Early design of the MOSAIC antenna

Abstract

The work of this thesis has been carried out in the framework of the project Multi-Object Spectrometer with an Array of superconducting Integrated Circuits, also known as MOSAIC. The aim of this instrument is to resolve the Cosmic Infrared Background (CIB) from a 10 m diameter ground-based telescope. MOSAIC will be the first multi-object three-dimensional (3D) camera for astronomy with independently electrically-steered pixels. Two spatial dimensions will be readily available from a matrix of 5-by-5 pixels and the third dimension (distance) will be derived from the spectrum of the redshifted signals captured. Thanks to the electrical beam-steering of each of the pixels and to the very sensitive and high-resolution sensors attached to them, 25 astronomical objects from different regions of the sky will be spectrally resolved in simultaneously. For this very reason the whole ALMA (Atacama Large Millimeter/submillimeter Array) observatory could be outperformed for just a fraction of its cost. Foundations for such improvements stem from two successful earlier projects making use of broadband antennas and KIDs (Kinetic Inductance Detectors): DESHIMA (Deep Spectroscopic High-redshift Mapper) and A-MKID (Array of Microwave KIDs). The former as an infrared camera of the sky mapping the location of astronomical sources, and the later as a high resolution spectrometer looking at the already pinpointed sources. This thesis contributes to MOSAIC with the early stage design process of the integrated, broadband and electrically beam-steered antennas implementing each of the pixels. The connected array is chosen as the antenna solution to fulfil the requirements: fully planar, broadband and electrically steerable. Fundamental studies on the antenna dimensions, input impedance and efficiency in terms of surface waves are carried out and traded-off in order to satisfy the requirements of the instrument whilst conforming to the manufacturing constraints and the optical front-end of the Atacama Submillimeter Telescope Experiment (ASTE) in Chile, where MOSAIC will be eventually installed. Among the plethora of options, some of the proposed set-ups in this thesis will stand out as more appropriate candidates for the instrument. Aiming at developing a first prototype of MOSAIC, a reduced-bandwidth antenna is investigated with one of the most promising set-ups previously studied. More realistic structures accounting for the finiteness of the antenna and including the actual feeding network are investigated in order to provide considerations on the final design to be manufactured.