Microwave devices and components. Phase delay and propagation velocity. The propagation constant. Transmission line distortion. Wave reflection and the reflection. coefficient. Standing wave ratio. Fundamental waveguide characteristics. Microwave passive components. The directional coupler. Waveguide junctions. Cavity resonators. Circulators and isolators. Microwave active devices. Solid-state devices. Microwave tubes. Multicavity magnetrons.
The brothers Russell and Sigurd Varian of Stanford University are the inventors of the klystron. Their prototype was completed in August 1937. Upon publication in 1939, news of the klystron immediately influenced the work of US and UK researchers working on radar equipment. The Varians went on to found Varian Associates to commercialize the technology (for example to make small linear accelerators to generate photons for external beam radiation therapy). In their 1939 paper, they acknowledged the contribution of A. Arsenjewa-Heil and Oskar Heil (wife and husband) for their velocity modulation theory in 1935.
The work of physicist W.W. Hansen was instrumental in the development of klystron and was cited by the Varian brothers in their 1939 paper. His resonator analysis, which dealt with the problem of accelerating electrons toward a target, could be used just as well to decelerate electrons (i.e., transfer their kinetic energy to RF energy in a resonator). During the second World War, Hansen lectured at the MIT Radiation labs two days a week, commuting to Boston from Sperry gyroscope company on Long Island. His resonator, called a "hohlraum" by nuclear physicists and coined "rhumbatron" by the Varian brothers, is used in 2009 in the National Ignition Facility investigating nuclear fusion. Hansen died in 1949 as a result of exposure to beryllium oxide (BeO).
During the second World War, the Axis powers relied mostly on (then low-powered) klystron technology for their radar system microwave generation, while the Allies used the far more powerful but frequency-drifting technology of the cavity magnetron for microwave generation.