A compact microstrip antenna on a cross-shape slotted ground with a switchable circular polarization

A compact circular microstrip patch antenna with a switchable circular polarization (CP) is proposed at 2.4 GHz. An unequal cross-shaped slot on a ground plane is utilized as a perturbation. By switching pin diodes mounted on the slot, the CP sense of each antenna can be simply switched from left-handed (LH) CP to right-handed (RH) CP vice versa. Since the perturbation can be made on the ground plane and no bias circuit is required on the patch side, there is less distortion on the radiation pattern. From the experimental results for both CP senses, the impedance bandwidth and CP bandwidth of the proposed antenna are up to 150 MHz and 35 MHz, respectively.