Near-Field Transmission Imaging by 60 GHz Band Waveguide-Type Microscopic Aperture Probe

Somboon THEERAWISITPONG
Toshitatsu SUZUKI
Tadahiro NEGISHI
Yasuo WATANABE

Publication
IEICE TRANSACTIONS on Communications   Vol.E90-B    No.9    pp.2387-2393
Publication Date: 2007/09/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.9.2387
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on 2006 International Symposium on Antennas and Propagation)
Category: Measurements
Keyword: 
near-field,  dielectric material imaging,  microscopic aperture probe,  millimeter wave,  

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Summary: 
Near-field imaging has been intensively investigated to observe the shape and the physical properties of objects, aiming at wide applications in the areas of science and engineering. In this research, by using 60 GHz band waveguide-type microscopic aperture probe, the characteristics of the near-field imaging in transmission mode have been studied by simulation and experiment. The probe is made of a WR-15 rectangular waveguide with end-shielded metal plate and a 0.5 mm-diameter aperture. In the simulation, at first, the electric field distribution at the aperture, at the rear (waveguide) and the front positions (free space) are presented. Second, the transmitted electric fields are presented for three cases: (a) scanning of a dielectric slit, (b) by varying the distance between the aperture and a dielectric sample, and (c) scanning of a dielectric groove. In the experiment, the lateral resolution with a two-slit and the depth resolution with grooves having various depths in rectangular format are described and the results show both resolutions to be much shorter than the wavelength. Finally, the scanned images of the letter N punched through a dielectric material and a leaf are demonstrated.