Adaptive RF Self-interference Canceller Control and Spectrum Sensing in Full-Duplex EW Radio

Simultaneous transmission and reception at the same frequency would facilitate future military radios to implement efficiently tactical communications, electronic warfare (EW), and signals intelligence as well as combinations thereof. The main problem in implementing such full-duplex capability is the large amount of self-interference (SI) between the transmit and receive chains. The challenge has been largely solved for commercial applications, but military radios require new solutions due to higher SI levels and lower operating frequencies. This paper presents a full-duplex transceiver for communications or simultaneous signals intelligence and jamming at 225-400 MHz with up to 100 W radiated transmit power. Co-designed analog canceller and isolating antennas are employed, and an original control algorithm utilizing least squares algorithm and estimation of scattering parameters is designed to continuously tune the analog cancellation. Furthermore, a modified version of a cell-averaging constant false alarm rate detector is implemented for sensing signals-of-interest amidst residual self-inteference. Under a channel emulation over cables, 55-64 dB of analog cancellation is demonstrated with the canceller converging to the optimum quickly within four iterations, which could yield a free-space link budget of around 10 km for successful full-duplex signal reception under the target 100 W transmit power. This paper was originally presented at the NATO Science and Technology Organization Symposium (ICMCIS) organized by the Information Systems Technology (IST) Panel, IST-205-RSY - the ICMCIS, held in Koblenz, Germany, 23-24 April 2024.