Design of second‐order lumped‐element reconfigurable diplexers

Abstract

This paper presents a new type of second-order reconfigurable diplexers by using common lumped-element dual-resonance resonator (LE-DRR) and LC resonators. As examples, a 0.9/1.8 GHz second-order diplexer is firstly designed to investigate the design theory, which has merits of wide passband, low insertion loss and extremely compact size. Then, a second-order switchable diplexer is simply designed by embedding two p-i-n diodes in two end-stage LC resonators of the above diplexer to switch on/off each channel independently. Finally, the capacitors of the above diplexer are replaced by the varactor diodes, so that a second-order tunable diplexer with two independently tuned channels is proposed. Measured results of proposed tunable diplexer show that its lower channel can be tuned from 0.492 GHz to 0.995 GHz with corresponding frequency tuning range (FTR) of 66.58%, while its upper channel can be tuned from 0.974 GHz to 1.7 GHz with FTR of 51.92%. K E Y W O R D SRF and microwave diplexer, switchable diplexer, tunable diplexer