An Inductor-Less All-Passive Higher-Order N-Path Filter Based on Rotary Clocking in N-Path Filters

In this paper, we present a widely-tunable, higher-order N-path filter with passive voltage gain that exploits (i) an inductor-less, all-passive higher-order filter topology and (ii) a rotary-clock-path N-path filter that achieves center-frequency shifting without needing a tunable clock frequency or the use of active circuitry. The proposed N-path filter achieves >10dB voltage gain, >16dB selectivity (rejection at 1BW offset from the center), and 30–50dB out-of-band (OOB) rejection, while consuming only 18mW at 500MHz and 0.56mm² active area.