Novel Miniaturized Harmonic Suppression Branch-Line Coupler Using Artificial Transmission Lines for UHF Applications

Chia-Hao KU  Hsien-Wen LIU  Yu-Shu LIN  Kuei-Yi LIN  Pao-Jen WANG  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.7   pp.1237-1239
Publication Date: 2011/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.1237
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Microwaves, Millimeter-Waves
branch-line coupler,  harmonic suppression,  artificial transmission line,  UHF band,  

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A planar miniaturized branch-line coupler with harmonic suppression property for UHF band applications is presented in this paper. By properly synthesizing the LC-tanks that employ artificial transmission lines, two pairs of quarter-wavelength branch-lines to respectively meet characteristic impedances of 35.4 and 50 ohms can be obtained with the coupler. For the operating band, it can achieve good 3 dB power division with a 90° phase difference in the outputs of the through and coupled arms. The coupler also has a small area of 20.5(L)18(W) mm2, corresponding to 0.11 λg0.1 λg at 922 MHz. Compared with conventional couplers, the proposed design not only offers a wide bandwidth of more than 230 MHz within 1° or 1 dB, but also works with additional harmonic suppression for achieving better performance. Therefore, the proposed branch-line coupler with a compact size is well suitable for power division application.