Analysis of the Effect of Switch Parasitic Resistance and Capacitance on N-Path Filters Using State Space Representation

Abstract

This brief suggests a new method for analyzing the effects of nonideal properties of CMOS switches on N-path filters by expanding the linear periodically time-variant (LPTV) method to state space equations. The proposed technique provides an algorithm for analytical derivation of the harmonic transfer functions (HTF) and the noise figure (NF) of the N-path filter across all frequencies and harmonics. The analysis results show that for constant switch resistance and shunt capacitance product, a trade-off exists between out of band rejection, NF and insertion loss.