An overlapped-aperture multi-beam array feed and a design method thereof

Abstract

The application provides an overlapped-aperture multi-beam array feed and a design method thereof, and relates to the field of antennas. The array feed adopts two groups of H-plane horn units as focal plane array units, the two groups of units are staggered, and all the units are the same in structure and are closely stacked together; the units in the same group adopt equal-phase unequal-amplitude synthesis to perform beam synthesis, and the units in different groups do not perform synthesis. The application staggeredly distributes different groups of feed array, performs beam synthesis between the arrays in the same group, breaks through the limitation of the physical size of the feed array on the beam overlap level in the general method, utilizes the mutual coupling between the electrically small units, and performs unequal-amplitude excitation and feed according to the focal surface field distribution, so that multiple beams with high efficiency and continuous space coverage can be obtained, and the application is suitable for the scene of high-gain and limited area beam coverage application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of antennas, in particular to an overlapping-aperture multi-beam array feed and a design method thereof. BACKGROUND

[0002] Multi-beam reflector antenna uses focal plane array to illuminate reflector, and utilizes defocus feed to form multiple beams with different directions. According to different composition principles, the focal plane array can be divided into two types: feed group and phased array feed. The former realizes multiple beams by placing multiple feeds near the focal point. Each unit of the focal plane array is a well-performing feed, and each unit is independent of each other. The scanning or multi-beam operation is realized by beam switching. By laterally deviating the feed from the focal point, the interference of each feed in space is solved, and the beams have different directions. Each unit of the feed group is independent of each other, so the number of beams of the antenna is consistent with the number of feeds. The phased array feed is a small two-dimensional phased array antenna. Through a beam synthesis network, the illumination of the reflector is realized by the subarray or the entire array with appropriate excitation. The local or entire feed array is equivalent to a feed. The number and direction of the beams of the phased array feed mainly depend on the processing capacity of the beam synthesis network.

[0003] The main disadvantage of using the feed group technology to realize multi-beam is that due to the limitation of physical size, the phase centers of each feed are far apart. Since the direction of the beam is closely related to the defocus distance of the feed, the interval between the beams is large, and continuous sky coverage cannot be realized. The phase center of the phased array feed is related to the excitation. The phase centers of the feeds corresponding to the synthesized beams can be very close, which makes the beams overlap with each other and realize continuous sky coverage. However, the careful design of the beam synthesis network greatly increases the complexity of the system, resulting in high cost of the feed system and high dependence on channel calibration. Even at the millimeter wave band, it is difficult to apply to super large aperture antennas. SUMMARY

[0004] The present application aims to avoid the shortcomings in the background art and provide an overlapping-aperture multi-beam array feed and a design method thereof. The present application staggeredly distributes different groups of feed arrays, and synthesizes beams between the arrays in the same group. The present application breaks through the limitation of the physical size of the feed array on the beam overlap level in the general method. By utilizing the mutual coupling between the electrically small units and unequally exciting the units in the same group according to the focal plane field distribution, multiple beams with high efficiency and continuous spatial coverage can be obtained, which is suitable for scenarios of high-gain and limited-area beam coverage applications.

[0005] The technical solutions adopted by the present application are as follows:

[0006] An overlapped aperture multi-beam array feed source adopts two groups of H-plane horn units as focal plane array units, the two groups of units are staggered arranged, all the units are same in structure and closely stacked together, the E-plane outer dimension b of the H-plane horn unit is less than lambda / 2, lambda is wavelength; the units in the same group adopt equal phase and unequal amplitude synthesis mode to perform beam synthesis, and the units between different groups do not perform synthesis.

[0007] A design method of an overlapped aperture multi-beam array feed source, comprising the following steps:

[0008] (1) according to the focal ratio of the applied reflector antenna, the frequency range and the beam overlap requirement, the value range of the physical size and the structure parameter of the H-plane horn unit is determined;

[0009] (2) taking the performance parameter of the synthesized beam as the evaluation standard, the number of units required for synthesizing a single beam and the corresponding amplitude excitation coefficient of each unit are determined;

[0010] (3) taking the performance parameter of the synthesized beam as the evaluation standard, the design parameters of the H-plane horn unit are optimized by using an optimization algorithm, the design parameters of the H-plane horn unit that make the performance of each beam of the reflector antenna optimal are obtained, and the design parameters are used as the final design parameters of the array feed source;

[0011] (4) for other performances of the array feed source, the antenna structure parameters are optimized in the simulation software, the optimized antenna structure parameters are applied on the premise of not affecting the performance of the synthesized beam; then, the corresponding power division network is designed according to the amplitude excitation coefficient;

[0012] The design of the overlapped aperture multi-beam array feed source is completed.

[0013] Further, the focal ratio of the reflector antenna in step (1) is the equivalent focal ratio for a multi-reflector antenna.

[0014] Further, the performance parameter of the synthesized beam in step (2) refers to the gain and antenna efficiency calculated by entering the reflector antenna system.

[0015] Further, the other performances of the array feed source in step (4) include the voltage standing wave ratio of each unit and the port isolation.

[0016] Compared with the background art, the present application has the following advantages:

[0017] 1. The present application breaks the limitation of the physical size of the feed source array on the beam overlap level in the general method, for reflector antennas with different focal ratios, the array units arranged staggered can flexibly control the feed point spacing, and high overlap level is achieved.

[0018] 2, the application utilizes the coupling between the electrically small size units, and the antenna efficiency can be ensured through the beam synthesis between the units in the same group, so that the physical interference contradiction between high efficiency and high beam overlap is solved, and multiple beams with high efficiency and continuous spatial coverage are realized.

[0019] 3, compared with the phased array feed technology, the number of channels is less, the cost is lower, and the application is suitable for the design of various reflector antenna multi-beam feed. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the structure diagram of the overlapping aperture multi-beam array feed.

[0021] Figure 2 is the focal plane field division schematic diagram.

[0022] Figure 3 is the feed arrangement schematic diagram.

[0023] Figure 4 is the structure diagram of the H-plane horn unit.

[0024] Figure 5 is the top view of Figure 4 .

[0025] Figure 6 is the beam synthesis schematic diagram. DETAILED DESCRIPTION

[0026] Referring to Figures 1-6 , an overlapping aperture multi-beam array feed adopts two groups of H-plane horn units as focal plane array units, the two groups of units are staggered arrangement, all the units are the same structure and closely stacked together, the E-plane outer dimension b of the H-plane horn unit is less than λ / 2, and λ is the wavelength; the units in the same group adopt equal-phase unequal-amplitude synthesis mode for beam synthesis, and the units between different groups do not perform synthesis.

[0027] Suppose that the focal plane field region is regarded as equal-interval division, each region corresponds to a receiving / transmitting feed, for the main plane where the narrow side of the feed is located, the feed spacing, the number of beams, the number of units, the number of units required for synthesizing a single beam, and the power division ratio of the feed network need to be designed according to the required frequency, the illumination angle and the antenna performance requirements. This embodiment adopts two groups of H-plane horn units as focal plane array units, the units in the same group perform beam synthesis, the units between different groups do not perform synthesis, the two groups of units are staggered arrangement, and all the units are the same structure and closely stacked together. The focal plane field division and the H-plane horn arrangement are shown in Figure 2 , 3 .

[0028] By using staggered arrangement of elements and beamforming of some elements, flexible control of the feed point spacing can be achieved, enabling high beam overlap levels that are unattainable in traditional feed array technology. For phased array feed technology, this reduces the number of channels.

[0029] Assuming three units combine to form a beam, the beamforming diagram is as follows: Figure 6 As shown in the figure, solid lines and dashed lines represent different groups of units.

[0030] A schematic diagram of the H-shaped horn and parameters of each part are shown below. Figure 4 , 5 As shown.

[0031] The grating lobe suppression condition for a phased array antenna is:

[0032]

[0033] Where d is the center distance between two adjacent units in the same group, and θ 0max This is the maximum scanning angle. This result is based on an omnidirectional array element pattern within the scanning plane. For directional array element patterns, larger spacing is allowed because they reduce the sidelobe effect. The feed of a reflector antenna does not require beam scanning; the beam deflection of the reflector antenna is formed through defocusing. Therefore, for array element patterns pointing only along the axis, a larger spacing is allowed, in which case θ0 = 90°. For staggered H-plane horn elements, d = 2 × b. Therefore, the out-of-plane dimension b of the H-plane horn needs to satisfy the condition: 2 × b < λ, i.e., b < λ / 2.

[0034] During the synthesis, equal-phase unequal-amplitude synthesis is adopted. It is assumed that three elements are synthesized into one beam, and the amplitude excitation coefficients corresponding to each element of the two sets of feeds are x1, x2, and x3.

[0035] The design method for the aforementioned overlapping aperture multi-beam array feed is as follows:

[0036] (1) Determine the approximate range of physical dimensions and structural parameters of the H-plane horn unit based on the focal diameter ratio, frequency range and beam overlap requirements of the applied reflector antenna.

[0037] (2) For the staggered H-plane horn units, adjacent units are independent of each other, and beamforming is performed between spaced units; the performance parameters of the synthesized beam are used as evaluation criteria to determine the number of units required to synthesize a single beam and the amplitude excitation coefficient corresponding to each unit.

[0038] (3) taking the performance parameters of the synthetic beam as the evaluation standard, using optimization algorithms such as genetic algorithm and differential evolution algorithm to optimize the design parameters of the H-plane horn array unit, so as to obtain the design parameters of the H-plane horn array unit that make the performance of each beam of the reflector antenna optimal, and the design parameters are taken as the final design parameters of the feed array;

[0039] (4) for other performance parameters of the array feed, the antenna structure parameters are optimized in the simulation software, and the optimized antenna structure parameters are selected under the premise that the performance of the synthetic beam is not affected; then, the corresponding power division network is designed according to the amplitude excitation coefficient, and the power division network can be realized by transitioning the feed port to a standard waveguide port and an unequal division structure.

[0040] Thus, the design of the overlapped aperture multi-beam array feed is completed.

[0041] In the step (1), the focal ratio of the reflector antenna is the equivalent focal ratio for the multi-reflector antenna; and the unit spacing in the step (1) refers to the spacing between the interval units for beam synthesis.

[0042] The performance parameters of the synthetic beam in the step (2) refer to the gain and antenna efficiency calculated by entering the reflector antenna system.

[0043] The center distance d of the unit for beam synthesis in the step (2) needs to meet the grid suppression condition:

[0044]

[0045] Wherein, θ 0max is the maximum scanning angle, and for the feed of the reflector antenna, the beam is only directed to the axial direction, at this time, θ0=90°, and thus the condition that d needs to meet is:

[0046] d < l.

[0047] The other performance parameters of the array feed in the step (4) mainly include the voltage standing wave ratio of each unit and the port isolation degree.

[0048] In summary, the different groups of feed arrays are staggered in the application, the beams between the arrays in the same group are synthesized, the limitation of the physical size of the feed array on the beam overlap level in the general method is broken, the mutual coupling between the electrically small units is utilized, and the same group of units is unequally excited according to the focal plane field distribution, so that multiple beams with high efficiency and continuous spatial coverage can be obtained, which is suitable for the scenarios of high gain and limited area beam coverage applications.

Claims

1. A feed source for an overlapping aperture multi-beam array, characterized in that, Two sets of H-plane horn units are used as focal plane array units. The two sets of units are staggered and all units have the same structure and are tightly stacked together. The outer dimension b of the E-plane of the H-plane horn unit is less than λ / 2, where λ is the wavelength. The units in the same group are combined in an equal phase unequal amplitude way for beam combining, and no combining is performed between units in different groups.

2. A design method for an overlapping aperture multi-beam array feed, characterized in that, The design of the overlapping aperture multibeam array feed source according to claim 1 includes the following steps: Step 1: Determine the physical dimensions and structural parameter range of the H-plane horn unit based on the focal diameter ratio, frequency range, and beam overlap requirements of the applied reflector antenna. Step 2: Using the performance parameters of the synthesized beam as the evaluation criteria, determine the number of elements required to synthesize a single beam and the amplitude excitation coefficient corresponding to each element; Step 3: Using the performance parameters of the synthesized beam as the evaluation standard, the design parameters of the H-plane horn unit are optimized using an optimization algorithm to obtain the H-plane horn unit design parameters that make the performance of each beam of the reflector antenna optimal, and these parameters are used as the final design parameters of the array feed. Step 4: Optimize the antenna structure parameters in the simulation software for other performance aspects of the array feed, and apply the optimized antenna structure parameters without affecting the performance of the synthesized beam. Then, design the corresponding power distribution network according to the amplitude excitation coefficient; Complete the design of the overlapping aperture multi-beam array feed.

3. The design method according to claim 2, characterized in that, The focal diameter ratio of the reflector antenna mentioned in step 1 is the equivalent focal diameter ratio for multi-reflector antennas.

4. The design method according to claim 2, characterized in that, In step 2, the performance parameters of the synthesized beam refer to the gain and antenna efficiency calculated by substituting them into the reflector antenna system.

5. The design method according to claim 2, characterized in that, Other performance characteristics of the array feed in step 4 include the voltage standing wave ratio (VSWR) of each element and port isolation.

Images