Traveling-wave tubes (TWTs), such as the Ka-band (26-GHz) model recently developed for the Lunar Reconnaissance Orbiter, are essential as communication amplifiers in spacecraft for virtually all near- and deep-space missions. This innovation is a computational design algorithm that, for the first time, optimizes the efficiency and output power of a TWT while taking into account the effects of dimensional tolerance variations.

Because they are primary power consumers and power generation is very expensive in space, much effort has been exerted over the last 30 years to increase the power efficiency of TWTs. However, at frequencies higher than about 60 GHz, efficiencies of TWTs are still quite low. A major reason is that at higher frequencies, dimensional tolerance variations from conventional micromachining techniques become relatively large with respect to the circuit dimensions. When this is the case, conventional design-optimization procedures, which ignore dimensional variations, provide inaccurate designs for which the actual amplifier performance substantially underperforms that of the design. Thus, this new, robust TWT optimization design algorithm was created to take account of and ameliorate the deleterious effects of dimensional variations and to increase efficiency, power, and yield of high-frequency TWTs.

This design algorithm can help extend the use of TWTs into the terahertz frequency regime of 300–3000 GHz. Currently, these frequencies are underutilized because of the lack of efficient amplifiers, thus this regime is known as the “terahertz gap.” The development of an efficient terahertz TWT amplifier could enable breakthrough applications in space science molecular spectroscopy, remote sensing, nondestructive testing, high-resolution “through-the-wall” imaging, biomedical imaging, and detection of explosives and toxic biochemical agents.

This work was done by Jeffrey D. Wilson of Glenn Research Center and Christine T. Chevalier of Analex Corp. For more information, download the Technical Support Package (free white paper) at under the Electronics/Computers category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18378-1.