Zhipeng Liang

Investigation of a 30-GHz Relativistic Diffraction Generator with a Coaxial Reflector

This paper studies a 30-GHz relativistic diffraction generator with a coaxial reflector. The high frequency system is a disk-loaded cylindrical overmoded slow-wave structure. In order to decrease the energy leaking out from the diode end and increase output power, a coaxial reflector is placed upstream at the slow-wave structure. The reflector is designed with a center frequency of 30 GHz. Simulations and experiments of the device have been carried out. The measured microwave power is over 300 MW, and the pulse duration is about 20 ns. The microwave output power can be enhanced by adding a reflector to the devices.

Research on Three Types of Rhombus Lattice Photonic Band Structures

The gap-midgap ratio for three types of rhombus lattice photonic band structures are analyzed by plane wave expansion method, which is confirmed by the HFSS simulation. Firstly, general wave vectors in the first Briliouin zone are derived. Secondly, the gap-midgap ratios as a function of filling factor and background material are investigated, respectively. These results would provide theoretical instruction for designing arbitrary bend waveguides or other optical integrated devices using photonic crystal with a rhombus lattice.

Design of License Plate RFID Tag Antenna Using Characteristic Mode Pattern Synthesis

A novel design of the passive license plate radio frequency identification tag antenna in UHF band based on the characteristic mode theory (CMT) is proposed in this paper. The license plate is operated as a tag antenna since it is conductor (made of aluminum). A desired up-tilted pattern beam is achieved successfully by using a direct CMT-based radiation pattern synthesis procedure. The pattern can be expanded as a superposition of some specific characteristic modes pattern, which is identified according to characteristic mode analysis of the plate. Four coupling slots are exploited to excite the selected modes current distribution. The mode weighting coefficients can be tuned to form the desired pattern beam by changing the relative phase between the coupling slots. The feed structure is carefully designed without damaging the layout of characters and numbers on the license plate. The synthesized radiation pattern corresponds with the pattern simulated by HFSS. The measured radiation pattern proves that the proposed design is reliable and applicable. The measured read range is about 20 m, which can satisfy the actual requirements.

A hybrid GA-PSO optimization algorithm for conformal antenna array pattern synthesis

Abstract This paper introduces a hybrid genetic algorithm and particle swarm optimization algorithm (GA-PSO) dedicated to pattern synthesis of conformal antenna arrays. Taking advantages of both methods, the proposed hybrid GA-PSO optimization algorithm has fast convergence speed and high convergence accuracy when applied to antenna array pattern synthesis. To show the performance of the hybrid optimization algorithm, several typical test functions and optimization examples of a linear array pattern synthesis are illustrated. Finally, a 4 × 2 cylindrical conformal microstrip antenna array as a practical synthesis example is studied to demonstrate the proposed algorithm. The simulated and measured results have shown the proposed method is effective and reliable for conformal antenna array pattern synthesis.

Design and characteristic mode analysis of a low-profile wideband patch antenna using metasurface

ABSTRACT A low-profile linearly polarized patch antenna using metasurface is proposed for wideband operation at 5-GHz Wi-Fi bands. The antenna is comprised of a rectangle patch sandwiched between a lattice of 3u2009×u20093 periodic metasurface and the ground plane. The adopted coaxial probe feed is easy to fabricate and match. Characteristic mode analysis (CMA) is utilized to explain and understand the working mechanism of the proposed antenna. It is found that two dominant characteristic modes are well excited, leading to the broadband operation and linearly polarized radiation. The proposed dielectric-filled antenna with a low profile of 0.057λ0 (λ0 is the operating wavelength at 5.7u2009GHz in free space) attains about 30% measured −10u2009dB impedance bandwidth (4.89–6.62u2009GHz) with 7.28u2009dBi average gain. Across the bandwidth, the antenna efficiency is greater than 90%, and cross-polarization levels are less than 18u2009dB.

The impact of introduced coupling elements on characteristic mode

This paper gives a detail discussion about the impact of introduced coupling elements on characteristic mode. Different types of inductive coupling elements (ICEs) and capacitive coupling elements (CCEs) placed on plate structure and box structure have been taken into account. The eigenvalue, mode current and far-field of the combined structure with coupling elements are evaluated. In comparison with the original body, mode current of combined structure has changed in some degrees due to the presence of the coupling elements. But eigenvalue and mode far-field are in close proximity to the original. The impact on characteristic mode provides physical explanation about how coupling elements excite the desired characteristic modes. Information provided by CM of the combined structure can be used to optimize the size and geometry of the coupling elements.

Radar cross section reduction of dipole antenna using checkerboard surface

The radar cross section (RCS) reduction technique for dipole antenna using checkerboard surface is investigated. The checkerboard surface is used as ground of dipole antenna instead of a metal ground. In the operating frequency band of the antenna, the checkerboard surface can reflect electromagnetic wave nearly in phase, thus the radiation performance of the antenna is not degraded. However, for the out of band case, the scattered fields by two types of subarrays of the checkerboard surface are out of phase, which lead to reduced RCS of the antenna when compared with that loaded with metal ground. Results show that broadband RCS reduction can be achieved with few influence on the radiation properties in terms of both S-parameter and radiation pattern.

Scattering and radiation simulation by discontinuous Galerkin time domain method

In this paper, the implementation of the sources for scattering and radiation of the discontinuous Galerkin time domain method (DGTD) are presented. Based on formulations of the DGTD method, the sources implementation procedure is given, including the incident plane wave generated for scattering and the modeling of a coaxial port feed for antenna radiation. Numerical examples of PEC almond scattering and a microstrip antenna radiation are demonstrated the accuracy and efficiency for the source implementation in DGTD method.

A small RFID tag antenna for metallic object using characteristic mode

A small UHF RFID tag antenna for metallic object using characteristic mode theory (CMT) is presented in this paper. The tag antenna is composed of a rectangle loop and the metallic object. The rectangle loop is used as an inductive coupler element (ICE) to excite a specified characteristic mode current of the metallic object. In this case, the metallic object itself will act as the main radiator. The loop is printed on the ceramic material with a high relative dielectric constant and placed at a current maximum of a desired mode. The satisfactory result proves that the desired characteristic mode has been partially excited by this small loop.

Physical optics method over high-order triangular element for complex source beam applications

A method that combines high-order triangular element and PO method over electrically large conducting targets illuminated by a complex source beam (CSB) is developed in this paper. High-order triangular element is used to subdivide the surface of target and PO result is obtained to investigate the scattering properties. This method has the merit of being very accurate and efficient, and its computation cost does not increase with frequency. Numerical examples are also given in this paper to demonstrate the efficiency of this method.