Separable two-dimensional non-uniformly arranged wide bandwidth angular scanning array antenna design method

Abstract

The application provides a separable two-dimensional non-uniform layout broadband wide-angle scanning array antenna design method and belongs to the technical field of antennas. The method comprises the following steps: converting the broadband wide-angle scanning beam synthesis problem into the synthesis of the broadside pattern at a single design frequency by using the concept of "design frequency". The non-uniform layout of the high-gain beam at the design frequency point is obtained by position perturbation. The optimized non-uniform linear array is copied along the horizontal direction at equal intervals to obtain the array with separable two-dimensional non-uniform layout. The same height of several units in the horizontal direction can be regarded as a subarray, and the accurate shaped beam synthesis of the subarray is considered by taking the directional pattern of the active unit into account, so that the requirement of the azimuth dimension wide beam is realized. The array layout structure provided by the application is simple, the array channel is less, and the system cost is low.

Description

Technical Field

[0001] This invention relates to the field of array antenna technology, and specifically to a design method for a separable two-dimensional non-uniform layout wide bandwidth angle scanning array antenna. Background Technology

[0002] Wideband antennas play a crucial role in wireless communication, radar detection, and navigation. In practical applications, antennas often need to achieve beam scanning over a wide angle range in the elevation plane, while simultaneously achieving the required gain coverage within a wide beam in the azimuth plane during scanning. However, there is an inherent contradiction between wideband high-gain performance and wide beam scanning. On the one hand, beamwidth is related to the antenna's operating frequency; for example, the beamwidth at low frequencies is wider than the beamwidth at high frequencies in the elevation and azimuth planes. On the other hand, beamwidth is related to the scanning angle; at the same operating frequency, the beamwidth increases with the scanning angle. As the beam widens, the gain decreases to some extent. Therefore, achieving high-gain coverage within a wide beam in the azimuth plane during wideband wide-angle scanning presents a significant challenge.

[0003] As is well known, when designing broadband arrays using traditional uniform spacing, small element spacing makes it difficult to achieve broadband element antenna structure design and easily leads to strong mutual coupling at low-frequency operating points; while large element spacing easily causes grating lobe problems during beam scanning at high-frequency points. The presence of grating lobes disperses radiated energy to a certain extent, thereby reducing the gain of the main lobe.

[0004] To suppress grating lobes, Chinese patent CN201611199282.8 discloses a method for designing an ultra-wideband grating-lobe-free sparse linear array with controllable minimum spacing. This patent uses the level value of the grating lobe / sidelobe region within a wide bandwidth as the optimization target, and minimizes the peak level of the grating sidelobes to the greatest extent through non-uniform array arrangement. However, this patent does not address the scanning beamwidth and gain performance. Although the optimized array has a low grating sidelobe level, it suffers from the problem of insufficient beamwidth for high-gain coverage. Chinese patent CN00812635.6 discloses another sparse array antenna. This antenna no longer requires a non-uniform layout, but instead uses a triangular grating array technique, overcoming the problem of grating lobes appearing during scanning. Furthermore, if the azimuth beamwidth of the array beam with the triangular grating layout does not meet the requirements, azimuth beamforming can be performed using potential array elements to broaden the beam. However, this method requires a large number of array channels. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a design method for a separable two-dimensional non-uniform layout wideband wide-angle scanning array antenna. The antenna designed using this method employs a non-uniform layout based on positional perturbation in the vertical direction to enhance gain over a wide bandwidth and large scanning angle; it also features a uniform array in the horizontal direction with amplitude and phase optimization to broaden the azimuth beam, ultimately generating a high-gain wideband beam with a large scanning azimuth dimension required for practical applications. This method results in a simple layout structure, fewer array channels, and low system cost.

[0006] The technical solution adopted in this invention is as follows:

[0007] A design method for a separable two-dimensional non-uniform layout wide bandwidth scanning array antenna includes the following steps:

[0008] Step 1: Transform the wide-bandwidth, wide-angle scanning beam synthesis problem into side-fire pattern synthesis at a single design frequency;

[0009] Step 2: Optimize the gain at the design frequency point through position perturbation, thereby enhancing the scan angle gain within the operating frequency band;

[0010] Step 3: Copy the optimized non-uniform linear array at equal intervals along the horizontal direction to obtain a separable two-dimensional non-uniform array; wherein, the elements at the same height in the horizontal direction are regarded as a subarray; perform precise beamforming synthesis on the subarray considering the radiation pattern of the active elements to achieve the requirement of azimuth-dimensional wide beam.

[0011] Furthermore, the specific method for step 1 is as follows:

[0012] The problem of wide-bandwidth angle-scanning beam synthesis is transformed into a single design frequency. The following is a comprehensive side-projection pattern; among which, The highest frequency in the antenna's operating band With the lowest frequency The ratio; This is the beam scanning range ratio, used to measure the increase in the visible space after beam scanning. It is the maximum scanning angle deviating from the normal; the side-fire pattern at the design frequency contains all the information of all scanning beams across the entire frequency range.

[0013] Furthermore, in step 2, optimizing the gain at the design frequency is equivalent to optimizing the array directivity coefficient without considering the array's radiation efficiency. The maximum directivity coefficient at the design frequency after position perturbation is:

[0014] (1)

[0015] in, Indicates the beam at the designed frequency; This is the array pattern after position perturbation, where θ is the scan angle. N is the number of array elements; This is the array pattern before the perturbation. This represents the position of the array element on the z-axis before the perturbation. This represents the position perturbation of the nth array element.

[0016] Furthermore, the optimization problem for optimizing the gain at the design frequency in step 2 can be expressed as:

[0017] (2)

[0018] in, The magnitude of the positional perturbation is determined. It is the minimum element spacing allowed by the array. It is the maximum aperture allowed by the array. It is the peak level of the given sidelobe region;

[0019] The problem in equation (2) is solved by iterative optimization using a sequential quadratic programming method, and finally a high-gain sparse linear array layout is obtained.

[0020] Furthermore, in step 3, the subarray undergoes precise beamforming synthesis considering the active element radiation patterns, which can be described as follows:

[0021] (3)

[0022] The optimization objective is to maximize the minimum directivity coefficient within the horizontal beamwidth range, and the calculation of the directivity coefficient includes the radiation pattern information of the active elements; the constraint condition is to constrain the excitation amplitude.

[0023] The problem in equation (3) is solved by iterative optimization using a sequential quadratic programming method.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention enables the design of a separable two-dimensional non-uniform layout wide-bandwidth angle scanning array antenna. The so-called separable two-dimensional non-uniform layout means that each column is a non-uniform linear array, while each row is a uniformly spaced linear array. The array element layout in each column is obtained by maximizing the array gain, and each element in each row can be used as a subarray for beamforming, thereby obtaining the high-gain wide beam in the azimuth dimension required for practical applications. This layout requires the same number of array channels as a non-uniform linear array, saving system costs.

[0026] 2. In the layout and design of the wide-bandwidth, wide-angle scanning array, this invention employs a non-uniform layout in the vertical direction with the optimization objective of enhancing the gain of the wide-bandwidth, large-scan-angle array. After replicating this non-uniform linear array at equal intervals along the horizontal direction to obtain a separable two-dimensional non-uniform array, precise beamforming synthesis is performed on a subarray composed of several elements at the same height in the horizontal direction. This achieves the requirement of high gain and wide beamwidth in the azimuth dimension, and allows for control of the excitation dynamic range. The array layout proposed in this invention has a simple structure, fewer feeding channels, and low system cost. Attached Figure Description

[0027] Figure 1 This is a flowchart of the present invention.

[0028] Figure 2 This is a diagram showing the element positions of the optimized non-uniform array.

[0029] Figure 3(a) shows the maximum scanning beam of the high-frequency elevation plane when the array is uniformly arranged with the minimum allowable spacing.

[0030] Figure 3(b) shows the maximum scanning beam of the high-frequency elevation plane when the array is optimized for non-uniform configuration.

[0031] Figure 4 It is a separable two-dimensional non-uniform array layout.

[0032] Figure 5(a) shows the elevation plane array pattern of the separable two-dimensional non-uniform array pointing to the maximum scanning angle at a frequency of 1602MHz.

[0033] Figure 5(b) shows the azimuth array pattern of the separable two-dimensional non-uniform array pointing to the maximum scanning angle at a frequency of 1602MHz.

[0034] Figure 6(a) shows the elevation plane array pattern of the separable two-dimensional non-uniform array pointing to the maximum scanning angle at a frequency of 1227MHz.

[0035] Figure 6(b) shows the azimuth array pattern of the separable two-dimensional non-uniform array pointing to the maximum scanning angle at a frequency of 1227MHz. Detailed Implementation

[0036] The technical solution of the present invention will be further explained below with reference to specific embodiments and accompanying drawings, but the embodiments are not intended to limit the present invention.

[0037] A design method for a separable two-dimensional non-uniform layout wide-bandwidth angle-scanning array antenna is proposed. The basic idea is as follows: First, the non-uniform array problem of wide-bandwidth angle-scanning is transformed into an array layout problem based on a single design frequency by introducing the concept of a "design frequency." Second, the gain at the design frequency is optimized through multi-step position perturbation, while constraints are imposed on the minimum element spacing, array aperture, and sidelobe level during the optimization process. Finally, the optimized non-uniform linear array is replicated at equal intervals in the horizontal direction to obtain a separable two-dimensional non-uniform layout array. Amplitude and phase optimization is then performed on subarrays composed of elements at the same height in the vertical direction to achieve the requirement of a wide azimuth beam. During the subarray optimization process, the excitation dynamic range ratio can be controlled.

[0038] Specifically, the following steps are included:

[0039] Step 1: Transform the wideband wide-angle scanning beam synthesis problem into side-fire pattern synthesis at a single design frequency using the concept of "design frequency". Design Frequency ,in, The highest frequency in the antenna's operating band With the lowest frequency The ratio; This is the beam scanning range ratio, used to measure the increase in the visible space after beam scanning. It is the maximum scan angle deviating from the normal. The side-fire pattern at the design frequency contains all the information of all scanned beams across the entire frequency range. In essence, beam scanning can be seen as another way to increase bandwidth.

[0040] Step 2: Obtain the non-uniform layout of high-gain beams at the design frequency by position perturbation.

[0041] Step 2-1: Perform position perturbation on an N-element linear array placed along the z-axis. Without considering the radiation characteristics of the elements, the side-emitting radiation pattern at the design frequency is expressed as follows:

[0042] (1)

[0043] in, Indicates the beam at the design frequency. The positions of the array elements before the perturbation. Let n represent the position perturbation of the nth array element. A first-order Taylor approximation is used. , Expanding the above equation, we get

[0044] (2)

[0045] in, Array pattern before perturbation

[0046] Step 2-2: When the radiation efficiency of the array is not considered, optimizing the array gain is equivalent to optimizing the array directivity coefficient. The maximum directivity coefficient at the design frequency after position perturbation can be expressed as...

[0047] (3)

[0048] Therefore, the gain optimization problem at the design frequency can be expressed as:

[0049] (4)

[0050] in, The magnitude of the positional perturbation is determined. It is the minimum element spacing allowed by the array. It is the maximum aperture allowed by the array. This is the peak level of the given sidelobe region. This synthesis problem can be solved through multiple iterations of Sequential Quadratic Programming (SQP) to ultimately obtain a high-gain sparse linear array layout.

[0051] Step 3: The optimized non-uniform linear array is replicated at equal intervals along the horizontal direction to obtain a separable two-dimensional non-uniform array. Several elements at the same height in the horizontal direction can be regarded as a subarray, and the subarray is subjected to precise shaped beamforming synthesis considering the radiation pattern of the active elements, thereby achieving the requirement of azimuth-wide beam. Considering the design of the feed network and radiation efficiency, certain constraints are imposed on the dynamic range ratio of the excitation amplitude during the synthesis process. The shaped synthesis problem can be expressed as:

[0052] (5)

[0053] The optimization objective is to maximize the minimum directivity coefficient within a certain beamwidth range in the horizontal dimension, and the calculation of the directivity coefficient includes the radiation pattern information of the active elements; the constraint condition is to constrain the excitation amplitude. This synthesis problem can also be solved by multiple iterations using the SQP method.

[0054] Here is a more specific example:

[0055] Design objective: To design a separable two-dimensional non-uniform array antenna that can operate in the 1100MHz to 1700MHz frequency band, with 16*4=64 elements, a minimum element spacing of 0.1m, and a maximum aperture of 2m. Its radiation pattern achieves a beam scanning range of ±50° in the elevation plane and a gain coverage of 10dBi with a bandwidth of 120° in the azimuth plane, with a sidelobe level below -10dB.

[0056] like Figure 1 As shown, proceed with the following steps:

[0057] Step 1: Transform the wide-bandwidth scanning beam synthesis problem into a side-fire pattern synthesis problem at a single design frequency.

[0058] Consider an N=16 element linear array placed on the z-axis, with the array operating in the frequency range of... ~ That is, the ratio of the highest frequency to the lowest frequency is Because the beam's scanning angle range in the elevation plane is... ,in That is the maximum scanning angle. At this time, the scanning range is greater than... For wideband scanning antennas, the optimization process needs to consider the beam characteristics at different frequencies and scanning angles, which significantly increases the time and memory costs. To reduce optimization time and memory costs, the concept of design frequency can be applied. The array optimization problem of wide bandwidth angle scanning is transformed into a single design frequency. The side-projection pattern is optimized. Based on the bandwidth and beam scanning range in this embodiment, the design frequency is... 2829MHz.

[0059] Step 2: Obtain the non-uniform layout of the high-gain beam at the design frequency through position perturbation. First, perform an initial array layout, such as a uniform array based on half the wavelength of the intermediate frequency. When the radiation characteristics of the elements are not considered, the side-emitting radiation pattern at the design frequency can be represented as...

[0060] (6)

[0061] in, This indicates the beam at the designed frequency.

[0062] To enhance the array gain while reducing the peak level of the grating sidelobes, a non-uniform array arrangement is achieved through multi-step position perturbation. The array pattern after position perturbation is expressed as follows:

[0063] (7)

[0064] in Let n represent the position perturbation of the nth array element. A first-order Taylor approximation is used. , Expanding the above equation, we get

[0065] (8)

[0066] When the radiation efficiency of the array is not considered, optimizing the array gain is equivalent to optimizing the array directivity. The maximum directivity at the design frequency after position perturbation can be expressed as:

[0067] (9)

[0068] Therefore, the gain optimization problem at the design frequency can be expressed as:

[0069] (10)

[0070] in, The magnitude of the positional perturbation is determined. It is the minimum element spacing allowed by the array. It is the maximum aperture allowed by the array. This is the peak level of the given sidelobe region. In this example... for This comprehensive problem can be optimized through multiple iterations using Sequential Quadratic Programming (SQP) to ultimately obtain a high-gain sparse linear array layout. Figure 2 The optimized non-uniform layout is presented, with a minimum spacing of 0.1m and an array aperture of 1.9m, both satisfying the given parameter values. Figure 3(a) shows the array pattern at a large scan angle at a high frequency of 1700MHz with uniform array spacing at the allowed minimum. As shown in the figure, grating lobes appear, and the directivity coefficient is 11.12 dBi. For comparison, Figure 3(b) shows the array pattern at a large scan angle at a high frequency of 1700MHz with optimized non-uniform spacing. This layout overcomes the appearance of grating lobes, and the maximum sidelobe level drops to a preset -10.5dB, with a directivity coefficient of 12.36dBi.

[0071] Step 3: Copy the optimized non-uniform linear array at equal intervals along the horizontal direction 4 columns to obtain a separable two-dimensional non-uniform layout array, such as... Figure 4 As shown, the array is placed in the yoz plane, with its length aligned along the z-axis and its width aligned along the y-axis. Several elements at the same height in the width dimension can be considered as a subarray. Precise beamforming synthesis considering the radiation patterns of the active elements is performed on the subarrays to achieve the requirement of a wide beam in the azimuth dimension. Due to considerations of feed network design and radiation efficiency, certain constraints are imposed on the dynamic range ratio of the excitation amplitude during the synthesis process. The beamforming synthesis problem can be expressed as:

[0072] (11)

[0073] The optimization objective is to maximize the minimum directivity coefficient within a certain beamwidth range in the horizontal dimension; the constraint is to constrain the excitation amplitude. This comprehensive problem can also be solved through multiple iterative optimizations using the SQP method. In this example, the excitation amplitude range ratio is set to DRR=I. max / I min =10. In the shaping optimization process of this embodiment, the array unit used is a commonly used right-hand circularly polarized unit, whose normal 3dB beamwidth is approximately 85° to 110°.

[0074] This embodiment presents the array beam patterns at typical high and low frequency points of 1227MHz and 1602MHz in navigation applications. Figures 5(a) and (b) show the elevation and azimuth beam patterns of the two-dimensional separable non-uniform array at 1227MHz when scanning to the maximum scan angle of 50°. It can be seen that the maximum elevation gain is 13.9 dB, the sidelobe level is -12.2 dB, and the beamwidth with a horizontal gain greater than 10 dB is 128.5°. Figures 6(a) and (b) show the elevation and azimuth beam patterns of the array at 1602MHz when scanning to the maximum scan angle of 50°. It can be seen that the maximum elevation gain is 12.7 dB, the sidelobe level is -10.4 dB, and the beamwidth with a horizontal gain greater than 10 dB is 121.5°.

[0075] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A design method for a separable two-dimensional non-uniform layout wide bandwidth angle scanning array antenna, characterized in that, Includes the following steps: Step 1: Transform the wide-bandwidth, wide-angle scanning beam synthesis problem into side-fire pattern synthesis at a single design frequency; the specific method is as follows: The problem of wide-bandwidth angle-scanning beam synthesis is transformed into a single design frequency. The following is a comprehensive side-projection pattern; among which, The highest frequency in the antenna's operating band With the lowest frequency The ratio; This is the beam scanning range ratio, used to measure the increase in the visible space after beam scanning. It is the maximum scanning angle deviating from the normal; the side-fire pattern at the design frequency contains all the information of all scanning beams across the entire frequency range; Step 2: Optimize the gain at the design frequency point through position perturbation, thereby enhancing the scan angle gain within the operating frequency band; Step 3: Copy the optimized non-uniform linear array at equal intervals along the horizontal direction to obtain a separable two-dimensional non-uniform array; wherein, the elements at the same height in the horizontal direction are regarded as a subarray; perform precise beamforming synthesis on the subarray considering the radiation pattern of the active elements to achieve the requirement of azimuth-dimensional wide beam.

2. The design method for a separable two-dimensional non-uniform layout wide bandwidth scanning array antenna according to claim 1, characterized in that, In step 2, optimizing the gain at the design frequency is equivalent to optimizing the array directivity coefficient without considering the array's radiation efficiency. The maximum directivity coefficient at the design frequency after position perturbation is: (1) in, Indicates the beam at the designed frequency; This is the array pattern after position perturbation, where θ is the scan angle. N is the number of array elements; This is the array pattern before the perturbation. The position of the array element on the z-axis before the perturbation. This represents the position perturbation of the nth array element.

3. The design method for a separable two-dimensional non-uniform layout wide bandwidth scanning array antenna according to claim 2, characterized in that, The optimization problem for optimizing the gain at the design frequency in step 2 is expressed as: (2) in, The magnitude of the positional perturbation is determined. It is the minimum element spacing allowed by the array. It is the maximum aperture allowed by the array. It is the peak level of the given sidelobe region; The problem in equation (2) is solved by iterative optimization using a sequential quadratic programming method, and finally a high-gain sparse linear array layout is obtained.

4. The design method for a separable two-dimensional non-uniform layout wide bandwidth angle scanning array antenna according to claim 3, characterized in that, In step 3, the subarray undergoes precise shaped beamforming synthesis considering the active element radiation patterns, which is described as follows: (3) The optimization objective is to maximize the minimum directivity coefficient within the horizontal beamwidth range, and the calculation of the directivity coefficient includes the radiation pattern information of the active elements; the constraint condition is to constrain the excitation amplitude. Indicates the incentive level. , Indicates the maximum and minimum values ​​of the incentive amplitude; The problem in equation (3) is solved by iterative optimization using a sequential quadratic programming method.

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