摘要：
A kind of compound optical lens (COL) inspired by metamaterials whose unit cell is a closed symmetric S-type resonator (CSSR) is designed to enhance the gain and directivity of the antipodal Vivaldi antenna (AVA). COL, composed of a plano-convex lens and a double-convex lens, can generate a very narrow beam with a half-power beamwidth of 11.2 degrees at 12 GHz. Traditional metamaterial lenses can only convert spherical waves into plane waves. Although the gain will increase, the beamwidth of the antenna is still very wide. COL can focus the plane wave transformed from the spherical wave, which makes the radiation beam extremely narrow. The proposed antenna has a -10 dB impedance bandwidth of 169.2% (1.0-12.0 GHz) and a -3 dB gain bandwidth of 133.3% (2.0-10.0 GHz) and a maximum gain enhancement of 5 dBi. The experimental results of the antennas agree with the simulation results. The proposed antenna is eventually a suitable candidate for wireless communications and radar applications.
摘要：
We present a metamaterial polarization converter consisting of a spindle-shaped metal top and a gradient grating-like metal bottom. It can realize half reflection and half transmission cross-polarization conversion. The simulation and experimental results show that the metamaterial polarization converter can realize the half reflection and half transmission cross-polarization conversion at 12.51 GHz-13.67 GHz, and realize the transmission cross-polarization conversion at 2.58 GHz-14.85 GHz. Combining the characteristics of general reflection polarization converter, transmission polarization converter, and half mirrors, the design of polarization converter is an enlightening exploration for the multi-functional integration of metamaterials and is conducive to the miniaturization and integration of optical systems. It has potential applications in antennas, imaging systems, remote sensors and radiometers. (C) 2020 Elsevier B.V. All rights reserved.
期刊：
Journal of Physics D: Applied Physics,2021年54(20):205104 ISSN：0022-3727
通讯作者：
Yang, Helin
作者机构：
[Cheng, Houyuan; Li, Yujun; Yang, Helin; Hua, Lina; Yang, Dong; Wu, Jiong] Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan 430079, Peoples R China.;[Wang, Youcheng] Sci & Technol Complex Syst Control & Intelligent, Beijing 100074, Peoples R China.
通讯机构：
[Yang, Helin] C;Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan 430079, Peoples R China.
关键词：
Vivaldi antenna;metamaterials;beam control
摘要：
A compact antipodal Vivaldi antenna (AVA) with metamaterial half-lens (MHL) for beam control is proposed. The proposed AVA has three different beam forms in the operating frequency band, including end beam from 3 GHz to 9 GHz, beam splitting at 12.2 GHz, and 30 degrees beam deflection at 13 GHz. Furthermore, it can perform 18 degrees beam scanning by adjusting operating frequency from 12.7 GHz to 13.5 GHz. The simulation indicates that the proposed AVA has a -10 dB impedance bandwidth of 143.6% (2.3-14.0 GHz) and a -3 dB gain bandwidth of 100% (4.5-13.5 GHz), which is consistent with the experimental results. Besides, the gain of the proposed AVA has an improvement of about 2 dB in the working band. As a new method to control the beam, the loading of MHL realizes the design of a small size and multi-function antenna, which can be widely used in wireless communication systems.
摘要：
A transmissive water-based metamaterial absorber(TWMA) is designed, simulated, and measured, which uses 3D-printing to manufacture. The TWMA uses a circular column and rectangular water layer structure and has no metal backplane. We have proved theoretically and experimentally that the TWMA has absorption rate exceeds 90% in the frequency ranging from 6.5 to 21.4 GHz. Furthermore, the TWMA is thermo-tunable when temperatures change from 10 to 60 degrees C and has the characteristics of wide angle incidence and polarization insensitivity. It can be applied to a variety of electromagnetic applications, such as reducing broadband scattering and collecting electromagnetic energy in a variable temperature environment.
通讯机构：
[Yang, Helin] C;Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan 430079, Peoples R China.
关键词：
metamaterials;low frequency;absorber;multiple frequency
摘要：
Designing high efficiency microwave absorbers with frequencies in 1 GHz is still a huge challenge in practical applications. We design and present a novel microwave metamaterials absorber at six frequency points of 160, 442, 530, 723, 765 and 965 MHz with absorptances up to 90%, which is insensitive to polarization, viable at wide incidence angle and relatively simple in structure. We demonstrate the absorption characteristics of the absorber and explain the mechanism by means of equivalent impedance theory, surface current and energy distribution. The experimental results verify the correctness of the simulation and provide valuable reference for the design of broad-band microwave absorber in lower frequency band.
期刊：
Materials Research Express,2020年7(2):025802- ISSN：2053-1591
作者机构：
[Lu, Taoming; Yang, Helin; Wu, Jiong; Zhou, Yanfei] Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan 430079, Peoples R China.;[Wang, Youcheng] Sci & Technol Complex Syst Control & Intelligent, Beijing 100074, Peoples R China.;[Huang, Xiaojun] Xian Univ Sci & Technol, Coll Commun & Informat Engn, Xian 710054, Peoples R China.
关键词：
metamaterial;dihedral corner;RCS;absorption
摘要：
In this paper, the absorbing property of metal-cross shaped metamaterial dihedral (MCMD) and cross-cross shaped metamaterial dihedral (CCMD) with the same parameters are investigated. In TE mode, the absorptivities are 91.1% at 9.17 GHz for MCMD and 99.7% at 9.20 GHz for CCMD. For MCMD and CCMD, the absorptivities are 90.5% and 99.8% at 9.2 and 9.17 GHz respectively for the TM polarized incident wave. The results of simulation and measurement show that CCMD has better multi-band absorption performance and lower radar cross-section than MCMD. Experiments have demonstrated the reflection coefficient can be utilized to analyze the electromagnetic characteristics of dihedral corner as well. The study of dihedral corner reflector is of great importance as it is used in modeling many areas such as stealth technology, electromagnetic compatibility and target recognition.
摘要：
This paper designs a planar electromagnetically induced transparency (EIT) metamaterial, which comprises an asymmetric ellipse split resonance ring (AESRR) and cut wire (CW). The proposed EIT metamaterial works in the wide range of incident angles and has polarization-sensitive at two transmission dips. The frequency of transparency peak is 10.67 GHz and maintains a high quality-factor (180.84). By calculating the multipole's radiated power, it can be found that the toroidal dipole response is enhanced, while the electric dipole response is suppressed at the transparency peak. Interestingly, this paper firstly uses the radiated power of electric dipole to elucidate the polarization sensitivity in two minimal transmissions. Meanwhile, the coupling mechanism of the EIT metamaterial is analyzed by the two-oscillator model and equivalent circuit.
摘要：
A novel compact Vivaldi Antenna (CVA) for short-pulse ground penetrating radar (GPR) systems is presented. Artificial materials lens (AML) and sidelobe suppressor (SSR) are loaded to improve GPR Antenna & x2019;s radiation capability in the aperture and the flanks of the CVA. The simulation and experimental results indicate that the proposed CVA has a & x2212;10 dB impedance bandwidth of 100 & x0025; (0.7-2.1 GHz) and a & x2212;3 dB gain bandwidth of 70.9 & x0025; (1.0-2.1 GHz). Within the operating bandwidth of the CVA, AML primarily enhances the CVA & x2019;s high-frequency gain (1.4-2.1GHz), while the SSR primarily enhances the CVA & x2019;s low-frequency gain (0.7-1.4 GHz). Moreover, the CVA loaded with two kinds of artificial materials (AMs) has an average gain of 1 dB and 2 dB in the low-frequency and high-frequency parts, respectively. In addition, the transmission response with small ringing in time domain makes the proposed CVA suitable for short-pulse GPR systems. AML and SSR effectively enhance the gain of the CVA with a compact and space-saving loading method, which provides a new idea to enhance the gain of the CVA by artificial material.
通讯机构：
[Yang, Helin] C;Cent China Normal Univ CCNU, Sch Phys Sci & Technol, Wuhan 430079, Peoples R China.
摘要：
The electromagnetic parameter retrieval method based on scattering ( S ) parameters is widely used because S parameters are easy to obtain. As a classic S parameters retrieval method, the Nicolson–Ross–Weir (NRW) algorithm has problems such as half-wave resonance, phase angle jump, and multivaluedness. In this work, an electromagnetic parameter retrieval method based on deep learning is proposed, which aims to solve the multivaluedness problem in the traditional NRW method. The method we proposed is suitable for retrieval of inhomogeneous medium that satisfies the theory of effective medium. The simulation shows that the electromagnetic parameter retrieval method based on deep learning has high calculation accuracy without the multivaluedness problem.
摘要：
The natural water has frequency dispersion and its permittivity is also related to temperature, which are important factors to design temperature insensitive absorber at microwave frequency. Here, a water-based metamaterial absorber which is fabricated by 3D-printing is proposed. The absorber can perform stably at different temperatures and it also shows 90% absorption in the frequency range of 7.9-21.7 GHz. The experiment proves that the absorber can work at a wide incident angle and is polarization insensitive. Based on these features, the water-based absorber could be applied to various electromagnetic scenarios such as stealth technology and electromagnetic compatibility in temperature-variable environment. (C) 2019 Elsevier B.V. All rights reserved.
关键词：
antenna radiation patterns;electromagnetic coupling;slot antennas;microwave antenna arrays;slot antenna arrays;antenna feeds;antenna arrays;broadband antennas;broadband antipodal tapered slot antenna array;low mutual coupling;high gain properties;strong mutual coupling;radiation capability;array elements;radiation performance;split-ring resonators unit cells;entire operating frequency band;4-10 GHz;gain reduction;low- frequency gain;high-frequency gain;ATSA array;lower mutual coupling properties;gain-enhancing mechanism;antenna designs;noise figure 3;2 dB;frequency 1;4 GHz to 10;0 GHz;noise figure 35;0 dB
摘要：
Strong mutual coupling always exists between the elements of the antenna array, thereby affecting its radiation capability. For this problem, an efficient method for suppressing the mutual coupling of array elements and improving the radiation performance of the antenna is proposed. In this study, take the antipodal tapered slot antenna (ATSA) array, for instance, a set of split-ring resonators (SRRs) unit cells is incorporated into the design to reduce leakage of the side walls at first. With the adding of SRRs, the mutual coupling in the entire operating frequency band (1.4-10 GHz) gets reduced, and the maximum reduction of 35 dB can be achieved. In addition, in order to compensate for the gain reduction caused by the isolation material, the grooves and semi-circular dielectric lens were introduced to enhance the low- and high-frequency gain, respectively. The gain of the proposed ATSA array can be improved by similar to 3.2 dB. At last, the proposed ATSA array has broadband, high gain with lower mutual coupling properties. This decoupling and gain-enhancing mechanism can be applied to other antenna designs.
