Effect of Metal Resistive Losses on the Gain of a THz Planar Spiral Antenna

Abstract

We are living in interesting times for astronomy science, since the birth of the radio astronomy field in the 20th century by Karl Jansky, the availability of new and better radio astronomy receivers is in increasing demand to push the human understanding of the universe. In this thesis, various components (antennas, baluns, antenna-arrays, and radiometers) are proposed for radio astronomy receivers. The proposed designs are belonging to three receiver topologies (direct detection, down-conversion, and up-conversion) that operate at different frequency bands from MHz up to a few of THz. Also, to demonstrate that the same proposed design is capable of working efficiently at different operating frequencies, multiple adjusted designs are presented for several practical radio astronomy and space applications.Firstly, a receiver based on the direct detection of the Electromagnetic (EM) radiation through a radio telescope working on cryogenic cooling conditions. In this part, the focus is on designing conical log-spiral antennas and baluns (balanced to unbalanced transformers) to be used as feeds for VLBI Global Observing System (VGOS) ground-based radio telescopes. The feeds cover the Ultrawideband (UWB) from 2 GHz to 14 GHz with Circular Polarization (CP) radiation and stable radiation patterns. After integration of the feeds to the radio telescope, the whole system operates with high aperture efficiency and high System Equivalent Flux Density (SEFD) over the whole required wide range. The fabrication, assembly, and measurements for single-element and four-elements array are provided for achieving the requirements for single CP and dual CP operation. Also, in the same first part, the proposed single-element feed (antenna + balun) is readjusted for being used for CryoRad spaceborne Earth observations. This feed has a single CP over low-frequency UWB from 400 MHz to 2 GHz with low weight and physical size compared to standard horn feeds.

Standing-Wave Feeding for High-Gain Linear Dielectric Resonator Antenna (DRA) Array

“…The utilization of antennas had to wait for a long time, until Long et al presented the first cylindrical dielectric resonator antenna (DRA) in 1983 [2]. Ever since then, dielectric antennas have been intensively studied as potential substitutions of traditional less efficient metal radiators, which have serious problems at high frequencies [3][4][5]. There are some metal antennas such as lens [6] and slot [7] antennas that can avoid such losses and provide high gain with high efficiency, but they still have the drawbacks of being bulky and complex, respectively.…”