Analysis of a two-port aperture-coupled microstrip antenna

A two-port microstrip antenna is investigated the method of moment. The antenna is a two-layer structure. The field coming from one microstrip line on the circuit layer is fed into the patch through an aperture on the ground plane. Part of the field is then coupled back to a second microstrip line through another aperture on the same ground. This configuration serves not only as a radiator but also as a feedback resonator, which is useful in designing an active antenna with a broad injection-locking bandwidth. Numerical results together with some measurements are illustrated and discussed.