Lowpass–Bandpass Triplexer Integrated Switch Design Using Common Lumped-Element Triple-Resonance Resonator Technique

This paper presents a lowpass-bandpass triplexer integrated switch using common lumped-element triple-resonance resonator (LE-TRR) technique. First, a lowpass-bandpass triplexer that has one lowpass channel (LPC) and two bandpass channels (BPCs) is designed. The proposed lowpass-bandpass triplexer design method is different from the conventional lowpass-bandpass multiplexer in which the feeding line is designed with lowpass response to combine bandpass structures to form lowpass-bandpass response. In this design, one branch of LE-TRR together with inductors and capacitors and another two branches of LE-TRR together with classical LC resonators are proposed to constitute one LPC and two BPCs, respectively. The LPC design combines the lowpass transformation method and parameters optimization, and two BPCs can be synthesized by classical coupled-resonator filter design theory. The designed lowpass-bandpass triplexer exhibits extremely compact size of 0.125λ
_g
× 0.086λ
_g
, and also has merits of low insertion loss, good return loss, wide bandwidth, and high port-to-port isolation. And then, p-i-n diodes are loaded on the lowpass-bandpass triplexer to realize a lowpass-bandpass triplexer integrated switch that combines both the triplexer and microwave switch function. One LPC and two BPCs are able to be switched ON/OFF separately, and the lowpass-bandpass triplexer integrated switch has eight independent states in total. The OFF-state suppression of LPC is better than 36 dB, and the OFF-state suppression of two BPCs are better than 46 and 45 dB, respectively.