Ultra-low profile broadband circularly polarized microstrip patch antenna array and design method thereof

Abstract

The invention discloses an ultra-low profile broadband circularly polarized microstrip patch antenna array and a design method thereof, the antenna array is constructed on a single-layer thin dielectric substrate, and an antenna unit is formed by combining a substrate integrated waveguide resonant cavity and a microstrip patch resonator embedded in the center of the substrate integrated waveguide resonant cavity. On the premise that the antenna size is not increased, the combination of the double resonators is realized. The adjacent antenna units are arranged at zero intervals and share the metal columns surrounding the edge of the substrate integrated waveguide resonant cavity. Two pairs of polarization orthogonal degenerate modes with similar resonance characteristics are introduced by utilizing a central gap, an annular gap and four symmetrical gaps connected with the central gap and the annular gap, so that four resonance points with similar radiation characteristics and similar resonance frequencies and two axial ratio zero points are formed, and synchronous broadening of impedance bandwidth and axial ratio bandwidth is realized. In addition, a radiation zero point is generated at the position close to the upper edge of the passband along the radiation counteracting effect on the two sides of the annular gap, and therefore the out-of-band rejection performance of the antenna is improved.

Description

Technical Field

[0001] The 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 communication. Background Art

[0002] With the rapid development of modern wireless communication technology, circularly polarized array antennas are widely used in emerging hot fields such as satellite communications, mobile Internet, global positioning, and real-time navigation due to their excellent ability to suppress multipath interference and effectively reduce polarization mismatch. At the same time, microstrip patch antennas are widely studied and applied due to their advantages such as small size, light weight, low cost, simple processing, and easy integration. Therefore, in recent years, circularly polarized antenna arrays based on microstrip patch resonators have received extensive and in-depth attention and research.

[0003] Generally speaking, traditional microstrip patch array antennas often achieve circularly polarized radiation by adding stubs, slots, vias, etc. Although this method is simple and direct, its available bandwidth is relatively limited. At present, in order to broaden the bandwidth of circularly polarized antennas, the following three methods are commonly used. First, the optimization and improvement of the feeding structure, including the introduction of phase shifters, power dividers, and the use of rotary feeding. However, the implementation of these methods will inevitably increase the insertion loss of the antenna, and often requires the use of complex multi-layer structures. Second, the introduction of additional structures, such as parasitic units, superposition slots, multiple patches, metasurface materials, etc., but these structures will take up additional space, thereby increasing the overall size of the antenna array and increasing the complexity of the structure; third, using the multi-mode resonance theory, by adjusting the patch resonator structure to excite multiple resonant modes, the bandwidth can be effectively increased, but it often also brings about an increase in size, and with the increase in the number of modes, the difficulty of mode regulation increases sharply, especially the radiation characteristics of multiple modes.

[0004] At present, the proposed broadband circularly polarized microstrip patch antenna array designs almost only focus on the impedance bandwidth of the array, and do not fully consider the radiation performance in the passband. In addition, the array structure is also relatively complex. Therefore, how to achieve the simultaneous widening of the impedance bandwidth, radiation bandwidth, and axial ratio bandwidth while maintaining the structural advantages and performance characteristics of the conventional microstrip patch antenna array is a key technical problem that needs to be solved urgently. Summary of the invention

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

[0006] The present invention adopts the following technical solutions to solve the above technical problems: 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: 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 any positive integers; a slot is opened at 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 arranged on each antenna unit.

[0007] 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 that are symmetrical about the center of the corresponding substrate integrated waveguide resonant cavity; a central slot is etched in the center of each microstrip patch resonator. By using the central slot, the annular slot and the four symmetrical slots, two pairs of degenerate modes with orthogonal polarization and similar resonance characteristics are introduced, thereby forming four resonance points with similar radiation characteristics and similar resonance frequencies and two axial ratio zero points, 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 point near the upper edge of the passband, thereby improving the out-of-band suppression performance of the antenna.

[0008] 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.

[0009] As a further optimization solution of the present invention: the shape of each of the annular gaps is consistent with the contour shape of the corresponding microstrip patch resonator.

[0010] As a further optimization scheme 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.

[0011] As a further optimization scheme of the present invention: the shape of the substrate integrated waveguide resonant cavity is a symmetrical shape such as a square, a circle, an ellipse, a diamond, a rectangle, a polygon, etc.

[0012] As a further optimization scheme of the present invention: the shape of the central gap is a symmetrical shape such as a rectangle, a cross, or an H shape, and its inclination angle relative to the row or column direction of the array is +45° or −45° or 0° or 90°.

[0013] As a further optimization scheme of the present invention: the shape of the symmetrical gap is a symmetrical shape such as a rectangle, a cross, a T-shape, etc., and its inclination angle relative to the row or column direction of the array is +45° or −45° or 0° or 90°.

[0014] As a further optimization scheme of the present invention: the coaxial probe is arranged in a microstrip patch resonator or a substrate integrated waveguide resonant cavity.

[0015] As a further optimization solution of the present invention: the inclination angle of the coaxial probe relative to the central gap is +45° or −45°.

[0016] On the other hand, an ultra-low profile broadband circularly polarized microstrip patch antenna array manufactured by the above-mentioned design method is provided.

[0017] As a further optimization solution of the present invention: the antenna array includes m×n antenna units, where m and n are any positive integers.

[0018] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: The present invention can completely retain the advantages and performance characteristics of the traditional microstrip patch array antenna structure, by embedding the microstrip patch resonator into the substrate integrated waveguide resonant cavity, slotting the center of the microstrip patch resonator, and setting a coupling slot between the microstrip patch resonator and the substrate integrated waveguide resonant cavity, so that the antenna unit generates two pairs of degenerate modes with orthogonal polarization and similar resonance characteristics, which are the main mode on the microstrip patch resonator and the first odd mode on the substrate waveguide resonant cavity. On this basis, four resonance points with similar radiation characteristics and similar resonance frequencies and two axial ratio zero points are formed, thereby achieving the synchronous broadening of the impedance bandwidth and the axial ratio bandwidth. At the same time, the radiation cancellation effect on both sides of the annular gap is used to generate a radiation zero point near the upper edge of the passband, thereby improving the out-of-band suppression performance of the antenna. When the dielectric substrate is a high dielectric constant plate, the antenna array also has a wide-angle scanning characteristic; when the dielectric substrate is a low dielectric constant plate, the antenna array also has a high gain characteristic. The antenna array designed by the present invention fully retains the structural advantages and performance characteristics of the traditional microstrip patch array antenna, and also has the characteristics of low profile, small size, simple structure, wide bandwidth, stable radiation, easy processing and integration, can achieve wide-angle scanning or high-gain characteristics, and is suitable for antenna arrays of any scale, so it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The front structure and reference coordinates of the antenna are shown in Figure 1. 1 is a microstrip patch resonator, 2 is a substrate integrated waveguide resonator, 3 is an annular gap, 4 is a central gap, 5 is a symmetrical gap, 6 is a coaxial probe, 7 is a metal column, 8 is a dielectric substrate, and 9 is a ground plane.

[0020] Figure 2 The antenna frequency response results calculated using HFSS software, where (a) is the reflection coefficient and axial ratio, and (b) is the far-field radiation gain and efficiency.

[0021] Figure 3 The antenna radiation pattern is calculated using HFSS software. (a) and (b) are the 3.48GHz axial ratio zero frequency. φ =45° and φ =-45° directional diagram, (c) and (d) are 3.61GHz axial ratio zero frequency at φ =45° and φ =-45° directivity diagram. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings: The present invention proposes an ultra-low profile broadband circularly polarized microstrip patch antenna array and a design method thereof, which achieves simultaneous broadening of impedance bandwidth, radiation bandwidth, and axial ratio bandwidth, as well as significant improvement of out-of-band suppression, while fully retaining the structural advantages and performance characteristics of the traditional microstrip patch array antenna. The designed antenna array has a low profile, small size, simple structure, wide bandwidth, stable radiation, easy processing and integration, can achieve wide-angle scanning or high-gain characteristics, and is suitable for antenna arrays of any size, so it has broad application prospects.

[0023] In one embodiment, Figure 1 As shown, the antenna array is made on a medium 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° inclination angle is provided in the center of the circular microstrip patch resonator 1. A circular ring slot 3 and four rectangular slots 5 symmetrically distributed along the diagonal of the square substrate integrated waveguide resonator cavity 2 are provided between the circular microstrip patch resonator 1 and the square substrate integrated waveguide resonator cavity 2. The antenna units are arranged with zero spacing and share a metal column 7 surrounding the edge of the square substrate integrated waveguide resonator cavity 2. The dielectric substrate 8, the floor 9 and the substrate integrated waveguide resonator cavity 2 are of the same size.

[0024] In one embodiment, a 2 × 2 array structure is adopted, and an F4B dielectric substrate with a dielectric constant of 2.2 and a thickness of 3 mm is adopted. The size of the antenna unit is designed as follows: the diameter of the circular microstrip patch resonator is 29.5 mm, and the length and width of the central slot are 16.3 mm and 1.8 mm respectively. The side length of the square substrate integrated waveguide resonant cavity is 63.2 mm (i.e., the center distance between two adjacent antenna array elements), the diameter of the surrounding metal columns and the distance between adjacent metal columns are 0.5 mm and 0.9 mm respectively, the width of the circular annular slot is 4.6 mm, the length and width of the four symmetrical rectangular slots are 7.5 mm and 6.2 mm respectively, and the distance between the feeding point and the center of the circular microstrip patch resonator is 6.3 mm. The radiation characteristics of the antenna are obtained by simulation and calculation using HFSS software.

[0025] 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 TM on a circular microstrip patch resonator. 11 +45° and TM 11 -45° and TM on rectangular substrate waveguide resonator 21 +45° and TM 21 -45°The mode has a center frequency of 3.5 GHz, a -10dB impedance bandwidth of 10.3% (3.28~3.64 GHz), a 3dB axial ratio bandwidth of 5.7% (3.43~3.63 GHz), and two axial ratio zeros at 3.48 GHz and 3.61 GHz respectively. The radiation gain in the operating frequency band is stable at around 14 dBi, and the radiation efficiency is higher than 90%. In addition, a radiation zero is generated at a frequency of 3.7 GHz, which effectively improves the out-of-band suppression level of the upper stopband.

[0026] Figure 3 The antenna radiation pattern calculated by HFSS software, (a) and (b) are the radiation patterns at two axial ratio zero point frequencies (3.48 GHz and 3.61 GHz). φ =45° and φ =-45° The two planes have similar radiation characteristics. In addition, the directivity patterns at the two null points are highly consistent. The antenna array radiates right-hand circular polarization (RHCP) and has a good cross-polarization level.

[0027] In summary, the ultra-low profile broadband circularly polarized microstrip patch antenna array and its design method involved in the present invention can well excite two pairs of polarization orthogonal degenerate modes, realize four-mode resonance and two points of dual-axis ratio, and form a wide-band operation with stable radiation and high efficiency. At the same time, the radiation zero point in the upper stopband has effective passband selectivity and out-of-band suppression level. The designed antenna array has a low profile, small size, simple structure, wide bandwidth, stable radiation, easy processing and integration, can achieve wide-angle scanning or high-gain characteristics, and is suitable for antenna arrays of any size, so it has broad application prospects.

[0028] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0029] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technology can understand and think of any changes or substitutions within the technical scope disclosed by the present invention, which should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be based on 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 comprises: Forming m*n identical substrate integrated waveguide resonant cavities (2) on a dielectric substrate (8), wherein the m*n substrate integrated waveguide resonant cavities (2) are arranged in an array; A slot is formed in the center of each substrate integrated waveguide resonant cavity (2), and an identical 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 substrate integrated waveguide resonant cavity (2) and the 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, so as 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 microstrip patch resonators (1); A coaxial feeding probe (6) is arranged on each of the antenna units.

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

4. The design method according to claim 1, characterized in that: The shape of the microstrip patch resonator (1) is a symmetrical shape.

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

6. The design method according to claim 1, characterized in that: The shape of the substrate integrated waveguide resonant cavity (2) is a symmetrical shape.

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

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

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

10. An ultra-low profile broadband circularly polarized microstrip patch antenna array, characterized in that: The antenna array is obtained by the method according to any one of claims 1 to 9.

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