Theoretical and experimental investigation of novel varactor-tuned switchable microstrip ring resonator circuits

Abstract

A microstrip ring resonator circuit loaded with two p-i-n diodes has been developed for use as a switchable filter. By replacing one p-i-n diode with a varactor diode, the switchable filter can be made electronically tunable. Isolation exceeding 20 dB with 9% tuning bandwidth was demonstrated. An analysis based on transmission line theory was used to model both circuits. The analysis includes the effects of diode parasitics, coupling gaps, dispersion, and mounting-gap capacitance. The experimental results agree very well with the theoretical calculation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>