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Confocal ellipsoidal reflector system for a mechanically scanned active terahertz imager

N. Llombart ; K. B. Cooper ; R. J. Dengler ; Tomas Bryllert (Institutionen för mikroteknologi och nanovetenskap, Terahertz- och millimetervågsteknik ) ; P. H. Siegel
IEEE Transactions on Antennas and Propagation (0018-926X ). Vol. 58 (2010), 6, p. 1834-1841.
[Artikel, refereegranskad vetenskaplig]

We present the design of a reflector system that can rapidly scan and refocus a terahertz beam for high-resolution standoff imaging applications. The proposed optical system utilizes a confocal Gregorian geometry with a small mechanical rotating mirror and an axial displacement of the feed. For operation at submillimeter wavelengths and standoff ranges of many meters, the imaging targets are electrically very close to the antenna aperture. Therefore the main reflector surface must be an ellipse, instead of a parabola, in order to achieve the best imaging performance. Here we demonstrate how a simple design equivalence can be used to generalize the design of a Gregorian reflector system based on a paraboloidal main reflector to one with an ellipsoidal main reflector. The system parameters are determined by minimizing the optical path length error, and the results are validated with numerical simulations from the commercial antenna software package GRASP. The system is able to scan the beam over 0.5 m in cross-range at a 25 m standoff range with less than 1% increase of the half-power beam-width.

Nyckelord: Reflector antennas; scanning antennas, submillimeter-wavelength imaging, terahertz radar, THz

Denna post skapades 2011-04-20.
CPL Pubid: 139556


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