Microfabricated, 71-76 GHz, Helical Traveling Wave Tube

ABSTRACT: Teraphysics Corporation proposes to design and develop a microfabricated, 71-76 GHz, helical traveling wave tube (TWT) providing at least 100 W of output power with greater than 50% efficiency. In Phase I, we plan to prove feasibility by completing electrical designs of all major components, and performing thermal and mechanical analyses. If awarded, in Phase II we would complete the mechanical design, fabrication, assembly, and test of a laboratory model that would be well-suited for space qualified operation and high data rate transmission. To successfully complete this program, Teraphysics will apply our expertise in vacuum electronics focusing on mm-wave and THz devices; expertise in high level, three-dimensional, computational modeling; high data rate, distortion mitigation and linearization expertise; novel, patent protected, helical TWT designs for mm-wave and THz operation; and novel, patent protected, helical TWT microfabrication techniques. Teraphysics"innovations have been proven on a 94 GHz TWT program, including reinventing the helix geometry and fabrication to be compatible with lithographic, microfabrication techniques; novel mechanical design where electron gun, circuit and collector are fabricated simultaneously for alignment within two microns; and novel, compact, periodic permanent magnet configuration. The result is a compact device approximately 2.6"long, 1.9"in diameter, weighing 1 lb. BENEFIT: The contiguous spectrum available between 71 and 76 GHz provides the capacity to achieve a high data rate downlink. However, a wideband, high power amplifier supplying at least 100 W with minimal distortion to the complex modulation signal is critical. Further, the amplifier must be compact and efficient to satisfy the payload size and weight requirements, and proven to be reliable with long lifetimes in space. To the author"s knowledge, the helical TWT is the only high power amplifier capable of satisfying these criteria. The most common TWT slow-wave circuit is the helix because it offers very large bandwidth and high efficiency. Unfortunately, in its classic form, it becomes extremely difficult to fabricate the helix at V-band because of its small size. Secondly, as frequency increases, and component parts become commensurately smaller, it is extremely challenging to achieve the necessary tolerances and alignment of the electron gun with the slow-wave circuit using conventional fabrication and alignment techniques. To get around these challenges, Teraphysics has developed several innovations that have been proven on our NASA JPL, 94 GHz TWT program. These include reinventing the helix geometry and fabrication to be compatible with lithographic, microfabrication techniques; a novel mechanical design where the electron gun, circuit and collector are fabricated simultaneously for alignment within two microns; and a novel, compact, periodic permanent magnet configuration. The result is a compact device approximately 2.6"long, 1.9"in diameter, and weighing 1 lb. In general, the target commercial market includes users of compact, high efficiency (>50%), high frequency (>60 GHz) amplifiers. Military applications include high data rate, network-centric communications and anti-jam and low detection warfare communications; airborne, ship borne, and ground-based radar; jamming; and decoy applications. NASA applications include high data rate communications, radar, spectroscopy and remote sensing. Commercial applications include wireless and satellite communications, radar, imaging, and materials processing. We project that we will be able to bring the 71-76 GHz TWT to market within three years of demonstrating the first prototype. Within five years we expect to have captured at least 50% market share with revenues projected to be approximately $20 M over 5 years. A slightly modified version of the Teraphysics TWT at 71-76/81-86 GHz, 140 GHz and/or 220 GHz could be the enabling technology for ultra-high data rate transmission (10"s to 100"s GBPS) for commercial communications or military applications. Our TWTs would enable these data rates at E-band, 140 GHz and 220 GHz as they can deliver 10"s of Watts of output power with greater than 50%, and<1 dB gain variation over the bandwidth. The commercial potential is enormous for wireless communications, particularly to increase through put for backhaul applications.