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Active and Passive Electronic Components
Volume 2008 (2008), Article ID 391745, 6 pages
http://dx.doi.org/10.1155/2008/391745
Research Article

Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence

Laboratory for Micro- and Photonelectronics, Department of Electronics and Informatics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Belgium

Received 30 November 2007; Accepted 15 May 2008

Academic Editor: Tibor Berceli

Copyright © 2008 Saiful Islam et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper presents the design, construction, and testing of grounded frequency selective surface (FSS) array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter). The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT), fabricated by etching technique, and characterized the S-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.