E-band Traveling Wave Tube Amplifier with Innovative Carbon Nanotube Cathode

ABSTRACT: Existing satellite communication devices use Travelling Wave Tube Amplifiers (TWTAs), which operate in the ultra-high frequency, super-high frequency, or extremely-high frequency bands. Because these TWTAs use thermionic cathodes, they are bulky and heavy, and take valuable volume and weight budget in a satellite. Recently, the Air Force identified needs for a compact (<30 lb) TWTA operating in the output frequency of 71 to 76 GHz (E-band) and at an output power>50 W. To address these critical needs CFD Research Corporation teamed with University of Tennessee Space Institute to develop the design of E-band TWTA with innovative carbon nanotube (CNT) cathode (emitter). In Phase I, we will (1) fabricate innovative prototype emitter consisting of CNTs with precisely controlled diameter, length, and the neighboring spacing using a method of serial patterning with a femto-second laser, (2) adopt and validate CFDRC electro-magnet software CFD-ACE+ for computational design of CNT-based TWTA in triode configuration, and (3) conduct computational parametric studies to achieve an emission current density of 12 A/cm2, an output power>50 W, and a power efficiency>20%. The Phase II work will fabricate prototype CNT E-band TWTA and optimize its performance for output power, operating frequency range, linearity, operating temperature range, radiation tolerance and reliability specified by the Air Force. BENEFIT: The Air Force will directly benefit from the proposed work by using it in the development of new communication devices for high data rate battlefield communications with the following advantages: (1) Access to the 5 GHz of spectrum enabling satellite communications uplinks to operate at multi-gigabit per second data rates and (2) Well understood weather attenuation factors, such as rain fade. The initial market for this technology is expected to be limited to DoD applications. However, if price for the fabrication of CNT based TWTA will drop, there is a potential for the proposed technology to be used in civilian applications such as cellular and wideband mobile communications and high speed data transfer.