A novel self-interference cancellation architecture based on asymmetrical power divider and its closed-loop control

The asymmetric radio frequency (RF) self-interference cancellation (SIC) architecture is studied, and the closed-loop control of RF SIC based on software radio is realized. This system uses a circulator to isolate the receiving and transmitting chains, and its RF reconstruction chain is composed of a 4-tap filter with fixed delay and tunable attenuation for each tap. The optimization of tap filter and asymmetric power divider's power allocation ratio is discussed. In the experiment, sensing, calibration, optimization algorithms and hardware control programs were proposed. A closed-loop gradient descent algorithm for tuning the variable attenuator is implemented on the GNU Radio. From 910 MHz to 930 MHz, the isolation between the receiving and transmitting ports increases 40 dB, achieving an isolation of more than 65 dB and the transmission energy efficiency increases by 60%.