TheUbitron as a high-power millimeter wave amplifier

The Ubitron is a traveling-wave amplifier based on the interaction between a 1arge-diameter magnetically undulated electron beam and the TE01 mode in circular waveguide. The interaction, is of the periodic beam type, which is sometimes referred to as ‘fast wave’ because the coupling of the beam and r. f.-wave can be obtain ed without slowing the phase velocity of the wave to less than-the velocity of light. The simplicity and large physical size of the r.f.-circuit used in the Ubitron and the large diameter of the beam make the tube extremely attractive for high pulsed power at millimeter and sub-millimeter wavelengths. The circuit diameter is an order of magnitude greater than that of the conventional traveling-wave tube (ka is about 4 compared with 0.4 for conventional tubes). With this size advantage one can expect to obtain the same order of magnitude of power at 100 Gc/s from a Ubitron as one would obtain at 10 Gc/s from a conventional TWT. Experimental results obtained at K -band lend credence to this comparison.