A phased array and sum-difference amplitude direction finding method for a full-band satellite ground station

Abstract

This invention relates to the field of direction finding for satellite ground station signals, specifically to a phased array and sum-difference amplitude comparison direction finding method for a full-band satellite ground station. The technical solution includes: determining the L, C, K, and Qv bands of the signal under test based on its frequency and bandwidth, and determining the DDC frequency and bandwidth; performing a four-sided scan using a phased array antenna of the corresponding band according to a set scanning step size; after scanning, determining the coarse measurement interval based on the scanning beam with the largest sum signal amplitude; and calculating the incident direction of the signal using a sum-difference amplitude comparison algorithm based on the sum and difference signals in the coarse measurement interval. The use of a phased array antenna and sum-difference amplitude comparison direction finding technology significantly improves the speed, accuracy, and robustness of direction finding. This invention is applicable to direction finding for satellite ground station signals.

Description

Technical Field

[0001] This invention relates to the field of satellite ground station signal direction finding, specifically to a phased array and sum-difference amplitude direction finding method for a full-band satellite ground station. Background Technology

[0002] With the rapid development of satellite communication technology, satellite ground stations are widely used in military reconnaissance, civilian communications, meteorological 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, necessitating efficient and accurate full-band signal direction finding technology to achieve real-time monitoring, positioning, and interference tracing of satellite signals.

[0003] Current direction finding technologies face the following challenges:

[0004] Wideband coverage: Satellite communication frequency bands cover L, S, C, Ku, Ka, etc. (1 GHz to 40 GHz), making it difficult for traditional direction finding equipment to achieve high-sensitivity reception across the entire frequency band.

[0005] Multiple signal interference: Multiple satellite signals, ground interference, and noise may exist in the same frequency band, requiring high-resolution signal separation technology.

[0006] Dynamic signal environment: The high-speed movement of low-Earth orbit (LEO) satellites causes Doppler frequency shift, requiring the direction finding system to have a fast response capability.

[0007] Complex modulation types: Modern modulation methods such as QPSK, OFDM, and spread spectrum increase the difficulty of signal parameter estimation. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a phased array and sum-difference amplitude direction finding method for a full-band satellite ground station, which greatly improves the accuracy of direction finding.

[0009] This invention achieves the above objectives by adopting the following technical solution: This invention provides a phased array and sum-difference amplitude direction finding method for a full-band satellite ground station, comprising:

[0010] S1. Determine the L, C, K, and Qv bands of the signal under test based on its frequency and bandwidth, and determine the DDC frequency and bandwidth.

[0011] S2. According to the set scanning step size, perform four-sided scanning using a phased array antenna of the corresponding band;

[0012] S3. After the scan is completed, determine the coarse measurement interval based on the scanning beam with the largest signal amplitude;

[0013] S4. Based on the sum and difference signals in the coarse measurement interval, the incident direction of the signal is calculated using the sum-difference amplitude ratio algorithm.

[0014] Furthermore, the specific incident direction of the signal calculated using the sum-difference amplitude comparison algorithm includes:

[0015] Based on the principle of sum-difference single-pulse amplitude comparison direction finding, a half-array method is used to form the sum and difference beams. Assuming the element spacing is d, the number of elements is 2N, θ is the incident direction of the target radiation source signal, and the beam direction is... ,but:

[0016]

[0017]

[0018] In the formula, 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 the natural constant.

[0019] The beam output is then:

[0020]

[0021] In the formula Indicator and beam output;

[0022] The difference beam output is:

[0023]

[0024] In the formula, Indicates differential beam output;

[0025] The angle error signal is:

[0026]

[0027] In the formula, This indicates the angle error signal;

[0028] set up , Substituting into the above formula, we get

[0029]

[0030] If the angle of incidence of the target radiation source signal deviates from the beam center by less than the set value, then take... ,but:

[0031]

[0032] In the formula, Nu represents the number of effective elements of the antenna array, and j represents the imaginary unit;

[0033] right exist Performing a first-order Taylor expansion at the given point, and discarding minimal quantities, we get: ;

[0034] The final result is:

[0035]

[0036] In the formula The angle between the incident angle of the target radiation source signal and the deflection angle of the beam direction;

[0037] The deviation is determined by judging the direction of the phase difference between the sum and difference signals, as follows:

[0038] Direction determination:

[0039]

[0040] In the formula, The complex signal representation of the difference signal, The complex conjugate of the signal is indicated by sign[], which indicates whether the instantaneous phase of the signal is positively or negatively shifted, and Im() indicates the extraction of the imaginary part of the complex number.

[0041] Linear approximation algorithm:

[0042]

[0043]

[0044] Exact Algorithm: ,

[0045] ,

[0046] , .

[0047] The beneficial effects of this invention are as follows:

[0048] (1) High-precision direction finding

[0049] Multi-beam joint solution: A phased array antenna can generate sum and difference beams in the horizontal (azimuth) and elevation planes by scanning in four directions, thus realizing two-dimensional direction finding;

[0050] Slope enhancement: The differential beam has a high slope near the axial zero point. Small angle changes will result in significant differential beam / beam changes, improving sensitivity.

[0051] (2) Rapid response

[0052] Real-time performance: Sum and difference beams are generated rapidly through analog synthesis or digital beamforming without iterative search (faster than interferometers).

[0053] Typical latency: <1ms (suitable for dynamic target tracking, such as drones and electronic warfare);

[0054] (3) Anti-interference capability

[0055] Multipath suppression: The null point of the difference beam can suppress interference from non-main lobe directions (such as reflected signals);

[0056] Strong signal adaptation: The amplitude comparison method is sensitive to amplitude differences, but the saturation effect can be mitigated by normalization (difference beam / sum beam). Attached Figure Description

[0057] Figure 1 This is a flowchart 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;

[0058] Figure 2 This is a schematic diagram of the half-array method and the difference ratio amplitude direction finding principle provided in the embodiments of the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0060] This invention employs a four-sided phased array antenna, with each side divided into four frequency bands: L, C, K, and Qv. The four sides are scanned in a time-division manner, and the four frequency bands are scanned in parallel. Specifically, the RF receiver consists of one dual-channel receiver for each of the L, C, K, and Qv bands. The digital board is divided into four signals corresponding to each frequency band. Each digital board contains two receiving channels, respectively receiving a sum signal (Σ) and a difference signal (Δ). The sum signal is used for monitoring and coarse direction finding, while the sum and difference signals are used together for fine direction finding.

[0061] 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:

[0062] S1. Determine the L, C, K, and Qv bands of the signal under test based on its frequency and bandwidth, and determine the DDC frequency and bandwidth.

[0063] S2. According to the set scanning step size, perform four-sided scanning using a phased array antenna of the corresponding band;

[0064] S3. After the scan is completed, determine the coarse measurement interval based on the scanning beam with the largest signal amplitude;

[0065] S4. Based on the sum and difference signals in the coarse measurement interval, the incident direction of the signal is calculated using the sum-difference amplitude ratio algorithm.

[0066] Specifically, the incident direction of the signal, calculated using the sum-difference amplitude comparison algorithm, includes:

[0067] Based on the principle of sum-difference single-pulse amplitude ratio direction finding, such as Figure 2 As shown, a half-array method is used to form a sum and difference beam. Assuming the element spacing is d, the number of elements is 2N, θ is the incident direction of the target radiation source signal, and the beam direction is... ,but:

[0068]

[0069]

[0070] In the formula, P1 is the combined power of array elements 1 to N, and P2 is the combined power of array elements N+1 to 2N.

[0071] The beam output is then:

[0072]

[0073] In the formula Indicator and beam output;

[0074] The difference beam output is:

[0075]

[0076] In the formula, Indicates differential beam output;

[0077] The angle error signal is:

[0078]

[0079] In the formula, This indicates the angle error signal;

[0080] set up , Substituting into the above formula, we get

[0081]

[0082] If the angle of incidence of the target radiation source signal deviates from the beam center by less than the set value, then take... ,but:

[0083]

[0084] In the formula, Nu represents the number of effective elements of the antenna array, and j represents the imaginary unit;

[0085] right exist Performing a first-order Taylor expansion at the given point, and discarding minimal quantities, we get: ;

[0086] The final result is:

[0087]

[0088] In the formula The angle between the incident angle of the target radiation source signal and the deflection angle of the beam direction;

[0089] The deviation is determined by judging the direction of the phase difference between the sum and difference signals, as follows:

[0090] Direction determination:

[0091]

[0092] In the formula, The complex signal representation of the difference signal, The complex conjugate of the signal is indicated by sign[], which indicates whether the instantaneous phase of the signal is positively or negatively shifted, and Im() indicates the extraction of the imaginary part of the complex number.

[0093] A real-time, fast response is achieved through a linear approximation algorithm, which is as follows:

[0094]

[0095]

[0096] When the signal deviates significantly (such as during initial acquisition) or when high-precision positioning is required, a precise algorithm ensures global accuracy. The precise algorithm is as follows:

[0097] , , u This represents an intermediate variable, quantifying the deviation between the actual direction of the signal and the beam direction;

[0098] ,

[0099] , .

[0100] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of 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 under test based on its frequency and bandwidth, and determine the DDC frequency and bandwidth. S2. According to the set scanning step size, use the phased array antenna of the corresponding band to perform four-sided scanning; S3. After the scan is completed, determine the coarse measurement interval based on the scanning beam with the largest signal amplitude; S4. Based on the sum and difference signals of the coarse measurement interval, the incident direction of the signal to be measured is calculated using the sum-difference amplitude ratio algorithm. Based on the principle of sum-difference single-pulse amplitude comparison direction finding, a half-array method is used to form the sum and difference beams. Assuming the element spacing is *d*, the number of elements is 2N, θ is the incident angle of the target radiation source signal, and the beam direction is... ,but: In the formula, 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 the natural constant. The beam output is then: In the formula Indicator and beam output; The difference beam output is: In the formula, Indicates differential beam output; The angle error signal is: In the formula, This indicates the angle error signal; set up , Substituting into the above formula, we get If the angle of incidence of the target radiation source signal deviates from the beam center by less than the set value, then take... ,but: In the formula, Nu represents the number of effective elements of the antenna array, and λ represents the wavelength of the electromagnetic wave. right exist Performing a first-order Taylor expansion at the given point, and discarding minimal quantities, we get: ; The final result is: In the formula The angle between the incident angle of the target radiation source signal and the deflection angle of the beam direction; The deviation is determined by judging the direction of the phase difference between the sum and difference signals, as follows: Direction determination: In the formula, The complex signal representation of the difference signal, The complex conjugate of the signal is indicated by sign[], which indicates whether the instantaneous phase of the signal is positively or negatively shifted, and Im() indicates the extraction of the imaginary part of the complex number. Linear approximation algorithm: Exact Algorithm: , , u Indicates intermediate variables; ， ， 。

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