Modelling a planar phase switched structure (PSS) in Ansoft HFSS (high frequency structure simulator)

A PSS is a new type of microwave absorber that utilises the principle of phase modulation to produce a reflected field with a low time-averaged energy spectral density. It consists of one or more active layers whose impedance properties can be controlled electronically. The active layer of the PSS under consideration consists of a periodic grid of bow-tie dipole elements arranged in a rectangular grid. The control of its impedance is achieved by loading the centre of each dipole with a PIN diode. Traditionally, a TL model is used to model the PSS but this presents complications when trying to accurately model the periodicity and reactance of the active layer of the PSS, and when modelling finite structures. Ansoft HFSS (high frequency structure simulator) is an interactive software package for calculating the electromagnetic behaviour of a structure. HFSS uses the finite element method (FEM) to compute solutions. It allows for the computation of the basic electromagnetic field quantities, S-parameters, and resonance of a structure. This paper, describes how HFSS was used to model a PSS and various FSSs. Furthermore, predicted and measured results for normal incidence are compared to results from the HFSS models.