US Patent 10581155 Active interference cancellation

Antenna structures and methods of operating the same are described. One apparatus includes a processing device that executes an active interference cancellation (AIC) algorithm and radio frequency front-end (RFFE) circuitry coupled to the processing device. The RFFE circuitry includes two RF couplers, a fixed-delay filter, and an interference compensation circuit part of an electrical path between the two RF couplers. The AIC algorithm is operable to control the interference compensation circuit to adjust a phase, an amplitude or both of a copy of a first RF signal transmitted on a first antenna to remove corresponding interference in a second RF signal received at a second antenna that is caused by the first RF signal. The processing device triggers a re-calibration in the AIC algorithm when the digital values, received from a power detector circuit, indicate a change in impedance that exceeds a threshold.