Location of Multiple Transmission Zeros by Tap-Coupling Technique for Bandpass Filters and Duplexers Using Short-Ended λ/2 Resonators

Kouji WADA  Yoshiyuki AIHARA  Tomohide KAMIYAMA  Osamu HASHIMOTO  

IEICE TRANSACTIONS on Electronics   Vol.E86-C   No.12   pp.2403-2411
Publication Date: 2003/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Recent Trends on Microwave and Millimeter Wave Application Technology)
Category: Passive(Filter)
short-ended λ/2 resonator,  multiple transmission zeros,  tap-coupling,  bandpass filter,  duplexer,  

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In this paper, the method of locating multiple transmission zeros by the tap-coupling technique is described for bandpass filters (BPFs), using short-ended λ/2 resonators and its application to a duplexer. First, the method of locating the transmission zero using the short-ended λ/2 resonators is examined with various excitation methods. We focus on four types of short-ended λ/2 resonators: the end-coupling type, tap-coupling type, capacitive tap-coupling type and inductive tap-coupling type. Secondly, the BPFs based on the basic characteristics of the respective resonators are proposed and designed on the basis of a general filter theory with narrow band approximation. Lastly, we propose and design new duplexers consisting of the proposed BPFs. The results lead to the conclusion that the basic characteristics of the short-ended λ/2 resonators are useful for realizing a BPF with multiple transmission zeros and a high-performance duplexer fabricated without increasing the number of elements.