An ultra-low profile wideband circularly polarized microstrip patch antenna array and a design method thereof

Abstract

The application discloses an ultra-low profile wideband circularly polarized microstrip patch antenna array and a design method thereof, the antenna array is constructed on a single-layer thin dielectric substrate, the antenna unit is composed of a substrate integrated waveguide resonant cavity and a microstrip patch resonator embedded in the center, and the combination of the double resonators is realized without increasing the size of the antenna. Adjacent antenna units are arranged with zero spacing, and share a metal column around the edge of the substrate integrated waveguide resonant cavity. By using the center slot, the ring slot and the four symmetrical slots connected thereto, two pairs of degenerate modes with orthogonal polarization and similar resonant characteristics are introduced, thereby forming four resonant points with similar radiation characteristics and similar resonant frequencies and two axial ratio zero points, so that the synchronous expansion of the impedance bandwidth and the axial ratio bandwidth is realized. In addition, the radiation cancellation effect along the two sides of the ring slot produces a radiation zero point near the upper edge of the passband, thereby improving the out-of-band suppression performance of the antenna.

Description

Technical Field

[0001] The present invention relates to an ultra-low profile broadband circularly polarized microstrip patch antenna array and a design method thereof, and belongs to the fields of antenna and microwave technology and wireless communications. Background Art

[0002] With the rapid development of modern wireless communication technology, circularly polarized array antennas, thanks to their superior multipath interference suppression and effective polarization mismatch reduction, are widely used in emerging and popular fields such as satellite communications, mobile internet, global positioning, and real-time navigation. At the same time, microstrip patch antennas, with their advantages of small size, light weight, low cost, simple processing, and ease of integration, are widely researched and applied. Consequently, circularly polarized antenna arrays based on microstrip patch resonators have garnered extensive and in-depth attention and research in recent years.

[0003] Traditional microstrip patch array antennas typically achieve circularly polarized radiation by adding stubs, slots, and vias. While this approach is simple and straightforward, its usable bandwidth is relatively limited. Currently, three methods are commonly used to broaden the bandwidth of circularly polarized antennas. First, optimizing and improving the feed structure, including the introduction of phase shifters, power splitters, and the use of rotary feeds, increases antenna insertion loss and often requires complex multilayer structures. Second, introducing additional structures such as parasitic elements, stacked slots, multiple patches, and metasurfaces takes up additional space, increasing the overall size of the antenna array and increasing structural complexity. Third, leveraging multimode resonance theory, adjusting the patch resonator structure to excite multiple resonant modes can effectively increase bandwidth, but this often also results in increased size. Furthermore, as the number of modes increases, the difficulty of controlling the modes increases dramatically, particularly with multimode radiation characteristics.

[0004] Currently, proposed broadband circularly polarized microstrip patch antenna array designs almost exclusively focus on the array's impedance bandwidth, without fully considering the radiation performance within the passband. Furthermore, the array structure is relatively complex. Therefore, achieving simultaneous broadening of the impedance bandwidth, radiation bandwidth, and axial ratio bandwidth while maintaining the structural advantages and performance characteristics of conventional microstrip patch antenna arrays is a key technical challenge that urgently needs to be addressed. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an ultra-low-profile, broadband, circularly polarized microstrip patch antenna array and a design method thereof. This design method achieves simultaneous broadening of impedance bandwidth, radiation bandwidth, and axial ratio bandwidth, as well as improved out-of-band suppression, while fully retaining the structural advantages and performance characteristics of traditional microstrip patch array antennas. The designed antenna array features a low profile, small size, simple structure, wide bandwidth, stable radiation, and ease of fabrication and integration. It can achieve wide-angle scanning or high-gain characteristics and is suitable for antenna arrays of any size, thus possessing broad application prospects.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] On the one hand, a design method for an ultra-low profile broadband circularly polarized microstrip patch antenna array is provided, the design method comprising:

[0008] m*n identical substrate-integrated waveguide resonant cavities are formed on a dielectric substrate, and the m*n substrate-integrated waveguide resonant cavities are arranged in an array; wherein m and n are arbitrary positive integers; a slot is formed in the center of each substrate-integrated waveguide resonant cavity, and an identical microstrip patch resonator is embedded in the center of each slot to form an antenna unit, and a coaxial feeding probe is provided on each antenna unit.

[0009] There is an annular gap between each substrate-integrated waveguide resonant cavity and the microstrip patch resonator at its center, and the width of the annular gap is uniform or non-uniform; the slotted edge at the center of each substrate-integrated waveguide resonant cavity continues to be slotted outward to form four symmetrical slots symmetrical about the center of the corresponding substrate-integrated waveguide resonant cavity; and a central slot is etched in the center of each microstrip patch resonator. Utilizing the central slot, the annular slot, and the four symmetrical slots, two pairs of degenerate modes with orthogonal polarization and similar resonant characteristics are introduced, thereby forming four resonant points with similar radiation characteristics and close resonant frequencies, as well as two axial ratio zeros, thereby achieving synchronous broadening of the impedance bandwidth and the axial ratio bandwidth. In addition, the radiation cancellation effect along both sides of the annular slot produces a radiation zero near the upper edge of the passband, thereby improving the out-of-band suppression performance of the antenna.

[0010] As a further optimization solution of the present invention: the m*n substrate integrated waveguide resonant cavities are arranged with zero spacing and share a metal column surrounding the edge of each substrate integrated waveguide resonant cavity.

[0011] As a further optimization solution of the present invention: the shape of each of the annular gaps is consistent with the outline shape of the corresponding microstrip patch resonator.

[0012] As a further optimization solution of the present invention: the shape of the microstrip patch resonator is a symmetrical shape such as a circle, a square, an ellipse, a diamond, a rectangle, a polygon, etc.

[0013] As a further optimization of the present application: the shape of the substrate integrated waveguide resonant cavity is square, circular, elliptical, diamond, rectangular, polygonal, etc.

[0014] As a further optimization of the present application: the shape of the center slit is rectangular, cross-shaped, H-shaped, etc.

[0015] As a further optimization of the present application: the shape of the symmetric slit is rectangular, cross-shaped, T-shaped, etc.

[0016] As a further optimization of the present application: the coaxial probe is arranged in the microstrip patch resonator or the substrate integrated waveguide resonant cavity.

[0017] As a further optimization of the present application: the tilt angle of the coaxial probe relative to the center slit is +45° or -45°.

[0018] In another aspect, an ultra-low profile broadband circularly polarized microstrip patch antenna array is provided, which is prepared by the above design method.

[0019] As a further optimization of the present application: the antenna array contains m x n antenna units, and m and n are any positive integers.

[0020] Compared with the prior art, the present application has the following technical effects:

[0021] While fully preserving the structural advantages and performance characteristics of traditional microstrip patch array antennas, the present invention embeds a microstrip patch resonator within a substrate-integrated waveguide resonator cavity, slots the center of the microstrip patch resonator, and provides a coupling slot between the microstrip patch resonator and the substrate-integrated waveguide resonator cavity. This allows the antenna unit to generate two pairs of degenerate modes with orthogonal polarization and similar resonant characteristics: the main mode on the microstrip patch resonator and the first odd mode on the substrate waveguide resonator cavity. This creates four resonant points with similar radiation characteristics and near-similarity resonant frequencies, as well as two axial ratio nulls, thereby achieving simultaneous broadening of the impedance bandwidth and axial ratio bandwidth. Simultaneously, the radiation cancellation effect on both sides of the annular slot creates a radiation null near the upper edge of the passband, improving the antenna's out-of-band rejection performance. When the dielectric substrate is a high-dielectric-constant plate, the antenna array also exhibits wide-angle scanning characteristics; when the dielectric substrate is a low-dielectric-constant plate, the antenna array also exhibits high gain characteristics. The antenna array designed by the present invention fully retains the structural advantages and performance characteristics of traditional microstrip patch array antennas. It also has the characteristics of low profile, small size, simple structure, wide bandwidth, stable radiation, easy processing and integration. It can achieve wide-angle scanning or high-gain characteristics and is suitable for antenna arrays of any scale. Therefore, it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The front structure and reference coordinates of the antenna are shown in Figure 1. 1 is the microstrip patch resonator, 2 is the substrate integrated waveguide resonator, 3 is the annular slot, 4 is the central slot, 5 is the symmetrical slot, 6 is the coaxial probe, 7 is the metal post, 8 is the dielectric substrate, and 9 is the ground plane.

[0023] Figure 2 The antenna frequency response results calculated using HFSS software are shown in Figure 1. (a) represents the reflection coefficient and axial ratio, and (b) represents the far-field radiation gain and efficiency.

[0024] Figure 3 The antenna radiation pattern is calculated using HFSS software. Among them, (a) and (b) are the 3.48GHz axial ratio zero point frequency. φ =45° and φ =-45°, (c) and (d) are the axial ratio zero point frequency of 3.61GHz. φ =45° and φ =-45° directivity pattern. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings:

[0026] This paper proposes an ultra-low-profile, broadband, circularly polarized microstrip patch antenna array and its design method. While fully preserving the structural advantages and performance characteristics of traditional microstrip patch array antennas, it simultaneously broadens the impedance bandwidth, radiation bandwidth, and axial ratio bandwidth, while significantly improving out-of-band suppression. The designed antenna array features a low profile, small size, simple structure, wide bandwidth, stable radiation, and ease of fabrication and integration. It can achieve wide-angle scanning or high-gain characteristics and is suitable for antenna arrays of any size, thus possessing broad application prospects.

[0027] In one embodiment, Figure 1 As shown, the antenna array is fabricated on a dielectric with a dielectric constant of 1-20. The antenna unit consists of a circular microstrip patch resonator 1 and a square substrate integrated waveguide resonator cavity 2. The circular microstrip patch resonator 1 is embedded in the center of the square substrate integrated waveguide resonator cavity 2. A rectangular slot 4 with a 45° angle is located in the center of the circular microstrip patch resonator 1. A circular ring slot 3 and four rectangular slots 5 are symmetrically distributed along the diagonals of the square substrate integrated waveguide resonator cavity 2. The antenna units are arranged with zero spacing and share a metal post 7 that surrounds the edge of the square substrate integrated waveguide resonator cavity 2. The dielectric substrate 8, floor 9, and substrate integrated waveguide resonator cavity 2 are all the same size.

[0028] In one embodiment, a 2 × 2 array structure is employed, using an F4B dielectric substrate with a dielectric constant of 2.2 and a thickness of 3 mm. The antenna unit dimensions are designed as follows: the diameter of the circular microstrip patch resonator is 29.5 mm, and the length and width of the center slot are 16.3 mm and 1.8 mm, respectively. The side length of the square substrate integrated waveguide resonator is 63.2 mm (i.e., the center-to-center distance between two adjacent antenna elements), the diameter of the surrounding metal pillars and the spacing between adjacent metal pillars are 0.5 mm and 0.9 mm, respectively. The width of the circular slot is 4.6 mm, and the length and width of the four symmetrical rectangular slots are 7.5 mm and 6.2 mm, respectively. The distance between the feed point and the center of the circular microstrip patch resonator is 6.3 mm. HFSS software simulation calculations were used to obtain the antenna's radiation characteristics.

[0029] Figure 2 The antenna array frequency response results calculated using HFSS software include reflection coefficient, axial ratio, radiation gain and efficiency indicators. The antenna array works on the circular microstrip patch resonator TM 11 +45° and TM 11 -45° and TM on rectangular substrate waveguide resonator 21 +45° and TM 21 -45°The center frequency is 3.5 GHz, the impedance bandwidth of -10 dB is 10.3% (3.28~3.64 GHz), the 3dB axial ratio bandwidth is 5.7% (3.43~3.63 GHz), and the two axial ratio zeros are located at 3.48 GHz and 3.61 GHz respectively; the radiation gain in the working frequency band is stable at about 14 dBi, and the radiation efficiency is higher than 90%. In addition, a radiation zero point is generated at 3.7 GHz frequency, thereby effectively improving the out-of-band suppression level of the upper stop band.

[0030] Figure 3 The antenna radiation patterns calculated by the HFSS software are shown in the figures, wherein (a) and (b) are the patterns at the two axial ratio zero frequencies (3.48 GHz and 3.61 GHz) respectively. As shown in the figures, each axial ratio zero point has similar radiation characteristics in the two planes of φ =45° and φ =-45°, in addition, the patterns at the two zero points are consistent, the antenna array radiates right-hand circular polarization (RHCP), and has a good cross-polarization level.

[0031] In summary, the ultra-low profile wideband circularly polarized microstrip patch antenna array and the design method thereof can well excite two pairs of polarization-orthogonal degenerate modes, realize four-mode resonance and double-axial-ratio two-point, form a wide frequency band with stable radiation and high efficiency. At the same time, the radiation zero point in the upper stop band effectively selects the passband and improves the out-of-band suppression level. The designed antenna array has low profile, small size, simple structure, wide bandwidth, stable radiation, easy processing and integration, can realize wide-angle scanning or high-gain characteristics, and is suitable for antenna arrays of any scale, so it has wide application prospects.

[0032] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless otherwise defined.

[0033] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can understand and think of the transformation or replacement within the technical range disclosed by the present application, which should be covered in the inclusive scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A design method for an ultra-low profile broadband circularly polarized microstrip patch antenna array, characterized in that: The design method includes: Forming m*n identical square substrate integrated waveguide resonant cavities (2) on a dielectric substrate (8), wherein the m*n square substrate integrated waveguide resonant cavities (2) are arranged in an array; A slot is formed in the center of each square substrate integrated waveguide resonant cavity (2), and an identical circular microstrip patch resonator (1) is embedded in the center of each slot to form an antenna unit; There is an annular gap (3) between each of the square substrate integrated waveguide resonant cavities (2) and the circular microstrip patch resonator (1) at its center; The inner edge of each annular slot (3) is slotted toward the center of the antenna unit, or the outer edge of each annular slot (3) is slotted away from the center of the antenna unit, to form four symmetrical slots (5) that are symmetrical about the center of the corresponding substrate integrated waveguide resonant cavity (2); Etching a central slot (4) at the center of each of the circular microstrip patch resonators (1); A coaxial feeding probe (6) is provided on each of the antenna units.

2. The design method according to claim 1, characterized in that: The m*n square substrate integrated waveguide resonant cavities (2) are arranged at zero spacing and share a metal column (7) surrounding the edge of each square substrate integrated waveguide resonant cavity (2).

3. The design method according to claim 1, characterized in that: The shape of each annular gap (3) is consistent with the outline shape of the corresponding circular microstrip patch resonator (1).

4. The design method according to claim 1, characterized in that: The m and n are any positive integers.

5. The design method according to claim 1, characterized in that: The shape of the central gap (4) is rectangular, and its inclination angle relative to the row or column direction of the array is +45°, −45°, 0°, or 90°.

6. The design method according to claim 1, characterized in that: The shape of the symmetrical gap (5) is rectangular, and its inclination angle relative to the row or column direction of the array is +45°, −45°, 0°, or 90°.

7. The design method according to claim 1, characterized in that: The inclination angle of the coaxial feeding probe (6) relative to the central slot (4) is +45° or −45°.

8. An ultra-low profile broadband circularly polarized microstrip patch antenna array, characterized in that: The antenna array is manufactured by the design method described in any one of claims 1 to 7.

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