Distributed RC notch filters based on a circular geometry

The analysis for a distributed RC transmission line based on a circular geometry in which a plane circular resistive sheet is separated from a circular conductor by a dielectric is developed. Connections to this sheet are made using an outer circumferential electrode and an inner central circular electrode. Two types of notch filter are then analyzed, one incorporating a single discrete resistor and having a fixed notch frequency, and a second with a discrete resistor and a discrete capacitor in series combination that has a variable notch frequency. In common with notch filters based on linearly and exponentially tapered transmission lines, the filters described demonstrate improved selectivity compared with zero-tapered lines. The effect of loading that is likely to be encountered in experimental conditions is discussed.