High-Average-Power W-band TWT Development

A PPM-focused TWT for airborne applications producing over 400 W of peak RF output power at 90.6 GHz and average-power levels between 150 and 180 W is described. Design goals of 1% bandwidth, 250 W of peak power, and 30 dB of gain have all been met despite the invariable fabrication errors in this nascent type of tube. The TWT utilizes a novel integral-pole-piece ferruleless-coupled-cavity-class folded-waveguide circuit that features thick iron pole pieces with hollowed out centers, and a gridded gun for fast beam modulation. This thermally robust circuit plus the tetrode gun represent two key enabling technologies for compact high-average-power TWTs in W-band.