A wideband high-gain circularly polarized end-fire antenna based on coupled multi-cavity structure

Abstract

The application relates to a wide-band high-gain circularly polarized end-fire antenna based on a coupled multi-cavity structure and belongs to the technical field of electromagnetic waves and antennas. The antenna adopts a full-metal integrated structure, comprises an air medium filling parallel plate transmission line formed by metal plates arranged in parallel, and eight pairs of complementary open cavity resonant units arranged in a periodic staggered mode along the two sides of the transmission line. Each unit is composed of an open cavity and a back-shaped array, wherein the open cavity is equivalent to a magnetic current element, the back-shaped array constitutes an electric current element, and the two form an inherent 90-degree phase difference through space coupling, so that circularly polarized radiation is realized. The antenna has stable end-fire patterns and a low profile. The full-metal structure is simple to process and low in cost, is suitable for satellite communication, millimeter wave radar and 5G / 6G high-density integrated systems, and solves the technical bottleneck of narrow bandwidth and insufficient gain of traditional end-fire antennas.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic waves and antenna technology, and relates to a wideband high-gain circularly polarized end-fire antenna based on a coupled multi-cavity structure. Background Technology

[0002] With the rapid development of modern wireless communication technology, especially the rise of 5G and future 6G communication, satellite communication, and the Internet of Things, higher requirements are being placed on antenna performance. Wideband, high-gain, circularly polarized, and end-fire antennas have become research hotspots to meet the ever-increasing demands for communication capacity, transmission rate, and system reliability.

[0003] Traditional end-fire antennas, such as Yagi antennas and helical antennas, while simple in structure and low in cost, generally suffer from narrow bandwidth (approximately 10%) and relatively low gain, making it difficult to meet the demands of modern communication systems for wide bandwidth, high performance, and miniaturization. In recent years, novel circularly polarized end-fire antennas based on substrate integrated waveguides (SIW) and magnetoelectric dipoles have made some progress in performance, with bandwidth expandable to around 20% and circular polarization gain increased to 12-13 dBi. However, they still suffer from relatively large size (generally 3λ0-9λ0) and complex structures, as well as difficulties in fabrication, which limits their practical applications. Summary of the Invention

[0004] This invention discloses an all-metal broadband circularly polarized end-fire antenna based on an air-filled parallel plate transmission line and several periodic complementary open-cell resonant units. It has a stable end-fire radiation mode, a wide-band circular polarization bandwidth, and high-gain radiation characteristics. The purpose is to solve the technical problems of limited gain and narrow axial ratio bandwidth of current circularly polarized end-fire antennas.

[0005] This invention provides a wideband high-gain circularly polarized end-fire antenna based on a coupled multi-cavity structure, the specific technical solution of which is as follows.

[0006] This invention provides a broadband circularly polarized end-fire antenna with all-metal characteristics, consisting of upper and lower parallel plate waveguides and several periodic complementary cavity resonator pairs, which are excited by spatial coupling feeding. One end is connected to an SMA coaxial feed, and the other end is connected to a 50-ohm matched load.

[0007] This invention consists of a transmission line of upper and lower parallel metal plates and several complementary open-cell resonant units. Air is used as the filling medium, and the excitation of the resonant units is achieved through a series coupling feeding mechanism.

[0008] The main body of the radiating unit consists of a pair of periodic complementary resonant units arranged in parallel on both sides, and is spatially coupled and fed by a foam-supported parallel double wire with an approximate air-filled medium.

[0009] Among them, the spacing between the eight arrays on both sides is the same, all around a quarter wavelength.

[0010] The antenna's overall structure is made of pure metal, with SMA interfaces and matching loads at both ends.

[0011] The upper and lower double-conductor metal plates are filled and fixed by pmi foam with a dielectric constant close to 1.

[0012] The total dimensions of the end-fire array are 206mm*55mm*10mm (2.3λ0*0.6λ0*0.1λ0).

[0013] In this invention, the complementary open-cavity resonant unit is composed of a 21mm*14mm*10mm open-cavity copper plate and a 6mm*23mm spiral copper strip, with a chamfer angle of 19.6° and a copper thickness of 0.5mm.

[0014] The beneficial effects of this invention are as follows:

[0015] To address the problems existing in the prior art, a broadband, high-gain circularly polarized end-fire antenna based on a coupled multi-cavity structure is proposed, which is of great significance. This antenna utilizes the edge field of multiple resonant cavities coupled to a parallel-plate waveguide to generate excitation, thus extending the operating bandwidth. By optimizing the cavity structure parameters and the coupling feeding method, high gain and good circular polarization characteristics are achieved. Furthermore, due to the new feeding method and component design, the antenna has a smaller relative size (2.3λ0) and employs end-fire radiation, providing a new technical path for the development of future high-performance, miniaturized circularly polarized end-fire antennas.

[0016] This invention employs an open-cavity complementary resonant unit structure to achieve broadband circular polarization radiation. Its core mechanism lies in utilizing the open-cavity structure to form an equivalent magnetic flux element M and its connected loop dipoles to form a current element J. Based on the inherent 90° phase difference generated by two orthogonal electromagnetic modes, a stable circular polarization beam is formed. At the same time, due to the stable phase constant of the air-filled parallel plate end-fire antenna, it has the characteristics of high-gain broadband circular polarization.

[0017] This antenna is made entirely of metal using a one-piece metal forming process. While ensuring the stability of the end-fire beam, it achieves circular polarization characteristics with low profile and wide axial ratio bandwidth. It is suitable for high-density integrated millimeter-wave communication systems, with a simple structure and low processing cost. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the high-gain broadband circularly polarized end-fire antenna of the present invention.

[0019] Figure 2 This is a top view of the high-gain broadband circularly polarized end-fire antenna of the present invention.

[0020] Figure 3 This is a front view of the high-gain broadband circularly polarized end-fire antenna of the present invention.

[0021] Figure 4 These are schematic diagrams of S11 and S12 of the antenna simulation of this invention.

[0022] Figure 5 This is a schematic diagram of the antenna gain, axial ratio, and antenna efficiency in the antenna simulation of this invention.

[0023] Figure 6 These are the simulated normalized radiation patterns of the E-plane and H-plane of the antenna at 2.8 GHz, 3.1 GHz, and 3.4 GHz.

[0024] In the diagram, 1. Port 1; 2. Air-filled transmission line parallel plate; 3. Corrugated array; 4. Open cavity body; 5. Port 2. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] To illustrate the advantages of this invention, specific embodiments are described in detail. Note that these embodiments are for illustrative purposes only and do not limit the scope of the invention.

[0027] The principle of the invented antenna will be explained in detail below with reference to the accompanying drawings.

[0028] This invention discloses an all-metal broadband circularly polarized end-fire antenna based on an air-filled dielectric parallel-plate transmission line and a complementary open-cell resonant array. The air-filled parallel-plate transmission line, with its all-metal structure, achieves approximately identical propagation and phase shift constants. A leakage radiation mechanism is formed by periodically arranging complementary open-cell resonant units to couple the spatial field of the parallel plate. This antenna offers the following advantages: By optimizing the structure of the complementary open-cell resonant units, precise control of the far-field amplitude and phase of the orthogonal polarization components is achieved, resulting in a wideband circularly polarized axial ratio bandwidth. The periodic resonant unit layout enhances the end-fire antenna gain. The all-metal integrated design and air filling eliminate dielectric losses, resulting in high radiation efficiency and a stable end-fire radiation pattern.

[0029] This invention achieves wide axis ratio bandwidth characteristics through the coupling effect of the cavity complementary resonant unit structure; reduces gain loss caused by dielectric loss by using an air dielectric transmission line; and simultaneously obtains a phase shift constant close to that in a vacuum to achieve stable end-fire circular polarization characteristics within a wide bandwidth.

[0030] like Figure 1 As shown, the antenna consists of five parts, including port 1, air-filled transmission line parallel plate 2, loop array 3, open mouth body 4, and port 2 5.

[0031] The antenna of this invention has a 50-ohm load connected to port one and an SMA connected to port two for excitation.

[0032] The present invention is as follows Figure 2 and Figure 3 As shown, this all-metal dual-port antenna employs an air-dielectric transmission line coupled with a complementary dipole element-coupled radiation array design. Its working mechanism comprises three core elements: an air-filled parallel plate structure serves as the primary energy feed, enabling longitudinal energy transmission through the dual ports to form a traveling wave distribution, which is then laterally coupled to the radiating elements; the array layout uses eight pairs of complementary dipole elements arranged in a staggered configuration, achieving spatial energy coupling through optimized element spacing and phase synchronization techniques; and end-fire radiation characteristics are achieved through a resonant cavity and a multi-element arrangement of returning dipole pairs. This design reduces transmission loss and optimizes the phase shift constant through the air medium, achieving a stable end-fire radiation mode.

[0033] The antenna of this invention has a foam of PMI material between the upper and lower metal plates, with a relative permittivity of 1.09.

[0034] Each complementary element pair of the antenna of the present invention consists of an open cavity and a loop-shaped element. The open cavity can be equivalent to magnetohydrodynamic radiation according to the electromagnetic field boundary conditions, and the loop-shaped element constitutes a current element. The inherent 90-degree phase difference of the complementary dipole resonant element pair is superimposed in the far-field radiation field to form left-hand circularly polarized end-fire radiation.

[0035] The antenna described in this invention achieves efficient energy transmission and radiation through a dual-path coupling mechanism: the transmission line adopts a parallel dual-line structure design, and energy attenuation is reduced by optimizing the impedance matching characteristics of the transmission line, ensuring that the near-end units receive consistent coupling energy; the spatial coupling of the parallel radiating units forms electromagnetic field interaction, and differential feeding is constructed using an asymmetric parallel radiating unit configuration; the complementary resonant unit structure is periodically introduced to form a one-dimensional linear array to enhance end-fire gain.

[0036] The present invention, based on an air-filled parallel plate structure, designs a high-gain broadband circularly polarized end-fire antenna array, comprising the following steps:

[0037] (1) Select the center frequency.

[0038] (2) To achieve the design goal of wide circular polarization, simulation optimization was used to determine the size of the complementary open-mouth body element and the orthogonal position distribution of the oscillating array.

[0039] (3) The spacing between the radiating elements is selected to be 24 mm (0.27λ0) to meet the array factor conditions for end-fire radiation.

[0040] (4) In order to achieve a stable phase shift constant, an air medium structure is adopted for the target design.

[0041] (5) By coupling power supply, fine-tuning the unit size and distance, coupling energy between arrays, and realizing uniform electric field spatial coupling excitation.

[0042] (6) Figure 4-6 The simulated S-parameters, gain, radiation efficiency, and radiation pattern of the antenna are shown below, indicating that the simulation results are consistent with expectations.

[0043] The present invention is as follows Figure 4 As shown, the antenna's reflection coefficient varies with frequency. The antenna's reflection coefficient remains below -10dB across the entire operating frequency band from 2.4GHz to 3.6GHz, exhibiting excellent impedance matching characteristics. The antenna displays two distinct resonant points at 2.63GHz and 3.38GHz, forming a wideband operating characteristic.

[0044] The present invention is as follows Figure 5 As shown, simulation results of the antenna's gain-to-axis ratio and radiation efficiency as a function of frequency show that: within the 2.5GHz-3.5GHz frequency band, the antenna's 3dB gain-to-axis ratio bandwidth can basically cover this frequency band, with the highest gain reaching 12.5dB; at the same time, the axial ratio curve maintains good performance of less than 3dB throughout the 2.5GHz-3.5GHz frequency band; in addition, the antenna's radiation efficiency remains above 90% throughout the entire operating frequency band, exhibiting good radiation characteristics.

[0045] The present invention is as follows Figure 6 The simulation results shown demonstrate that the antenna exhibits strong directivity and end-fire characteristics at three frequency points: 2.8 GHz, 3.1 GHz, and 3.4 GHz. The main lobe radiation is significant, while the sidelobes are well suppressed. These results indicate that the antenna possesses excellent broadband characteristics and stable end-fire radiation performance.

[0046] This invention provides a high-gain circularly polarized antenna array design method, characterized in that: through parametric scanning and other techniques, the spacing between antenna array elements is optimized and analyzed to determine the optimal element spacing as 24mm, so that the antenna array gain reaches a maximum value of 12.5dBi; at the same time, through the coordinated optimization of the length, width and the included angle with the cavity of the spiral copper strip vibrator, a 30% axial ratio bandwidth is achieved.

[0047] This invention achieves a stable circularly polarized end-fire radiation mode through far-field superposition of orthogonal antenna elements. The circular polarization characteristics can be quantitatively characterized by the key parameter of axial ratio, whose mathematical expression is:

[0048]

[0049] in and The electric fields represent the two polarization components, respectively. , These represent the ratio of the phase difference and amplitude of the electric fields in the two polarizations, respectively. To achieve a low axial ratio circularly polarized antenna, the amplitude ratio... K The values ​​should be as close to 1 as possible, and the phase difference should be maintained at approximately 90°. The amplitude and phase difference of the two orthogonal electric field components can be tuned independently by adjusting the dimensions of the open cavity and the eccentric inductor separately.

[0050] By continuously optimizing and adjusting the parameters of the spiral copper array, the axial ratio is brought closer to 0 dB, generating a circularly polarized beam. This technical solution achieves excellent circular polarization performance, with the axial ratio remaining below 3 dB within 30% of the bandwidth, improving the antenna's polarization matching efficiency and signal transmission quality.

[0051] The antenna of this invention can achieve a circular polarization gain of 12.5 dBi and a circular polarization bandwidth of 2.5 GHz to 3.54 GHz (30%), thus possessing good antenna transmission performance. It is suitable for wireless communication systems with stringent requirements for equipment integration and radiation performance, such as spaceborne communication and millimeter-wave radar.

[0052] The basic principles, main features, and advantages of this invention have been explained in the foregoing. For those skilled in the art, this invention is not limited to the specific embodiments described herein; these examples are merely illustrative, and the invention can be implemented in other forms without departing from its core concept. The scope of protection of the invention is determined by the appended claims, not the specific embodiments in the specification. This invention is intended to cover all modifications that conform to the equivalent scope of the claims.

[0053] Referring to the accompanying drawings, the shape and structural features of the invention are clearly and completely described, and the technical features are explained in detail so that those skilled in the art can understand and implement them.

Claims

1. A wideband high-gain circularly polarized end-fire antenna based on a coupled multi-cavity structure, characterized in that, The antenna comprises: a metal plate (2) arranged in parallel from top to bottom, which constitutes an air-filled parallel-plate transmission line for traveling wave energy transmission; periodically arranged complementary open cavity resonant units distributed on both sides of the parallel-plate transmission line, each unit being composed of an open cavity (4) and a meander array (3), the complementary open cavity resonant units being staggered on both sides of the parallel-plate transmission line to form multiple pairs of complementary open cavity resonant unit pairs; the open cavity (4) is equivalent to a magnetic current element according to electromagnetic field boundary conditions, and the meander array (3) constitutes an electric current element, both of which are arranged in parallel and form an inherent 90° phase difference to generate circularly polarized radiation; the antenna is a full-metal integrated structure as a whole, one port is connected to a 50-ohm load, and the other port is connected to an SMA coaxial RF connector for feeding; The distance between the complementary open cavity resonant unit pairs is a quarter of the working wavelength The wide axial ratio bandwidth AR < 3dB and end-fire radiation mode are realized in the working frequency band. the meander array (3) is formed by bending a metal strip and is fixed on the opening side of the open cavity (4), the extension direction of the metal strip is inwardly inclined relative to the surface of the open cavity (4), the inclination angle is 19.6°, the positions of the meander arrays (3) in the open cavity resonant units on both sides of the parallel-plate transmission line relative to the open cavities (4) are mirror-symmetrically distributed, the size of the metal strip is 6mm*23mm, and the thickness is 0.5mm, the size of the open cavity (4) is 21mm*14mm*10mm; the height of the meander array (3) is greater than the height of the metal plate (2) arranged in parallel from top to bottom, and the upper and lower surfaces of the meander array (3) both exceed the edge portion of the metal plate (2).

2. The circularly polarized end-fire antenna of claim 1, wherein, The parallel-plate transmission line is internally filled with PMI foam with a dielectric constant close to 1, which is used to fix the upper and lower metal plates and reduce dielectric loss.

3. The circularly polarized end-fire antenna of claim 1, wherein, The number of the complementary open cavity resonant unit pairs is 8, forming a one-dimensional linear array.

4. The circularly polarized end-fire antenna of claim 1, wherein, The total size of the array formed by the antennas is .

5. A wireless communication system, characterized by The wide-band high-gain circularly polarized end-fire antenna according to any one of claims 1-4 is applied to a satellite communication, a millimeter wave radar or a high-density integrated 5G / 6G communication system.

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