Vivaldi antenna capable of realizing low return loss and high gain at low frequency
阅读说明：本技术 一种在低频处实现低回波损耗、高增益的Vivaldi天线 (Vivaldi antenna capable of realizing low return loss and high gain at low frequency ) 是由 杜伯学 宁江涛 于 2019-10-25 设计创作，主要内容包括：本发明公开一种在低频处实现低回波损耗、高增益的Vivaldi天线,其特征在于,在CAVA外侧加载指数渐变槽,EGSA天线,包括介质基板、金属辐射片、微带巴伦、椭圆槽线和指数渐变槽,金属辐射片分别固定在介质基板顶面与底面,阻抗匹配微带巴伦由线性渐变微带线与开有椭圆槽线金属贴片构成。采用在金属辐射片外侧加载指数渐变槽结构(EGS),EGSA在S<Sub>11</Sub><-10dB的工作带宽增加为CAVA的185％,EGS结构有效地改善了低频段的回波损耗。(The invention discloses a Vivaldi antenna for realizing low return loss and high gain at a low frequency, which is characterized in that an index gradual change groove is loaded on the outer side of CAVA, the EGSA antenna comprises a dielectric substrate, a metal radiating sheet, a microstrip balun, an elliptical slot line and an index gradual change groove, the metal radiating sheet is respectively fixed on the top surface and the bottom surface of the dielectric substrate, and an impedance matching microstrip balun is composed of a linear gradual change microstrip line and a metal patch provided with an elliptical slot line. An exponential gradient groove structure (EGS) is loaded on the outer side of the metal radiating sheet, and EGSA is loaded on S 11 <The-10 dB operating bandwidth is increased to 185% of the CAVA, and the EGS structure effectively improves the return loss of the low frequency band.)
1. A Vivaldi antenna realizing low return loss and high gain at a low frequency is characterized in that an index gradual change groove is loaded on the outer side of a CAVA, the EGSA antenna comprises a dielectric substrate, a metal radiating strip, a microstrip balun, an elliptical groove line and an index gradual change groove, the metal radiating strip is respectively fixed on the top surface and the bottom surface of the dielectric substrate, and an impedance matching microstrip balun is composed of a linear gradual change microstrip line and a metal patch provided with an elliptical groove line.
2. A Vivaldi antenna achieving low return loss and high gain at low frequencies as claimed in claim 1, wherein the metallic radiating patch has an exponentially-graded slot line with a flared opening symmetrical about its horizontal central axis, and the metallic radiating patch has a corrugated exponentially-graded slot on its outer sidewall.
3. A Vivaldi antenna for achieving low return loss and high gain at low frequencies as claimed in claim 1, wherein the exponentially-graded slot structure is used to confine surface waves smoothly with an exponentially-graded curve, thereby achieving a broadening of the frequency band towards low frequencies.
Technical Field
The invention belongs to the technical field of antennas, and particularly relates to a Vivaldi antenna capable of realizing low return loss and high gain at a low frequency.
Background
With the development of communication technology, broadband, high-gain, and good-directivity antennas have attracted increasing attention. The Vivaldi antenna, i.e. the exponential tapered slot antenna, is an end-fire tapered slot antenna proposed by Gibson in 1979, the current of which is intensively distributed near the slot line which changes exponentially, and the slot lines with different widths correspondingly radiate electromagnetic waves with different frequencies. Theoretically, such an antenna can achieve a very wide operating bandwidth. In addition, Vivaldi antennas also have high gain and good end-fire performance. And thus is widely used in communication and electronic countermeasure systems.
For the traditional opposite extension Vivaldi antenna, although the narrow end of the antenna radiates high-frequency electromagnetic waves, the small electromagnetic waves in the conducting area at the narrow end are easy to radiate and are less reflected; but the wide end of the antenna radiates low-frequency electromagnetic waves, and part of energy of the low-frequency electromagnetic waves is reflected by the tail end of the antenna, so that the return loss at the low frequency is not more than-10 dB. The return loss and the gain of the Vivaldi antenna at low frequency are difficult to improve by the prior art.
Disclosure of Invention
The Vivaldi antenna aims to solve the technical problem that the Vivaldi antenna is difficult to realize low return loss at a low frequency, and particularly has poor performance at a low frequency band.
The invention provides a Conventional opposite extension Vivaldi antenna (CAVA for short). On the premise of not increasing the plane size, the radiation characteristic parameter at the low frequency is improved.
The technical scheme adopted by the invention is as follows: a method for improving the low-frequency radiation characteristic of a pair-extension Vivaldi antenna. An Exponential gradient slot (EGS for short) is loaded on the outer side of the CAVA, and the slot structure adopts a constraint surface wave which can be smooth by an Exponential gradient curve, so that the frequency band is widened to a low frequency position. The EGSA antenna comprises a dielectric substrate, a metal radiating plate, a microstrip balun, an elliptical slot line and an Exponential Gradient Slot (EGS). The metal radiating pieces are respectively fixed on the top surface and the bottom surface of the dielectric substrate, and the impedance matching microstrip balun is composed of a linear gradient microstrip line and a metal patch provided with an elliptical slot line. The metal radiating sheet is provided with an index gradual change groove line with a horn-shaped opening and symmetrical about a horizontal central axis, and the outer side wall of the metal radiating sheet is provided with a corrugated index gradual change groove.
Advantageous effects
The invention has the following beneficial effects:
(1) an exponential gradient groove structure (EGS) is loaded on the outer side of the metal radiating sheet, and EGSA is loaded on S 11<The-10 dB operating bandwidth is increased to 185% of the CAVA, and the EGS structure effectively improves the return loss of the low frequency band.
(2) The loading of the EGS structure improves the radiation gain of the antenna in a low frequency band, restrains the electric field offset of a full frequency band, reduces side lobes and enhances the radiation stability.
(3) The structure is simple, the cost is low, the large-scale processing and production are convenient, and the device is suitable for ultrahigh frequency detection, communication and electronic countermeasure systems.
Drawings
Fig. 1 is a schematic diagram of a Conventional Antipodal Vivaldi Antenna (CAVA) structure according to the present invention.
FIG. 2 is a schematic structural diagram of an exponentially-graded slot Vivaldi antenna (EGSA) according to the present invention.
FIG. 3 is a comparison graph of return loss simulation results of CAVA and EGSA.
FIG. 4 is a graph comparing the results of CAVA and EGSA gain simulation.
Fig. 5 shows the radiation patterns of the CAVA and EGSA in the E-plane and H-plane at frequencies of 1.5, 2, 2.5, and 3 GHz.
Detailed Description
The invention is further described below with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1CAVA and fig. 2EGSA, the EGSA provided by the present invention includes a
In this embodiment, the FR-4 dielectric board has a length of 99mm, a width of 99mm, a thickness of 2mm, a relative dielectric constant of 4.4, and a dielectric loss tangent of 0.02.
The expression of the two exponential
wherein, the curvature b and the starting point and the end point of the two exponential groove lines are determined as a, c, W 0The width of the microstrip feed line is 50 omega. Ratio of major axis to minor axis of elliptical trough line＝0.107,L 0The lateral distance from the focus of the ellipse to the edge of the dielectric plate.
In order to widen the impedance frequency band at low frequency without increasing the size, the surface current distribution path length of the patch can be increased by slotting, thereby achieving a correspondingly lower working frequency. By utilizing the quarter-wavelength slot line open circuit principle, a structure with infinite impedance can be formed by slotting at the outer edge of CAVA, so that radiation generated by surface waves at the edge is effectively inhibited, and current flows along the gradual change slot line to radiate.
In this embodiment, EGS is opened at the outer side of CAVA, and the total side length of the groove is 68mm corresponding to 1.1GHz lambda l/4. The slot structure adopts an exponential gradient curve to smoothly constrain surface waves. The expression is as follows:
after the HFSS software optimization, the EGSA antenna specific parameters were finally determined as table 1.
TABLE 1 antenna construction parameters
The present embodiment performs modeling simulation in the electromagnetic simulation software HFSS. FIG. 3 is a schematic diagram showing the comparison of the return loss simulation results of CAVA and EGSA, S 11<The EGSA working frequency band at minus 10dB is 0.77-3GHz, compared with 0.76-1.26GHz,1.65-2.21GHz and 2.83-3.0GHz of CAVA, the working bandwidth is increased to 185% of the conventional bandwidth, and the EGS structure effectively improves the return loss of a low frequency band;
the gain of EGSA is compared with CAVA as shown in FIG. 4. The gains are similar in the range of 0.5-1.3 GHz. In the frequency range of 1.3-2.1GHz, the EGSA gain is obviously higher than that of CAVA, and the maximum gain is improved by 2.1 dB. The EGS structure is introduced to effectively improve the gain of a low frequency band. The gain of the EGSA is stably increased in a UHF frequency range and reaches 4.2-7.9dB at 1.5-3 GHz;
fig. 5 shows the E-plane and H-plane patterns of the CAVA and EGSA antennas of the present embodiment at frequencies of 1.5, 2, 2.5, and 3 GHz. It can be seen that the side lobe of EGSA is less than or less than CAVA, indicating that EGS effectively suppresses edge current and surface wave current and beam stability is improved. EGSA has better symmetry than CAVA directional pattern, and the antenna also has better directivity.