Wideband, scanning array for simultaneous transmit and receive

We present a low profile wideband spiral antenna array with high transmit/receive (Tx/Rx) isolation and beam steering capability for simultaneous transmit and receive (STAR) systems. STAR increases a channel's spectral efficiency by transmitting and receiving across the full bandwidth of a channel. To our knowledge, this is the first wideband STAR spiral array with scanning. Each 4-arm spiral element consists of two arms for Tx and two more for Rx. To suppress grating lobes, the element spacing is kept at λ
_HIGH
/2. Full wave infinite array simulations show the port-to-port Tx/Rx isolation is >40dB at boresight across a 3 GHz bandwidth from 2-5GHz (2.5:1). This level of port-to-port isolation reduces to about 30dB when scanning down to 30°. In addition, VSWR is <; 2 and axial ratio <; 3dB. A 3×3 array was fabricated and showed an average Tx/Rx isolation of 36dB with VSWR <; 2.4.