Omnibearing signal direction finding method based on uniform nine-array-element circular array

Abstract

The invention discloses an omni-directional signal direction finding method based on a uniform nine-array-element circular array. The omni-directional signal direction finding method comprises the following steps: S1, constructing a uniform nine-array-element circular array structure; s2, constructing a reference-target interference pair by adopting a dual-channel switching receiving strategy; s3, executing dual-channel time-sharing sampling to obtain an interference phase difference observation value; s4, performing time compensation on the observation phase data; and S5, substituting observation phase data into the angle estimation model, and obtaining a target azimuth angle by adopting a least square method. Under the condition that hardware resources are limited, the system implementation cost can be effectively reduced, meanwhile, the direction estimation precision is remarkably improved, and the method is suitable for various high-precision and low-cost direction detection application scenes.

Description

Technical Field

[0001] This invention relates to the field of direction finding technology, and in particular to an omnidirectional signal direction finding method based on a uniform nine-element circular array. Background Technology

[0002] Existing wireless direction finding systems struggle to balance direction finding accuracy, system complexity, and cost control in environments with high bandwidth, multi-source interference, and limited resources. Traditional narrowband array antenna solutions suffer from problems such as frequency-dependent radiation pattern drift and severe beam broadening. Interferometer methods offer advantages such as simple structure and high accuracy, making them suitable for target direction estimation in the low to mid-frequency range. However, for interferometric direction finding systems with multi-element arrays and high-frequency coverage requirements, hardware resources are severely strained. Therefore, this paper proposes a nine-element circular array structure utilizing channel multiplexing and phase compensation to construct an efficient and compact direction finding system, which has significant engineering value. Summary of the Invention

[0003] To address the problems of high hardware cost, limited number of channels, and insufficient direction estimation accuracy in existing direction-finding systems, this invention provides an omnidirectional signal direction-finding method based on a uniform nine-element circular array. By combining array structure optimization, channel multiplexing control, time compensation mechanisms, and direction estimation algorithms, high-precision two-dimensional direction estimation is achieved under conditions of limited receiving channels. This invention is implemented through the following technical solutions.

[0004] A method for omnidirectional signal direction finding based on a uniform nine-element circular array, characterized in that the method includes: S1, construct a uniform nine-element circular array structure; S2 employs a dual-channel switching reception strategy; S3, perform dual-channel time-division sampling to obtain the observed values ​​of the interferometric phase difference; S4, Time compensation for observed phase data; S5. Substitute the observed phase data into the angle estimation model and use the least squares method to obtain the target azimuth.

[0005] Furthermore, step S1, which involves constructing a uniform circular array structure, specifically includes the following steps: S11, the antenna array is arranged in a perfect circle, with a total aperture of 2R and a corresponding circular array radius of R; S12 consists of nine array elements evenly spaced along a circle. They are numbered clockwise from the bottom of the array, labeled as Antenna 1 to Antenna 9. The angular position (polar angle) of each element on the circle can be represented as: ; Where n is the array element number, and the corresponding angle range is... (Due south) to The angle between any two adjacent array elements is 40°. The position coordinates of each array element in the two-dimensional Cartesian coordinate system are determined by its polar angle and radius, specifically expressed as follows: .

[0006] Furthermore, step S2, which employs a dual-channel switching reception strategy, specifically includes the following steps: S21, assign antennas 1, 4, and 7 to channel Ch1 and connect them to the first switching switch as a reference antenna group; S22, assign antennas 2, 3, 5, 6, 8, and 9 to channel Ch2 and connect them to the second switching switch as the target antenna group; S23, through channel control strategy, dynamically constructs reference-target interferometric pairs, and in each round of measurement, prioritizes the target antenna that forms the longest geometric baseline with the reference antenna; at the same time, it supplements the acquisition of several medium and short baseline combinations.

[0007] Furthermore, step S3, which involves obtaining the interferometric phase difference observation value using time-division sampling, specifically includes: Antennas n and m are selected; the interference phase difference between antenna n and antenna m is: ; The interference phase vector can be expressed as: .

[0008] Furthermore, step S4, which involves time compensation of the observed phase data, specifically includes the following steps: Let the sampling time of the nth antenna be tn, and the sampling time of the reference channel be tm. Then, its original observed phase ϕn(tn) should be converted into the equivalent phase value at the reference time, which can be achieved through the linear compensation formula: .

[0009] Furthermore, step S5, which substitutes the observed phase data into the angle estimation model and uses the least squares method to obtain the target azimuth angle, specifically includes the following steps: Estimate θ so that As close as possible Minimize the sum of squared errors: ; make ,because It can be rewritten as ; This is a standard linear least squares problem. The solution is: ; After obtaining the estimated vector, the recovered direction angle is: .

[0010] The present invention adopts the above technical solution and has the following beneficial effects: This invention utilizes an optimized uniform nine-element circular array structure and an innovative dual-channel multiplexing reception strategy, requiring only two channels to drive nine array elements. It introduces a time compensation mechanism based on instantaneous frequency and a least-squares estimation method. Compared to traditional high-cost, multi-channel direction-finding schemes that are susceptible to broadband frequency drift and multi-source interference, this invention significantly reduces system hardware complexity and cost. It effectively overcomes time-division sampling errors and frequency drift problems, ensuring the accuracy and consistency of interferometric phase data across the entire frequency band. This achieves high-precision two-dimensional azimuth estimation and improves the system's anti-interference capability and robustness in complex environments. It is particularly suitable for portable, vehicle-mounted, and other low-cost direction-finding systems with stringent requirements for cost, size, and real-time performance. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the circular antenna array distribution structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the nine-element circular array dual-channel direction finding method according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the maximum baseline connection of the nine array elements dual channels in an embodiment of the present invention. Detailed Implementation

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0013] Figure 2 The flowchart of the nine-element circular array dual-channel direction finding method shown in the embodiment of the present invention is as follows: Figure 2 As shown, the method in this embodiment includes S1. Construct a uniform nine-element circular array structure. The array elements are evenly distributed on a circular fixed plate with a diameter of 1030 mm. The center of the array is set as antenna 1, and the remaining antennas are numbered 2 to 9 in sequence, forming a circular array coordinate system. The system is equipped with a dual-channel receiver. As shown in Table 1 below, antennas 1, 4, and 7 are connected to the first switching switch, and antennas 2, 3, 5, 6, 8, and 9 are connected to the second switching switch. The system controller uses high-speed control logic to poll and switch the connection relationship between each antenna and the channel, ensuring that the phase measurement and acquisition of all array elements are completed within a stable time window.

[0014]

[0015] Table 1 See Figure 1The nine-element circular array antennas are numbered sequentially from antenna 1 to antenna 9, starting from the top south of the array and proceeding clockwise. The angular position (polar angle) of each element on the circumference can be represented as:

[0016] Where n is the array element number, and the corresponding angle range is... (Due south) to The angle between any two adjacent array elements is 40°. The position coordinates of each array element in the two-dimensional Cartesian coordinate system are determined by its polar angle and radius, specifically expressed as follows:

[0017] For any two array elements i and j, their geometric baseline vector is:

[0018] The corresponding baseline length is:

[0019] Simplified to:

[0020] This structure has the characteristics of rotational symmetry and equal angular spacing, which facilitates theoretical modeling and error equalization of interference phase difference. At the same time, it can maximize the use of spatial aperture to achieve high direction finding angle resolution.

[0021] We assume the target radiation source is located in the far field and is incident on the antenna array from a two-dimensional plane with an angle θ ∈ [0, 2π]. Let the signal wavelength be λ, the center frequency be fc, and its envelope be A(t), that is, the signal can be expressed as:

[0022] Since the incident signal is a plane wave, the different positions of the antenna array elements will result in different arrival times. Under ideal narrowband conditions, we can model the signal received by each antenna n as follows:

[0023] in: Let n be the spatial coordinates of antenna n; : is the unit direction vector corresponding to the azimuth angle; : Local white Gaussian noise superimposed on the received signal; : Represents the spatial phase delay of the array element caused by the incident direction.

[0024] S2 employs a dual-channel switching receiver strategy to construct a reference-target interferometric pair. To ensure consistently high directional resolution under different incoming wave directions, the system is based on a nine-element uniform circular array structure, combined with a dynamic channel switching mechanism, prioritizing the interferometric pair with the longest geometric baseline for phase observation, thereby enhancing the sensitivity of the interferometric phase to changes in the incoming wave angle. Figure 3 As shown in the figure, the interference pairs (such as antennas 1–5, 1–6, 4–8, 4–9, 7–2, and 7–3) are typical long baselines with a span, covering the main diagonal direction of the array structure. They have the maximum spatial projection length and stronger resolution for small angular changes. Table 2 lists the lengths and included angles of these baselines. These baseline lengths are close to the maximum possible aperture of the array, thus providing higher spatial resolution in direction estimation.

[0025]

[0026] Table 2 In addition, to avoid phase ambiguity and multi-value estimation problems that occur at high frequencies, the system introduces a multi-baseline auxiliary strategy: after observing the main baseline (such as 1–5), several medium and short baselines (such as 1–2, 1–3, etc.) are further collected to form spatial diversity. These baselines have different projection distributions in different directions, which can be used to construct angle uniqueness conditions, thereby effectively suppressing ambiguity and fuzziness.

[0027] S3, perform dual-channel time-division sampling to acquire the observed interference phase difference. Using the relative phase difference between the received signals from the antennas, antenna n (1, 4, 7) is selected as the reference element, and the other antennas m (2, 3, 5, 6, 8, 9) form the interference baseline with it. The interference phase difference between antenna n and antenna m is:

[0028] Organizing all the interference phase differences between antenna m and antenna 1 into a vector form is called the interference phase vector:

[0029] Let the position difference matrix in the above formula be D∈R6×2, that is:

[0030] The interference phase vector can be further simplified as follows:

[0031] S4. Time compensation is performed on the observed phase data. The signals from each antenna are not sampled at the same time point, especially the elements in the multiplexed channel, whose sampling time has a delay difference relative to the reference channel. Therefore, directly using the original phase data will lead to phase mismatch and direction-finding errors. To eliminate this effect, time compensation processing is required for the observed phase of each non-reference antenna. Specifically, let the sampling time of the nth antenna be tn, and the sampling time of the reference channel be tm. Then, its original observed phase ϕn(tn) should be converted into the equivalent phase value at the reference time, which is achieved through a linear compensation formula.

[0032] Here, Δω represents the instantaneous frequency of the signal, which can be estimated using methods such as the Hilbert transform or the short-time Fourier transform (STFT). This compensation process effectively aligns the phase values ​​sampled at different times, ensuring that the interference phase difference after multi-channel stitching has a consistent reference plane, thereby guaranteeing the accuracy of subsequent direction estimation algorithms.

[0033] S5. Substitute the observed phase data into the angle estimation model and use the least squares method to obtain the target azimuth angle. Given the array structure (i.e., D is known) and the signal frequency (i.e., λ is known), the phase difference between the antennas is measured. We can construct an estimation problem for the direction vector u(θ), and then deduce θ.

[0034] We want to estimate θ such that As close as possible Minimize the sum of squared errors:

[0035] make ,because It can be rewritten as

[0036] This is a standard linear least squares problem. The solution is:

[0037] After obtaining the estimated vector, the recovered direction angle is: .

[0038] The above description is merely a preferred embodiment of the present invention, but the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the principles and spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for omnidirectional signal direction finding based on a uniform nine-element circular array, characterized in that, The method includes: S1, construct a uniform nine-element circular array structure; S2, a dual-channel switching reception strategy is used to construct a reference-target interference pair; S3, perform dual-channel time-division sampling to obtain the observed values ​​of the interferometric phase difference; S4, Time compensation for observed phase data; S5. Substitute the observed phase data into the angle estimation model and use the least squares method to obtain the target azimuth.

2. The omnidirectional signal direction finding method based on a uniform nine-element circular array according to claim 1, characterized in that, The step S1 of constructing a uniform circular array structure specifically includes the following steps: S11, the antenna array is arranged in a perfect circle, with a total aperture of 2R and a corresponding circular array radius of R; S12 consists of nine array elements evenly spaced along a circle. They are numbered clockwise from the bottom of the array, labeled as Antenna 1 to Antenna 9. The angular position (polar angle) of each element on the circle can be represented as: ； Where n is the array element number, and the corresponding angle range is... (Due south) to The angle between any two adjacent array elements is 40°. The position coordinates of each array element in the two-dimensional Cartesian coordinate system are determined by its polar angle and radius, specifically expressed as follows: .

3. The omnidirectional signal direction finding method based on a uniform nine-element circular array according to claim 1, characterized in that, Step S2, which employs a dual-channel switching reception strategy, specifically includes the following steps: S21, assign antennas 1, 4, and 7 to channel Ch1 and connect them to the first switching switch as a reference antenna group; S22, assign antennas 2, 3, 5, 6, 8, and 9 to channel Ch2 and connect them to the second switching switch as the target antenna group; S23, through channel control strategy, dynamically constructs reference-target interferometric pairs, and in each round of measurement, prioritizes the target antenna that forms the longest geometric baseline with the reference antenna; at the same time, it supplements the acquisition of several medium and short baseline combinations.

4. The omnidirectional signal direction finding method based on a uniform nine-element circular array according to claim 1, characterized in that, Step S3, which involves obtaining the interferometric phase difference observation value using time-division sampling, specifically includes: Antennas n and m are selected; the interference phase difference between antenna n and antenna m is: ； The interference phase vector can be expressed as: 。 5. The omnidirectional signal direction finding method based on a uniform nine-element circular array according to claim 1, characterized in that, Step S4, which performs time compensation on the observed phase data, specifically includes the following steps: Let the sampling time of the nth antenna be tn, and the sampling time of the reference channel be tm. Then, its original observed phase ϕn(tn) should be converted into the equivalent phase value at the reference time, which can be achieved through the linear compensation formula: 。 6. The omnidirectional signal direction finding method based on a uniform nine-element circular array according to claim 1, characterized in that, Step S5, which involves substituting the observed phase data into the angle estimation model and using the least squares method to obtain the target azimuth angle, specifically includes the following steps: Estimate θ so that As close as possible Minimize the sum of squared errors: ； make ,because It can be rewritten as ； This is a standard linear least squares problem. The solution is: ； After obtaining the estimated vector, the recovered direction angle is: 。

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