Ultra-wideband dual polarization arrays with collocated elements for high isolation simultaneous transmit and receive systems

In Simultaneous Transmit and Receive (STAR) systems, antenna port isolation is important as it reduces coupling between transmit and receive chains. If the coupling is too high, the transmit signal can leak into the receive path and saturate the receiver. In this paper, we present a dual-polarized four-arm spiral array operating from 3 to 5 GHz for concurrent right hand and left hand circular polarizations for transmit and receive systems. To improve low frequency axial ratio and realized gain, each spiral arm is terminated with a single chip resistor. Simulations show that for a single element four-arm spiral, the port-to-port isolation is greater than 50 dB and the gain is approximately 5 dB over the entire 2 GHz bandwidth. Similarly, for a 3×3 finite array, port-to-port isolation remains at least 52 dB with a gain greater than 10 dB across most of the bandwidth.