A phase open-loop hierarchical phase-shift beamforming method

Abstract

This invention discloses a phase-open-loop hierarchical phase-shifting beamforming method, comprising the following steps: Step 1: uniformly dividing the array beam scanning space into N Scan Step 1: Inject random phase weights into the first phase shifter at the first stage; Step 2: Scan angle θ i Step 4: Apply a scanning phase to the first-stage phase shifter and calculate the phase shift of the first-stage phase shifter; Step 5: Calculate the phase shift of the second to Nth-stage phase shifters using a penetration beamforming algorithm; Step 6: Correct the median shift of the phase shift of each stage phase shifter; Step 7: Repeat steps 3 to 5 until all scanning angles are traversed, and record the maximum grid lobe sidelobe level within all scanning angles as L. l Step 7: Repeat steps 2 through 6 until the maximum number of iterations is reached; Step 8: L l The minimum is L best The corresponding iteration uses the optimal beam phase weight for the full-scan spatial domain. This invention can effectively reduce the grating lobe sidelobe level, is simple to implement, and is suitable for low-cost antenna arrays.

Description

Technical Field

[0001] This invention relates to the field of antenna and microwave technology, and specifically to a phase open-loop hierarchical phase-shifting beamforming method. Background Technology

[0002] Phased array antenna technology plays a crucial role in both military missions such as early warning and detection, space surveillance, and battlefield reconnaissance, and civilian applications such as 5G communication, air traffic control, and collision avoidance radar. With increasing demands for radar power, measurement accuracy, and communication quality, radar antenna arrays are becoming larger, leading to a rise in the manufacturing cost of phased array antennas. Active channels constitute the largest cost component in phased array antenna manufacturing; reducing the number of active channels is the most direct and effective way to lower manufacturing costs. Subarray technology effectively reduces the number of active channels but introduces grating lobes, reducing antenna gain. To address the grating lobe problem introduced by subarray technology, subarray rotation technology, subarray translation technology, irregular subarray technology, and hierarchical phase shifting technology have received widespread attention. Hierarchical phase shifting is a technique that employs multiple stages of phase shifters. In phased array antennas using this technique, each subarray uses a single active channel only at the stage of phase shifters furthest from the radiating element; active channels are not used at other stages of phase shifters. Therefore, this technique reduces the number of active channels. Compared to other subarray techniques, hierarchical phase shifting offers higher beam control freedom, higher beam pointing accuracy, and better bandwidth adaptability, making it suitable for systems with high requirements for beam pointing and bandwidth.

[0003] While higher order and bit depth in a phased-array antenna array generally result in better beamforming performance, they also increase control complexity and losses. Therefore, to meet beamforming performance requirements, the order and bit depth of the phased-array antenna array need to be as low as possible. Existing phased-array beamforming methods, at low order and bit depths, offer limited suppression of beam grating lobes, especially during beam scanning, where significant grating lobes can still be observed at certain scanning angles. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a phase-open-loop hierarchical phase-shifting beamforming method. The antenna array used consists of M subarrays, where M is a positive integer greater than or equal to 2. Each subarray contains... There are one phase shifter, and the number of bits in each phase shifter is as follows:

[0005] Bit1, Bit2, ..., Bit m ,…,Bit M The minimum step sizes are Step1, Step2, ..., Step m Step M M is a positive integer greater than or equal to 2, and includes the following steps:

[0006] Step 1: Divide the array beam scanning space into N uniformly Scan An angle, denoted as θ i (i = 1, 2, ..., N) Scan );

[0007] Step 2: At level 1 Each phase shifter is injected with random phase weights, denoted as...

[0008] Where l is the current iteration number, and Max is the maximum number of iterations for optimization;

[0009] Step 3: The scanning angle is θ i At that time, a scanning phase is added to the first-stage phase shifter, and the first-stage phase is calculated. Phase shift amount of each phase shifter;

[0010] Step 4: Calculate the phase shift of the 2nd to Nth stage phase shifters using the penetration beamforming algorithm;

[0011] Step 5: Correct the midpoint of the phase shift in each stage of the phase shifter;

[0012] Step 6: Repeat steps 3 to 5 until all scan angles have been traversed, and record the maximum grid lobe sidelobe level within all scan angles as L. l ;

[0013] Step 7: Repeat steps 2 through 6 until the maximum number of iterations is reached;

[0014] Step 8: L l The minimum is L best The corresponding iteration uses the phase weight. This is the optimal beam phase weight for the full-scan spatial domain.

[0015] Furthermore, in step 3, the first level of the first... The formula for calculating the phase shift of a phase shifter is:

[0016]

[0017] in, is the spacing of the first-stage phase shifter, and k is the free space wavenumber.

[0018] Furthermore, the formula for calculating the phase shift of the 2nd to Nth stage phase shifters in step 4 is as follows:

[0019]

[0020] in, The spacing of the m-th stage phase shifter is... Let m be the phase shift amount of the (m-1)th stage phase shifter; m = 2, 3, ..., M.

[0021] Furthermore, for all phase shifters except the first-stage phase shifter, the phase shift is open-loop, i.e. Among them, Step m And Bit m These are the minimum step size and the number of bits for the m-th stage phase shifter, respectively.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. An open-loop hierarchical phase-shifting technique is adopted to reduce the grid lobe level and link loss in the scanning spatial domain.

[0024] 2. The injection permeation beam optimization technique is adopted to further reduce the level of the grating lobe sidelobe.

[0025] 3. The overall optimization technique is adopted, which is simple to implement. Only one set of phase weights is used in the entire scanning space. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a hierarchical phase-shifting array according to an embodiment of the present invention.

[0027] Figure 2 This is a flowchart of a beamforming method according to an embodiment of the present invention.

[0028] Figure 3 This is a comparison diagram of the grating lobe and sidelobe levels in an embodiment of the present invention.

[0029] Figure 4 This is a comparison diagram of the radiation patterns of an embodiment of the present invention. Detailed Implementation

[0030] The following describes in detail, with reference to the accompanying drawings, a specific embodiment of the phase open-loop hierarchical phase-shifting beamforming method of the present invention.

[0031] The antenna array of this invention is composed of multiple array elements, which can be arbitrarily arranged in a horizontal plane, not limited to a uniform linear array or a uniform circular array; and each array element has its own radiation pattern, which can be the same or different, and can be a directional antenna or an omnidirectional antenna. The antenna array used in this embodiment consists of M levels of subarrays, where M is a positive integer greater than or equal to 2, and each level of subarray contains... There are several phase shifters, with each phase shifter having bits 1, 2, ..., 3. m ,…,Bit M The minimum step sizes are Step1, Step2, ..., Step m Step MM is a positive integer greater than or equal to 2; for example Figure 2 As shown, the method includes the following steps:

[0032] Step 1: Divide the array beam scanning space into N uniformly Scan An angle, denoted as θ i (i = 1, 2, ..., N) Scan );

[0033] Step 2: At level 1 Each phase shifter is injected with random phase weights, denoted as... Where l is the current iteration number, and Max is the maximum number of iterations for optimization;

[0034] Step 3: The scanning angle is θ i When a scanning phase is applied to the first-stage phase shifter, the first-stage phase shifter... The phase shift of each phase shifter is in, , where is the spacing between the first-stage phase shifters, and k is the free-space wavenumber;

[0035] Step 4: Using the penetration beamforming algorithm, calculate the phase shift of the 2nd to Nth stage phase shifters, and the phase shift of the mth stage phase shifter is... in, The spacing of the m-th stage phase shifter is... Let m be the phase shift amount of the (m-1)th stage phase shifter; m = 2, 3, ..., M.

[0036] Step 5: Correct the median shift of the phase shift in each stage of the phase shifter. After correction, the final phase shift of the first-stage phase shifter is: Except for the first-stage phase shifter, the final phase shift of the m-th stage phase shifter is: Where median is the median operator;

[0037] Step 6: Repeat steps 3 to 5 until all scan angles have been traversed, and record the maximum grid lobe sidelobe level within all scan angles as L. l ;

[0038] Step 7: Repeat steps 2 through 6 until the maximum number of iterations is reached;

[0039] Step 8: L l The minimum is L best The corresponding iteration uses the phase weight. This is the optimal beam phase weight for the full-scan spatial domain.

[0040] The beamforming method employs open-loop hierarchical phase shifting technology, where the phase shift of each stage of phase shifter, except for the first-stage phase shifter, is open-loop. Among them, Step m And Bitm These represent the minimum step size and number of bits for the m-th stage phase shifter, respectively. This technique can reduce the grid lobe level and link loss in the scanned spatial domain.

[0041] The beamforming method employs injection-penetration beam optimization technology, injecting optimized phase weights into the first-stage phase shifter. For phase shifters other than the first stage, the phase shift amount is set according to the remaining phase penetrating from the previous stage phase shifter. This technology can further reduce the grating lobe sidelobe level.

[0042] The beamforming method employs an overall optimization technique, which is simple to implement. Only one set of optimized phase weights is used throughout the entire scanning airspace.

[0043] During the implementation of this embodiment, as follows Figure 1 As shown, a one-dimensional uniform linear array of 128 elements is used to scan the spatial domain from 0° to 45°, which is uniformly divided into 46 angles, i.e., θ. i (i = 1, 2, ..., 46); the maximum number of iterations to optimize is...

[0044] 1001 times. The element spacing d = 0.58 wavelengths, employing a two-stage phase shifter: the first-stage phase shifter uses a 6-phase shifter with a step size of 5.625°; the second-stage phase shifter uses a 2-phase shifter with a step size of 50°. One first-stage phase shifter connects to two second-stage phase shifters, with a one-to-one correspondence between the second-stage phase shifters and antenna elements, resulting in a total of 128 second-stage phase shifters and 64 first-stage phase shifters. Therefore, the spacing between the second-stage phase shifters is 0.58 wavelengths, and the total spacing between the second-stage phase shifters is 1.16 wavelengths. In this embodiment, through hierarchical phase shifting technology, the number of active channels is 64, and the ratio of active channels to antenna elements is 1:2, reducing the number of active channels by 50%.

[0045] In the actual implementation of this embodiment, the phase shifters other than the first-stage phase shifter, i.e., the second-stage phase shifter, have an open-loop phase shift, i.e., 50° < 360° / 2. 2 =90°, this technique can reduce grating lobe level and link loss in the scanned spatial domain. For example Figure 3 As shown, in the scanning spatial domain, the conventional closed-loop phase-shifting scheme has a high grating lobe level in some areas. By using open-loop phase-shifting technology, the maximum grating lobe level can be improved from -4.1dB to -6.4dB, effectively suppressing the grating lobe.

[0046] In the actual implementation of this embodiment, optimized phase weights are injected into the first-stage phase shifter. For phase shifters other than the first stage, the phase shift amount is set according to the remaining phase permeated by the upper-stage phase shifter. This technique can further reduce the gate lobe sidelobe level. For example... Figure 4 As shown, after optimization using the injection permeation beam, the grating lobe level decreased from -6.4dB to -25.3dB when scanning at 29°, and the grating lobe was further suppressed.

[0047] In practice, this embodiment is simple to implement; only one set of optimized phase weights is used throughout the entire scanned spatial domain. For example... Figure 3 As shown, the average sidelobe grid voltage is below -20dB throughout the entire scanned spatial domain.

[0048] In summary, the phase open-loop hierarchical phase-shifting beamforming method proposed in this invention can effectively reduce the level of grating lobe sidelobes, is simple to implement, and is suitable for low-cost antenna arrays.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phase-open-loop hierarchical phase-shifting beamforming method, wherein the antenna array used consists of M-level subarrays. For each positive integer greater than or equal to 2, each subarray contains... There are one phase shifter, and the number of bits in each phase shifter is as follows: The minimum step size is respectively , It is a positive integer greater than or equal to 2, characterized in that, The phase shift of all phase shifters except the first-stage phase shifter is open-loop, i.e. ,in, and Let m be the minimum step size and the number of bits for the m-th stage phase shifter, respectively, and include the following steps: Step 1: Divide the array beam scanning space evenly One angle, denoted as ; Step 2: At level 1 Each phase shifter is injected with random phase weights, denoted as... Where l is the current iteration number and Max is the maximum number of iterations for optimization; Step 3: Scan angle is At that time, a scanning phase is added to the first-stage phase shifter, and the first-stage phase is calculated. Phase shift amount of each phase shifter; Step 4: Calculate the first step using a penetration beamforming algorithm. Phase shift amount of the first phase shifter; The formula for calculating the phase shift of a phase shifter is: in, The spacing of the m-th stage phase shifter is... This represents the phase shift amount of the (m-1)th stage phase shifter; ; Step 5: Correct the midpoint of the phase shift in each stage of the phase shifter; Step 6: Repeat steps 3 to 5 until all scan angles have been traversed, and record the maximum grid lobe sidelobe level within each scan angle as . ; Step 7: Repeat steps 2 through 6 until the maximum number of iterations is reached; Step 8: Minimum is L best The corresponding iteration uses the phase weight. This is the optimal beam phase weight for the full-scan spatial domain.

2. The phase open-loop hierarchical phase-shifting beamforming method according to claim 1, characterized in that, Step 3, Level 1 The formula for calculating the phase shift of a phase shifter is: in, denoted as the spacing between the first-stage phase shifters, and k as the free-space wavenumber.

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