A 0.18 μm CMOS programmable interference canceller for cognitive radio front-end

A fully-integrated programmable interference canceller is presented for the cognitive radio RF front-end, which is based on a double-loop cancellation technique. For a frequency division duplexing system (FDD), this interference canceller can suppress the Tx leakage and its associated noise at the Rx band. A negative delay line and a positive delay line are required for the double cancellation paths in this architecture. In this work, the series LC tank can be used as the negative delay line and the parallel LC tank as the positive delay line. Switch and capacitor arrays are used to tune the cancellation bands. The interference canceller is designed by the 0.18 μm RF CMOS process, which can achieve the additional maximum suppression of 18 dB and dissipate a total power of 28.3 mW under 1.8 V power supply.