A 1.5–4-GHz Reconfigurable N-Path Notch Filter with >40-dBc Rejection and >15-dBm B1dB

A reconfigurable N-path notch filter with enhanced notch rejection and power-handling capability is presented. The proposed architecture employs a hybrid reflective–absorptive mechanism that decouples blocking power handling from switch linearity constraints. The filter comprises a 90° quadrature coupler, an N-path resonant unit, and a tunable passive resistor, where the resonant unit and resistor are connected in parallel and terminated at the through and coupled ports of the coupler. Under high-power excitation, desired signals are primarily reflected by the N-path resonator, while strong interferers are absorbed by the passive resistor, thereby significantly improving blocking rejection. A prototype implemented in a 65-nm CMOS process demonstrates a tunable notch frequency from 1.5 to 4 GHz, notch depth exceeding 40 dBc (up to 50 dBc) with a 120-MHz 3dB bandwidth, a measured B1dB above 15 dBm, and an IIP3 of 27 dBm, while occupying 0.9 mm² and consuming 14–33 mW.