Development of high efficiency backward wave oscillators for submillimeter applications

Summary form only given. Calabazas Creek Research Inc. is funded by the National Aeronautics and Space Administration to develop efficient, light-weight, backward wave oscillators (BWOs) for applications from 300 GHz to 1 THz. These devices are needed as local oscillator sources in heterodyne receivers. Very low noise heterodyne receivers are needed at submillimeter wavelengths for low-background radio astronomy observations and remote sensing of comets, Earth, and other planetary atmospheres. Above 100 GHz, only BWOs have broad tunability (over 100 GHz) and high output power (/spl sim/1 mW); however, they are heavy (over 20 kG), consume a lot of power (270 W), require water cooling, and have poor output mode purity. The current development will incorporate energy recovery, air cooling, and significant weight reductions using an improved magnet design and lighter, advanced magnetic materials. An improved coupler was developed to transform the generated RF power to a high purity Gaussian output mode. The design and construction of a 600-700 GHz BWO is underway using advanced electric discharge machining techniques developed by RWI. The program goal is to reduce the total input power to less than 50 W, the weight to less than 10 kg, and the output mode purity to more than 98%. Design details and progress to date will be presented.