Branch-Line Couplers Using Defected Ground Structure

Y.J. SUNG  C.S. AHN  Y.-S. KIM  

IEICE TRANSACTIONS on Communications   Vol.E88-B   No.4   pp.1665-1667
Publication Date: 2005/04/01
Online ISSN: 
DOI: 10.1093/ietcom/e88-b.4.1665
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Devices/Circuits for Communications
DGS,  hybrid coupler,  size reduction,  harmonic suppression,  

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In this letter, a novel design of a branch-line coupler with considerable reduction in its size and suppressed harmonic passband is proposed. By embedding a defected ground structure (DGS) unit cell under a microstrip line, compact branch-line couplers are easily achieved. The electrical length is scaled appropriately according to the slow-wave effect. In this case, the experimental coupling (S21 or S31) is comparable to that of conventional branch-line couplers. Also, experimental results indicate that DGS section is quite effective for the suppression of higher order harmonics.