Extracting Circuit Model of Filtering Antenna Without Cross-Coupling by Vector Fitting

A method for extracting the circuit model of the filtering antenna without cross-coupling is introduced in this paper. Unlike the filter, the filtering antenna is a one-port device and its last resonator is a radiating resonator with a low radiation Q factor. So, the traditional two-port circuit model extraction method for the filter is no longer suited for the filtering antenna. For a lossy filtering antenna without any cross-coupling, it is possible to extract the circuit model from the input admittance. Specifically, the vector fitting method is used to fit the simulated input admittance and correct the reference plane. Then, the circuit elements can be extracted one by one by the fitted input admittance. For validation, a three-order SIW filtering antenna is simulated and used to test the method. The extracted results agree well with the simulated one.