A Half-Sized Post-Wall Short-Slot Directional Coupler with Hollow Rectangular Holes in a Dielectric Substrate

Shin-ichi YAMAMOTO  Jiro HIROKAWA  Makoto ANDO  

IEICE TRANSACTIONS on Electronics   Vol.E88-C   No.7   pp.1387-1394
Publication Date: 2005/07/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.7.1387
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Technologies of Microwave and Millimeter-Wave Devices Focusing on Miniaturization and Advancement in Performance with Their Applications)
Category: Passive Circuits
short-slot coupler,  length reduction,  Butler matrix,  post-wall waveguide,  dielectric substrate,  rectangular hole,  

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The authors realize a 50% length reduction of short-slot couplers in a post-wall dielectric substrate by two techniques. One is to introduce hollow rectangular holes near the side walls of the coupled region. The difference of phase constant between the TE10 and TE20 propagating modes increases and the required length to realize a desired dividing ratio is reduced. Another is to remove two reflection-suppressing posts in the coupled region. The length of the coupled region is determined to cancel the reflections at both ends of the coupled region. The total length of a 4-way Butler matrix can be reduced to 48% in comparison with the conventional one and the couplers still maintain good dividing characteristics; the dividing ratio of the hybrid is less than 0.1 dB and the isolations of the couplers are more than 20 dB.