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ILASH - Integrated Dielectric Lenses for mm- and sub-mm Wave Imaging

Fernandes, C. A. ; Costa, J.R. ; Silveirinha, M. G. ; Lima, E.B.

ILASH - Integrated Dielectric Lenses for mm- and sub-mm Wave Imaging, Proc Encontro Nacional de Astronomia e Astrofísica - ENAA, Aveiro, Portugal, Vol. -, pp. - - -, July, 2009.

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Abstract
Dielectric lens antennas are an effective solution for radiometric and for quasi-optical imaging applications, either as stand-alone antennas or as feeds for reflector antennas. The main objective of ILASH project was to develop and deliver to ESA-ESTEC a validated software tool for the design, analysis and optimization of high permittivity circular symmetric integrated lens antennas (ILA) for quasi-optical imaging applications – the ILASH tool. By integrated lens it is meant that the feed is positioned (eventually printed) directly in contact with the lens base. Although single material lenses can be found in the literature for this application, this project aimed at a novel concept of double-shell integrated lenses developed at Instituto de Telecomunicações to cope with very stringent requirements in terms of efficiency and bandwidth.
One of the main challenges in this project was the unusual requirement for 100% lens operation bandwidth, to match the large bandwidths of emerging integrated quasi-optical receivers. This means that the lens focal plane and its general electromagnetic performance must remain fairly stable over this huge bandwidth. Shape optimization of the two refracting surfaces of the double-shell lens was the key approach to cope with this problem.
The other challenge was the minimization of internal reflections at the high contrast lens surfaces. High permittivity of the lens materials is dictated by the need to enhance the power coupling from the single-layer printed metallic feeds into the lens but reflection loss is prohibitive. Again the developed double-shell lens approach provided the appropriate ultra wideband solution for this problem. New dedicated ultra-wideband printed feeds were developed for the excitation of these lenses.
All the concepts developed in the ILASH project were fully tested and validated with measurements on tens of fabricated scaled prototypes at 40 GHz and 60 GHz.