Compact Rat-Race Hybrid Coupler Using Slow Wave and Left-Handed Transmission Lines

Tack-Gyu KIM  Bomson LEE  

IEICE TRANSACTIONS on Electronics   Vol.E92-C   No.12   pp.1535-1537
Publication Date: 2009/12/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E92.C.1535
Print ISSN: 0916-8516
Type of Manuscript: BRIEF PAPER
Category: Microwaves, Millimeter-Waves
metamaterial,  slow wave,  rat-race coupler,  compact,  

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Based on provided convenient design equations for slow wave transmission lines and metamaterial line, a very compact rat-race hybrid coupler is proposed using three slow wave lines and one metamaterial line. At the design frequency of 2 GHz, the size of the proposed coupler is 2.3 cm2.7 cm, which is a 74% reduction compared with the conventional one. Despite the considerable size reduction, the theoretical bandwidths based on | S11|, | S31|, ∠ S21-∠ S31, and ∠ S24-∠ S34, have been improved by 9%, 7%, 31%, and 59%, respectively. The measured performances are in reasonable agreement with the theoretical ones.