Wu Ren

Full-wave analysis of broad wall slot's Characteristics in rectangular waveguides

A rigorous analysis of the resonant characteristics for a broad wall waveguide slot by using the finite-difference time-domain method is presented. Four types of slots including a radiating longitudinal shunt slot, a longitudinal/transverse coupling slot, a centered-inclined coupling slot and a compound coupling slot are analyzed. Lots of slot characteristics such as the resonant length, scattering parameters and normalized admittance in different offsets, tilt angles or slot sizes are obtained. Because the shape of slots is a rectangle with rounded ends in practical fabrication, an accurate modeling and computation for the slots with rounded ends is implemented, and the resonant lengths calculated coincide well with the Stegens measured data and method of moments results. From these computed results, it is found that all the resonant characteristics of the slots with rounded ends are significantly different from those with normal rectangular ends.

Research on a New Kind of High Directivity End-Fire Antenna Array

In this paper, a new kind of end-flre array was built by employing high directivity plate end-flre antenna as the basic element based on electromagnetic surface wave theory. Being difierent from normal end-flre array, in the new array, high directivity plate end- flre antenna elements were arranged end to end along the end-flre direction, and the interelement spacing and uniform progressive phase were carefully adjusted to achieve high directivity. The simulations and measurements showed that the whole array achieved 19.2dB directivity with four elements at 14.7dB directivity each.

Low-RCS High-Gain Partially Reflecting Surface Antenna With Metamaterial Ground Plane

In this communication, a high-gain partially reflecting surface (PRS) antenna with both in-band and out-of-band radar cross section (RCS) reduction (RCSR) is presented. A microstrip patch antenna acts as the source and is surrounded by the metamaterial ground plane (MGP), which is to reduce the in-band RCS of the proposed antenna. A PRS is located approximately one-half of the wavelength above the MGP to enhance the antenna directivity. In addition, an absorbing surface is adopted to reduce the out-of-band RCS. The design procedure of the antenna is illustrated, and the simulated results reveal that a significant RCSR has been accomplished in the frequency ranges of 8-17 GHz. Compared with the reference antenna, the average out-of-band RCSR is about 13 dB for both TE and TM polarization incident waves. What is more, the in-band RCSR is about 17 dB for the TM polarization incident wave. The simulated results match the measured results well, and the peak gain of the proposed antenna is 18.4 dBi at the operating frequency of 10 GHz.

Particle Swarm Optimization of frequency selective surface

Particle Swarm Optimization (PSO) has been successfully applied in the design and optimization of electromagnetic structures. Combined with FDTD technique, PSO is applied in the design of frequency selective surfaces. Together with the GPU acceleration, the FDTD program runs about 100 times faster while preserves the broad-band nature of the algorithm. Standard PSO and binary PSO are applied to deal with known cell structure and unknown cell structure optimization respectively. The entire optimization scheme is verified by the numerical results.

Design and analysis of a 3GHz printed dipole antenna

A printed dipole antenna for wireless communication applications is designed, simulated and optimized by HFSS, FEM electromagnetic EM simulator. Numerical and measured results of the antenna radiation characteristics, including input SWR, radiation pattern coverage and beam pattern, are presented and compared.

Analysis and application of new quasi-network characteristics of nonuniform mesh in FDTD simulation

The equation of computing the reflection coefficient between two meshes of different sizes is derived. Using the equation, quasi-network characteristics of nonuniform mesh for the finite-difference time-domain technique is found and analyzed. The so-called mesh network (MN) here is a kind of structure composed of the sections of mesh in cascade. The cell sizes of these sections change regularly. By means of choosing the number of mesh sections, length of each section, and cell sizes, some novel network characteristics are obtained, which can be used to match the reflecting wave of nonuniform mesh or improve the transmitted characteristics for a mesh wave to travel along the nonuniform mesh. Formulas for analyzing the MN are given. The characteristics are realized in both one- and three-dimensional cases. The applications and advantages of the MN are shown by computing three different structures, i.e., microstrip-gap capacitor, parallel-coupling filter, and microstrip slot-line transformer.

Research on the array weighting of plate end-fire antenna with the effect of mutual coupling

This paper focus on the array weighting of the plate end-fire antenna array with the effect of mutual coupling. The far field pattern distortions of array caused by mutual coupling were analyzed. Then, the efficacies of amplitude weighting and phase weighting in plate end-fire antenna array were discussed. Under strong mutual coupling, the efficacy of amplitude weighting was affected evidently, and the designing target was hard to be achieved. Meanwhile, the efficacy of phase weighting was achieved exactly in a large range of scanning.

The analysis of 3 dB microstrip directional coupler in time-varying media by FDTD method

The characteristics of time-varying media are very important for electromagnetic research; many microwave components should be studied in time-varying media, and some of these will not work well because of the influence of the time-varying medium. In this paper, FDTD difference equations in time-varying media are deduced in the three-dimension case, and then using it to simulate the electromagnetic pulses propagation in a 3 dB microstrip directional coupler to show whether the transmission characteristic will be changed when the media parameters vary by some rules. By comparing its operating characteristics with that in homogenous static media, we can see that it does not work well.

A dielectric embedded antenna for super wideband applications

A dielectric embedded monopole antenna is proposed for super wideband(SWB)applications. The antenna is designed become inverted cone in order to expand the bandwidth, and the SWB antenna possesses a method to minimize the size of antenna by dielectric embedded to lower the height. The antenna is simulated and measured after practically fabricated. Measured results show a good agreement with simulated results that a -10dB bandwidth of 43.5GHz (4.5-48GHz) is achieved with ratio bandwidth 10.7:1.The antenna prototype shows good impedance matching, stable far-field radiation patterns, and constant group delay over the super wideband.

Research on arrays of microstrip magnetic dipole Yagi antennas

Research is done on arrays composed high gain Yagi antennas with end-fire radiation and vertical polarization. This paper mainly studies different arraying methods of the Yagi antennas and analyzes the coupling effect between array units. It includes arraying in three directions (X, Y and Z). The Yagi antenna unit is microstrip magnetic dipole antenna of which the elements are based on a new microstrip antenna that has one edge opened and the other three edges shorted, working as a “magnetic dipole”. The proposed antenna unit could produce a beam radiating at exactly end-fire for infinite ground plane with vertical polarization in the horizontal plane, but has a little beam-tilted angle for finite ground. The performances of arrays on the three different directions are deeply analyzed and explained specifically.