Enhanced Passive Mixer-first Receiver Driving an Impedance with 40dB/decade Roll-off, Achieving +12dBm Blocker-P1dB, +33dBm IIP3 and sub-2dB NF Degradation for a 0dBm Blocker

A "second order" passive mixer-first receiver is proposed to improve channel selectivity, linearity and noise figure in the presence of out-of-band blockers, by presenting an impedance which rolls off at 40dB/decade as the load to an N-path filter. The synthesis of this impedance is described in a step-by-step manner starting from the required impedance transfer function to its actual circuit realization. An integrated circuit prototype was fabricated in 28nm bulk CMOS as proof of concept. The receiver, capable of broadband operation from 0.2-2GHz, achieves an out-of-band IIP3 of +33dBm and a blocker P1dB of +12dBm. Additionally, it achieves a NF of 4.4dB with less than 2dB degradation in NF for a 0dBm blocker.