Microstrip diplexers design with common resonator sections for compact size, but high isolation

• Published in: IEEE transactions on microwave theory and techniques Vol. 54; no. 5; pp. 1945 - 1952
• Main Authors: CHEN, Chi-Feng, HUANG, Ting-Yi, CHOU, Chi-Ping, WU, Ruey-Beei
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Band pass filters; Bandpass filter; Bandpass filters; Channels; Circuit properties; Circuit simulation; Circuits; Coupling circuits; diplexer; Diplexers; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Filtering theory; Frequency filters; Frequency response; microstrip filter; Microstrip filters; Microstrip resonators; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwaves; Optical losses; Oscillators, resonators, synthetizers; Resonant frequencies; Resonant frequency; Resonator filters; Resonators; Simulation; stepped-impedance resonator (SIR); transmission zero; Microstrip filters; Resonator; transmission zero; Multivariable control; Stepped impedance device; Variable frequency; Multichannel filter; Bandpass filter; Simulation; Resonance frequency; Parallel connection; Band pass filter; microstrip filter; Frequency response; Miniaturization; stepped-impedance resonator (SIR); Diplexer
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2006.873613

High isolation and compact size microstrip diplexers designed with common resonator sections have been proposed. By exploiting the variable frequency response of the stepped-impedance resonator, resonators can be shared by the two filter channels of the desired diplexer if their fundamental and the first spurious resonant frequency are properly assigned. Size reduction are, therefore, achieved by introducing a few common resonator sections in the circuit. This concept has been verified by the experimental results of two diplexer circuits. One of the diplexers is composed of two three-pole parallel-coupled bandpass filters and the other is composed of two four-pole cross-coupled bandpass filters, which are formed by only five and six resonators, respectively. Both of them occupy extremely small areas while still keeping good isolations. Good agreements are also achieved between measurement and simulation.