A design method for overlapping multi-beam feed

Abstract

The present invention relates to a design method for an overlapping multi-beam feed, and belongs to the field of antennas. The method comprises the following steps: determining initial design parameters; estimating the equivalent radiation aperture required by the feed array unit; using a strongly coupled array unit as the feed array unit according to the ratio of the physical size of the feed array unit to the equivalent radiation aperture; using the gain value of each beam of the reflector antenna and the antenna aperture efficiency as evaluation functions, and using an optimization method to optimize the structural design parameters of the feed array unit to obtain the final design parameters of the feed array. The method solves the physical interference contradiction between the unit aperture and the defocus distance of the feed array, and can achieve multiple beams with high efficiency and continuous spatial coverage.

Description

Technical Field

[0001] The present invention relates to the field of antennas, and in particular to a design method for a low-cost and high-efficiency overlapping multi-beam feed source. Background Art

[0002] The multi-beam antenna technology with co-aperture or partial co-aperture can effectively improve the working efficiency of the antenna, and a single antenna can be used to achieve beam coverage of multiple points or specific areas. It has a wide range of applications in radar, communication, microwave reception, radio astronomy and other fields, and the reflector antenna fed by the focal plane array is one of the main forms of multi-beam antennas, especially in situations where the gain requirements are high, its cost-effectiveness is more obvious.

[0003] The multi-beam reflector antenna uses a focal plane array to illuminate the reflector and uses defocused feeding 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 focus of the antenna. Each unit of this focal plane array is a feed with good performance. Each unit is independent of each other, and scanning or multi-beam operation is realized through beam switching. By laterally deviating the feed from the focus, not only the interference of each feed in space is solved, but also the beam has different directions. The units of the feed group are 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 the beam synthesis network, it is properly excited to realize the illumination of the reflector with a subarray or the entire array. Make the local or entire feed array equivalent to a feed. The number and direction of the beam of the phased array feed mainly depend on the processing power of the beam synthesis network.

[0004] The main disadvantage of using feed group technology to achieve 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 intervals between each beam are large, and continuous sky coverage cannot be achieved. The phase center of the phased array feed is related to the excitation, and the phase centers of the feeds corresponding to the synthesized beam can be very close, which makes the beams overlap and achieve continuous sky coverage. However, the carefully designed beam synthesis network greatly increases the complexity of the system, resulting in a high cost of the feed system. At the same time, it is highly dependent on channel calibration, and it is even difficult to achieve ultra-large aperture antenna applications in the millimeter wave band. Summary of the invention

[0005] The purpose of the present invention is to avoid the shortcomings of the background technology and provide a low-cost and high-efficiency design method of overlapping multi-beam feeds.

[0006] The technical solution adopted by the present invention is:

[0007] A method for designing an overlapping multi-beam feed comprises the following steps:

[0008] Step 1: Determine the initial design parameters, including the physical size of the feed array unit, the spacing between the units, and the illumination angle, and select the illumination level according to the focal diameter ratio of the reflector antenna used and the beam overlap requirements;

[0009] Step 2, estimating the equivalent radiation aperture required by the feed array unit according to the initial design parameters selected in step 1;

[0010] Step 3, according to the ratio of the physical size of the feed array unit to the equivalent radiation aperture, the strongly coupled array unit is used as the feed array unit;

[0011] Step 4, calculating the antenna aperture efficiency according to the gain value of the beam, taking the gain value of each beam of the reflector antenna and the antenna aperture efficiency as the evaluation function, and using the optimization method to optimize the structural design parameters of the feed array unit, to obtain the structural design parameters of the feed array unit that make the performance of each beam of the reflector antenna reach the best, and use them as the final design parameters of the feed array;

[0012] Complete the design of the multi-beam feed.

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

[0014] Furthermore, the strongly coupled array unit in step (3) includes a Vivaldi unit, a dipole unit of a cross-digital structure, and a chessboard array unit.

[0015] Furthermore, in step (3), non-radiating additional units are provided at the edge of the feed array to ensure the continuity of the coupling current of the radiating unit. The number of additional units is determined by the distribution range of the coupling current. The specific method is to analyze the current intensity of other aperture surfaces when a single unit is fed, add different numbers of additional units through simulation, and determine the number of additional units according to the performance of the feed unit.

[0016] Furthermore, the optimization method in step (4) is a differential evolution method, in which the semi-irradiation angle of the reflector antenna is set to a fixed value, and after the population is initialized, the generated variables are passed to the model in the full-wave simulation software, and the calculation results are read after the solution model is called, and the cross-sectional radiation pattern data is used to calculate the antenna efficiency of each frequency point to obtain a single result.

[0017] Compared with the background technology, the present invention has the following advantages:

[0018] 1. The present invention breaks the design thinking that the physical aperture of the feed array unit corresponds to the radiation aperture. It realizes high overlap level by exploring the "shared radiation aperture" of the phased array feed, and expands the equivalent radiation aperture of the feed array unit by the strong mutual coupling characteristics between the feed array units, thereby obtaining a beam width that is much narrower than the physical size of a single feed array unit. It realizes "radiation aperture sharing" without the need for beam synthesis, solves the physical interference contradiction between high efficiency and high beam overlap, and realizes multiple beams with high efficiency and continuous spatial coverage.

[0019] 2. The present invention breaks through the design idea of ​​corresponding physical aperture to radiation aperture and balancing radiation efficiency with beam overlap level in general methods. By utilizing the mutual coupling between electrically small-sized units, the equivalent radiation aperture of a single feed array unit is expanded, and a narrower radiation pattern than the pattern corresponding to the physical size of the feed array unit is obtained. Therefore, without the need for beam synthesis, the physical interference contradiction between the unit aperture and the defocus distance of the feed array is fundamentally solved, and multiple beams with high efficiency and continuous spatial coverage can be achieved. It is suitable for antenna design for high-gain and limited-area beam coverage applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle of an embodiment of the present invention.

[0021] Figure 2 It is a flow chart of a method according to an embodiment of the present invention.

[0022] The figure includes: feed array unit 1, equivalent radiation aperture 2, radiation unit coupling current 3, and additional unit 4. DETAILED DESCRIPTION

[0023] Reference Figure 1 and Figure 2 , a design method of an overlapping multi-beam feed, comprising the following steps:

[0024] A method for designing an overlapping multi-beam feed comprises the following steps:

[0025] (1) Determine the initial design parameters based on the focal diameter ratio of the reflector antenna and the beam overlap requirements, including the physical size of the feed array unit, the spacing between the units, and the illumination angle, and select the illumination level; the feed array can be arranged in a square;

[0026] (2) Estimate the equivalent radiation aperture required by the feed array unit according to the initial design parameters selected in step (1);

[0027] (3) Based on the ratio of the physical size of the feed array unit to the equivalent radiation aperture, the strongly coupled array unit is used as the feed array unit;

[0028] (4) Calculate the antenna aperture efficiency based on the gain value of the beam. Take the gain value of each beam of the reflector antenna and the antenna aperture efficiency as the evaluation function, and use the optimization algorithm to optimize the structural design parameters of the feed array unit. Obtain the structural design parameters of the feed array unit that optimize the performance of each beam of the reflector antenna, and use them as the final design parameters of the feed array.

[0029] Complete the design of the multi-beam feed.

[0030] The focal diameter ratio of the reflector antenna in step (1) is an equivalent focal diameter ratio for multiple reflector antennas.

[0031] The strongly coupled array units in step (3) include but are not limited to Vivaldi units, dipole units of a cross-digital structure, and chessboard array units.

[0032] In step (3), in order to ensure the unit illumination efficiency at the edge of the feed array, it is necessary to add non-radiating additional units at the edge of the feed array to ensure the continuity of the coupling current of the radiating units. The number of additional units is determined by the distribution range of the coupling current, which is determined by analyzing the current intensity of other aperture surfaces when a single unit is fed, and then by simulating the performance of the feed unit after adding different numbers of additional units.

[0033] The optimization algorithm in step (4) includes global and local optimization algorithms. The specific optimization process is as follows:

[0034] Differential evolution and other algorithms are used to optimize the structural parameters of the array units. First, the range of parameters to be optimized, population size, number of iterations, frequency range, field monitor, etc. are set in the optimization program. The semi-irradiation angle of the reflector antenna is a fixed value. After the population is initialized, the generated variables are passed to the model in the full-wave simulation software. After calling the solution model, the calculation results are read, and the antenna efficiency of each frequency point is calculated using the cross-sectional radiation pattern data to obtain a single result, and then the subsequent operations of the algorithm are executed.

[0035] In summary, the present invention breaks through the design idea of ​​balancing radiation efficiency and beam overlap level in general methods. By utilizing the mutual coupling between electrically small-sized units, the equivalent radiation aperture of a single feed array unit is expanded, and a radiation pattern that is much narrower than the physical size of a single feed array unit is obtained. Therefore, without the need for beam synthesis, the physical interference contradiction between the unit aperture and the off-focus distance of the feed array is fundamentally solved, and multiple beams with high efficiency and continuous spatial coverage can be achieved. The antenna design is suitable for high-gain, limited-area beam coverage applications.

Claims

1. A design method for an overlapping multi-beam feed, characterized in that: The steps include: Step 1: Determine the initial design parameters, including the physical size of the feed array unit, the spacing between the units, and the illumination angle, and select the illumination level according to the focal diameter ratio of the reflector antenna used and the beam overlap requirements; Step 2, estimating the equivalent radiation aperture required by the feed array unit according to the initial design parameters selected in step 1; Step 3, according to the ratio of the physical size of the feed array unit to the equivalent radiation aperture, the strongly coupled array unit is used as the feed array unit; Step 4, calculating the antenna aperture efficiency according to the gain value of the beam, taking the gain value of each beam of the reflector antenna and the antenna aperture efficiency as the evaluation function, and using the optimization method to optimize the structural design parameters of the feed array unit, to obtain the structural design parameters of the feed array unit that make the performance of each beam of the reflector antenna reach the best, and use them as the final design parameters of the feed array; Complete the design of the multi-beam feed.

2. The method for designing an overlapping multi-beam feed according to claim 1, characterized in that: For a multi-reflector antenna, the focal diameter ratio of the reflector antenna described in step (1) is an equivalent focal diameter ratio.

3. The method for designing an overlapping multi-beam feed according to claim 1, characterized in that: The strongly coupled array units in step (3) include Vivaldi units, dipole units of a cross-digital structure, and chessboard array units.

4. The method for designing an overlapping multi-beam feed according to claim 1, characterized in that: In step (3), non-radiating additional units are also provided at the edge of the feed array to ensure the continuity of the coupling current of the radiating unit. The number of additional units is determined by the distribution range of the coupling current. The specific method is to analyze the current intensity of other aperture surfaces when a single unit is fed, add different numbers of additional units through simulation, and determine the number of additional units according to the performance of the feed unit.

5. The method for designing an overlapping multi-beam feed according to claim 1, characterized in that: The optimization method in step (4) is a differential evolution method, in which the semi-irradiation angle of the reflector antenna is set to a fixed value. After the population is initialized, the generated variables are passed to the model in the full-wave simulation software. After the solution model is called, the calculation results are read and the cross-sectional radiation pattern data is used to calculate the antenna efficiency at each frequency point to obtain a single result.

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