CN109560375B

CN109560375B - Periodic orthogonal meander line leaky-wave antenna

Info

Publication number: CN109560375B
Application number: CN201811407512.4A
Authority: CN
Inventors: 程思卓; 李元新
Original assignee: National Sun Yat Sen University
Current assignee: National Sun Yat Sen University
Priority date: 2018-11-23
Filing date: 2018-11-23
Publication date: 2020-09-25
Anticipated expiration: 2038-11-23
Also published as: CN109560375A

Abstract

Aiming at the technical problem that the existing periodic leaky-wave antenna is difficult to inhibit an open stop band, the periodic orthogonal meander line leaky-wave antenna which has the advantages of simple structure, easy processing, larger beam scanning range and capability of realizing non-attenuation scanning in the edge radiation direction is provided. The antenna structure comprises a dielectric plate, a metal transmission line, a metal floor and a feed joint. The metal transmission line is formed by periodically connecting horizontal and vertical transmission lines in two vertical orthogonal directions. In actual measurement and use, one feed joint is connected with a high-frequency signal source, and the other feed joint is connected with a 50-ohm load to serve as a terminal pure resistance load, so that transmission line terminal reflection is reduced. Impedance matching between the periodic structures can be realized by changing the distance and the width of the transmission line in the vertical direction, so that the open circuit stop band phenomenon is inhibited, and non-attenuation scanning in the edge-emitting direction is realized.

Description

Periodic orthogonal meander line leaky-wave antenna

Technical Field

The invention relates to the field of radio, in particular to a periodic orthogonal meander line leaky-wave antenna.

Background

The traditional uniform leaky-wave antenna can only realize forward scanning of a main beam (0 degrees < theta <90 degrees), the beam scanning range is small, the periodic leaky-wave antenna has the capability of forward and backward scanning (-90 degrees < theta <90 degrees), the scanning range is wider, and the practical application value is higher. However, when a main beam scans in the side-emitting direction (θ is 0 °), an "Open Stopband" (Open Stopband) phenomenon generally occurs in the conventional periodic leaky-wave antenna, that is, when the beam scans in the side-emitting direction, attenuation of gain generally occurs, which results in degradation of a directional pattern. The structure of the model is improved through a proper design method, and the matching characteristic of the antenna structure under the frequency during edge-fire scanning can be improved, so that energy is effectively conducted and leaky waves are radiated in the structure, and the non-attenuation scanning in the edge-fire direction is realized.

Disclosure of Invention

Aiming at the technical problem that the conventional periodic leaky-wave antenna is difficult to inhibit an open stop band, the invention provides the periodic orthogonal meander line leaky-wave antenna which has the advantages of simple structure, easiness in processing, miniaturization, larger beam scanning range and capability of realizing non-attenuation scanning in the edge-emitting direction.

In order to realize the purpose, the technical scheme is as follows:

the periodic orthogonal zigzag line leaky-wave antenna comprises a dielectric plate, a metal transmission line, a metal floor and a feed joint; the metal transmission line is connected to one side of the dielectric plate, the metal floor is connected to the other side of the dielectric plate, the central feed pin of the feed connector is connected with the metal transmission line, and the outer conductor of the feed connector is connected with the metal floor. In actual measurement and use, one feed joint is connected with a high-frequency signal source, and the other feed joint is connected with a 50-ohm load to serve as a terminal pure resistance load, so that transmission line terminal reflection is reduced.

Preferably, the medium plate is a solid medium or an air medium.

Preferably, the metal transmission line is a microstrip line structure formed by periodically connecting horizontal and vertical transmission lines in two orthogonal directions, and the microstrip line structure is represented by a periodic S-shaped zigzag line. The width of the two vertical transmission lines of the periodic structure and the distance between the two transmission lines determine the impedance characteristic (Bloch impedance) of the periodic structure, so that the matching performance of the whole structure is influenced, and parameters such as return loss, main beam gain and the like are reflected.

Preferably, the metal transmission line and the metal floor are planar metal structures tightly attached to the dielectric plate. The periodic spacing of the metallic transmission lines and the length of the vertical transmission lines determine the operating frequency range of the antenna.

Furthermore, the size of the metal transmission line, the thickness of the dielectric plate and its relative dielectric constant determine the propagation constant (including the attenuation constant and the phase constant) of the antenna. Specific propagation constant values can be extracted through the measured scattering coefficients.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a periodic orthogonal meander line design, realizes the forward and backward scanning of the main beam of the antenna, solves the problem of open stopband in the side-emission direction through reasonable periodic structure impedance matching optimization, and realizes the non-attenuation scanning of the main beam of the working frequency band.

Drawings

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

FIG. 2 is a schematic backside view of the present invention;

FIG. 3 is a side schematic view of the present invention;

FIG. 4 is a schematic front view of an optimized structure of the present invention;

FIG. 5 is a graph of the reflection coefficient for the initial and optimized structures;

FIG. 6 is an E-plane pattern (with attenuation) near the edge scan of the initial structure;

FIG. 7 is an E-plane pattern (no attenuation) near the edge scan of the optimized structure;

FIG. 8 is an E-plane pattern (forward-backward sweep) for the optimized structure;

FIG. 9 is a graph of the propagation constants of the initial and optimized structures;

fig. 10 is a plot of Bloch impedance for the initial and optimized structures.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

the invention is further illustrated below with reference to the figures and examples.

Example 1

The periodic orthogonal meander line leaky-wave antenna is a planar structure as shown in fig. 1, fig. 2 and fig. 3, the antenna can be decomposed into a dielectric plate 1, a metal transmission line 2, a metal floor 4 and a feed connector 3, the metal transmission line 2 and the metal floor 4 are tightly attached to two sides of the dielectric plate 1 and are excited by the feed connector 3, and the other connector is connected with a 50 ohm load. The optimized metal transmission line 2 is shown in fig. 4, and the specific optimization process is as follows:

(1) firstly, the distance between two vertical transmission lines of the periodic structure is changed to be equal to one fourth of the working wavelength, and reflected waves caused by one vertical transmission line can be absorbed by the other transmission line;

(2) the widths of the two vertical transmission lines in the periodic structure are changed, so that the periodic unit structure has asymmetry, and the impedance value of the periodic structure can be adjusted.

The reflection coefficient curves of the initial and optimized structures are shown in fig. 5, and the reflection coefficient of the initial structure from 4.5GHz to 4.9GHz is greater than-10 dB, which shows that most of the input energy of the frequency band is reflected without forming a space radiation wave; the optimized structure has S in the working frequency band₁₁|<-10dB, when most of the energy is conducted in the form of traveling waves on the structure, the radiation performance is good.

From fig. 6, it can be seen that the gain of the initial structure beam scanned near the broadside direction (4.8GHz,4.9GHz) is reduced by about-3 dB, while fig. 7 illustrates that the improved structure can achieve unattenuated scanning in the broadside direction through optimization. Fig. 8 shows that the inventive arrangement can achieve a scan range of-60 deg. to 60 deg..

The propagation constant curve of the initial and optimized structures is shown in fig. 9, and the phase constant and the attenuation constant of the optimized structure are smoother, because the abrupt change of performance caused by the open stop band is suppressed, so that the change of the scanning angle is smoother, and the energy attenuation is reduced. Fig. 10 shows the essence of the optimization method proposed by the present invention, which is to change the Bloch impedance of the periodic structure to be as stable as possible around 50 ohms, thereby realizing impedance matching between periods.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. The periodic orthogonal meander line leaky-wave antenna is characterized by comprising a dielectric plate (1), a metal transmission line (2), a metal floor (4) and a feed joint (3); the metal transmission line (2) is connected to one side of the dielectric plate (1), the metal floor (4) is connected to the other side of the dielectric plate (1), a central feed pin of the feed joint (3) is connected with the metal transmission line (2), and an outer conductor of the feed joint (3) is connected with the metal floor (4);

the metal transmission line (2) is a microstrip line structure formed by periodically connecting horizontal and vertical transmission lines in two orthogonal directions, and is represented as a periodic S-shaped zigzag line, wherein the distance between the two vertical metal transmission lines (2) in the periodic structure is changed to be equal to one fourth of the working wavelength; the widths of two vertical metal transmission lines (2) in the periodic structure are changed, so that the periodic unit structure has asymmetry.

2. The periodic orthogonal meander line leaky-wave antenna according to claim 1, characterized in that said dielectric plate (1) is a solid medium or an air medium.

3. The periodically orthogonal meander line leaky-wave antenna as claimed in claim 1, wherein said metal transmission line (2) and metal floor (4) are planar metal structures closely attached to the dielectric plate (1).