Control and measurement system for multi-channel microwave radiometer

摘要

The Laboratory of Space Technology has built several microwave radiometers over the years, and in 1994 the laboratory purchased a used short SC7 skyvan aircraft in order to perform airborne measurements with these radiometers. The large rear door opening allowed more instruments to be fitted at the same time, and it was decided to build additional radiometer receivers in order to more completely match the frequencies of the near-future satellite microwave radiometers. To accomplish matching frequencies, new receivers were needed at frequencies 6.8 GHz, 10.65 GHz and 18.7 GHz.This thesis describes the control and measurement system for these three new receivers. Chapter 1 briefly describes the background motivation behind the HUTRAD system, and chapter 2 contains a short theoretical introduction to different radiometer types.The general design of the measurement system is described in chapter 3, and all the different subsystems are presented briefly at a block diagram level. The computer hardware and associated interfacing cards used are also described here. The measurement software is also briefly presented, even though the software is not part of the work of this thesis.Chapter 4 contains the most important part of the author's work for this thesis. A special low-frequency amplifier with an integrating analog-to-digital conversion system based on a monolithic voltage-to-frequency converter chip was designed, and is described in detail here. There are also a few additional electronic circuits designed by the author described here.The functionality tests and some measurement results are presented in chapter 5, and the conclusions from these measurements and the most important lessons learned from this work are presented in chapter 6.