Design of Active N-Path Filters

Abstract

A design methodology for synthesis of active N-path bandpass filters is introduced. Based on this methodology, a 0.1-to-1.2 GHz tunable 6th-order N-path channel-select filter in 65 nm LP CMOS is introduced. It is based on coupling N-path filters with gyrators, achieving a “ flat” passband shape and high out-of-band linearity. A Miller c ompensation method is utilized to considerably improve the passband shape of the filter. The filter has 2.8 dB NF, +25 dB gain, +26 dBm wideband IIP ₃ (M H z ) ,a n out-of-band 1 dB blocker compression point B of +7 dBm (Δf = +50 MHz) and 59 dB stopband rejection. The analog and digital part of the filter draw 11.7 mA and 3–36 mA from 1.2 V , respectively. The LO leakage to the input port of the filter is ≤- 6 4d B ma tac l o c kf r e q u e n c yo f1G H z .T h ep r o p o s e dfilter only consists of inverters, switches and capacitors and therefore it is friendly with process scaling.