Advances in Microwaves, Volume 3 covers the advances and applications of microwave signal transmission and Gunn devices. This volume contains six chapters and begins with descriptions of ground-station antennas for space communications. The succeeding chapters deal with beam waveguides, which offer interesting possibilities for transmitting microwave energy, as well as with parallel or tubular beams from antenna apertures. A chapter discusses the electron transfer mechanism and the velocity-field characteristics, with a particular emphasis on the microwave properties of Gunn oscillators. The last chapters survey the specific physical and operating characteristics of the various high power amplifiers and oscillators, which have been developed for operation at millimeter wavelengths. These chapters also examine the nonlinear interactions of spin waves and elastic waves.