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Broadband Reflector Fed by Integrated Lens Antenna with Frequency Constant Directivity

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

Broadband Reflector Fed by Integrated Lens Antenna with Frequency Constant Directivity, Proc IEEE AP-S/URSI International Symp., Toronto, Canada, Vol. -, pp. - - -, July, 2010.

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Bolometers are the most common detectors in submillimeter wave radio telescopes [1].
When the bolometers are integrated with broadband antennas it is possible to achieve
more than 100% broadband receivers [2]. The bolometer is placed at the terminals of a
single planar metallization broadband antenna (like spiral or log-periodic) that is printed
directly at the base of a high dielectric lens. The lens forces the printed element radiation
pattern to become predominantly directed into the first reflector of the quasi-optical
system of a radio telescope. To maximize the aperture efficiency of the telescope’s main
dish it is required that it be illuminated by a frequency constant beamwidth. In this
communication a new broadband axial symmetric lens configuration is presented that
when combined with a reflector produces a frequency constant beam. The lens has two
shaped shells that favor low internal reflections. The Geometric Optics (GO) based Abbe
sine condition is used to design a collimated double shell lens [3], subject to a slight
change in formulation, in order to increase the number of degrees of freedom during
optimization. With a collimated lens it is possible to reduce the reflector illuminated area
as frequency increases, thus leading to constant reflector output beam. The main
objective of the communication is to evaluate the concept rather than obtaining a finished
submillimeter wave product.