Reduced Branch-Line Coupler Using Radial Stubs

Yanna HAO  Iwata SAKAGAMI  Akihiro TOKUNOU  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E87-C   No.9   pp.1615-1620
Publication Date: 2004/09/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
Keyword: 
reduced,  radial,  branch,  coupler,  

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Summary: 
This study proposes a 3 dB branch-line coupler using radial stubs to achieve reduced coupler size and simplified stub arrangement. As the electrical lengths of stubs used here are less than 90at center frequency, a method of comparing input impedances to obtain radial stubs that are equivalent to straight stubs is discussed. The frequency characteristics of the proposed coupler are derived by combining classical transmission line theory with the computed data of radial stub input impedances. The methods presented here increase possibilities for realizing reduced branch-line couplers by means of stub design. Experimental results agree well with theoretical results except for slight differences in the high frequency region.