CN109687126B

CN109687126B - Circularly polarized microstrip antenna with quasi-C-shaped structure

Info

Publication number: CN109687126B
Application number: CN201811527789.0A
Authority: CN
Inventors: 程云鹏; 单志勇; 鲁思维
Original assignee: Donghua University
Current assignee: Donghua University
Priority date: 2018-12-13
Filing date: 2018-12-13
Publication date: 2021-05-11
Anticipated expiration: 2038-12-13
Also published as: CN109687126A

Abstract

The invention relates to a circularly polarized microstrip antenna with a quasi-C-shaped structure, wherein a top layer radiation metal patch and a bottom layer earth plate metal layer are respectively arranged on the upper side and the lower side of a medium substrate, the top layer radiation metal patch comprises a quasi-C-shaped monopole, an L-shaped strip, an 1/4 wavelength impedance converter and a microstrip line, the quasi-C-shaped monopole is opened at the lower left side and is connected with one end of the 1/4 wavelength impedance converter, the other end of the 1/4 wavelength impedance converter is connected with the microstrip line, the L-shaped strip is connected with the upper right corner of the quasi-C-shaped monopole, and a rectangular gap is formed by the L-shaped strip and two edges of the quasi-C-shaped monopole; an F-shaped patch is attached to the back surface of the quasi-C-shaped monopole, the F-shaped patch is coplanar with the bottom grounding plate metal layer, and a rectangular strip perpendicular to the F-shaped patch is arranged on the left side of the bottom grounding plate metal layer; the rectangular strip faces the F-shaped patch. The invention can be effectively applied to the WiMAX system.

Description

Circularly polarized microstrip antenna with quasi-C-shaped structure

Technical Field

The invention relates to the technical field of wireless communication, in particular to a circularly polarized microstrip antenna with a quasi-C-shaped structure.

Background

In recent years, with the development of modern wireless communication technology, there is an increasing demand for a miniaturized wideband circularly polarized antenna. Circularly polarized antennas have received much attention because of the ability to reduce polarization mismatch and multipath interference. Specifically, the circularly polarized antenna can receive incoming waves with any polarization, and the radiation waves of the circularly polarized antenna can also be received by the antenna with any polarization; the electromagnetic wave with different rotation directions has great polarization isolation and the like, and has important application in the aspects of satellite communication, radar, electronic countermeasure and electronic reconnaissance, broadcast television and the like. Generally, circular polarization can be achieved by exciting two orthogonal resonant modes of equal amplitude and 90 phase difference. However, most conventional microstrip antennas have limited average bandwidth and large size, which is disadvantageous for integration and application of wireless systems. Therefore, it is an important research subject to improve a broadband miniaturized antenna.

Many antenna designers have attracted attention because of the advantages of relatively simple monopole antenna structures, light weight, wide impedance bandwidth, high radiation efficiency, and the like. In recent years, a monopole antenna variant capable of deriving circular polarization has also been proposed, such as a Y-shaped monopole antenna with unequal arms, to generate circular polarization. Also, the inventor proposes a CPW feed monopole antenna having both linear and circular polarization, which can realize broadband and circular polarization performance by introducing an asymmetric ground plane and an inverted L strip. However, these antennas have only a narrow 3dB bandwidth and 23% AR bandwidth. Moreover, these antennas are relatively large in size and not easily integrated. Therefore, the design of the communication size and AR bandwidth of a monopole antenna remains a challenging problem for antenna designers.

Disclosure of Invention

The invention aims to provide a circularly polarized microstrip antenna with a quasi-C-shaped structure, which can improve the performance of the antenna.

The technical scheme adopted by the invention for solving the technical problems is as follows: the circularly polarized microstrip antenna comprises a medium substrate, wherein a top layer radiation metal patch and a bottom layer earth plate metal layer are respectively arranged on the upper side and the lower side of the medium substrate, the top layer radiation metal patch comprises a quasi C-shaped monopole, an L-shaped strip, an 1/4 wavelength impedance converter and a microstrip line, the quasi C-shaped monopole is opened towards the lower left side and is connected with one end of the 1/4 wavelength impedance converter, the other end of the 1/4 wavelength impedance converter is connected with the microstrip line, the L-shaped strip is connected with the upper right corner of the quasi C-shaped monopole, and a rectangular gap is formed by the L-shaped strip and two edges of the quasi C-shaped monopole; the bottom grounding plate metal layer is coplanar with the F-shaped patch, and a rectangular strip vertically connected with the bottom grounding plate metal layer is arranged on the left side of the bottom grounding plate metal layer; the rectangular strip faces the F-shaped patch.

The L-shaped strip and two edges of the quasi-C-shaped monopole enclose a rectangular gap with the size of 1mm multiplied by 1 mm.

The gap between the F-shaped patch and the upper part of the C-like monopole is 1.5 mm.

The rectangular strips are 6mm from the left border of the media substrate.

The 1/4 wavelength impedance transformer is in the shape of an elongated rectangle with dimensions of 3.5mm x 2 mm.

The size of the microstrip line is 2mm multiplied by 3mm, and the feeding mode adopts microstrip line feeding.

Advantageous effects

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects: the invention is composed of a C-shaped monopole, an F-shaped patch on the back of the monopole and a modified bottom ground plate metal layer. The C-type monopole can be thought of as a rectangular ring, open at the lower left and connecting the L-type strips, thus exciting the lower CP mode. The F-shaped patch and the ground plate are coplanar and connected with the elongated rectangle perpendicular to the ground plate metal layer, so that the wide impedance bandwidth is realized, the axial ratio bandwidth of the antenna is improved, and the requirement of strong anti-interference circularly polarized waves when the antenna transmits radio waves is met finally. The whole antenna structure is very simple, has small size and is easy to be integrated into a plurality of communication application systems, in particular to a WiMAX system. Simulation results show that the impedance bandwidth of the antenna-10 dB is 81.6% (6.2GHz, 4.5-10.7GHz), and the axial ratio bandwidth AR is 75% (5.4GHz, 4.5-9.9 GHz). The invention breaks through the defect of narrow frequency band and widens the application range of the microstrip antenna in the frequency band.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of return loss of the circularly polarized microstrip antenna of the present invention;

FIG. 3 is a schematic diagram of axial ratio parameters of the circularly polarized microstrip antenna of the present invention;

FIG. 4 is a schematic diagram of gain parameters of the circularly polarized microstrip antenna of the present invention.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The embodiment of the invention relates to a circularly polarized microstrip antenna with a quasi-C-shaped structure, which comprises a dielectric substrate 1, wherein a top layer radiation metal patch and a bottom layer grounding plate metal layer 7 are respectively arranged on the upper side and the lower side of the dielectric substrate 1. The top-layer radiation metal patch comprises a quasi-C-shaped monopole 2, an L-shaped strip 3, an 1/4 wavelength impedance converter 4 and a microstrip line 5, wherein the quasi-C-shaped monopole 2 is opened at the lower left side and is connected with one end of the 1/4 wavelength impedance converter 4, the other end of the 1/4 wavelength impedance converter 4 is connected with the microstrip line 5, the L-shaped strip 3 is connected with the upper right corner of the quasi-C-shaped monopole 2, and a rectangular gap is formed by the L-shaped strip 3 and two edges of the quasi-C-shaped monopole 2; an F-shaped patch 6 is pasted on the back surface of the quasi-C-shaped monopole 2, the F-shaped patch 6 is coplanar with a bottom layer grounding plate metal layer 7, and a rectangular strip 8 perpendicular to the bottom layer grounding plate metal layer 7 is arranged on the left side of the bottom layer grounding plate metal layer 7; the rectangular strip 8 is opposite the F-shaped patch 6.

The quasi-C-shaped monopole in this embodiment can be considered as a rectangular ring, which is opened at the lower left and connected with an L-shaped strip at the upper right corner, so that a lower CP mode can be excited. Through with F type paster and bottom ground plate metal level coplane to with slender rectangle strip perpendicular to ground plate metal level, realize wide impedance bandwidth, improve the axial ratio bandwidth of antenna simultaneously, the requirement that the anti-interference is strong circular polarized wave when finally satisfying the antenna transmission radio wave.

The whole antenna structure is very simple, small in size and easy to integrate into many communication application systems. The dielectric substrate is made of FR4, has a relative dielectric constant of 4.4 and a dielectric loss of 0.02. The length of the dielectric substrate is 25mm, the width of the dielectric substrate is 25mm, and the thickness of the dielectric substrate is 1 mm. The specific dimensional parameters of the antenna are shown in table 1.

Antenna size parameter	Parameter value (mm)	Antenna size parameter	Parameter value (mm)
				L	25	a	2
W	25	b	2
				h	1	c	1
L1	2	W1	3
				L2	3.5	W2	1.2
L3	7	W3	8.5
				L4	17	W4	16
L5	2.5	W5	2
				L6	6.5	W6	2
L7	2	W7	9
				L8	2.5	W8	2
L9	4.5	W9	2
				Ls	5.5	Ws	9
Lg	6	Wf	4.5
						Wt	6

TABLE 1 basic parameters of the antenna

Because the antenna works in free space, in order to enable the designed antenna working parameters to be closer to reality, after the antenna structure model is established, when HFSS is used for analyzing the antenna performance parameters, the boundary condition of the antenna needs to be set as an ideal conductor boundary, the distance between the radiation boundary surface (namely an air cavity surface) and a radiator needs to be not less than that, the bottom surface of the antenna model dielectric substrate needs to be set as an ideal boundary, the input port of the antenna is set as coplanar lumped port excitation, the microstrip feeder line is positioned at the center of the port, the antenna is set as a fast frequency sweeping type, and the performance of the antenna in a frequency band of 4GHZ-11GHZ is analyzed and calculated.

The radio frequency signal power output by the radio transmitter is output to the transmitting antenna through the feeder line, and is radiated out by the antenna as electromagnetic waves. The antenna acts as a load for the transmitter and radiates the power received from the transmitter into space, and therefore the antenna is matched to the impedance of the feed line, the degree of matching directly affecting the efficiency of power transfer. The microstrip feeder line of the antenna is positioned in the center of the top layer of the whole structure and is tightly connected with the metal patch of the top layer, when the antenna works, signals are fed in by the microstrip feeder line of the top layer, and the metal radiation patches of the top layer and the bottom layer and the dielectric substrate form a broadband antenna which meets the application requirements together. The circular polarization of the antenna is mainly generated by a quasi-C-shaped monopole and an L-shaped strip structure, and the antenna can have good circular polarization characteristics by adjusting the quasi-C-shaped monopole and the L-shaped strip structure. Meanwhile, the broadband characteristic is realized through the coupling of the F-shaped patch and the C-shaped monopole and the coplanarity of the F-shaped patch and the C-shaped monopole and the grounding plate.

The invention adopts HFSS full-wave simulation software based on finite element algorithm to simulate the antenna structure, and simulation results of S11 parameters, AR parameters and Gain parameters of the antenna are shown in figures 2, 3 and 4. It can be seen from the figure that the frequency band range of the antenna with the S11 parameter less than-10 dB is 4.5GHz-10.7GHz, the relative working bandwidth is as high as 81.6%, the AR parameter achieves 4.5GHz-9.9GHz, the Gain parameter is above 3dB in the same bandwidth range, the extreme value reaches 5.1dB, the frequency band of the S11 parameter completely contains the frequency band of AR, and covers the frequency band of WiMAX operation, which meets the working conditions in practical application. The invention fully exerts the characteristics of small volume, low profile, easy integration, easy realization of wide frequency band and the like of the microstrip patch antenna, breaks through the defect of narrow frequency band and expands the application range of the microstrip antenna in the frequency band.

Claims

1. A circularly polarized microstrip antenna with a quasi-C-shaped structure comprises a dielectric substrate (1), wherein the upper side and the lower side of the dielectric substrate (1) are respectively provided with a top radiation metal patch and a bottom grounding plate metal layer (7), the top-layer radiating metal patch is characterized by comprising a quasi-C-shaped monopole (2), an L-shaped strip (3), an 1/4 wavelength impedance converter (4) and a microstrip line (5), wherein the quasi-C-shaped monopole (2) is opened towards the lower left, and is connected with one end of the 1/4 wavelength impedance converter (4), the other end of the 1/4 wavelength impedance converter (4) is connected with the microstrip line (5), the upper right corner of the C-like monopole (2) is connected with the L-shaped strip (3), a rectangular gap is formed by the L-shaped strip (3) and two edges of the quasi C-shaped monopole (2); the bottom ground plate metal layer (7) is coplanar with the F-shaped patch (6), and a rectangular strip (8) vertically connected with the bottom ground plate metal layer (7) is arranged on the left side of the bottom ground plate metal layer; the rectangular strip (8) is opposite to the F-shaped patch (6).

2. The circularly polarized microstrip antenna of a quasi-C configuration according to claim 1, wherein said L-shaped strip (3) and two sides of said quasi-C monopole (2) enclose a rectangular gap with a size of 1mm x 1 mm.

3. The circularly polarized microstrip antenna of a quasi-C configuration according to claim 1, characterized in that the gap between the F-shaped patch (6) and the upper part of the quasi-C monopole (2) is 1.5 mm.

4. A circularly polarized microstrip antenna according to claim 1, characterized in that said rectangular strip (8) is at a distance of 6mm from the left border of the dielectric substrate (1).

5. The circularly polarized microstrip antenna of claim 1, wherein the 1/4 wavelength impedance converter (4) is in the form of an elongated rectangle having dimensions 3.5mm x 2 mm.

6. The circularly polarized microstrip antenna of claim 1, wherein the microstrip line (5) has dimensions of 2mm x 3mm, and the feeding manner is microstrip line feeding.