A circular polarization ceiling antenna

Abstract

The present invention discloses a circularly polarized ceiling antenna, comprising a reflection grounding plate with one side grounded and a plurality of groups of dielectric plates vertically arranged on the reflection grounding plate, wherein the dielectric plates are arranged on the surface of the reflection grounding plate around the circumference with the center of the reflection grounding plate as the center of the circle; a radiation patch is etched on one side of each group of dielectric plates; and a gap for changing the current path is provided on the radiation patch. Coaxial feeding is performed through a through hole in the center of the reflection grounding plate, and this feeding method does not affect the characteristics of the antenna. The antenna is vertically welded on the reflection grounding plate by a substrate with radiation patches composed of rectangular microstrips and trapezoidal microstrips on four sides, and the back of the reflection grounding plate is grounded. This structure easily realizes circular polarization characteristics. Each radiation patch is loaded with an inverted L-shaped gap, and the inverted L-shaped gap is used to change the current path on the radiation patch, thereby enhancing the radiation intensity of the antenna in the radiation direction, thereby effectively solving the radiation zero point problem existing in the radiation direction of the antenna.

Description

Technical Field

[0001] The invention is applied to the technical field of microwave antennas, in particular to a circularly polarized ceiling antenna. Background Art

[0002] With the development of wireless communication technology, the number of communication systems is increasing. Multiple antennas must be used on the same wireless device, but these antennas have different polarization characteristics. Transceiver antennas with different polarization characteristics will produce polarization loss, etc. Circularly polarized (CP) antennas can receive incoming signals of any polarization, making wireless communication very flexible. It does not require strict alignment of the transmit and receive antennas, and can suppress multipath and provide more reliable sensitivity, which is very attractive in modern wireless communications.

[0003] The circular polarization of the antenna can be achieved by cutting corners, slot loading, and branch line loading, or by selecting the appropriate feeding point location and multiple feeding methods. The various performances of omnidirectional circularly polarized antennas are mutually restricted. To design a suitable omnidirectional circularly polarized antenna, it is necessary to weigh various factors. At present, the research on omnidirectional circularly polarized antennas is relatively mature.

[0004] In order to increase the range of indoor communications and wireless LANs, experts and scholars have designed various ceiling antennas.

[0005] Document 1: Jang YW; Go H CA low-profile broadband 16-mm-diameter post-type monopole antenna ceiling-mounted in a building. Microwave and optical technology letters, 2004, 41(5): 395-397. discloses a ceiling-mounted ceiling antenna, which consists of a cylindrical monopole, foam, a circular ground plane and an SMA connector and can be applied to mobile and satellite communication systems, but has the phenomenon of radiation characteristic distortion.

[0006] Reference 2: Ng KJ; Islam MT; Alevy A; et al. Azimuth Null-Reduced Radiation Pattern, Ultralow Profile, Dual-Wideband and Low Passive Intermodulation Ceiling Mount Antenna for Long Term Evolution Application. IEEE access, 2019, 7: 114761-114777. A monopole ceiling mount antenna based on an asymmetric dipole bias feed is disclosed, which reduces the radiation null and achieves lower passive intermodulation (PIM). However, it cannot provide an omnidirectional radiation pattern.

[0007] Reference 3: Zhou L; Qi Y; Jiao YC; et al. Wideband ceiling mount omnidirectional antenna for indoor distributed antenna system applications. Electronics letters, 2014, 50(4): 253-255. A broadband omnidirectional antenna is disclosed, which is composed of a central coaxial feed monopole formed by placing three metal patches on a circular ground plane, a short-circuit leg composed of three coupling patches on the monopole to extend the lowest frequency, and a metal plate loaded on the top of the coupling patch. Although a higher gain and better efficiency are achieved, there is a radiation null in the radiation direction.

[0008] Reference 4: Choo J; Yoo S; Choo H. Design of a ceiling-mounted reader antenna to maximize the readable volume coverage ratio for an indoor UHF RFID application. Microwave & Optical technology letters, 2017, 59 (9): 2136-2141. A multi-layer spiral structure circularly polarized ceiling antenna is disclosed. There is no radiation zero point in the radiation direction, but the antenna size is very large (1 × 3 × 3m 3 ), not suitable for mobile devices, this antenna is mainly used for indoor radio frequency identification.

[0009] Reference 5: A. Kaddour, S. Bories, A. Belicon, C. Delaveaud. 3-D-Printed Compact Wideband Magnetoelectric Dipoles With Circular Polarization. IEEE antennas and wireless propagation letters, 2018, (17) 11: 2026-2030. A cross-magnetoelectric dipole circularly polarized antenna with circular polarization performance obtained by connecting a 90° hybrid coupler circuit is disclosed. The square ring electric dipole is changed to a folded square ring to reduce the area and placed in a rectangular metal cavity with one side open. This design greatly improves the performance of the antenna, such as increasing the gain and the axial ratio bandwidth, but increases the complexity of the design structure and feeding method.

[0010] However, each type of antenna has some defects to a greater or lesser extent. Circularly polarized antennas not only require good axial ratio characteristics, but also need to radiate circularly polarized waves, and place higher requirements on the antenna's wide bandwidth, miniaturization, and multi-functionality. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a circularly polarized ceiling antenna in view of the deficiencies in the prior art.

[0012] In order to solve the above technical problems, a circularly polarized ceiling antenna of the present invention comprises a reflection grounding plate with one side grounded and a plurality of dielectric plates vertically arranged on the reflection grounding plate.

[0013] The dielectric plate is arranged on the surface of the reflecting ground plate around a circle with the center of the reflecting ground plate as the center;

[0014] A radiation patch is etched on one side of each group of dielectric plates;

[0015] The radiation patch is provided with a gap for changing the current path.

[0016] As a possible implementation manner, further, the gap is an inverted L-shaped gap, and the vertical gap of the inverted L-shaped gap is located on a side of the radiation patch close to the center of the reflection ground plate.

[0017] As a possible implementation manner, further, one side edge of the radiation patch close to the center of the reflection ground plate is connected to each other, and the connection point is located on the longitudinal projection line of the center of the reflection ground plate.

[0018] As a possible implementation manner, further, a through hole is opened in the center of the reflection ground plate, and a feed source is arranged in the through hole, and the feed source is coaxially fed through the through hole of the reflection ground plate.

[0019] As a possible implementation manner, further, the radiation patch is composed of a first radiation patch unit and a second radiation patch unit which are different in shape and adjacent to each other.

[0020] As a possible implementation manner, further, the first radiation patch unit is a rectangular patch, and the second radiation patch unit is a trapezoidal patch.

[0021] As a possible implementation manner, further, the long side of the radiation patch is closely attached to a side edge of the dielectric plate close to the center of the reflection ground plate.

[0022] As a possible implementation manner, further, the reflection ground plate is a circular plate, and the dielectric plate is a rectangular plate.

[0023] As a possible implementation manner, further, the number of the dielectric plates is four groups, and adjacent dielectric plates are perpendicular to each other.

[0024] The present invention adopts the above technical solution and has the following beneficial effects: the present invention performs coaxial feeding through the through hole in the center of the reflection ground plate, and this feeding method will not affect the characteristics of the antenna. The antenna is vertically welded on the reflection ground plate by a substrate with rectangular microstrips and trapezoidal microstrips on four sides to form radiation patches, and the back of the reflection ground plate is grounded. This structure can easily achieve circular polarization characteristics. Each radiation patch is loaded with an inverted L-shaped gap, and the inverted L-shaped gap is used to change the current path on the radiation patch, thereby enhancing the radiation intensity of the antenna in the radiation direction, thereby effectively solving the radiation zero point problem of the antenna in the radiation direction. The present invention has a simple structure, compact antenna size, good reversibility, significant circular polarization characteristics, and will not produce radiation zero points in the radiation direction. It can meet the needs of places where ceiling antennas are required, such as carriages, subways, conference halls, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0026] Figure 1 It is a three-dimensional schematic diagram of the structure of the present invention;

[0027] Figure 2 It is a top view of the structure of the present invention;

[0028] Figure 3 This is a structural diagram of the radiation patch on one side of the dielectric plate of the present invention;

[0029] Figure 4 It is a test curve diagram of the reflection coefficient of the antenna of the present invention;

[0030] Figure 5 It is a test curve diagram of the standing wave ratio of the antenna of the present invention;

[0031] Figure 6 The axial ratio curve diagram of the antenna of the present invention tested in the frequency band of 6.3 GHz to 6.65 GHz;

[0032] Figure 7 The radiation patterns of the xoz plane and the yoz plane of the far-field radiation of the antenna of the present invention at different operating frequencies of 6.45 GHz, 6.5 GHz and 6.6 GHz;

[0033] Figure 8 is a measurement curve diagram of the peak gain of the antenna of the present invention;

[0034] Fig. 9 This is a table of preferred structural parameters related to the antenna of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0036] like Figure 1-9 As shown, the present invention provides a circularly polarized ceiling antenna, comprising a reflection grounding plate 1 with one side grounded and a plurality of groups of dielectric plates 2 vertically arranged on the reflection grounding plate 1, wherein the dielectric plates 2 are arranged on the surface of the reflection grounding plate 1 around the circumference with the center of the reflection grounding plate 1 as the center of the circle; a radiation patch 3 is etched on one side of each group of the dielectric plates 2; and a slit 4 for changing the current path is provided on the radiation patch 3. The slit 4 is an inverted L-shaped slit, and the vertical slit of the inverted L-shaped slit is located on the side of the radiation patch 3 close to the center of the reflection grounding plate 1. The side edges of the radiation patch 3 close to the center of the reflection grounding plate 1 are connected to each other, and the connection point is located on the longitudinal projection line of the center of the reflection grounding plate 1. A through hole 5 is provided in the center of the reflection grounding plate 1, and a feed source is provided in the through hole 5, and the feed source is coaxially fed through the through hole of the reflection grounding plate 1. The radiation patch 3 is composed of a first radiation patch unit 31 and a second radiation patch unit 32 of different shapes and adjacent splicing. The first radiation patch unit 31 is a rectangular patch, and the second radiation patch unit 32 is a trapezoidal patch. The long side of the radiation patch 3 is close to one side of the dielectric plate 2 close to the center of the reflection ground plate 1. The reflection ground plate 1 is a circular plate, and the dielectric plate 2 is a rectangular plate. There are four groups of dielectric plates 2, and the adjacent dielectric plates 2 are perpendicular to each other.

[0037] The ceiling antenna designed by the present invention has circular polarization characteristics. In order to generate circular polarization, the antenna needs to be able to generate two spatially orthogonal linearly polarized electric field components in the far field region and make the two amplitudes equal (i.e., degenerate mode) and the phase difference 90 degrees. The basic structure of the antenna is as follows Figure 1As shown, the circularly polarized antenna is based on a propeller structure. Rectangular and trapezoidal radiation patch units are etched on four rectangular dielectric plates and welded perpendicularly to a circular reflective dielectric plate. Therefore, horizontal polarization components and vertical polarization components can be directly generated. When the phase difference is constantly 90 degrees, the two can synthesize a circularly polarized wave in the far field.

[0038] The structure of the radiation unit loaded with an inverted L-shaped slot is as follows: Figure 3 As shown. The size of the rectangular patch is W1×L1, the lower base of the vertically placed trapezoidal patch is W1, the upper base is W2, and the height is g. The coaxial probe is fed from the back of the circular reflector. The inverted L-shaped slot is used to change the current path on the radiation patch, thereby enhancing the radiation intensity of the antenna in the +z direction. The horizontal part length of the inverted L-shaped slot is L2, the vertical part length is L3, and the width of the slot is d. The radiation pattern and impedance bandwidth of the antenna are optimized by adjusting the structural parameters of the antenna. The relevant preferred structural parameters are shown in Fig. 9 .

[0039] The return loss RL (Return Loss) of an antenna refers to the ratio of the power reflected from the RF input signal to the power of the input signal. It is measured in dB and is a negative number. Ideally, the impedance of the antenna and the RF circuit are perfectly matched, and there is no reflected power at all. In this case, the return loss is infinitely small. However, in engineering, it is impossible to perfectly match the impedance, so reflected power must exist. Figure 4 This is the return loss curve based on the antenna test. The measured reflection coefficient satisfies the bandwidth range of less than -10dB from 4.51GHz to 9.01GHz, and the bandwidth is 4.5GHz. Similarly, the standing wave ratio (VSWR) can also reflect the quality of antenna impedance matching. The greater the reflection, the greater the standing wave ratio. Therefore, for the technical parameter of standing wave ratio, the lower the value and the closer it is to 1, the better. Figure 5 This is a VSWR curve based on the test of this antenna. The measured VSWR frequency band is from 4.43GHz to 9.15GHz.

[0040] The trajectory of the electric field vector of a circularly polarized wave in space is a circle traced by a time function. In practical applications, elliptical polarization conditions close to circular polarization are called circular polarization. The parameter of this measurement is expressed by the axial ratio. Generally, the axial ratio of a circularly polarized antenna is required to be less than 3dB. Figure 6 It is the axial ratio curve within the tested frequency band of 6.3GHz to 6.65GHz. The frequency less than 3dB axial ratio is from 6.44GHz to 6.58GHz, the 3dB axial ratio bandwidth reaches 140MHz, the relative 3dB axial ratio bandwidth is 2.1%, and the impedance bandwidth completely includes the axial ratio bandwidth.

[0041] Figure 7The radiation patterns of the xoz and yoz planes for far-field radiation at different operating frequencies of 6.45 GHz, 6.5 GHz, and 6.6 GHz were tested respectively. The radiation patterns are all half-space radiation. Due to the through holes of the reflector, there is a certain amount of radiation leakage on the back.

[0042] Figure 8 It is the measurement curve of the antenna peak gain. The peak gain of the antenna fluctuates between 3.04dBi and 3.22dBi in the frequency band from 6.2GHz to 6.8GHz, with a fluctuation range of 0.18dB, and is relatively stable in the passband.

[0043] The above are embodiments of the present invention. For ordinary technicians in this field, according to the teachings of the present invention, all equivalent changes, modifications, substitutions and variations made within the scope of the patent application of the present invention without departing from the principles and spirit of the present invention should fall within the scope of the present invention.

Claims

1. A circularly polarized ceiling antenna, comprising a reflection ground plate with one side grounded and a plurality of dielectric plates vertically arranged on the reflection ground plate, characterized in that: The dielectric plate is arranged on the surface of the reflecting ground plate around a circle with the center of the reflecting ground plate as the center; A radiation patch is etched on one side of each group of dielectric plates; The radiation patch is provided with a gap for changing the current path; The gap is an inverted L-shaped gap, and the vertical gap of the inverted L-shaped gap is located on a side of the radiation patch close to the center of the reflection ground plate; A through hole is provided at the center of the reflection ground plate, and a feed source is provided in the through hole, and the feed source is coaxially fed through the through hole of the reflection ground plate; The radiation patch is composed of a first radiation patch unit and a second radiation patch unit which are different in shape and adjacent to each other; the first radiation patch unit is a rectangular patch, and the second radiation patch unit is a trapezoidal patch.

2. The circularly polarized ceiling antenna according to claim 1, characterized in that: The radiation patches are connected to each other at one side close to the center of the reflection ground plate, and the connection point is located on the longitudinal projection line of the center of the reflection ground plate.

3. The circularly polarized ceiling antenna according to claim 1, characterized in that: The long side of the radiation patch is in close contact with one side of the dielectric plate close to the center of the reflection ground plate.

4. The circularly polarized ceiling antenna according to claim 1, characterized in that: The reflection ground plate is a circular plate, and the dielectric plate is a rectangular plate.

5. The circularly polarized ceiling antenna according to claim 1, characterized in that: The number of the dielectric plates is four, and the adjacent dielectric plates are perpendicular to each other.

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