APPLICATION OF FINITE-DIFFERENCE TIME-DOMAIN METHOD FOR THE ANALYSIS AND DESIGN OF MICROSTRIP SLOT ANTENNA ARRAYS

Abstract

The Finite-Difference Time-Domain (FD-TD) Method which solves the Maxwell's time-dependent curl equations directly in the time-domain by converting them into finite-difference equations is employed to study the characteristics of microstrip slot antenna arrays. We have also made use of Berenger's perfectly matched layer (PML) boundary condition, the best known so far, as our terminating condition. The effectiveness of the FD-TD method employing Berenger's PML as absorbing boundary boundary condition (ABC) was verified by analysing and performing measurements on actual fabricated prototypes of 1-, 2-, 4- and 8-slot linear arrays. A very good agreement of FD-TD predictions with measurements was obtained. FD-TD was also applied to open-circuited stub tuned microstrip slot antenna where the optimum length of the stub for maximum gain was determined. Next, broadband log-periodic microstrip slot antenna arrays were studied using the FD-TD method. A 9-element log-periodic microstrip slot antenna array was successfully designed and fabricated for operation between 8 - 12 GHz. Effects of varying various parameters were also studied. Finally, a new equivalent model for the microstrip slot antenna was proposed. The new model is based on Axelrod model with the addition of two shunt capacitors and a voltage dependent current source. This model has been extended to 1-D and 2-D arrays (without mutual coupling) where the results compared favourably with the measurements. Such a model will enable more precise design and could bring about a significant saving in time and cost in designing microstrip slot antenna arrays.