This third volume of the Forschungsberichte presents a collection of nine technical papers on selected topics of microwave engineering, ranging from investigations of the plasma in a Tokamak to the modeling of Heterojunction Bipolar Transistors. The main focus, however, is on noise in transistors and circuits, and how to measure it. Eight of the contributions are original papers, and one is a reprint from Plasma Phys. Control. Fusion, it appears by courtesy of the Institute of Physics Publishing.