Plenary Speaker 2: Microwave technologies: The first century

Summary form only given. The talk describes the history of microwave technologies, reaching back to the late 1800s, a time of experimentation with spark-gaps and waveguides up to 60GHz. Marconi and Hertz also investigated this regime, but turned their attention to low frequencies. For decades crude galena rectifiers were used for detectors, setting the stage for the later development of semiconductor diodes. The triode tube was a great leap for radio, but not as a source of microwave power, due to its long transit times. The 1920 Barkhausen-Kurz oscillator made use of this transit time to generate frequencies up to 700MHz. Once the idea of exploiting transit times was out of the box, the majority of microwave power sources for the next several decades were based on such methods and some invoked the use of crossed magnetic and electric fields. The cavity magnetron, today found in every home, was invented in 1937 by Boot and Randall at Birmingham University in England. It possessed the astonishing ability to instantly convert simple DC power into RF power in the centimetre range of wavelengths with hitherto unimaginable efficiency. It was followed by a rash of amazing electron tubes with mysterious names: the klystron, twystron, dematron, amplitron, and the scary-sounding carcinotron. Later semiconductor devices would generate their own list of odd abbreviated names: BARRIT, TED, IMPATT, TRAPATT and LSA. The commercialization of radio communication systems has led to a greater emphasis on two imperatives: very high performance, and extremely low cost. Modern microwave technologies have moved into a new commodity phase, like plastics or steel. However, it is safe to say “You ain´t seen nuthin´ yet!”.