Tunable blocker-tolerant RF front-end filter with dual adaptive notches for reconfigurable receivers

This paper presents a novel design of a highly tunable active bandpass filter with adjustable notches close to the passband. The filter is based on two-path signal cancellation and consists of a tunable bandpass filter in parallel with a tunable bandstop filter. This combination ensures the correct amplitude and phase relationship across a wide tuning range to create adjustable transmission notches without sacrificing the gain of the passband. The proposed filter is implemented with high-Q N-path filter/resonator blocks in a 65-nm CMOS process. The passband of the filter is tunable from 0.2GHz to 1.2 GHz with a 3-dB bandwidth of 5.8-6.2 dB, a gain of 18.5-21 dB, a noise figure of 4.5-6.2 dB, and a total power consumption of 33-70mW. Transmission notches are created on both sides of the passband with a minimal offset of 20MHz and are tunable across a 20MHz range with up to 46 dB rejection. The blocker 1-dB compression point is 8dBm and the out-of-band IIP3 is 18 dBm. The reported filter provides a promising solution to multi-standard, multi-frequency software-defined radio applications.