Bandwidth Enhancement Utilizing Bias Circuit as Parasitic Elements in a Reconfigurable Circularly Polarized Antenna

A circularly polarized (CP) crossed-dipole antenna with switchable rotating sense is presented. The proposed design has two main attractive features. First, a wide overlapped CP bandwidth (BW) is realized for both operating states. Second, unlike existing designs targeting a similar functionality, no biasing wire through ground plane is required, which significantly reduces the design complexity. The proposed design employs parasitic elements for two different roles. For RF signal, these parasitic elements open an additional CP resonance band to enhance the axial-ratio (AR) BW. Additionally, through RF chokes, they provide a dc path to bias the p-i-n diodes. An antenna prototype was experimentally demonstrated with the capability of switching between two CP rotating senses in a frequency range from 1.1 to 2.02 GHz, equivalent to 58.9%. The antenna also exhibits a wide −10 dB impedance BW of 53.3% (1.1–1.9 GHz) with a peak gain of around 9.1 dBi and front-to-back ratio of more than 15 dB.