A Compact Microstrip Patch Antenna with Reconfigurable Feed Network for Polarization Diversity

A compact reconfigurable four-feeding microstrip antenna with polarization diversity is presented in this paper. With four triangle-shaped elements as the radiation patch, the proposed antenna can achieve good impedance match for linear polarization (LP), left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). A four-way power divider made by three Wilkinson power dividers and interconnected with PIN diodes is designed to feed the four elements. By controlling the states of the diodes, the antenna can produce LP, LHCP and RHCP. By using T-shaped slots on the patch and back to back geometry, a compact size of 0.6λ0 × 0.6λ0 × 0.02λ0 is achieved. The impedance bandwidth of LP is about 80MHz (3.3%), while the usable bandwidths (overlap of impedance bandwidth and AR bandwidth) of LHCP and RHCP are about 370MHz (15%) and 250MHz(10%). The average gain for LP is −2.1 dB, and that for CP is −3.3 dB. This reconfigurable patch antenna with switchable polarization has good performance and simple structure, which can be used for 2.4GHz wireless communication systems.