Circularly-polarized, unidirectional antennas for simultaneous transmit and receive (STAR) applications

The operational principles of circularly-polarized (CP) antenna elements for use in wideband simultaneous transmit and receive (STAR) antenna arrays are presented and discussed in this paper. Based on these operating principle, two designs of CP STAR array elements are presented. Both designs use the same cancellation technique to achieve STAR operation but they use different radiating elements. They provide isolation levels of 38 dB and 48 dB, respectively. In these STAR element designs, antenna bandwidth is primarily determined by the bandwidth of the CP element. Prototypes of each device are designed and discussed in the paper.