A Passive-Mixer-First Acoustic-Filtering Superheterodyne RF Front-End

This article presents an agile passive-mixer-first superheterodyne RF front-end that utilizes a gigahertz acoustic filter as its intermediate-frequency (IF) load-essentially mixer-first acoustic-filtering front-end. The passive mixer frequency-translates sharp but fixed-frequency response to much higher and mixer-clock-defined tunable frequency while preserves input matching, high linearity, introduces minimal loss. In contrast low- or zero-IF receivers which often use active filters at baseband, using the IF load is fraught with fundamental challenges. We introduce ON-chip LC tanks, impedance shaper, suppress components harmonic frequencies all-passive recombination network share one among multiple paths. Also, we extend existing analysis of front-ends from assuming low-pass having generic impedance. Our unveils aliasing in front-end, motivating need for shaper. A prototype 65-nm CMOS switched- followed by off-the-shelf 1.6-GHz surface-acoustic-wave (SAW) designed. measurement, operates across 2.5-to-4.5 GHz achieving 5.5-dB noise figure +29.4-dBm IIP3 1 × bandwidth offset.