Antenna cancellation for simultaneous cognitive radio communication and sensing

Concurrent communication and sensing is a vital cognitive radio (CR) functionality for real-time and accurate monitoring of the radio spectrum that totally depends on the ability of isolating the communication path from the sensing path to a level which ensures that the local transmissions do not overload the sensing unit. Upon discussing the basic challenges that restrain CR from simultaneously sensing the spectrum while transmitting in the same band, the paper presents a novel antenna cancellation approach that promises to empower CRs with concurrent transmission and sensing capabilities. The idea is to equip the CR with redundant transmit antennas to form a spatial filter that selectively cancels the transmit signal in the sensing direction. Such antenna cancellation resulted in an isolation level of 60dB that can be further increased when combined with active power cancellation in the RF or baseband stage.