A Reconfigurable Circularly-Polarized Antenna With Switchable Feed Network Featuring Half-Wave Length Microstrip Lines

The paper presents a circular polarized (CP) switchable antenna with difference-beam operation. The proposed antenna consists of a quadrature hybrid coupler and a single-pole double-throw switch employing a half-wavelength microstrip line. The hybrid coupler generates a 90° phase difference between the antenna elements for CP, and opposite feeding ensures an anti-phase relationship between the elements. By switching the diodes between ON and OFF states, the antenna can emit either right-hand or left-hand circularly polarized (CP) waves. A 5.8GHz prototype antenna is fabricated and measured inside an anechoic chamber. The measured results show an excellent 1.7% 10-dB impedance bandwidth. Axial ratio is below 2.1dB. The measured cross-polarization suppression and null depth exceed 15dB. The designed antenna characteristics are suitable for linear sensor networks.