Circular polarization switchable single layer microstrip array antenna

In this paper, a circular polarization switchable single layer microstrip array antenna is proposed and the performances of the array antenna are confirmed experimentally. The array antenna consists of the orthogonal dual linear polarized microstrip array antenna which has several air-bridges, a 90-deg. hybrid circuit and a SPDT switch circuit loading four PIN diodes on a single layer substrate. It is possible to entirely integrate RF circuits with array antennas due to realization of the novel SPDT switch. By integrating the array antenna with both the SPDT switch circuit and the 90-deg. hybrid circuit, the circular polarizations (RHCP, LHCP) can be easily switched by the diode ON/OFF conditions. The design frequency is 10GHz. In the measurement, the 3 dB axial ratio bandwidth of 3.8% is obtained. Therefore, excellent the circular polarization switching performances of the proposed array antenna has been verified.