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Proceedings Paper

Gain and far-field patterns for phase-correcting Fresnel zone plate antennas at millimeter-wave and terahertz frequencies
Author(s): James C. Wiltse
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Paper Abstract

The Fresnel zone plate lens antenna, which provides advantages compared to a normal paraboloidal or spherical lens, has been extensively investigated in the millimeter-wave and terahertz regions. The advantages include reduced weight, volume, and attenuation and simplicity of design. The principal disadvantage is that the zone plate sometimes provides reduced gain compared to a true lens. Particularly at high millimeter-wave or terahertz frequencies the low loss of the zone plate more than compensates for the reduced directivity. This paper investigates the gains and far-field patterns for a number of cases and gives both the analysis and numerical results for the examples. These cases have dealt with large-angle designs, where the focal length (F) and diameter (D) are comparable (F/D = 0.3 to 2.5), unlike the typical optical examples. The antenna patterns are found to have beamwidths and first sidelobes that are similar to what one would obtain with a standard lens, given the same aperture illumination. Appropriate feed designs are also described. For best aperture efficiency the illumination taper is about 10 dB, and this gives first sidelobe levels of about -24dB for a circular aperture. Far-out average sidelobes are not as low as for a true lens, and this is where the gain is affected.

Paper Details

Date Published: 4 May 2007
PDF: 11 pages
Proc. SPIE 6549, Terahertz for Military and Security Applications V, 65490T (4 May 2007); doi: 10.1117/12.719049
Show Author Affiliations
James C. Wiltse, Georgia Institute of Technology (United States)

Published in SPIE Proceedings Vol. 6549:
Terahertz for Military and Security Applications V
James O. Jensen; Hong-Liang Cui, Editor(s)

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