Tunable RF front-end filter with wideband blocker suppression for multi-standard applications

This paper presents a tunable active bandpass filter with bandwidth-adjustable notches close to the passband for wideband blocker suppression with high attenuation. The proposed filter is composed of a 3-pole N-path bandstop filter in cascade with an N-path bandpass filter, where the center frequency of the bandpass filter is offset from the bandstop filters. With proper tuning of the coupling capacitors in the bandstop filter, three adjacent notches can be created which provides a larger suppression bandwidth. An implementation of the filter in 65-nm CMOS exhibits a passband tunable between 0.1-1.1 GHz, with a 3-dB bandwidth of 12.4-14.2 MHz, a gain of 9.5-10.3 dB, a noise figure of 4.3-5.8 dB, and a total power consumption of 40-64.3 mW. The blocker 1-dB compression point is 6.5 dBm and the out-of-band IIP3 is 18.4 dBm. The reported filter provides a promising solution to multi-standard, multi-frequency software-defined radio applications.