Band-Broadening Design Technique of CRLH-TLs Dual-Band Branch-Line Couplers Using CRLH-TLs Matching Networks

Tadashi KAWAI  Miku NAKAMURA  Isao OHTA  Akira ENOKIHARA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.7   pp.1072-1077
Publication Date: 2010/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.1072
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Microwave and Millimeter-Wave Technologies)
Category: 
Keyword: 
branch-line coupler,  matching network,  CRLH-TL,  dual-band,  equivalent admittance approach,  size reduction,  

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Summary: 
This paper treats a band-broadening design technique of a dual-band branch-line coupler with matching networks composed of an impedance step and a short-circuited stub based on the equivalent admittance approach. By replacing each right-handed transmission line (RH-TL) with a composite right/left-handed transmission line (CRLH-TL), very flat couplings over a relative bandwidth of about 10% can be obtained at two arbitrary operating frequencies in comparison with previous CRLH-TLs branch-line couplers. Furthermore, by adding periodical open-circuited stubs into RH-TLs of the designed CRLH-TLs branch-line coupler with matching networks, the entire size of the coupler can be reduced to about 50%. Verification of these band-broadening and size-reduction design techniques can be also shown by an electromagnetic simulation and experiment.