Narrow-Band Switched-Capacitor Bandpass Filters

Novel circuits, based on the N-path (or pseudo-N-path) configuration, are described for the design of narrow-band switched-capacitor (SC) bandpass filters. For noncritical applications very simple and economical circuits, based on the simulation of passive or active RC circuits, can be used; for high-accuracy filtering tasks, more elaborate circuits (obtained from doubly terminated reactance ladders) are proposed. The resulting filters provide stable passband responses and low sensitivities to element-value variations even for extremely narrow relative bandwidths, where other design approaches fail.