Broadbanding of a Submillimetre-Wave Backward-Wave Oscillator

As a consequence of the interest shown by astronomers for observation on board a space platform in the submillimetre-wave range, the European Space Agency has initiated a research and development programme on components required for advanced submillimetre-wave heterodyne detection and particularly on the local oscillator. In order to cover the spectral range of interest (between about 0.3 and 1 mm) with as few components as possible, large tunability is required. Due to its continuous electronic tuning capability, a broadband BWO seems to be most appropriate choice. A design goal of 10 mW was selected in order not to limit unduly the choice of the detector-mixer, together with a tunability of 20% in the range 0.75 - 0.95 mm. A new tube model was devised and manufactured. Although every parameter has not been optimized, the above performances were obtained, up to 50 mW over most of the bandwidth. The power consumption (between 55 and 100 W) represents a large improvement with respect to existing submillimetre tubes.