Full-Duplex (FD) communications allow the concurrent operation of the transmitter (TX) and receiver (RX) of a radio frequency (RF) transceiver at the same frequency channel offering multiple advantages for wireless communications such as increased bandwidth efficiency. However, the RX of an FD node should tolerate high TX self-interference (TX SI) power levels (~ 30 dBm) while detecting small desired RX signals (~ -100 dBm). The required dynamic range (DR) is addressed through a variety of TX SI rejection techniques in the RF, analog, and digital domains.

This thesis presents an RF code-domain signal processing technique that increases the achieved rejection for FD radios. FD DR is enhanced by assigning orthogonal PN codes to the TX and RX signals of an FD transceiver and performing code correlation in the RF domain through code selective filters. RF code-domain signal processing increases the achieved TX-SI rejection by >50 dB along with enhancing the RX linearity by >20 dB while providing 9 dB SNR improvement in multipath environments.

The thesis reports various CMOS chip implementations of the proposed RF code-domain signal processing approach including code pass and code notch filters, a reconfigurable multi-band/high-order notch filter, a high-rejection code-domain receiver, and a 3-finger multipath tolerant rake RX. Moreover, the thesis presents an FD link demonstration combining the proposed code-domain approach with circulators and digital SI cancellation for a complete node evaluation with >100 dB TX SI rejection.