Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

Abstract

Abstract-A new integrated shaped lens antenna configuration is described with frequency stable radiation pattern and phase center position across a broad 1:3 frequency band, which can be used for focal plane reflector feeding in quasi-optical radio telescope systems. The lens is compatible with the integration of ultrawideband uniplanar printed feeds at its base and equally broadband mixing devices, like the Hot Electron Bolometer (HEB), although these are not used in the present work. Measurements on a scaled mm-wave lab prototype have confirmed stable performance versus frequency, with only 1 dB directivity variation, and better than 94% Gaussicity, thanks to the possibility to impose a predefined output radiation pattern template. Simulations were performed to test the illumination of an off-set parabolic reflector by the lens radiation pattern, which confirmed reasonably constant aperture efficiency in the order of 78% across the 100% bandwidth.Index Terms-Broadband stable radiation pattern, broadband stable phase center position, integrated lens antennas, millimeterand submillimeter wave antennas, reflector feed.

Review of 20 Years of Research on Microwave and Millimeter-wave Lenses at "Instituto de Telecomunicaço˜es"

“…By adding a second shell to a lens, it is possible to impose an additional design specification. Formulations were presented for double-shell axis-symmetric lenses combining a far-field template with a maximum power transfer condition [22] or alternatively with the specification of a well-defined phase center position [28]. These lenses were studied as high Gaussissity feeds for reflectors.…”

“…Integrated scanning lenses can be combined with a reflector to significantly increase the output gain. In this case, the beam collimation condition was replaced by another one imposing a well-defined phase center position lying far behind the lens body and coincident with the focus of the reflector [28]. This concept has been explored to produce multiple virtual foci in the reflector focal plane using a single lens [61], which is attractive to increase the number of beams using less space than conventional focal plane arrays.…”

“…The shaped double-shell dielectric lens antenna was designed by imposing simultaneously a well-defined phase center located below the lens body and an aberration condition, as shown in Figure 16(b) [28]. The 20 diameter lens prototype was made of MACOR and acrylic and was fed by the waveguide feed described in Section 2 with a special fixture to allow its precise positioning at different positions at the lens base.…”

“…An additional challenge was to cope with the bidirectional radiation pattern that is typical from printed feeds compatible both with THz fabrication technology and with the use of bolometer detectors [25], [26]. Therefore, double-shell shaped lenses with appropriate material permittivity were used to simultaneously maximize power coupling from the bidirectional feed to the lens and minimize internal reflection losses across the whole 100% bandwidth [27], [28].…”

Optimization of Micromachined Millimeter-Wave Planar Silicon Lens Antennas With Concentric and Shifted Matching Regions

“…The reported lens antennas have many advantages, including large bandwidths [3], frequency-stable far-fields, beam scanning capabilities [2,6,7] and frequency-stable phase center [3]. Planar lenses have many similarities with non-planar lenses, where there are many good references, see e.g., [8][9][10][11][12][13]. High-resistivity silicon is an excellent dielectric material for millimeter-wave planar lenses, due to its very small losses and accurate micromaching fabrication processes [14,15].…”