Realization of Attenuation Poles, Spurious Resonance Suppression and Size Reduction by Microstrip SIR Loaded with Dielectric Rods

Ramesh K. POKHAREL  Kouji WADA  Osamu HASHIMOTO  Takeshi TAKAHASHI 

Publication
IEICE TRANSACTIONS on Electronics  Vol.E88-C  No.12  pp.2302-2309
Publication Date: 2005/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Wireless Technologies and Computational Electromagnetics)
Category: Devices
Keyword: 
attenuation pole,  dielectric rods,  FDTD method,  spurious responses,  SIR,  tapped λ/2 microstrip resonator, 

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Summary: 
Characteristics of a class of stepped-impedance resonators (SIRs) which is loaded with two dielectric rods, are investigated by a Finite-Difference Time-Domain (FDTD) method. Dielectric rods to be inserted between a strip conductor and the ground plane have higher relative permittivity than that of the substrate. When a tapped half-wavelength (λ/2) microstrip resonator is loaded with two dielectric rods, the electric length of a loaded λ/2 resonator becomes longer than λ/2, which makes its fundamental resonant frequency () to be generated on the region lower than that of an unloaded λ/2 resonator (fr) and its first spurious response (fsp1) is generated on the region higher than 2. Therefore, to shift back to fr, the resonator's length is to be reduced, and this, in turns, suppress the spurious responses. Then, the resonant characteristics of an SIR employing the proposed method has also been investigated, and it is found that this is capable of suppressing the spurious responses in wideband together with an attenuation pole in the stopband, and of further reducing the resonator's length. Therefore, wide exploitation of the presented method can be expected in the filter design based on the LTCC technique.