A compact axial feed antenna based on parallel multi-feed points

Abstract

The present invention relates to an axially compact feed antenna based on parallel multi-feed points, comprising a dual-polarized Vivaldi antenna array, a short-circuit plate, a section of circular waveguide, a layer of absorbing material, and a feed network. The dual-polarized Vivaldi antenna array is installed in a metal circular waveguide, one port of which is directly connected to the short-circuit plate, and the other port is open. The antenna array placed in the waveguide cavity can effectively excite the main mode TE of the waveguide while maintaining a small axial length. 11 The mode radiates out through the open end of the waveguide, and the radiation section is close to a horn antenna, which can effectively improve the quality of the antenna radiation pattern. A layer of absorbing material is attached to the inner side of the short-circuit plate to suppress resonance and improve broadband matching performance. The working bandwidth of the present invention is 300MHz to 800MHz. Within the working bandwidth, the standing wave ratio is less than 2, the beam width range is 46° to 81°, and it has a very low cross-polarization level and a stable phase center. It can be used in test systems such as compact fields as a feed antenna.

Description

Technical Field

[0001] The present invention relates to the technical field of compact feed sources, and in particular to an axial compact feed antenna based on parallel multiple feed points. Background Art

[0002] Compact range testing is an internationally advanced indoor measurement technology that plays an irreplaceable role in communications, defense, aerospace, and other fields. With the advancement of electronic warfare technology and the demand for stealth, advanced radar, and communications, countries around the world have invested significant resources in the research and development of large-scale compact ranges. Compact ranges provide a high-performance quasi-plane wave test area at close ranges, enabling far-field measurements of antenna parameters or radar target scattering characteristics within a microwave anechoic chamber. To advance the development of stealth and counter-stealth technologies and meet the demands of stealth testing, compact range testing must move towards ultra-wideband and low frequencies.

[0003] Feed antenna design plays a crucial role in compact range testing. The advancement of compact range testing technology requires that feed antenna design also evolve towards broadband and low frequency. In broadband testing, a broadband feed can reduce the number of feed changes, avoiding issues such as reduced test accuracy caused by feed replacement. Low standing waves are a primary requirement for feed antenna design. To achieve higher test accuracy and efficiency, the feed must be designed to have a symmetrical radiation pattern within the illumination angle range, low cross-polarization, and a stable phase center. For low-frequency feeds, as the wavelength increases, the feed size increases. Most existing low-frequency feeds are relatively large, and this large size presents challenges for installation and testing. Therefore, miniaturization of the feed antenna is crucial while meeting performance requirements. Designing a compact feed antenna for low-frequency bands is of great practical significance.

[0004] The Vivaldi antenna, first proposed by P.J. Gibson, features a tapered structure that theoretically radiates traveling waves across a wide bandwidth, making it one of the most common broadband antennas. However, existing Vivaldi antennas must be longer than the wavelength corresponding to their lowest operating frequency, and their width must be greater than half the wavelength at that frequency. This results in a relatively large electrical footprint at low frequencies.

[0005] In summary, the development of compact radio ranges requires a low-frequency feed with good performance, but the existing technology has the problems of narrow bandwidth, narrow beam, large side lobes and back lobes of the radiation pattern, and the problem of large axial size of the low-frequency feed antenna in the existing technology. Summary of the Invention

[0006] The present invention solves the following technical problems: overcoming the narrow bandwidth, narrow beam, large side and back lobes of the radiation pattern, and the large axial size of the low-frequency feed antenna in the prior art. It provides an axially compact feed antenna based on parallel multiple feed points. This feed antenna can be applied to test systems such as compact range test systems, significantly improving the test efficiency of compact range test systems in the low-frequency band. The present invention uses electrically small Vivaldi antennas to form a tightly coupled array, which is an effective method for reducing the electrical size of low-frequency antennas. Furthermore, the feed antenna has the advantages of wide bandwidth, wide beam, dual-polarization operation, low side and back lobe levels, small axial size, and ease of processing.

[0007] The technical solution adopted by the present invention is: an axially compact feed antenna based on parallel multi-feed points, the antenna structure including a dual-polarized Vivaldi antenna array, a short-circuit plate, a section of circular waveguide, a layer of absorbing material, and a feed network. The Vivaldi antenna array is a 3×3 nine-element array with nine closely arranged elements. Each antenna element consists of two perpendicularly crossed single-polarized Vivaldi antennas. Each single-polarized Vivaldi antenna consists of a feed structure, a dielectric plate, and a metal radiating surface. The dielectric plate is located in the middle, and the feed structure and metal radiating surface are printed on either side of the dielectric plate. The metal radiating surface is composed of two symmetrical specific exponential curves, a transition slot line, and a circular cavity. The feed structure is a microstrip line to slot line balun structure. The short-circuit plate is a circular metal plate located behind the dual-polarized Vivaldi antenna array and directly connected to the bottom of the dual-polarized Vivaldi antenna array. The short-circuit plate is perpendicular to the axis of the dual-polarized Vivaldi antenna array. The entire Vivaldi antenna array is mounted within a metal circular waveguide. One port of the waveguide is directly connected to a short-circuit plate, while the other port is open and unconnected to any other structure. This is equivalent to short-circuiting one port of the circular waveguide while leaving the other port open for radiation. The radiating section of the feed antenna resembles a horn antenna, excited by the antenna array within the circular waveguide. The absorbing material is located on the inner side of the short-circuit plate and connected to its inner wall. The feed network consists of two parallel feed networks, providing nine parallel input signals for each of the two polarizations of the feed antenna, enabling parallel multi-feed point excitation.

[0008] The single-polarized Vivaldi antenna is made of a double-sided dielectric plate as the base material. One side of the double-sided dielectric plate is a metal radiating surface. The metal radiating surface is composed of two symmetrical specific exponential curves, a transition slot line, and a circular cavity. The specific exponential curve formula is:

[0009] y=±(C1e Rx +C2)

[0010]

[0011]

[0012] Here, (x1, y1) and (x2, y2) are the coordinates of the starting and ending points of the exponential curve, respectively. R is the curvature, which determines the curvature of the exponential curve. The other side of the double-sided dielectric board is a microstrip line, and the antenna is fed through a balun structure that converts the microstrip line to a slot line.

[0013] The length of a single single-polarized Vivaldi antenna ranges from 0.29 to 0.31λ c , the width range is 0.145~0.155λ c Nine 3×3 dual-polarized Vivaldi antennas are closely arranged, and the axial dimension is compressed by parallel feeding of the nine array elements. The total length of the array, that is, the axial dimension range is 0.29 to 0.31λ. c , the total array width range is 0.435~0.465λ c The compact feed antenna meets the dual-polarization working mode. Each polarization is fed through nine parallel paths. The microstrip line in each single-polarization Vivaldi antenna is connected to a feeding path. The microstrip line is connected to the RF connector SMA by welding. The RF connector SMA is connected to the external RF coaxial cable to achieve external feeding.

[0014] The feed network needs to provide two parallel feed networks, one for each polarization of the feed antenna. The feed network uses a power splitter to distribute one input signal to nine array elements. Each feed network provides nine parallel input signals to the feed source, connected via coaxial cables to SMA connectors for parallel feeding. Polarization switching can be achieved by controlling the on / off state of the two feed ports. The amplitude and phase configuration of each feed network channel can improve the radiation performance of the feed source. Amplitude configuration can be achieved by changing the power splitter ratio, while phase configuration can be achieved by controlling the length of each coaxial cable or by adding a phase shifter.

[0015] The short-circuit plate is located behind the dual-polarized Vivaldi antenna array. The plane of the short-circuit plate is perpendicular to the axis of the dual-polarized Vivaldi antenna array, and its inner side is directly connected to the bottom surface of the dual-polarized Vivaldi antenna array. The short-circuit plate is a circular metal plate with a thickness ranging from 0.002 to 0.005λ. c , whose diameter range is 0.602~0.61λ c , whose diameter is equal to the outer diameter of the circular waveguide, is connected to one port of the circular waveguide to close one port of the circular waveguide. There are 18 circular through holes on the short-circuit board, corresponding to 18 feeding points, and the diameter of each through hole ranges from 0.02 to 0.03λ c , the external cable is connected to the 18 SMA connectors of the dual-polarized Vivaldi antenna array inside the waveguide through the circular through-hole for feeding.

[0016] The outer diameter of the circular waveguide is equal to the diameter of the short-circuit plate, and the outer diameter range of the circular waveguide is 0.602~0.610λ c , the thickness range of circular waveguide is 0.001~0.005λ c , the inner diameter of the circular waveguide ranges from 0.592 to 0.608λ c One port of the circular waveguide is connected to a short-circuit plate, which is equivalent to short-circuiting one port of the circular waveguide while the other port is open for radiation. The entire dual-polarized Vivaldi antenna array is installed at the center of the circular waveguide. The entire feed antenna is similar to a circular horn antenna, and the antenna array located inside the circular waveguide excites the waveguide horn to radiate. The outer diameter of the circular waveguide is equal to the diameter of the short-circuit plate, and the length of the circular waveguide ranges from 0.38 to 0.39λ. c The circular waveguide length is longer than that of the dual-polarized Vivaldi antenna array, which can suppress the transmission of high-order modes and improve the mode purity of waveguide transmission, thereby improving the quality of the feed antenna radiation pattern. In addition, the thickness of the short-circuit plate ranges from 0.002 to 0.005λ. c The overall axial length of the axial compact feed antenna ranges from 0.382 to 0.395λ. c , the axial dimension of the feed antenna is less than 0.4 times the wavelength corresponding to the lowest operating frequency.

[0017] The absorbing material is located on the inside of the short-circuit plate and is directly attached to the inner wall of the short-circuit plate by gluing, thus suppressing resonance. The entire absorbing material has the same contour as the waveguide aperture. Due to the direct connection between the Vivaldi antenna array and the short-circuit plate and the cross-arrangement of the Vivaldi antenna array, the absorbing material cannot be attached at the connection point between the Vivaldi antenna and the short-circuit plate. Therefore, the entire absorbing material needs to be divided into five small pieces based on the arrangement of the Vivaldi antenna array and attached to the inner wall of the short-circuit plate.

[0018] The Vivaldi antenna is made of a double-sided copper-clad FR-4 laminate with a thickness of 2.4mm and a dielectric constant of 4.3. The short-circuit plate and circular waveguide are made of metal, which can be one of aluminum, iron, tin, copper, silver, gold or platinum, or an alloy of multiple combinations.

[0019] The principle of the present invention is that the Vivaldi antenna is a gradient slot antenna with characteristics such as ultra-wideband and low cross-polarization. According to the radiation principle of the Vivaldi antenna, the antenna can only produce effective radiation when the slot width is greater than half the wavelength of the operating frequency and less than twice the wavelength. In order to make the Vivaldi antenna obtain better low-frequency characteristics, it is necessary to increase the length and slot width of the antenna, that is, to increase the physical size of the antenna. If a single Vivaldi antenna is to produce effective radiation at 300MHz, the axial length of the Vivaldi antenna will exceed 1m. The present invention uses a small-sized Vivaldi antenna array to obtain better low-frequency characteristics. The Vivaldi antenna array is closely arranged. Each single-polarization Vivaldi antenna unit has one feeding point, and the dual-polarization Vivaldi antenna array has a total of 18 feeding points. The present invention uses this multi-feed point excitation method and utilizes the coupling effect between closely arranged array elements to achieve good low-frequency characteristics while only increasing the lateral size, effectively shortening the axial electrical size of the antenna.

[0020] The Vivaldi antenna consists of three parts: a feeding structure, a dielectric plate, and a metal radiating surface. The dielectric plate is located in the middle, and the feeding structure and the metal radiating surface are printed on both sides of the dielectric plate respectively. The metal radiating surface is composed of two symmetrical specific exponential curves, a transition slot line, and a circular cavity. The feeding structure is a balun structure of microstrip line to slot line. The Vivaldi antenna is fed by a balun structure of microstrip line to slot line. When the Vivaldi antenna is working, the fed energy is coupled to the slot line through the microstrip line, and then flows along the starting end of the gradient slot line to the end opening of the slot line and radiates out. When energy is coupled to the slot line through the microstrip line, most of the energy will propagate and radiate along the main radiation direction, and a small amount of energy will be transmitted in the direction opposite to the main radiation direction of the antenna. The role of the circular cavity is to reflect this part of the energy to the main radiation direction of the antenna. Considering the coupling effect between Vivaldi antenna elements, optimizing a single element is not very meaningful. Based on the ideal situation of infinite array arrangement, the present invention optimizes various Vivaldi parameters, including the curvature of a specific exponential curve, the size of the circular cavity, the distance between the end of the slot line and the coupling point, the size of the slot line end opening, and other parameters. Ultimately, the overall matching performance of the Vivaldi antenna nine-element array is good.

[0021] The radiation mechanism of the Vivaldi antenna determines its broadband characteristics, but the complex current distribution on the surface of the Vivaldi antenna will cause the antenna backlobe level to be relatively high. The metal short-circuit plate placed behind the Vivaldi antenna array can reflect the backward radiated signal to the main radiation direction, thereby reducing the backlobe level and effectively improving the radiation pattern. A layer of absorbing material attached to the inside of the metal short-circuit plate can reduce resonance and improve the overall matching performance. The present invention places the dual-polarized Vivaldi antenna array in a circular waveguide. The constraint of the metal boundary of the circular waveguide can reduce the sidelobe level and effectively improve the radiation pattern. The Vivaldi antenna array is fed in parallel by connecting the SMA connector via a cable, which can excite the main mode TE with the largest axial radiation energy of the circular waveguide. 11 The mode radiates through the open end of the waveguide, and a radiation pattern with good symmetry and low side lobes can be obtained. According to antenna theory, the size of the horn aperture will affect the beam width of the feed antenna. The smaller the electrical size of the circular waveguide aperture, the wider the beam width of the radiation pattern will be. However, considering that the smaller the circular waveguide aperture, the larger the corresponding transmission cutoff frequency will be, considering the requirements of beam width and frequency range, the present invention sets the inner diameter range of the circular waveguide to 0.592~0.608λ c .

[0022] The advantages of the present invention are:

[0023] (1) The present invention adopts a small-sized Vivaldi antenna array to obtain better low-frequency characteristics. The Vivaldi antenna array is closely arranged. Each single-polarized Vivaldi antenna unit has one feeding point. The dual-polarized Vivaldi antenna array has a total of 18 feeding points. The present invention uses this multi-feed point excitation method and the coupling between closely arranged array elements to achieve good low-frequency characteristics while only increasing the lateral size, effectively shortening the axial electrical size. The axial size range of the invented axial compact feed antenna based on parallel multi-feed is 0.382~0.395λ c , less than 0.4 times the wavelength corresponding to the lowest operating frequency.

[0024] (2) The working bandwidth of the present invention is 300MHz to 800MHz, the frequency octave bandwidth is 2.6, the matching is good within the working wide band, and the standing wave is less than 2. The combined design of the dual-polarized Vivaldi antenna array and the circular waveguide in the present invention can achieve a wide beam with broadband equalization, the beam width is greater than 45°, and the sidelobe and backlobe levels are low. The present invention can achieve a stable phase center, low cross-polarization and dual-polarization working mode. The broadband and dual-polarization operation of the feed antenna can greatly improve the efficiency of the compact field test system, and the wide beam and beam equalization performance can greatly improve the accuracy of the compact field test system.

[0025] (3) The feed antenna of the present invention satisfies the principle of proportional transformation. After the feed antenna is multiplied by a proportional factor K, the frequency bandwidth remains unchanged. Within the corresponding operating bandwidth of (300 / K) MHz to (800 / K) MHz, the various parameters of the antenna remain unchanged. Therefore, the present invention can be extended to other frequency bands through proportional transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of an axially compact feed antenna based on parallel multi-feed points according to the present invention. The left and right figures are schematic diagrams of the structure of the feed antenna viewed from two different directions. The right figure is a view of the left figure rotated 100 degrees to the left.

[0027] Figure 2 Schematic diagram of the structure of the absorbing material;

[0028] Figure 3 It is a structural diagram of the dual-polarized Vivaldi antenna;

[0029] Figure 4 A schematic diagram of the structure of a polarized Vivaldi antenna;

[0030] Figure 5 A schematic diagram of the structure of a Vivaldi antenna with another polarization;

[0031] Figure 6 This is a structural diagram of a feeding network.

[0032] The meanings of the reference numerals in the figure are: 1 is a dual-polarized Vivaldi antenna array, 2 is a short-circuit plate, 3 is a circular waveguide, 4 is an absorbing material, 5 is a dual-polarized Vivaldi antenna, 6 is a single-polarized Vivaldi antenna, 7 is a feeding structure, 8 is a dielectric plate, 9 is a metal radiation surface, and 10 is an RF connector SMA. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0034] The specific concept of the present invention is as follows: Invent an axial compact feed antenna based on parallel multi-feed points, the antenna structure includes a dual-polarized Vivaldi antenna array, a short-circuit plate, a section of circular waveguide, a layer of absorbing material and a feeding network. Among them, the dual-polarized Vivaldi antenna array is a 3×3 nine-unit array, the nine units are closely arranged, and each antenna unit is a dual-polarized Vivaldi antenna composed of two vertically crossed single-polarized Vivaldi antennas. The short-circuit plate is located behind the dual-polarized Vivaldi antenna array, and its main purpose is to suppress the back lobe level of the antenna. The entire Vivaldi antenna array is installed in a metal circular waveguide. The circular waveguide can help effectively reduce the side lobe level. One port of the circular waveguide is directly connected to the short-circuit plate, and the other port is open. The antenna array placed in the waveguide cavity can effectively excite the main mode TE of the waveguide under the premise of a very small axial length. 11 mode, radiating out through the open end of the waveguide, and the radiation section is close to a horn antenna. A layer of absorbing material is attached to the inner side of the short-circuit plate to suppress resonance and improve broadband matching performance. The feeding network consists of two sets of parallel feeding networks, which provide nine parallel input signals for the two polarizations of the feed antenna, respectively, to achieve parallel multi-feed point excitation. The working bandwidth of the present invention is 300MHz to 800MHz. Within the working bandwidth, the standing wave ratio is less than 2, the beam width range is 46° to 81°, it has a very low cross-polarization level and a stable phase center, and can be applied to test systems such as compact fields as a feed antenna.

[0035] According to the concept of the above invention, the present invention adopts the following technical solutions:

[0036] like Figure 1 As shown in FIG. 1 , an axially compact feed antenna based on parallel multi-feed points of the present invention comprises a dual-polarized Vivaldi antenna array 1, a short-circuit plate 2, a section of circular waveguide 3, and a layer of absorbing material 4. The dual-polarized Vivaldi antenna array 1 is a 3×3 nine-element array consisting of nine closely arranged dual-polarized Vivaldi antennas 5. The specific design of the Vivaldi antenna unit is as follows: Figure 3 、 Figure 4 、 Figure 5 As shown. The total length of the dual-polarized Vivaldi antenna array 1 is 0.3λ c , the total width of the dual-polarized Vivaldi antenna array 1 is 0.45λ c .

[0037] like Figure 1As shown, the short-circuit plate 2 is a circular metal plate located behind the dual-polarized Vivaldi antenna array 1. One port of the circular waveguide 3 is connected to the short-circuit plate 2, which is equivalent to short-circuiting one port of the circular waveguide 3 and leaving the other port open for radiation. The entire Vivaldi antenna array is installed within this circular waveguide 3. The entire feed antenna is similar to a horn antenna and is excited by the antenna array located inside the circular waveguide 3. There are 18 circular through-holes on the short-circuit plate 2, corresponding to 18 feeding points, and the diameter of each through-hole is 0.03λ. c The external cable is connected to the 18 RF connectors SMA10 inside the circular waveguide 3 through the circular through hole for feeding. The diameter of the short-circuit plate 2 is 0.602λ c Its diameter is equal to the outer diameter of circular waveguide 3, and it is connected to one port of circular waveguide 3, so that one port of circular waveguide 3 is closed. The inner diameter of circular waveguide 3 is 0.6λ c , the length of the circular waveguide 3 is 0.39λ c , the thickness of the short-circuit plate 2 is 0.002λ c The overall axial length of the axial compact feed antenna of the present invention is 0.392λ c The short-circuit plate 2 and the circular waveguide 3 are made of metal, which may be one of aluminum, iron, tin, copper, silver, gold or platinum, or an alloy of multiple combinations thereof.

[0038] like Figure 2 As shown, the overall shape of the absorbing material 4 is a circle, and its diameter is equal to the inner diameter of the circular waveguide 3, 0.6λ. c The absorbing material 4 is attached to the inner wall of the short-circuit plate 2. Due to the direct connection between the dual-polarized Vivaldi antenna array 1 and the short-circuit plate 2 and the cross arrangement of the dual-polarized Vivaldi antenna array 1, the absorbing material cannot be attached to the position where the Vivaldi antenna is connected to the short-circuit plate 2. Therefore, the entire absorbing material 4 needs to be divided into Figure 2 The five pieces shown are respectively attached to the inner wall of the short-circuit plate 2. Different types of absorbing materials can be selected, and the thickness of the absorbing material is determined according to the characteristics of the absorbing material. In this example, ECCOSORB LS-26 is used as the absorbing material with a thickness of 0.02λ. c .

[0039] like Figure 3 As shown, each dual-polarized Vivaldi antenna 5 is composed of two vertically crossed single-polarized Vivaldi antennas 6. Since the two polarized antennas need to be assembled together, it is necessary to design a slot on the antenna dielectric plate. The Vivaldi antenna unit is 0.3λ long. c , dielectric plate thickness 0.0024λ c, the metal radiation surface thickness is 0.035mm, a polarized antenna needs to open a 0.256λ from the center of the top of the antenna c Long slot, slot width is 0.0025λ c ,like Figure 4 As shown; the other polarized antenna needs to open a 0.044λ from the center of the antenna bottom c The width of the long slot is also 0.0025λ c ,like Figure 5 shown.

[0040] like Figure 4 and Figure 5 As shown, each single-polarized Vivaldi antenna 6 consists of a feed structure 7, a dielectric plate 8, and a metal radiating surface 9. The dielectric plate 8 is located in the center, while the feed structure 7 and metal radiating surface 9 are printed on either side of the dielectric plate 8. The metal radiating surface 9 is composed of two symmetrical exponential curves, a transition slot, and a circular cavity. The feed structure 7 is a microstrip-to-slotline balun structure. The Vivaldi antenna is fabricated using 2.4mm thick double-sided copper-clad FR-4 laminate with a dielectric constant of 4.3.

[0041] The feed antenna requires two sets of parallel feeding networks, which are used to feed the two polarizations of the feed antenna respectively. The feeding network uses a power divider to distribute one input signal to nine array elements. Each set of feeding networks provides nine parallel input signals for the feed source, which are connected to the RF connector SMA10 through a coaxial cable to realize parallel feeding. The amplitude and phase configuration of each channel of the feeding network can improve the radiation performance of the feed source. The amplitude configuration can be achieved by changing the power division ratio of the power divider, and the phase configuration can be achieved by controlling the length of each coaxial cable or adding a phase shifter. The embodiment of the present invention adopts a three-way power divider as shown in the following figure: Figure 6 The two-stage parallel feed network shown requires a 1-to-3 power splitter in the first stage and three 1-to-3 power splitters in the second stage. Pin represents the input port. A feed signal is input through this port and then split into nine signals via two-stage power splitters. These signals are output from nine output ports, Pout1 to Pout9, and then connected to the feed antenna via coaxial cables. The feed lines from the two-stage power splitters to each array element are of equal length, and the feed network provides parallel feeds of equal amplitude and phase to all nine elements. Switching the polarization of the feed antenna can be achieved by switching the two feed networks on and off.

[0042] The present invention relates to an axially compact feed antenna based on parallel multi-feed points. This feed antenna can be used as a feed in compact range testing, which can improve the efficiency and accuracy of the compact range testing system to a certain extent. This feed antenna can also be used as a feed for satellites or radio astronomy.

Claims

1. An axially compact feed antenna based on parallel multi-feed points, characterized by: It includes a dual-polarized Vivaldi antenna array (1), a short-circuit plate (2), a section of circular waveguide (3), an absorbing material (4) and a feeding network; The dual-polarized Vivaldi antenna array (1) is a 3×3 nine-element array, and the 3×3 nine-element array is closely arranged, and the axial size is compressed by parallel feeding of the nine array elements; each antenna unit in the dual-polarized Vivaldi antenna array (1) is composed of two vertically crossed single-polarized Vivaldi antennas, and each single-polarized Vivaldi antenna (6) is composed of a feeding structure (7), a dielectric plate (8) and a metal radiation surface (9), the dielectric plate (8) is located in the middle, the feeding structure (7) and the metal radiation surface (9) are printed on both sides of the dielectric plate, respectively, the metal radiation surface (9) is composed of two symmetrical exponential curves and a transition slot line and a circular cavity, the feeding structure (7) is a microstrip line to slot line balun structure, the microstrip line is connected to the radio frequency connector SMA (10), and the feeding is achieved by connecting to an external radio frequency cable through the SMA (10); The short-circuit plate (2) is located behind the dual-polarized Vivaldi antenna array (1) and is directly connected to the bottom of the dual-polarized Vivaldi antenna array (1). The plane of the short-circuit plate (2) is perpendicular to the axis of the dual-polarized Vivaldi antenna array (1). The dual-polarized Vivaldi antenna array (1) is installed in a circular waveguide (3), one port of the circular waveguide (3) is directly connected to the short-circuit plate (2), and the other port is open and not connected to any other structure. This is equivalent to short-circuiting one port of the circular waveguide (3) and opening the other port for radiation. The feed antenna radiation section is close to a horn antenna and is excited by the antenna array located inside the circular waveguide; The absorbing material (4) is located on the inner side of the short-circuit plate (2) and is connected to the inner wall of the short-circuit plate (2), thereby suppressing resonance. The feeding network consists of two sets of parallel feeding networks, which provide nine parallel input signals for the two polarizations of the feed antenna respectively. The signals are transmitted through coaxial cables and connected to the SMA connectors of each Vivaldi antenna unit to realize parallel feeding for the feed antenna.

2. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The length of the single-polarized Vivaldi antenna is in the range of 0.29 to 0.31λ. c , the width range is 0.145~0.155λ c The total length of the array composed of 3×3 nine-element arrays, i.e., the axial dimension range is 0.29~0.31λ c , the total array width range is 0.435~0.465λ c ,λ c is the wavelength corresponding to the lowest operating frequency of the axial compact feed.

3. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The compact feed antenna meets the dual-polarization working mode. Each polarization is fed through nine parallel paths. The microstrip line in each single-polarization Vivaldi antenna is connected to a feeding path. The microstrip line is connected to the RF connector SMA by welding. The RF connector SMA is connected to an external RF coaxial cable to achieve external feeding.

4. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The short-circuit plate (2) is a circular metal plate with a thickness ranging from 0.002 to 0.005λ. c , whose diameter range is 0.602~0.610λ c , whose diameter is equal to the outer diameter of the circular waveguide, and is connected to one port of the circular waveguide, so that one port of the circular waveguide is closed; there are 18 circular through holes on the short-circuit plate (2), corresponding to 18 feeding points, and the diameter range of each through hole is 0.02~0.03λ c The externally fed coaxial cable is connected to the 18 SMA connectors of the dual-polarized Vivaldi antenna array inside the waveguide through a circular through hole for feeding, λ c is the wavelength corresponding to the lowest operating frequency of the axial compact feed.

5. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The outer diameter of the circular waveguide (3) is equal to the diameter of the short-circuit plate (2), and the outer diameter range of the circular waveguide (3) is 0.602~0.610λ c , the thickness of the circular waveguide ranges from 0.001 to 0.005λ c , the inner diameter of the circular waveguide ranges from 0.592 to 0.608λ c The length of the circular waveguide (3) is in the range of 0.38 to 0.39λ. c The circular waveguide is longer than the dual-polarized Vivaldi antenna array to suppress the transmission of high-order modes and improve the mode purity of waveguide transmission, thereby improving the quality of the feed antenna radiation pattern; plus the thickness of the short-circuit plate ranges from 0.002 to 0.005λ c The overall axial length of the axial compact feed antenna is in the range of 0.382~0.395λ c ,λ c is the wavelength corresponding to the lowest operating frequency of the axial compact feed.

6. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The outer contour of the absorbing material (4) is the same as the diameter of the circular waveguide (3). Due to the influence of the cross structure of the antenna array, the entire absorbing material (4) is divided into 5 small pieces.

7. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The feed network uses a power splitter to distribute one input signal to nine array elements. Each feed network group provides nine parallel input signals for the feed source, which are connected to the SMA connector via coaxial cables to achieve parallel feeding. The switching of the two polarizations of the feed antenna is achieved by controlling the on and off of the two groups of feed ports. The amplitude and phase configuration of each channel of the feed network improve the radiation performance of the feed source. The amplitude configuration is achieved by changing the power division ratio of the power splitter, and the phase configuration is achieved by controlling the length of each coaxial cable or adding a phase shifter.

8. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The single-polarized Vivaldi antenna is manufactured using a double-sided dielectric plate as a basic material.

9. The axial compact feed antenna based on parallel multi-feed points according to claim 1, characterized in that: The single-polarized Vivaldi antenna is made of a double-sided copper-clad FR-4 plate with a thickness of 2.4 mm and a dielectric constant of 4.3; the short-circuit plate and the circular waveguide are made of metal, which is one of aluminum, iron, tin, copper, silver, gold or platinum, or an alloy of multiple metals.

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