Backward-wave oscillators for the frequency range from 600 GHz to 1800 GHz

The authors describe an effort to develop O-type backward-wave oscillators for the frequency range from 600-1800 GHz for local oscillators in spectroscopy measurements in space applications. Recent interdigital O-type backward-wave oscillators have yielded RF output in the frequency range from 200-800 GHz. One of these oscillators used aluminium metallization on a type-2A diamond substrate. A second interdigital circuit was built to gain more experience with this type of circuit at a lower frequency. The circuit was fabricated with aluminium metallization on a crystalline quartz substrate, but with only the metallization etched to form the interdigital circuit and no etching of the substrate. A third tube utilizes a tapered slot antenna to radiate the RF output to a hemispherical lens. The 44- mu m circuit used aluminium metallization on crystalline quartz, with no etching of the quartz.<>