Design of Broadband Aperture-Stacked Patch Microstrip Antennas Based on Third Order Filtering Equivalent Circuits

In this paper the authors describe the design of a broadband aperture-stacked patch (ASP) microstrip antenna based on a filtering equivalent circuit. The antenna consists of two stacked microstrip patches that are fed by a microstrip line through a resonant aperture. An equivalent circuit is proposed for the antenna consisting of three LC parallel resonators, out of which two resonators are inductively coupled and two resonators are capacitively coupled. The equivalent circuit is de-embedded from the antenna response by means of the least squares method, and the dimensions of the antenna are adjusted in such a way their equivalent circuit matches the response of a broadband third order filter. The reference filter is used as a mean to ensure broadband matching of the antenna. Following this design strategy, a broadband ASP antenna has been designed, fabricated and measured at a center frequency of 5.5 GHz with a bandwidth of roughly 45%.