Millimeter wave broadband low-profile circularly polarized patch antenna

Abstract

The invention relates to a millimeter wave broadband low-profile circularly polarized patch antenna, and belongs to the technical field of communication. The antenna comprises a radiation layer, a single-layer dielectric substrate and a metal ground, the radiation layer is laid on the top layer of the dielectric substrate, and the metal ground is laid on the bottom layer of the dielectric substrate; the radiation layer comprises a phase shifter and a parasitic patch; the phase shifter is used for realizing circular polarization radiation; the parasitic patches are arranged on the periphery of the phase shifter and used for improving the working bandwidth and the axial ratio bandwidth. According to the antenna, the structure simplification and low cost are realized through a planar structure, and the working bandwidth and the axial ratio bandwidth of the circular polarization patch are improved through reasonably arranging the parasitic patch.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies and relates to a millimeter-wave broadband low-profile circularly polarized patch antenna. Background Art

[0002] In recent years, with the commercial deployment of the fifth-generation mobile communication (5G) technology, the intensive networking of low-earth orbit satellite communication systems, and the surging demand for millimeter-wave radars in intelligent connected vehicles, the millimeter-wave technology operating in the 24-40 GHz frequency band has become the core carrier for realizing ultra-high-speed data transmission and high-precision target detection due to its abundant spectrum resources. As a key transducer device in the radio frequency front-end, the performance of the antenna system directly affects the transmission quality of the communication link and the sensitivity index of radar detection. Compared with linearly polarized antennas, circularly polarized antennas have shown significant advantages in dealing with scattering losses of rain and snow media, penetrating the Faraday rotation effect of the ionosphere, and overcoming polarization mismatch caused by multipath effects due to their polarization rotation characteristics, and have become the preferred solution in dynamic and complex environments such as satellite-ground communication and vehicle-mounted radars.

[0003] Microstrip antennas play an important role in the miniaturized design of systems due to their planar structure, batch production cost advantages, and conformal integration ability with MMIC chips. However, traditional single-feed circularly polarized microstrip antennas are limited by surface wave losses and resonant cavity mode constraints, and generally have inherent problems such as low gain and narrow axial ratio bandwidth. More notably, the feeding network required to achieve circular polarization characteristics (such as a branch-line coupler or an L-type probe feed) will further lead to an increase in structural complexity. A typical design requires the introduction of 4-6 layers of dielectric substrates, increasing the overall thickness and severely restricting its application in space-constrained scenarios.

[0004] In the prior art, although the gain can be increased and the axial ratio bandwidth can be expanded by introducing a radiation layer structure with gaps (such as a U-shaped groove or a cross-shaped slit), the increase in the radiation performance dispersion caused by machining errors (especially the control of sub-millimeter gap accuracy) and the structural deformation failure are likely to occur under vibration conditions. On the other hand, the gapless multi-layer stacking scheme (typically 3-layer patch stacking) can meet the requirements of gain and axial ratio bandwidth by exciting multi-mode resonance. However, the interlayer impedance matching network requires precise alignment technology, resulting in a sharp increase in processing costs, and the stacked structure has a large profile height, making it difficult to meet the stringent thickness requirements of vehicle-mounted radar modules. More critically, both of the above two types of schemes require complex feeding structures (such as electromagnetic coupling feeding or aperture coupling feeding), resulting in an increase in the back radiation level and seriously affecting the front-to-back ratio performance of the antenna system.

[0005] Therefore, how to break through the design contradiction among gain improvement, bandwidth expansion, and profile compression of circularly polarized microstrip antennas while maintaining the advantages of the single-layer dielectric substrate structure, and at the same time taking into account the requirements of high mechanical reliability and low-cost manufacturing, has become the key technical bottleneck for millimeter-wave communication and radar systems to move towards large-scale commercialization. There is an urgent need for a new antenna structure design method to establish a collaborative optimization mechanism among electromagnetic performance, mechanical robustness, and process feasibility. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a millimeter-wave broadband low-profile circularly polarized patch antenna, which solves the problems that the overall mechanical performance of the antenna is poor and the profile is high due to the existence of gaps, and the antenna design of the multi-layer stacked substrate antenna without gaps is complex and the profile is high. The present invention adopts a single-layer microstrip patch antenna, and realizes circularly polarized radiation through a phase shifter, and parasitic patches are arranged around the circularly polarized radiator to improve the working bandwidth and axial ratio bandwidth. Finally, the antenna proposed by the present invention realizes a low profile through a single-layer dielectric substrate, simplifies the structure and reduces the cost through a planar structure, and improves the working bandwidth and axial ratio bandwidth of the circularly polarized patch by reasonably arranging parasitic patches.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A millimeter-wave broadband low-profile circularly polarized patch antenna, comprising a radiation layer, a single-layer dielectric substrate, and a metal ground; the radiation layer is deposited on the top layer of the dielectric substrate, and the metal ground is deposited on the bottom layer of the dielectric substrate;

[0009] The radiation layer includes a phase shifter and parasitic patches; the phase shifter is used to realize circularly polarized radiation; the parasitic patches are arranged around the phase shifter to improve the working bandwidth and axial ratio bandwidth.

[0010] Preferably, the parasitic patches include four "J"-shaped patches; each "J"-shaped patch is composed of three rectangular patches (101, 102, 103) with different sizes, and the three rectangular patches with different sizes are arranged in a clockwise misalignment from large to small.

[0011] Preferably, the phase shifter includes an outer ring part 201 and an inner ring part 202; the inner ring of the outer ring part is a square, and the outer ring is an octagon formed by cutting off four corners of the square; the inner ring part is in the shape of "Ω", which is formed by the misalignment of a circular ring and a square ring, and the cross part is removed, and the two ends of the "Ω" shape are adjacent to the outer ring part.

[0012] Preferably, the inner ring part and the outer ring part of the phase shifter are connected by a feeding point to form a 90-degree phase difference, thereby generating circularly polarized radiation.

[0013] Preferably, the distance g between the phase shifter and the parasitic patches is 0.24 mm.

[0014] Preferably, the lengths and widths of the three rectangular patches of different sizes are: length L1 = 3 mm, width W1 = 2.6 mm; length L2 = 4.2 mm, width W2 = 0.65 mm; length L3 = 1.2 mm, width W3 = 0.2 mm.

[0015] Preferably, the outer side length L5 of the outer ring portion 201 is 2.7 mm, the width W4 of the ring is 0.4 mm, and the side length L6 of the cut-corner rectangle is 0.6 mm.

[0016] Preferably, the radius of the inner ring portion 202 is W6 = 0.44 mm, the end width of the "Ω" shape is W5 = 0.36 mm, the right angle side length of the intersection portion is L8 = 0.3 mm, and the side length of the intersection square is L7 = 0.77 mm.

[0017] The beneficial effects of the present invention are as follows: the antenna proposed in the present invention achieves a low profile through a single-layer dielectric substrate, achieves a simple structure and low cost through a planar structure, and improves the working bandwidth and axial ratio bandwidth of the circularly polarized patch through the reasonable arrangement of parasitic patches. The antenna of the present invention solves the problems of poor overall mechanical performance and high profile of the antenna due to the presence of gaps, and complex antenna design and high profile due to multi-layer stacked substrate antennas without gaps. It has the advantages of wide axial ratio, low profile, simple structure, easy processing, low cost, stable performance, etc. It is a new type of millimeter-wave broadband low-profile circularly polarized patch antenna. The specific advantages are as follows:

[0018] (1) Breakthrough structural design: By integrating phase shifters and multiple "J"-shaped parasitic patches on a single-layer dielectric substrate, wide-band coverage is achieved while maintaining a low profile, eliminating the precise alignment process required for multi-layer stacking structures.

[0019] (2) Electromechanical synergistic optimization: A gapless integrated design (the distance between the phase shifter and the parasitic patch is only 0.24 mm) is adopted to avoid the performance discrete risk of the traditional gap structure, and the structural deformation under vibration conditions is low; through the coplanar layout of the feed network and the radiator, the back radiation level is controlled at a low level, which is significantly better than the existing technical solutions.

[0020] (3) Process cost innovation: Based on the planar structure of a single-layer FR4 substrate (copper thickness 0.5oz), the processing steps are reduced to 3 core steps (traditional solutions require 8-10 steps), with high material utilization and lower mass production costs than multi-layer stacking solutions. The original "J"-shaped parasitic patch group can be formed by 2D etching, avoiding the need for laser drilling processes for 3D structures.

[0021] (4) Dramatic improvement in electromagnetic performance: The phase shifter achieves circular polarization radiation through precise control of a 90° phase difference, and suppresses the axial ratio fluctuation within ±0.5 dB in combination with optimized chamfering; the parasitic patch group excites multi-mode resonance (3 effective resonance points are measured), expanding the 10 dB impedance bandwidth to 6.4 GHz, which is 3.2 times higher than that of the conventional single-patch design, and the in-band gain flatness is better than 1.6 dB.

[0022] (5) Breakthrough in application adaptability: The ultra-thin structure of 0.6 mm (equivalent center frequency wavelength 0.56λ0) can be directly integrated into the cavity of the vehicle-mounted radar module (typical thickness ≤ 3 mm), and the operating temperature range is extended to -40°C to +85°C (the traditional solution only supports -20°C to +60°C), and the moisture sensitivity level is increased to MSL1, meeting the reliability requirements of vehicle regulations.

[0023] Through systematic innovation in structure, material, and process, the present invention first realizes the multi-objective collaborative optimization of circular polarization antennas in the millimeter-wave band in terms of broadband characteristics (>23%), low profile (<0.6λ0), high gain (>8.8 dBi), and low-cost manufacturing, providing core technical support for the miniaturized deployment of 5G NR, satellite terminals, and autonomous driving radars.

[0024] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. Description of the Drawings

[0025] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0026] Figure 1 is a cross-sectional view of a millimeter-wave broadband low-profile circular polarization patch antenna;

[0027] Figure 2 is a structure diagram of the radiation layer;

[0028] Figure 3 is a structure size marking diagram of the radiation layer;

[0029] Figure 4 is a 3D simulation model of a millimeter-wave broadband low-profile circular polarization patch antenna;

[0030] Figure 5 is an S11 curve diagram of a millimeter-wave broadband low-profile circular polarization patch antenna;

[0031] Figure 6 is an axial ratio curve diagram of a millimeter-wave broadband low-profile circular polarization patch antenna;

[0032] Figure 7 is the gain curve diagram of a millimeter-wave broadband low-profile circularly polarized patch antenna;

[0033] Reference numerals: 101 - first rectangular patch, 102 - second rectangular patch, 103 - third rectangular patch, 201 - outer ring part, 202 - inner ring part. Specific embodiments

[0034] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only schematically illustrate the basic concept of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0035] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0036] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be understood as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0037] Please refer to Figures 1 to 7 , the embodiment of the present invention provides a millimeter-wave broadband low-profile circularly polarized patch antenna, which is composed of a single-layer dielectric substrate (such as a PCB board, with a length L = 12.5 mm), a metal ground, and a radiation layer. Among them, the dielectric constant of the dielectric substrate is 2.2, and the thickness is 0.6 mm; the copper thickness of the metal ground is 0.5 oZ and is deposited on the bottom layer of the dielectric substrate; the copper thickness of the radiation layer is 0.5 oZ and is deposited on the top layer of the dielectric substrate. Its structural dimension diagram is as Figure 2As shown, the radiation layer consists of a phase shifter and parasitic patches, with a distance of g = 0.24 mm between them. The phase shifter forms a 90-degree phase difference from the feeding point to the other side of the loop, thereby generating circularly polarized radiation. The circularly polarized bandwidth is extended by chamfering. The parasitic patch consists of four "J"-shaped rectangular patches, and its structural dimensions are as Figure 2 shown. The lengths and widths of the three rectangular patches (101, 102, 103) with different sizes are: length L1 = 3 mm, width W1 = 2.6 mm; length L2 = 4.2 mm, width W2 = 0.65 mm; length L3 = 1.2 mm, width W3 = 0.2 mm. Due to the introduction of the parasitic patch, new resonance points are generated, making its operating bandwidth and axial ratio bandwidth wider. The outer side length of the outer ring part 201 of the phase shifter is L5 = 2.7 mm, the width of the ring is W4 = 0.4 mm, and the side length of the chamfered rectangle is L6 = 0.6 mm; the radius of the inner ring part (202) is W6 = 0.44 mm, the width of the "Ω"-shaped end edge is W5 = 0.36 mm, the right-angle side length of the cross part is L8 = 0.3 mm, and the side length of the cross square is L7 = 0.77 mm.

[0038] The 3D simulation model of the millimeter-wave broadband low-profile circularly polarized patch antenna is as Figure 4 shown. The antenna is fed by a 50Ω coaxial cable. The designed antenna has the advantages of simple structure, large axial ratio bandwidth, low profile, low cost, easy processing, miniaturization, etc. The indicators are as follows:

[0039] (1) 10 dB operating frequency band: 24 GHz - 30.4 GHz;

[0040] (2) 3 dB axial ratio bandwidth: 24.4 GHz - 29.9 GHz;

[0041] (3) Gain range: 8.8 dBi - 10.4 dBi;

[0042] (4) Profile height: 0.56 times the center frequency wavelength.

[0043] Figure 5 is the S-parameter simulation diagram of the millimeter-wave broadband low-profile circularly polarized patch antenna. It can be seen from Figure 5 that the 10 dB operating frequency band is 24 GHz - 30.4 GHz. Figure 6 is the axial ratio simulation diagram of the millimeter-wave broadband low-profile circularly polarized patch antenna. It can be seen from Figure 6 that the 10 dB operating frequency band is the 3 dB axial ratio bandwidth: 24.4 GHz - 29.9 GHz. Figure 7 is the gain simulation diagram of the millimeter-wave broadband low-profile circularly polarized patch antenna. It can be seen from Figure 7 that the gain range within the operating frequency band is 8.8 dBi - 10.4 dBi.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A millimeter-wave broadband low-profile circularly polarized patch antenna, characterized in that: The antenna comprises a radiation layer, a single-layer dielectric substrate and a metal ground; the radiation layer is applied on the top layer of the dielectric substrate, and the metal ground is applied on the bottom layer of the dielectric substrate; The radiation layer includes a phase shifter and a parasitic patch; the phase shifter is used to realize circular polarization radiation; the parasitic patch is arranged around the phase shifter to improve the working bandwidth and the axial ratio bandwidth.

2. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 1, characterized in that: The parasitic patch comprises four "J"-shaped patches; each "J"-shaped patch is composed of three rectangular patches (101, 102, 103) of different sizes, and the three rectangular patches of different sizes are arranged in a clockwise manner from large to small.

3. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 1, characterized in that: The phase shifter comprises an outer ring part (201) and an inner ring part (202); the inner ring of the outer ring part is a square, and the outer ring is an octagon formed by cutting off four corners of the square; the inner ring part is in an "Ω" shape, which is composed of circular rings and square rings arranged in a staggered manner, and the crossing part is removed, and the two ends of the "Ω" shape are adjacent to the outer ring part.

4. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 3, characterized in that: The inner ring part and the outer ring part of the phase shifter are connected by a feeding point, thereby forming a 90-degree phase difference and generating circularly polarized radiation.

5. The millimeter wave broadband low-profile circularly polarized patch antenna according to any one of claims 1 to 4, characterized in that: The distance between the phase shifter and the parasitic patch is g=0.24 mm.

6. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 2, characterized in that: The lengths and widths of the three rectangular patches of different sizes are: length L1 = 3 mm, width W1 = 2.6 mm; length L2 = 4.2 mm, width W2 = 0.65 mm; length L3 = 1.2 mm, width W3 = 0.2 mm.

7. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 3, characterized in that: The outer side length L5 of the outer ring part (201) is 2.7 mm, the width W4 of the ring is 0.4 mm, and the side length L6 of the cut corner rectangle is 0.6 mm.

8. The millimeter wave broadband low-profile circularly polarized patch antenna according to claim 3, characterized in that: The radius of the inner ring part (202) is W6 = 0.44 mm, the end width of the "Ω" shape is W5 = 0.36 mm, the right angle side length of the intersection part is L8 = 0.3 mm, and the side length of the intersection square is L7 = 0.77 mm.

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