Phased array sum-difference amplitude comparison direction finding method of full-band satellite ground station

Abstract

The invention relates to the field of satellite ground station signal direction finding, in particular to a phased array and sum-difference amplitude comparison direction finding method of a full-band satellite ground station. According to the technical scheme, the method comprises the following steps: determining L, C, K and Qv wave bands of a to-be-measured signal according to a frequency point and a bandwidth of the to-be-measured signal, and determining a DDC frequency point and a bandwidth; according to the set scanning step length, phased-array antennas of the corresponding wave bands are adopted for four-side scanning; after scanning is completed, a rough measurement interval is determined according to the scanning beam with the maximum sum signal amplitude; and according to the sum-difference signal of the rough measurement interval, the incident direction of the signal is calculated by using a sum-difference amplitude comparison algorithm. A phased-array antenna and a sum-difference amplitude comparison direction finding technology are adopted, so that the direction finding speed, precision and robustness are remarkably improved. The method is suitable for satellite ground station signal direction finding.

Description

Technical Field

[0001] The present invention relates to the field of satellite ground station signal direction finding, and in particular to a phased array and sum-difference amplitude ratio direction finding method for a full-band satellite ground station. Background Art

[0002] With the rapid development of satellite communication technology, satellite ground stations (SGSs) are widely used in military reconnaissance, civilian communications, weather monitoring, and navigation enhancement. However, due to the wide-area coverage of satellite signals, problems such as illegal interference, spectrum conflicts, and signal spoofing are becoming increasingly prominent. Efficient and accurate full-band signal direction-finding technology is urgently needed to enable real-time monitoring, positioning, and interference tracing of satellite signals.

[0003] Existing direction finding technologies face the following challenges: Wideband coverage: Satellite communication frequency bands cover L, S, C, Ku, Ka, etc. (1 GHz to 40 GHz). Traditional direction-finding equipment has difficulty achieving high-sensitivity reception across the entire frequency band.

[0004] Multiple signal mixing: Multiple satellite signals, ground interference and noise may exist in the same frequency band, requiring high-resolution signal separation technology.

[0005] Dynamic signal environment: The high-speed movement of low-orbit satellites (LEO) causes Doppler frequency shift, requiring the direction-finding system to have rapid response capabilities.

[0006] Complex modulation types: Modern modulation methods such as QPSK, OFDM, and spread spectrum increase the difficulty of signal parameter estimation. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a phased array and sum-difference amplitude ratio direction finding method for a full-band satellite ground station, which greatly improves the accuracy of direction finding.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose. The present invention provides a phased array and sum-difference amplitude ratio direction finding method for a full-band satellite ground station, comprising: S1. Determine the L, C, K, and Qv bands of the signal to be measured according to its frequency and bandwidth, and determine the DDC frequency and bandwidth. S2. Scan in four directions using a phased array antenna of the corresponding band according to the set scanning step size; S3. After the scan is completed, the coarse measurement interval is determined based on the scanning beam with the largest sum signal amplitude; S4. According to the sum signal and the difference signal in the rough measurement interval, the incident direction of the signal is calculated using the sum-difference amplitude ratio algorithm.

[0009] Furthermore, the incident direction of the signal calculated using the sum-difference amplitude ratio algorithm specifically includes: According to the principle of sum and difference single pulse amplitude comparison direction finding, the half array method is used to form the sum beam and difference beam. Assuming that the array element spacing is d, the number of array elements is 2N, θ is the incident direction of the target radiation source signal, and the beam pointing direction is ,but: Where P1 is the combined power of array elements 1 to N, P2 is the combined power of array elements N+1 to 2N, i represents the i-th antenna, j is the imaginary unit, λ represents the wavelength of the electromagnetic wave, and e represents a natural constant; Then the sum beam output is: In the formula Representation and beam output; The difference beam output is: Where, represents the difference beam output; The angle error signal is: Where, represents the angle error signal; set up , , substituting into the above formula, we get If the incident angle of the target radiation source signal deviates from the beam center by less than the set value, ,but: Where Nu represents the number of effective elements in the antenna array, and j represents the imaginary unit; right exist Perform a first-order Taylor expansion at , and discard the smallest amount, then: ; Then we finally get: In the formula is the deviation angle between the target radiation source signal incident angle and the beam pointing direction; The deviation is determined by determining the direction of the phase difference between the sum signal and the difference signal as follows: Direction determination: Where, The complex signal representation of the difference signal is represented by, Represents the complex conjugate of the sum signal, sign[] indicates whether the instantaneous phase of the signal is positively offset or negatively offset, and Im() indicates extracting the complex imaginary part; Linear approximation algorithm: Exact algorithm: , , , .

[0010] The beneficial effects of the present invention are: (1) High-precision direction finding Multi-beam joint solution: The phased array antenna performs four-way scanning to generate sum and difference beams in the horizontal plane (azimuth) and elevation plane, achieving two-dimensional direction finding; Slope enhancement: The difference beam has a high slope near the axial zero point. Small angle changes will lead to significant difference beam / sum beam changes, improving sensitivity.

[0011] (2) Quick response Real-time: Sum and difference beams are quickly generated through analog synthesis or digital beamforming, without the need for iterative search (faster than interferometers); Typical latency: <1ms (suitable for dynamic target tracking, such as drones and electronic warfare); (3) Anti-interference capability Multipath suppression: The null point of the difference beam can suppress interference from non-main lobe directions (such as reflected signals); Strong signal adaptation: The amplitude ratio method is sensitive to amplitude differences, but the saturation effect can be alleviated through normalization (difference beam / sum beam). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a flow chart of a phased array and sum-difference amplitude direction finding method for a full-band satellite ground station provided by an embodiment of the present invention; Figure 2 It is a schematic diagram of the principle of half array method and differential amplitude direction finding provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0013] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0014] The present invention uses a four-panel phased array antenna, each of which is divided into four frequency bands: L, C, K, and Qv. The four panels scan in time, and the four frequency bands scan in parallel. Specifically, the RF receiver consists of a dual-channel receiver for each of the four frequency bands: L, C, K, and Qv. The digital board divides the signal into four corresponding frequency bands. Each digital board contains dual receiving channels, one for each sum signal (Σ) and one for each difference signal (Δ). The sum signal is used for monitoring and coarse direction finding, while the sum and difference signals are combined for fine direction finding.

[0015] Based on this, the present invention provides a phased array and sum-difference amplitude direction finding method for a full-band satellite ground station, such as Figure 1 Shown, including: S1. Determine the L, C, K, and Qv bands of the signal to be measured according to its frequency and bandwidth, and determine the DDC frequency and bandwidth. S2. Scan in four directions using a phased array antenna of the corresponding band according to the set scanning step size; S3. After the scan is completed, the coarse measurement interval is determined based on the scanning beam with the largest sum signal amplitude; S4. According to the sum signal and the difference signal in the rough measurement interval, the incident direction of the signal is calculated using the sum-difference amplitude ratio algorithm.

[0016] Specifically, the incident direction of the signal calculated using the sum-difference amplitude ratio algorithm includes: According to the principle of sum and difference single pulse amplitude comparison direction finding, such as Figure 2 As shown in the figure, the sum beam and difference beam are formed by using the half array method. Assuming that the array element spacing is d, the number of array elements is 2N, θ is the incident direction of the target radiation source signal, and the beam pointing direction is ,but: Where P1 is the combined power of array elements 1 to N, and P2 is the combined power of array elements N+1 to 2N; Then the sum beam output is: In the formula Representation and beam output; The difference beam output is: Where, represents the difference beam output; The angle error signal is: Where, represents the angle error signal; set up , , substituting into the above formula, we get If the incident angle of the target radiation source signal deviates from the beam center by less than the set value, ,but: Where Nu represents the number of effective elements in the antenna array, and j represents the imaginary unit; right exist Perform a first-order Taylor expansion at , and discard the smallest amount, then: ; Then we finally get: In the formula is the deviation angle between the target radiation source signal incident angle and the beam pointing direction; The deviation is determined by determining the direction of the phase difference between the sum signal and the difference signal as follows: Direction determination: Where, The complex signal representation of the difference signal is represented by, Represents the complex conjugate of the sum signal, sign[] indicates whether the instantaneous phase of the signal is positively offset or negatively offset, and Im() indicates extracting the complex imaginary part; Real-time rapid response through linear approximation algorithm, the linear approximation algorithm is as follows: When the signal deviation is large (such as during initial capture) or high-precision positioning is required, the global accuracy is guaranteed by a precise algorithm. The precise algorithm is as follows: , , u Represents an intermediate variable that quantifies the deviation between the actual direction of the signal and the beam pointing direction; , , .

[0017] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A phased array and sum-difference amplitude direction finding method for a full-band satellite ground station, characterized in that: include: S1. Determine the L, C, K, and Qv bands of the signal to be measured according to its frequency and bandwidth, and determine the DDC frequency and bandwidth. S2. Scan in four directions using a phased array antenna of the corresponding band according to the set scanning step size; S3. After the scan is completed, the coarse measurement interval is determined based on the scanning beam with the largest sum signal amplitude; S4. According to the sum signal and the difference signal in the rough measurement interval, the incident direction of the signal to be measured is calculated using a sum-difference amplitude ratio algorithm.

2. The phased array and sum-difference amplitude ratio direction finding method for a full-band satellite ground station according to claim 1, characterized in that: The incident direction of the signal calculated using the sum-difference amplitude ratio algorithm specifically includes: According to the principle of sum and difference single pulse amplitude comparison direction finding, the half array method is used to form the sum beam and difference beam. Assuming that the array element spacing is d, the number of array elements is 2N, θ is the incident direction angle of the target radiation source signal, and the beam pointing is ,but: Where P1 is the combined power of elements 1 to N, P2 is the combined power of elements N+1 to 2N, i represents the i-th antenna, j is the imaginary unit, λ represents the wavelength of the electromagnetic wave, and e represents a natural constant. Then the sum beam output is: In the formula Representation and beam output; The difference beam output is: Where, represents the difference beam output; The angle error signal is: Where, represents the angle error signal; set up , , substituting into the above formula, we get If the incident angle of the target radiation source signal deviates from the beam center by less than the set value, ,but: Where Nu represents the number of effective elements in the antenna array, and λ represents the wavelength of the electromagnetic wave; right exist Perform a first-order Taylor expansion at , and discard the smallest amount, then: ; Then we finally get: In the formula is the deviation angle between the target radiation source signal incident angle and the beam pointing direction; The deviation is determined by determining the direction of the phase difference between the sum signal and the difference signal as follows: Direction determination: Where, The complex signal representation of the difference signal is represented by, It represents the complex conjugate of the sum signal, sign[] indicates whether the instantaneous phase of the signal is positively offset or negatively offset, and Im() indicates extracting the complex imaginary part; Linear approximation algorithm: Exact algorithm: , , u represents an intermediate variable; ， ， 。

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