Large-spacing thinned array flexible multi-beam reflector antenna

Abstract

The invention provides a large-spacing thinned array flexible multi-beam reflector antenna, which comprises a reflector and a feed source array, the reflector is a standard single-bias parabolic reflector, and the feed source array is composed of a plurality of feed source units which are the same in size and are arranged in a Fibonacci spiral array; and the feed source array is placed at a defocusing plane of a connecting line of the focus of the antenna and the center of the parabolic reflecting surface. According to the reflector antenna, grating lobe suppression of the large-spacing array feed reflector antenna can be realized. And the large spacing is that the spacing of the feed source unit is greater than or equal to 2.6 wavelengths. According to the optimized large-spacing disordered arrangement based on the annular sparse array, the beam gain and the C / I performance can be improved, and meanwhile, the grating lobe interference problem of a high-gain antenna during wide-angle scanning can be solved.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology and relates to spaceborne high-throughput multi-beam antennas, specifically to a flexible multi-beam reflector antenna with a large-spacing sparse array. Background Technology

[0002] Under the requirements of deploying a new generation of global high-orbit satellite internet, future active array multi-beam reflector antennas will inevitably develop towards high-capacity communication and flexible on-orbit applications. To improve communication capacity, it is desirable to use larger aperture reflectors and larger feed arrays to obtain higher gain and higher C / I (carrier-to-interference ratio). However, due to the limitations of satellite size and resources (power consumption, heat dissipation), it is not feasible to blindly install large-aperture reflectors and a large number of feed arrays on the satellite carrier. Therefore, under the constraint of a limited number of feeds, large-pitch feed arrays are particularly important.

[0003] Existing uniform periodic array multi-beam reflector antennas typically use formulas to determine the feed array spacing to avoid grating lobes. Small feed element spacing necessitates a large number of feed arrays to achieve high gain performance, resulting in a large and heavy number of active channels and increased antenna cost. Furthermore, directly implementing a large-spacing periodic array layout inevitably leads to grating lobes. Whether using commonly used triangular or rectangular grating arrangements, grating lobes degrade antenna radiation performance and distort or annihilate the desired received signal. Therefore, uniform periodic array multi-beam reflector antennas cannot meet the needs of future communication satellites. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a flexible multi-beam reflector antenna with a large-pitch sparse array, thereby solving the technical problem that the gain and C / I performance of active multi-beam reflector antennas need to be further improved under the constraints of satellite size and resources (power consumption and heat dissipation).

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A flexible multi-beam reflector antenna with a large-pitch sparse array includes a reflector and a feed array. The reflector is a standard single-bias parabolic reflector, and the feed array consists of multiple feed elements of the same size arranged in a Fibonacci spiral array. The feed array is placed at the defocus plane of the line connecting the focal point of the antenna and the center of the parabolic reflector.

[0007] This reflector antenna can achieve grating lobe suppression for large-pitch array-fed reflector antennas.

[0008] The aforementioned large spacing refers to a feed element spacing of ≥2.6 wavelengths.

[0009] The method for suppressing grating lobes of a large-pitch array-fed reflector antenna is as follows: the initial position coordinates of the feed array are established, and the optimized position coordinates of the feed array are obtained by adopting an optimization strategy of non-periodic sparse array element layout combined with subarray rotation. This forms a large-pitch disordered arrangement of the optimized ring sparse array, thereby achieving grating lobe suppression of the large-pitch array-fed reflector antenna.

[0010] Compared with the prior art, the present invention has the following technical effects.

[0011] (I) The optimized large-spacing disordered arrangement based on the ring sparse array of the present invention can improve beam gain and C / I performance, and at the same time solve the problem of grating lobe interference of high gain antennas during wide-angle scanning.

[0012] (II) This invention achieves grating lobe suppression of large-spacing array feed reflector antennas with a feed element spacing of ≥2.6 wavelengths by adopting an optimization strategy of non-periodic sparse array element layout combined with subarray rotation.

[0013] (III) The antenna of the present invention is based on optical principles and utilizes a reflective surface to further enlarge the aperture of the feed array, thereby obtaining higher gain and a narrower beam. The reflector is a single-biased standard parabolic reflector, which has a simple structure and strong engineering feasibility.

[0014] (IV) This invention can be applied to the wireless communication system of future high-throughput flexible payload satellites. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the antenna structure.

[0016] Figure 2 This is a schematic diagram of the Fibonacci spiral.

[0017] Figure 3 This is a schematic diagram of the polar coordinates of the feed element calculated using a Fibonacci grid.

[0018] Figure 4 This is a schematic diagram of 24 sampling points for two Fibonacci spirals.

[0019] Figure 5 This is a schematic diagram showing the initial position coordinates of the 96 feed arrays.

[0020] Figure 6 A schematic diagram showing the optimized position coordinates of the 96 feed arrays.

[0021] Figure 7(a) is a schematic diagram of the optimized feedforward array scanning up to 10° beam pattern.

[0022] Figure 7(b) is a schematic diagram of the optimized feed array scanning to a 10° beam pattern.

[0023] Figure 8 This is a schematic diagram of the gain contour lines for a flexible multi-beam reflector antenna with a large-spacing sparse array.

[0024] Figure 9 This is a schematic diagram of the C / I contour lines for a flexible multi-beam reflector antenna with a large-spacing sparse array.

[0025] Figure 10 This is a schematic diagram of a 91-element periodic triangular grid array.

[0026] Figure 11 This is a schematic diagram comparing the gain contour lines of a large-spacing sparse array and a periodic triangular grating array feed reflector antenna, respectively.

[0027] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, all components, unit devices, and algorithms in this invention are based on components, unit devices, and algorithms known in the prior art. For example, the feed unit adopts a feed unit known in the art.

[0029] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0030] Example: This embodiment presents a flexible multi-beam reflector antenna with a large-pitch sparse array, such as... Figure 1 As shown, it includes a reflector and a feed array. The reflector is a standard single-bias parabolic reflector. The feed array consists of multiple feed elements of the same size arranged in a Fibonacci spiral array. The feed array is placed at the defocus plane of the line connecting the focal point of the antenna and the center of the parabolic reflector.

[0031] This reflector antenna can achieve grating lobe suppression for large-pitch array-fed reflector antennas.

[0032] Large spacing means the distance between feed elements is ≥2.6 wavelengths.

[0033] In this embodiment, as Figure 1 As shown, the antenna parameters are selected as follows: reflector aperture D r The antenna has a focal length of 3m, a focal length F of 4.5m, and a reflection center offset H of 3.6m. It uses 96 feed elements with an aperture of 2.6 wavelengths (26mm). The antenna operates at 30GHz. The distance between the feed array and the focal point is... It is 1.7m.

[0034] As a specific embodiment, the distance between the feed array and the focal point of the antenna is... The radio frequency signal output from the feed array is reflected by the reflector and outputs as the secondary sub-beam of the antenna. The pattern of the secondary sub-beam is broadened into a gate shape, realizing the form of full-scale feed synthesis of each beam, and the beamforming is digital beamforming.

[0035] As a specific solution in this embodiment, the method for suppressing grating lobes of a large-pitch array-fed reflector antenna is as follows: establish the initial position coordinates of the feed array, and obtain the optimized position coordinates of the feed array by adopting an optimization strategy of non-periodic sparse array element layout combined with subarray rotation, forming a large-pitch disordered arrangement of the optimized ring sparse array, thereby achieving grating lobe suppression of the large-pitch array-fed reflector antenna.

[0036] As a further embodiment, the method for establishing the initial position coordinates of the feed array is as follows: Step 101: Taking the center of the feed array as the origin, the Fibonacci spiral discrete points are discretely selected based on the Fermat spiral. Based on the Fibonacci spiral discrete points, uniform sampling is performed with equal arc lengths, such as... Figure 2 As shown, the calculation of the Fibonacci grid is performed. The polar coordinates of the position of each feed element ( , ),like Figure 3 As shown.

[0037] The Fibonacci grid is as follows: ; In the formula: Indicates the first The polar angle of each feed element, similarly... Represents polar angle variables; Indicates the first The polar radius of the feed element; indicating the first... The distance from the position of each feed unit to the origin; Indicates the number of the feed unit; The Fibonacci angle represents the small angle obtained by dividing a circle according to the golden ratio, approximately 137.507764°. radian; This represents the pitch control factor between adjacent helices; It determines the tightness of the spiral.

[0038] In this embodiment, It is equivalent to a constant term.

[0039] Step 102, the feed unit is numbered as follows , , This indicates the number of feed elements; the polar angle of each feed element is rotated by 1 / φ relative to the previous feed element. 2 The polarity of each feed element is determined according to... Make a selection. The variable range is [1:N].

[0040] Step 103: To increase the feed array density, two spirals with different spacing are used for sampling. At the same time, with a single sampling point as the center, each sampling point is replaced with a group of four subarrays of centrally symmetrical sampling points, forming a total of N / 4 sampling points, and obtaining a total of N / 4*4=N initial position coordinates of the feed array.

[0041] In this specific embodiment, two Fibonacci spirals with different spacing are used to make 24 sampling points. For example... Figure 4 As shown.

[0042] In this specific embodiment, centered on 24 single sampling points, each sampling point is replaced with a subarray (four in a group) of four centrally symmetrical sampling points, forming a feed array with a total of 96 sampling points, resulting in the following... Figure 5 The initial position coordinates of the 96 feed arrays are shown.

[0043] As a further embodiment, the optimization strategy for the non-periodic sparse array element layout combined with subarray rotation is as follows: Step 201: Position the center of the subarray of the feed array. Combining to form optimization variables , Rotate the subarray of the feed array by an angle Combining to form optimization variables , ,Will and Merging to form location optimization variables , .in, This indicates transpose.

[0044] Step 202, Determine the location optimization variables Then, the range of scanning angles of the feed array intercepted by the reflecting surface is defined as [ , Construct the objective function within the scanning angle range of the feed array. Set the gain and low sidelobe requirements for the beam.

[0045] Step 203: Optimize the objective function using a global optimization algorithm. Optimization is performed. If the optimization result of the global optimization algorithm is less than the gain level and sidelobe level thresholds, the optimization ends, and the optimized subarray center position and subarray rotation angle are obtained. The optimized position coordinates of the feed array.

[0046] In this embodiment, the global optimization algorithm used is a global optimization algorithm known in the art.

[0047] In this embodiment, the center positions and rotation angles of the 24 feed array subarrays are used as optimization variables. A global optimization algorithm is employed for optimization. The sidelobe level threshold is ±10° of the scan, and the sidelobe level is less than -18dB within the angular domain range [-20°, 20°]. Optimization ends when the target value is less than the threshold. The optimized position coordinates of the 96 feed arrays are distributed as follows: Figure 6 As shown in Figure 7(a) and Figure 7(b), the radiation patterns of the feed array before and after optimization are shown in Figure 7(a) and Figure 7(b), respectively. After optimization, the sidelobe level is less than -18.5dB.

[0048] As a preferred embodiment, the minimum spacing of the feed elements is... There is no need to meet the requirement of no grating lobes in the coverage area of ​​the antenna synthesized beam:

[0049]

[0050] In the formula: This represents the ratio of the antenna beam gain when the feed array is located at the focal point and when the entire array is pushed forward and backward. Indicates the minimum spacing between feed elements; Indicates the operating wavelength; Indicates the maximum scanning angle of the antenna; This indicates the grating lobe position angle at the antenna's maximum scanning angle; Indicates the focal length of the antenna; This indicates the distance between the center of the feed array and the focal point of the antenna.

[0051] In this embodiment, based on the optimized coordinate position of the ring-shaped sparsely distributed feed array illuminating a 3m aperture reflector, the antenna beam gain is greater than 45dBi within a coverage range of ±1.5°. The gain contour lines are shown in the figure. Figure 8 As shown, under 12-color frequency multiplexing, C / I is greater than 11dB, and the C / I contour lines are as follows. Figure 9As shown, the solid line represents the coverage requirement of 121 beams in the service area, and the dashed line represents the contour lines of antenna beam performance.

[0052] Compared to a 91-element uniform periodic triangular grid array, such as Figure 10 With this antenna configuration, the feed spacing is designed to be 2.2 wavelengths, or 22mm, according to the formula.

[0053] For example, the same gain contour lines of two sets of feed arrays illuminating the reflectors are compared. Figure 11 As shown, the solid line represents the secondary beam of the ring-shaped sparse array reflector antenna, and the dashed line represents the secondary beam of the periodic triangular grating array reflector antenna. The sparse array beam has high gain, strong focusing ability, and fast roll-off.

Claims

1. A large-interval sparse-aperture array flexible multi-beam reflector antenna, characterized in that, The reflector is a standard single-bias parabolic reflector, and the feed array is composed of a plurality of feed units with the same size arranged in a Fibonacci spiral array. The reflector antenna can realize large-interval array feed reflector antenna grating lobe suppression. The large-interval is that the interval between the feed units is greater than or equal to 2.6 wavelengths.

2. The large-interval sparse array flexible multi-beam reflector antenna of claim 1, wherein, The distance between the center of the feed array and the focal point of the antenna is After the radio frequency signal is output from the feed array and reflected by the reflector, the antenna secondary sub-beam is output, the antenna secondary sub-beam pattern is widened into a gate shape, the form of full-scale feed synthesis per beam is realized, and the beam is formed into a digital beam.

3. The large-interval sparse array flexible multi-beam reflector antenna of claim 1, wherein, The method for realizing large-interval array feed reflector antenna grating lobe suppression is to establish initial position coordinates of the feed array, to obtain optimized position coordinates of the feed array by using a non-periodic sparse array unit layout combined with a subarray rotation optimization strategy, to form a large-interval disordered arrangement of an optimized annular sparse array, and to realize large-interval array feed reflector antenna grating lobe suppression.

4. The large-interval sparse array flexible multi-beam reflector antenna of claim 3, wherein, The method for establishing the initial position coordinates of the feed array is: Step 101, taking the center of the feed array as the coordinate origin, uniformly sampling the equi-arc length according to the Fibonacci spiral discrete points, and calculating the polar coordinates of the feed elements according to the Fibonacci grid , ). Step 102, the number of feed units is , , represents the number of the feed units; the polar angle of each feed unit is rotated 1 / φ 2 from the previous feed unit; the polar radius of each feed unit is selected according to ; Step 103, in order to increase the arrangement density of the feed array, two helixes with different intervals are used for sampling, and each sampling point is replaced by four sub-array center symmetric sampling points in a group to form a feed array with four sampling points, and the initial position coordinates of the feed array are obtained.

5. The large-interval sparse array flexible multi-beam reflector antenna of claim 3, wherein, The non-periodic sparse array unit layout combined with the subarray rotation optimization strategy is: Step 201, combining the position of the center of the subarray of the feed array Combining to form optimization variable , Step 202, combining the rotation angle of the subarray of the feed array Combining to form optimization variable , Step 203, combining the position of the center of the subarray of the feed array and Combining to form position optimization variable , ; Step 202, determining the position optimization variable Then, the reflection surface intercepts the feed array scanning angle range defined as , The target function is constructed in the feed array scanning angle range, and the gain and beam low sidelobe requirements are set. Step 203: Optimize the objective function using a global optimization algorithm. Optimization is performed. If the optimization result of the global optimization algorithm is less than the gain level and sidelobe level thresholds, the optimization ends, and the optimized subarray center position and subarray rotation angle are obtained. The optimized position coordinates of the feed array.

6. The large-interval sparse array flexible multi-beam reflector antenna of claim 4, wherein, Minimum spacing of feed elements Without satisfying the design requirement of no grating lobes in the coverage area of the antenna synthesized beam: In the formula, represents the ratio of the corresponding antenna beam gain with the feed array located at the focal point and the overall trowback of the two cases; represents the minimum spacing of the feed elements; representing the operating wavelength; denotes the maximum scanning angle of the antenna; represents the position angle of the grating lobe at the maximum scanning angle of the antenna; denotes the focal length of the antenna; denotes the distance between the center of the feed array and the focal point of the antenna.

Images