Circular polarization switchable microstrip antenna with SPDT switching circuit

In this paper, a circular polarization switchable microstrip antenna is proposed. In order to realize the circular polarization switchable microstrip antenna, the proposed antenna is excited by a feeding circuit that consists of a 90° hybrid circuit and a novel SPDT switching circuit. The proposed antenna is shown in Fig. 1. The proposed antenna consists of the CP antenna using 90° hybrid circuit and the SPDT switching circuit. It is well known that the CP antenna using a 90° hybrid circuit radiates the circular polarization in Fig. 1(c). According to selection of exciting part of 90° hybrid circuit, LHCP or RHCP is obtained. For circular polarization switching function, the proposed antenna is used the both of input ports of the 90° hybrid circuit and the novel SPDT switching circuit is proposed in Fig. 1(d). Therefore, the CP antenna can be realized to switch the circular polarization. In addition, for a gain enhancement, an array antenna is constructed using this concept as shown. The feeding circuit of the antennas uses a "Both-Sided MIC technology". The excellent design flexibility of the "Both-Sided MIC technology" is very effective for a array arrangement. Therefore, the circular polarization switching antennas are realized with simple structure and operation. In this paper, the characteristics of the integrated feeding circuit are investigated experimentally, and the characteristics of the proposed antennas are simulated by Agilent momentum. Consequently, it is verified that the circular polarization switchable microstrip antenna can be achieved.