Two-element dual-frequency microstrip antenna with high isolation

A compact design of a dual-frequency dual-polarised microstrip antenna structure with highly decoupled input ports is presented. The proposed antenna structure consists of two radiating elements, an annular ring and a circular disk, that are placed concentrically at the same layer. The two radiating elements are fed by an aperture-coupled feed and a coplanar-microstrip-line feed, respectively. Several prototypes of the proposed dual-frequency antennas operated at the frequency ratios ranged from 1.2 to 2.6 were constructed and tested. The experimental results show the input isolation of less than −50 dB is obtained.