A low-profile antenna based on a structural composite surface that combines phased array and reflector array

Abstract

This invention discloses a low-profile antenna that combines a phased array and a reflectarray, based on a structural composite surface. The antenna comprises two substrates, a radiating structure on the upper surface of the upper substrate, a prepreg sheet used to bond the upper and lower substrates, a slot-coupled feed structure on the upper surface of the lower substrate, and a feeder structure on the lower surface of the lower substrate. This invention utilizes a composite design of phased array and reflectarray antennas. The phased array antenna can achieve a ±45° scanning range, while the reflectarray antenna utilizes horn antenna offset feeding and normal radiation, greatly expanding the antenna's flexibility.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a low-profile antenna shared by a phased array and a reflective array based on a structural composite surface. Background Art

[0002] With the development of millimeter-wave technology and communication systems in fifth-generation mobile communications (5G), there is a need to increase the frequency of communication bands to expand the spectrum and improve communication speeds. Furthermore, the diversification of system functionality requires simultaneous access to multiple operating frequency bands (such as millimeter-wave bands and sub-6 GHz). This application context places new demands on various components in the communication system, including antennas. Antennas are a relatively special component in the entire communication system, as they interact with open space and are susceptible to external environmental influences. Antenna performance directly determines the quality of the entire communication system. While higher operating frequencies allow for faster information transmission and expand spectrum resources, the wavelength of the electromagnetic waves radiated by the antenna is also shorter, making them more susceptible to external interference. For example, in long-distance communications (such as satellite communications), increasing communication speeds has pushed the available frequency bands to millimeter waves, where energy loss due to path loss is significant. Furthermore, to meet the multi-band requirements of millimeter-wave communication systems, antennas must be able to operate simultaneously in multiple frequency bands. Traditionally, multiple antennas have been used to address this issue, but this undoubtedly significantly increases system redundancy. This can be attributed to three requirements for antenna design: (1) the antenna operating frequency needs to cover multiple frequency bands to achieve the diversification of the communication system; (2) the antenna has high radiation gain to combat path loss; and (3) the antenna structure needs to be lightweight and simple to facilitate system integration.

[0003] To address these three requirements, a multi-frequency array antenna based on structural reuse technology is a promising solution. In the paper "J. Lan, Z. Yu and J. Zhou, "A 3.5 / 28 GHz Beam-Steerable Shared-Aperture Antenna Based on Shorting-Vias-Loaded Patch," 2020 IEEE MTT-S International Wireless Symposium (IWS), 2020, pp. 1-3, doi:10.1109 / IWS49314.2020.9360209," Ji Lan et al. from Southeast University designed a dual-band structural reuse array antenna operating at 3.5 / 28 GHz. This antenna achieves structural reuse of a low-band patch antenna and a high-band SIW (substrate integrated waveguide) slot array antenna through multi-port coupled feeding, resulting in a very compact antenna structure. However, this antenna radiates directional radiation in both frequency bands and lacks a large array size, leaving room for improvement in antenna gain. In the paper "Y. Yao, X. Q. Lin, T. Qin, Y. Su, and X. Yang, "Shared-Aperture Ka-Band Reflectarray and X-Band Phased Array for Broadband Inter-Satellite Communication," in IEEE Transactions on Antennas and Propagation, vol. 70, no. 11, pp. 11199-11204, Nov. 2022, doi: 10.1109 / TAP.2022.3209249," Yao et al. from the University of Electronic Science and Technology of China proposed a co-aperture array antenna capable of operating simultaneously with both a Ka-band reflectarray and an X-band phased array. Because the reflectarray has a transmissive effect in the X-band, the Ka-band reflectarray can be stacked above the X-band phased array, improving aperture reuse. This array antenna offers high radiation gain, dual-band operation, and a simple structure. Finally, the phased array part of the array antenna operates at 7-11.1 GHz, with a relative bandwidth of 45.3% and a scanning range of ±45°; the reflector array part operates at 26.4-29.6 GHz, with a 3dB gain bandwidth of 11.4%.In the paper "DESerup, GFPedersen and S.Zhang,"Dual-Band Shared ApertureReflectarray and Patch Antenna Array for S-and Ka-Bands,"in IEEE Transactions on Antennas and Propagation,vol.70,no.3,pp.2340-2345,March 2022,doi:10.1109 / TAP.2021.3111171.", foreign scholars DESerup et al. proposed a structure in which the reflectarray antenna and the directional radiation antenna array units are nested on the same layer, so that the antenna can operate in the S-band and Ka-band. In this paper, the patch array is designed first, and then two types of reflectarray units are designed, which are used for nesting low-frequency patches and filling the gaps in the low-frequency array respectively. The reflectarray unit adopts a multi-layer structure, which improves the reflection phase of the reflectarray unit on the one hand and expands the bandwidth of the low-frequency patch array on the other hand. However, since the reflective array unit adopts a multi-layer structure, the cross-section of the antenna cannot be effectively reduced, which increases the cost of the antenna. Summary of the Invention

[0004] In response to the above background requirements and existing technical problems, the present invention, based on a structurally reused antenna design method, combines phased array antenna theory and reflectarray antenna theory, and invents and designs a low-profile antenna shared by a phased array and reflectarray based on a structural composite surface. In the present invention, only a single-layer unit structure is adopted to simultaneously realize the antenna unit design of a phased array and a reflectarray, which has the advantages of high aperture reuse rate and low profile. After simulation optimization, the operating frequency band of the phased array is 7.98-9.93GHz (relative bandwidth is 21.77%), which can cover a scanning range of ±45°. The effective peak gain of the phased array is 21.12dBi at 9GHz, and the corresponding radiation efficiency is 89.87%. The 3dB gain bandwidth of the reflectarray antenna is 25.10-30.51GHz (relative bandwidth is 19.46%), and the effective peak gain is 31.42dBi at 28GHz, and the corresponding radiation efficiency is 54.02%.

[0005] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions:

[0006] A low-profile antenna shared by a phased array and a reflectarray based on a structural composite surface includes two substrates, a radiation structure on the upper surface of the upper substrate, a prepreg used to bond the upper and lower substrates, a slot-coupled feeding structure on the upper surface of the lower substrate, and a feed line structure on the lower surface of the lower substrate.

[0007] Furthermore, the material of the two substrates is RF 35, the dielectric constant is 3.5, the thickness of the upper substrate is 1.524 mm, and the thickness of the lower substrate is 0.508 mm.

[0008] Furthermore, the radiation structure on the upper surface of the upper substrate includes a phased array unit.

[0009] Furthermore, the total number of the phased array units is 9×9, and the phased array units are arranged in a triangular shape.

[0010] Furthermore, the phased array unit is composed of 4×4 reflective array units.

[0011] Furthermore, the reflective array unit is evolved from a basic structure of a "U" type, including an outer frame, an inner frame and a hollow Jerusalem ring in the middle.

[0012] Furthermore, the prepreg is made of RO4350F, has a dielectric constant of 3.5, and a thickness of 0.1 mm.

[0013] Furthermore, the prepreg has two layers.

[0014] Furthermore, the slot adopts a narrow and long rectangular structure and is placed at the position of the symmetry axis of each phased array unit.

[0015] Furthermore, the feed line structure on the lower surface of the lower substrate adopts a transition structure design from SMA to microstrip line, which includes an SMA pad, a ground metallized via, and a central microstrip line structure. The SMA pad surrounds the central microstrip line structure, and a ground metallized via is processed on the pad. The pad connected to the SMA inner conductor gradually widens to become a microstrip feed line, so that the energy entering from the SMA connector is transmitted along the microstrip line through the coupling gap to the phased array unit, thereby realizing the operation of the phased array.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] 1. Nearly 100% aperture reuse and low profile. In this invention, the phased array and reflectarray utilize the same basic unit, and the primary structure of this unit requires only one layer of metal. Furthermore, the phased array antenna operates in the X-band, while the reflectarray antenna operates in the Ka-band, covering two commonly used microwave and millimeter-wave frequency bands.

[0018] 2. High radiation gain and efficiency. The reflectarray consists of 38×38 elements, with an effective peak radiation gain of 31.42 dBi at 28 GHz and a corresponding radiation efficiency of 54.02%. The phased array consists of 9×9 elements, with the middle 7×7 elements actually fed. At 9 GHz, the effective peak radiation gain is 21.12 dBi, with a corresponding radiation efficiency of 89.87%.

[0019] 3. Wide operating bandwidth. The phased array unit is composed of a 4×4 basic unit, a metasurface structure that successfully excites the structure's mode. The reflectarray unit is composed of a "U"-shaped structure with a hollow Jerusalem structure in the center, which has good frequency consistency and also contributes to the formation of a wide operating bandwidth. After optimization, the phased array operating frequency band is 7.98-9.93GHz (relative bandwidth is 21.77%), and the 3dB gain bandwidth of the reflectarray antenna is 25.10-30.51GHz (relative bandwidth is 19.46%).

[0020] 4. The present invention adopts a composite structural design of phased array antenna and reflectarray antenna. The phased array antenna can achieve a scanning range of ±45°, and the reflectarray antenna adopts horn antenna offset feeding and normal radiation, which greatly expands the flexibility of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the basic unit of the structure multiplexing antenna array in the present invention;

[0022] Figure 2 Schematic diagram of the radiation structure of the phased array unit in the present invention;

[0023] Figure 3 Schematic diagram of the feeding coupling gap of the phased array unit in the present invention;

[0024] Figure 4 Schematic diagram of the transition structure from the SMA pad of the phased array unit to the microstrip feed line in the present invention;

[0025] Figure 5 Schematic diagram of the arrangement of units in the overall array of the present invention;

[0026] Figure 6 Schematic diagram of the structure of the overall array in the present invention;

[0027] Figure 7 is a graph showing changes in the reflection phase of the reflector array unit according to the zoom ratio in the present invention;

[0028] Figure 8 The radiation patterns of the E-plane and H-plane of the reflector array in the present invention at 28 GHz;

[0029] Figure 9 This is a graph showing how the peak radiation gain of the reflective array varies with frequency in the present invention;

[0030] Figure 10 (a) is a graph showing the return loss versus frequency when the phased array scanning angle is Theta = 0° and Phi = 0° in the present invention;

[0031] Figure 10 (b) is the radiation pattern of the E-plane and H-plane when the phased array scanning angle is Theta = 0° and Phi = 0° in the present invention;

[0032] Figure 11 (a) is a graph showing the return loss versus frequency when the phased array scanning angle is Theta = 45° and Phi = 0° in the present invention;

[0033] Figure 11 (b) is the radiation pattern of the E-plane and H-plane when the phased array scanning angle is Theta = 45° and Phi = 0° in the present invention;

[0034] Figure 12 (a) is a graph showing the return loss versus frequency when the phased array scanning angle is Theta = 45° and Phi = 90° in the present invention;

[0035] Figure 12 (b) is the radiation pattern of the E-plane and H-plane when the phased array scanning angle is Theta = 45° and Phi = 90° in the present invention. DETAILED DESCRIPTION

[0036] The present invention aims to realize a low-profile antenna based on a structural composite surface, combining phased arrays and reflectarrays. The antenna comprises two substrates, a radiating structure on the upper surface of the upper substrate, a prepreg used to bond the upper and lower substrates, a slot-coupled feed structure on the upper surface of the lower substrate, and a feeder structure on the lower surface of the lower substrate. The substrates are made of RF 35 with a dielectric constant of 3.5. The upper substrate is 1.524 mm thick, while the lower substrate is 0.508 mm thick. The prepreg is made of RO4350F with a dielectric constant of 3.5 and a thickness of 0.1 mm. Two layers of prepreg are used to ensure a more secure bond between the upper and lower substrates.

[0037] The upper surface of the upper substrate is a radiating structure. The smallest unit of this radiating structure evolves from a basic "loop"-shaped structure. A Jerusalem cross ring structure with a hollowed-out center is loaded in the center of the "loop" structure. By maintaining the outer frame of the smallest unit unchanged and adjusting the size of the inner frame and the Jerusalem cross ring, a reflection phase covering 360° can be achieved, which is used to implement the design of a reflectarray antenna. Meanwhile, the phased array element is composed of 4×4 smallest units. Since the outer frame dimensions of the smallest unit remain unchanged, the metasurface operating mode of the 4×4 patch units can be stimulated, which helps to improve the operating bandwidth. Ultimately, the array surface is composed of 38×38 smallest units, forming a reflectarray scale. Each 4×4 smallest unit is a phased array unit, resulting in a total of 9×9 phased array units. The phased array units are arranged in a triangular pattern. To optimize the return loss of the phased array edge units, the actual feeding phased array units are the 7×7 in the center.

[0038] The prepreg is used to bond the upper and lower substrates to achieve a laminate effect, which helps to improve precision.

[0039] The upper surface of the lower substrate features a slot-coupled feed structure, primarily used to excite the phased array elements. The slots are narrow, rectangular structures, placed along the axis of symmetry of each phased array element. There are a total of 9 x 9 slots, and only the middle 7 x 7 slots are excited and fed.

[0040] The feed structure on the lower surface of the lower substrate is primarily implemented as a microstrip feed line. To facilitate soldering of the SMA connector, a transition structure from SMA to microstrip line is designed. This transition structure primarily includes the SMA pads. The pads connected to the SMA inner conductor gradually widen to form the microstrip feed line. This allows energy entering from the SMA connector to be transmitted along the microstrip line through the coupling gap to the phased array elements, enabling phased array operation.

[0041] In order to make the above-mentioned objects, advantages and features of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0042] Figure 1 It is the basic unit designed in the present invention and is also a unit of the reflective array. Figure 1 (a) is the unit structure of the original size, Figure 1 (b) shows the structure scaled down to 0.5 times its original size. 1 represents the size of the reflectarray element. When the element size is scaled, the line widths of the reflectarray element's outer frame 2, inner frame 3, and central hollow Jerusalem ring 4 remain unchanged. This allows the design of an active radiating antenna using the outer frame 2 of the basic element.

[0043] Figure 2This is a schematic diagram of the phased array unit radiation structure designed in the present invention. As can be seen from the figure, the phased array unit 5 is composed of 4×4 reflectarray elements. Because the unit's outer frame 2 remains unchanged during the expansion and contraction of the reflectarray unit, these 4×4 reflectarray elements together form a metasurface antenna subarray. Verification has shown that the expansion and contraction of the reflectarray unit intermediate structures 3 and 4 do not affect the subarray's performance. This demonstrates the high isolation between the reflectarray unit pattern and the antenna subarray pattern.

[0044] Figure 3 The feeding slot structure of the phased array unit in the present invention is placed on the upper surface of the lower substrate. The coupling slot 7 is located at the position of the symmetry axis of the metal patch 6.

[0045] Figure 4 This diagram shows the transition structure from the SMA pad of a phased array element to the microstrip feed line on the lower surface of the underlying substrate. This structure is placed on the lower surface of the underlying substrate. The SMA pad 10 surrounds the central microstrip line structure 8. To ensure proper grounding of the SMA connector, a grounding metallized via 9 is machined through the pad 10. The overall unit dimensions are shown in 11.

[0046] Figure 5 Figure 1 is a schematic diagram illustrating the arrangement of elements in the overall array plane of the present invention. In this diagram, the reflectarray elements 12 have been scaled according to the element phase shift, feed position, and illumination angle, resulting in a total of 38×38 elements. The phased array elements 13 are composed of 4×4 reflectarray elements in a triangular arrangement as shown in the figure, resulting in a total of 9×9 phased array elements. To optimize the return loss of the port, only the central 7×7 elements are excited.

[0047] Figure 6 It is a structural schematic diagram of the overall array surface 14 in the present invention.

[0048] Figure 7 Figure 2 shows the change in the reflection phase of the reflectarray unit with the scaling. It can be seen that when the scaling size of the reflectarray unit increases from 0.5 to 1.0, the reflection phase of the reflectarray unit covers 360°, and the overall downward trend of the curve is gentle, which is conducive to reducing processing errors and improving radiation efficiency.

[0049] Figure 8 Figure 2 is the E-plane and H-plane radiation pattern of the reflector array at 28 GHz. The effective peak radiation gain at 28 GHz is 31.42 dBi, and the corresponding radiation efficiency is 54.02%.

[0050] Figure 9 The curve of the peak radiation gain of the reflector array varying with frequency is shown in FIG. 1 , and its 3dB gain bandwidth is 25.10-30.51GHz (relative bandwidth is 19.46%).

[0051] Figure 10 (a) is a curve showing the return loss versus frequency when the phased array scanning angle is Theta = 0° and Phi = 0°. The selected ports in the figure are located on the diagonal of the quarter plane, and the operating frequency range is 7.98-9.93 GHz (relative bandwidth is 21.77%). Figure 10 (b) is the radiation pattern of the E-plane and H-plane when the phased array operates at a frequency of 9 GHz, the scanning angle is Theta = 0°, and the Phi = 0°. The effective peak radiation gain is 21.12 dBi, and the corresponding radiation efficiency is 89.87%. Figure 11 (a) is the curve of return loss changing with frequency when the phased array scanning angle is Theta = 45° and Phi = 0°; Figure 11 (b) shows the radiation pattern of the E-plane and H-plane when the phased array scanning angle is Theta = 45° and Phi = 0°. The effective peak gain at this time is 19.47dBi. Figure 12 (a) is the curve of return loss changing with frequency when the phased array scanning angle is Theta = 45° and Phi = 90°; Figure 12 (b) is the radiation pattern of the E-plane and H-plane when the phased array scanning angle is Theta = 45° and Phi = 90°. The effective peak gain at this time is 19.38dBi.

[0052] The advantages of the present invention are: (1) The flexibility of the antenna is greatly expanded through the structural composite design of the phased array antenna and the reflectarray antenna. The phased array antenna operates in the X-band and can achieve a scanning range of ±45°, and the reflectarray antenna operates at 28GHz and adopts directional radiation. (2) A wide operating bandwidth, high radiation efficiency and gain. (3) The present invention designs a single-layer unit that can serve as both a reflectarray and a phased array, so that the final array antenna achieves an aperture reuse rate close to 100% and a very low profile height.

Claims

1. A low-profile antenna based on a structural composite surface, used for both phased array and reflective array, characterized in that: It includes two substrates, a radiation structure on the upper surface of the upper substrate, a prepreg for bonding the upper and lower substrates, a slot coupling feeding structure on the upper surface of the lower substrate, and a feed line structure on the lower surface of the lower substrate; The radiation structure on the upper surface of the upper substrate includes a phased array unit; The total number of phased array units is 9×9, and the phased array units are arranged in a triangular pattern; The phased array unit is composed of 4×4 reflective array units; The reflective array unit is evolved from a basic "U"-shaped structure, including an outer frame, an inner frame and a hollow Jerusalem ring in the middle.

2. The low-profile antenna for phased array and reflectarray based on a structural composite surface according to claim 1, characterized in that: The material of the two substrates is RF 35 with a dielectric constant of 3.

5. The thickness of the upper substrate is 1.524 mm and the thickness of the lower substrate is 0.508 mm.

3. The low-profile antenna for phased array and reflectarray based on a structural composite surface according to claim 1, characterized in that: The prepreg is made of RO4350F, has a dielectric constant of 3.5, and a thickness of 0.1 mm.

4. The low-profile antenna shared by a phased array and a reflectarray based on a structural composite surface according to claim 1 or 3, characterized in that: The prepreg has two layers.

5. The low-profile antenna for phased array and reflectarray based on a structural composite surface according to claim 1, characterized in that: The slot adopts a narrow and long rectangular structure and is placed at the position of the symmetry axis of each phased array unit.

6. The low-profile antenna for phased array and reflectarray based on a structural composite surface according to claim 1, characterized in that: The feeder structure on the lower surface of the lower substrate adopts a transition structure design from SMA to microstrip line. The transition structure includes an SMA pad, a ground metallized via, and a central microstrip line structure. The SMA pad surrounds the central microstrip line structure, and a ground metallized via is processed on the pad. The pad connected to the SMA inner conductor gradually widens to become a microstrip feeder, so that the energy entering from the SMA connector is transmitted along the microstrip line through the coupling gap to the phased array unit, thereby realizing the operation of the phased array.

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