The positively tapered traveling-wave tube

A new and unexpected concept of TWT circuit modification which results in high basic beam and depressed collector efficiencies is described. The test results which are presented disclose that 50 percent depressed collector efficiency has been achieved over a 10 per cent bandwidth, and that maxima of 42 and 52 percent, respectively, of beam and depressed collector efficiency have been measured at spot frequencies. The tube which produced these results contained a single continuous helix tapered at the output end so that the phase velocity of the fundamental circuit wave was increased.