Guiping Zheng

A coplanar waveguide bow-tie aperture antenna

In this paper, a new design for a coplanar waveguide (CPW) fed, aperture antenna is introduced. This CPW aperture antenna is designed at a central frequency around 10 GHz with an input impedance of approximately 50 /spl Omega/. Numerical simulation is performed for antenna analysis using Momentum from the Advanced Design System (ADS) software package of Agilent Technologies. The bandwidth of this basic bow-tie aperture antenna is about 1 GHz and the return loss approximately -18 dB. Another advanced design for this basic bow-tie aperture antenna shows a bandwidth of 1.3 GHz with a return loss of -40 dB around 10 GHz. Simulation results for return loss, input impedance and radiation pattern are presented. These characteristics make these two antennas suitable for antenna arrays for radar applications.

A broad band printed bow-tie antenna with a simplified feed

A broad band printed bow-tie antenna with a simplified feeding mechanism is proposed. The printed bow-tie antenna is fed by a transmission line formed by two parallel strips printed on the opposite sides of the dielectric substrate. The parallel strips are connected to a microstrip line with a truncated ground plane. The analysis of the antenna is performed numerically using commercial FEM software, Ansoft High Frequency Structure Simulator (HFSS). A sample of the proposed antenna was built and experimentally validated, showing a good agreement with the simulation results.

A NOVEL IMPLEMENTATION OF MODIFIED MAXWELL'S EQUATIONS IN THE PERIODIC FINITE-DIFFERENCE TIME-DOMAIN METHOD

To model periodic structures with oblique incident waves/scan angles in FDTD, the field transformation method is successfully used to analyze their characteristics. In the field transformation method, Maxwells equations are Floquet-transformed so that only a single period of infinite periodic structure can be modeled in FDTD by using periodic boundary conditions (PBCs). A new discretization method based on the exponential time differencing (ETD) algorithm is proposed here for the discretization of the modified Maxwells equations in the periodic FDTD method. This new discretization method provides an alternative way to discretize the modified Maxwells equations with simpler updating forms that requires less CPU time and memory than the traditional stability factor method (SFM). These two methods have the same numerical accuracy and stability in the periodic FDTD method. Some validation cases are provided showing perfect match between the results of both methods.

IMPLEMENTATION OF MUR'S ABSORBING BOUNDARIES WITH PERIODIC STRUCTURES TO SPEED UP THE DESIGN PROCESS USING FINITE-DIFFERENCE TIME-DOMAIN METHOD

The finite-difference time-domain (FDTD) method is used to obtain numerical solutions of infinite periodic structures without resorting to the complex frequency-domain analysis, which is required in traditional frequency-domain techniques. The field transformation method is successfully used to model periodic structures with oblique incident waves/scan angles. Maxwell’s equations are transformed so that only a single period of the infinite periodic structure is modeled in FDTD by using periodic boundary conditions (PBCs). When modeling periodic structures with the transformed fields, the standard Mur second-order absorbing boundary condition cannot be used directly to absorb the outgoing waves. This paper presents a new implementation of Mur’s second-order absorbing boundary condition (ABC) with the transformed fields in the FDTD method. For designs that require multi-parametric studies, Mur’s ABCs are efficient and sufficient boundary conditions. If more accurate results are needed, the perfectly matched layer (PML) ABC can be used with the parameters obtained from the Mur solution.

Simplified feeding for a modified printed Yagi antenna

A modified printed Yagi antenna with a simplified feeding mechanism is proposed. In the new design, the driver dipole is fed by a transmission line formed by two parallel strips printed on the opposite sides of the dielectric substrate. The parallel strips are connected to a microstrip line with a truncated ground plane. This simplified feeding structure results in the reduction of the transmission line length, and, consequently, the radiation losses. The analysis of the modified Yagi antenna is performed numerically using commercial FEM and FD-TD software.

A mutual coupling reduction technique for dielectric resonator antennas over AMC surface

The purpose of this paper is to study a mechanism of the mutual coupling reduction between two dielectric resonator antenna (DRA) elements by the presence of an artificial magnetic conductor (AMC) ground plane. It is found that the mutual coupling between two DRA elements residing on the AMC ground plane and excited by horizontal probes aligned in the E-plane can be reduced up to 20 dB in comparison to the case of DRAs on the perfect electric conductor (PEC) ground plane and excited by vertical probes aligned in the H-plane. The simulation results are carried out using Ansoft HFSS

Discretization of Modified Maxwell's Equations using Exponential Time Differencing Algorithm in the Periodic FDTD Method

In the proposed method, a new discretization technique based on the exponential time differencing (ETD) algorithm is introduced to achieve the same numerical stability and accuracy as in the traditional periodic FDTD method. Compared to the stability factor method (SFM), the ETD algorithm has simpler updating forms, and it requires less CPU time and memory. Several validation cases are provided and excellent agreement between these two methods among all of the validation cases is obtained