THz Vector Beam Measurement System for APEX Instrument SHeFI and Microwave Cryogenic Low Noise Amplifier Design

Licentiate thesis, 2008

This licentiate thesis describes results of the author’s work on development of THz vector beam measurement system and microwave cryogenic low-noise amplifier. The first part, and the main focus, of the thesis covers the vector beam measurement system for frequency range 210-500 GHz developed to characterize/verify the cold optics of the APEX instrument SHeFI. The measurement system, based on a novel design employing combination of a single frequency source, comb-generator, and direct multiplication signal sources, is described in detail. The system configuration allows very narrow detection bandwidth giving the advantage of high dynamic range. With minor rearrangements, the same setup is used to characterize the three first receiving bands of SHeFI, covering the frequency range 211-500 GHz. In the first part of the thesis, the results from the measurements are presented and complemented with an extensive error analysis of the measurement setup. Additionally, we present results of the scalar beam characterization at 1334 GHz. One chapter of the thesis is also dedicated to describe the installation procedure at the telescope, where results from the first telescope pointing tests are presented. The second part of the thesis deals with the development of a three stage low-noise cryogenic amplifier based on InP-High Electron Mobility Transistors HEMTs for the frequency range 4-8 GHz. The design employs a combination of standard TRL, based on alumina substrate, and lumped element technology to achieve both ultimate noise performance over the specified band and a very compact size. Simulation results are presented together with the first preliminary measurement results (employing GaAs HEMTs).