Cavity model analysis of differential dual‐polarised annular‐ring patch antenna

The four‐port cavity model is presented to study a differential dual‐polarised annular‐ring patch antenna operating at higher order mode TM 12 . Acceptable agreements among calculated, simulated, and measured impedances and radiation patterns are obtained. Theoretical analysis shows that the differential port‐to‐port coupling impedance is zero, and its isolation is theoretically infinite. The differential input impedance is about four times of the single‐ended input impedance at the resonant frequency of higher order mode TM 12 . The differential operation can suppress the adjacent modes TM 02 and TM 22 near the operating mode TM 12 and lead to a more symmetrical E‐plane radiation pattern and lower cross polarisation level.