180-Degree Branch Line Coupler Composed of Two Types of Iris-Loaded Waveguides

Hidenori YUKAWA  Yu USHIJIMA  Naofumi YONEDA  Moriyasu MIYAZAKI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E104-C   No.2   pp.85-92
Publication Date: 2021/02/01
Publicized: 2020/08/14
Online ISSN: 1745-1353
DOI: 10.1587/transele.2020ECP5006
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
Keyword: 
waveguide,  branch line,  coupler,  iris-loaded,  phase shifter,  

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Summary: 
We propose a 180-degree branch line coupler composed of two types of iris-loaded waveguides. The proposed coupler consists of two main transmission lines and branch lines with different electrical lengths. Based on optimal electrical lengths, a 180-degree output phase difference can be achieved without additional phase shifters. The two main lines with different electrical lengths are realized by capacitive and inductive iris-loaded waveguides. The size of the proposed coupler is nearly half that of the conventional 180-degree branch line coupler with additional phase shifters. Thus, the proposed coupler is of advantage with respect to the conventional one. We designed a proposed coupler in the K-band for satellite communication systems. The measurement results demonstrate a reflection of -20 dB, isolation of -20 dB, coupling response of -3.1+0.1 dB/-0.1 dB, and phase differences of 0+0.1 deg/-1.4 deg and -180+0.5 deg/-2.3 deg at a bandwidth of 8% in the K-band.