of the number of processing channels, and it does not have the short pulse measurement function.

[0012] 2. Signal detection scheme based on shortwave direction finder broadband spectrum and direction finding data

[0013] Signal detection is completed based on adaptive thresholds, spectrum data, and direction-finding data, and multi-frame detection results are fused. For co-frequency time-division multiplexed signals such as TDD-LTE signals, the directions of uplink and downlink signal sources cannot be distinguished, and the flexible decision threshold may result in the loss of direction information of signals of interest with smaller amplitudes. Summary of the invention

[0014] In view of the above technical problems existing in the prior art, the present invention proposes a complex electromagnetic environment direction finding method based on a multi-mode cumulative phase difference method, which has a reasonable design, overcomes the shortcomings of the prior art, and has good effects.

[0015] In order to achieve the above object, the present invention adopts the following technical solution:

[0016] A complex electromagnetic environment direction finding method based on a multi-mode cumulative phase difference method, using a radio frequency channel and a direction finding signal processing board; comprising the following steps:

[0017] Step 1: Collect antenna array element signals;

[0018] Step 2: Calculate the FFT data of each antenna array element to obtain amplitude and phase information;

[0019] Step 3: Calculate the phase difference between each antenna array element;

[0020] Step 4: Accumulate the phase difference of all frequency points of each antenna array element in different modes;

[0021] Perform multi-mode accumulation operation on the phase difference of each antenna array element at each frequency point, and average the multiple accumulated phase difference data;

[0022] Step 5: Coherent operation;

[0023] Perform coherent calculation on the accumulated phase difference data of each antenna array element and the calibration library data;

[0024] Step 6: Fusion of direction finding results, output of direction finding signal list.

[0025] Preferably, step 1 specifically includes the following steps:

[0026] Step 1.1: synchronously sample the signal received by the antenna array element through the RF channel;

[0027] Step 1.2: Convert the received antenna array element signal to an intermediate frequency through the RF channel;

[0028] Step 1.3: Sample the intermediate frequency signal through the ADC on the direction finding signal processing board at a frequency that satisfies the bandpass sampling theorem.

[0029] Preferably, step 2 specifically includes the following contents: performing down-conversion filtering and FFT transformation on the sampled intermediate frequency signal to obtain amplitude data and phase data of each frequency point within the analysis bandwidth.

[0030] Preferably, step 3 specifically includes the following contents: performing phase difference on the phase data of each frequency point of each array element in sequence.

[0031] Preferably, in step 4, the specific steps of multi-mode cumulative phase difference data fusion and averaging are: for the N frequency points within the analysis bandwidth, determine in turn whether the amplitude of the frequency point meets the accumulation condition. If the accumulation condition is met, the phase difference is accumulated, and the accumulation number of the frequency point is increased by 1; if the accumulation condition is not met, the phase difference of the frequency point is discarded, and the accumulation number remains unchanged. After reaching the accumulation cycle judgment number, the sum of the phase differences of each frequency point is divided by the accumulation number of each frequency point to obtain the average phase difference of the frequency point.

[0032] Preferably, multi-mode accumulation includes continuous accumulation, over-threshold accumulation and hold accumulation, and different modes are selected according to different characteristic signals; the continuous accumulation mode accumulates all phase differences in the accumulation period, the over-threshold accumulation mode accumulates all signals exceeding the threshold value within the accumulation period, and the hold accumulation mode accumulates the latest over-threshold signal within the accumulation period.

[0033] Preferably, step 5 specifically includes the following contents: performing correlation operation on the accumulated average phase difference of each frequency point and the set calibration library phase difference data to obtain the direction finding angle of each frequency point.

[0034] Preferably, step 6 specifically includes the following contents: judging the validity of the direction finding results of each frequency point in combination with the spectrum data and fusing the results of the same signal to realize the list display of the center frequency, bandwidth and azimuth information of the direction finding signal.

[0035] Beneficial technical effects brought by the present invention:

[0036] The present invention adopts a multi-mode cumulative phase difference method to independently calculate the phase difference of each frequency point after FFT transformation, thereby realizing simultaneous direction finding of multiple targets in a complex electromagnetic environment, improving the direction finding resolution of multiple target signals, and being able to simultaneously find the direction of thousands of target signals within the analysis bandwidth without being limited by the signal processing path resources of the traditional direction finding method; different accumulation modes can be used to adapt to different characteristic signal types, thereby improving the direction finding capability of complex communication signals; and the direction finding accuracy and sensitivity are improved by accumulating multiple direction finding results. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] A method for direction finding in complex electromagnetic environment based on multi-mode cumulative phase difference method, the process is as follows: Figure 1 As shown, a radio frequency channel and a direction finding signal processing board are used; the following steps are included:

[0040] Step 1: Collect antenna element signals; specifically include the following steps:

[0041] Step 1.1: synchronously sample the signal received by the antenna array element through the RF channel;

[0042] Step 1.2: Convert the received antenna array element signal to an intermediate frequency through the RF channel;

[0043] Step 1.3: Sample the intermediate frequency signal through the ADC on the direction finding signal processing board at a frequency that satisfies the bandpass sampling theorem.

[0044] Step 2: Calculate the FFT data of each antenna array element to obtain amplitude and phase information; specifically, the following steps are included:

[0045] The sampled intermediate frequency signal is down-converted and filtered and FFT transformed to obtain the amplitude and phase data of each frequency point within the analysis bandwidth.

[0046] Step 3: Calculate the phase difference between antenna elements; specifically include the following steps:

[0047] The phase difference is made for the phase data of each frequency point of each array element in turn.

[0048] Step 4: Perform multi-mode accumulation operation on the phase difference of each frequency point of each antenna array element, and average the multiple accumulated phase difference data; the specific steps of fusing and averaging the multi-mode accumulated phase difference data are as follows:

[0049] For the N frequency points within the analysis bandwidth, determine in turn whether the amplitude of the frequency point meets the accumulation condition. If the accumulation condition is met, the phase difference is accumulated, and the accumulation times of the frequency point is increased by 1; if the accumulation condition is not met, the phase difference of the frequency point is discarded, and the accumulation times remain unchanged. After reaching the accumulation cycle judgment times, the sum of the phase differences of each frequency point is divided by the accumulation times of each frequency point to obtain the average phase difference of the frequency point.

[0050] Multi-mode accumulation includes continuous accumulation, over-threshold accumulation and hold accumulation. Different modes are selected according to different characteristic signals. The continuous accumulation mode accumulates all phase differences in the accumulation period, the over-threshold accumulation mode accumulates all signals exceeding the threshold value in the accumulation period, and the hold accumulation mode accumulates the latest over-threshold signal in the accumulation period.

[0051] Step 5: Perform coherent calculation on the accumulated phase difference data of each antenna array element and the calibration library data; specifically, the steps include:

[0052] The cumulative average phase difference of each frequency point is correlated with the phase difference data of the set calibration library to obtain the direction finding angle of each frequency point.

[0053] Step 6: Fusion of direction finding results, output of direction finding signal list; specifically includes the following steps:

[0054] Combined with spectrum data, the validity of the direction finding results at each frequency point is judged and merged with the results of the same signal to display the center frequency, bandwidth and azimuth information of the direction finding signal in a list.

[0055] The data processing time (including down-conversion FFT operation accumulation operation, etc.) is less than the antenna switching time plus the data acquisition time to ensure that each collected data can participate in the operation, thereby improving the signal processing efficiency of the direction finding system and the shortest single pulse direction finding capability.

[0056] The present invention is based on the method of adopting a multi-mode cumulative phase difference method, and independently calculates the phase difference of each frequency point after FFT transformation, so as to realize multi-target direction finding in a complex electromagnetic environment, improve the direction finding resolution of multi-target signals, and improve the direction finding accuracy and short pulse signal direction finding capability through different accumulation modes. There is no need to distinguish between broadband and narrowband signals, and the direction finding processing flow of broadband and narrowband signals is consistent, which simplifies the algorithm implementation method. Different characteristic measured signals use different mode accumulation methods, which can realize the direction finding of continuous wave, pulse, co-frequency time division multiplexing and other signals, and improve the multi-target direction finding capability in a complex electromagnetic environment.

[0057] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method, characterized in that: Using a radio frequency channel and a direction finding signal processing board; including the following steps: Step 1: Collect antenna array element signals; Step 2: Calculate the FFT data of each antenna array element to obtain amplitude and phase information; Step 3: Calculate the phase difference between each antenna array element; Step 4: Accumulate the phase difference of all frequency points of each antenna array element in different modes; Perform multi-mode accumulation operation on the phase difference of each antenna array element at each frequency point, and average the multiple accumulated phase difference data; Step 5: Coherent operation; Perform coherent calculation on the accumulated phase difference data of each antenna array element and the calibration library data; Step 6: Fusion of direction finding results, output of direction finding signal list.

2. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 1.1: Synchronously sample the signal received by the antenna array element through the RF channel; Step 1.2: Convert the received antenna array element signal to an intermediate frequency through the RF channel; Step 1.3: Sample the intermediate frequency signal at a frequency that satisfies the bandpass sampling theorem through the ADC on the direction finding signal processing board.

3. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Step 2 specifically includes the following contents: performing down-conversion filtering and FFT transformation on the sampled intermediate frequency signal to obtain amplitude data and phase data of each frequency point within the analysis bandwidth.

4. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Step 3 specifically includes the following contents: performing phase difference on the phase data of each frequency point of each array element in turn.

5. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: In step 4, the specific steps of fusion averaging of multi-mode accumulated phase difference data are as follows: for N frequency points within the analysis bandwidth, determine in turn whether the amplitude of the frequency point meets the accumulation condition; if the accumulation condition is met, perform phase difference accumulation, and the accumulation times of the frequency point are increased by 1; If the accumulation condition is not met, the phase difference of the frequency point is discarded, and the accumulation times remain unchanged. After reaching the accumulation cycle judgment times, the sum of the phase differences of each frequency point is divided by the accumulation times of each frequency point to obtain the average phase difference of the frequency point.

6. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Multi-mode accumulation includes continuous accumulation, over-threshold accumulation and hold accumulation. Different modes are selected according to different characteristic signals. The continuous accumulation mode accumulates all phase differences in the accumulation period, the over-threshold accumulation mode accumulates all signals exceeding the threshold value in the accumulation period, and the hold accumulation mode accumulates the latest over-threshold signal in the accumulation period.

7. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Step 5 specifically includes the following contents: performing correlation operation on the accumulated average phase difference of each frequency point and the set calibration library phase difference data to obtain the direction finding angle of each frequency point.

8. The method for direction finding in a complex electromagnetic environment based on a multi-mode cumulative phase difference method according to claim 1, characterized in that: Step 6 specifically includes the following contents: judging the validity of the direction finding results of each frequency point in combination with the spectrum data and fusing them with the results of the same signal, so as to realize the list display of the center frequency, bandwidth and azimuth information of the direction finding signal.

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