Analysis and optimisation of broadband stacked microstrip antennas using transmission line model

Abstract

This study presents a technique for analysis of multilayered stacked microstrip antennas using transmission-line (TRL) equivalent circuits, which has been validated by analysis of a broadband stacked antenna. A circuit model is developed by dividing the antenna into a number of metal patch pairs which are modelled as TRLs. A procedure has also been outlined for applying the proposed method to a large class of multilayered stacked patch antennas. The proposed method models all the coupling parasitics of the stacked antenna, responsible for its broadband operation, by using only closed-form equations for TRL model parameters without any curve fitting techniques. Different propagating modes are also considered in the model. The circuit model response for a three-layered broadband stacked antenna is seen to be in qualitative agreement with simulated and measured results at each stage. The method enables quick circuit level simulation and optimisation to arrive at an initial guess of antenna parameters for a given specification. This can be subsequently fine-tuned through full three-dimensional electromagnetic simulation, which is slow, but is effective if given a good initial guess.