A nonreciprocal-loss traveling-wave-tube circuit

After a review of other related work and our own initial work, a nonreciprocal-loss, traveling-wave-tube circuit consisting of a series of re-entrant cavities coupled through ferrite-loaded apertures is described. For the configuration discussed, which is of the periodic magnetically focused variety, some measured characteristics of a possibly typical circuit (one with a cold pass band for the desired interaction mode of 20 per cent width centered near 9 kMc) are as follows: 1) a loss ratio of nearly 10 to 1 in db at band center dropping to about 4 to 1 in db near the band edges, 2) a ratio of backward loss to usual forward gain per unit length adequately larger than unity, and 3) small and practically negligible changes in the phase velocity, interaction impedance, circuit-matching characteristics, and peak gap axial periodic-focusing magnetic field from these same properties in a non-ferrite-loaded circuit. Mention is made of the use of ferrite for obtaining reciprocal loss. Finally, the possible application of the ferrite-loaded-aperture non-reciprocal circuit in modified form to other kinds of traveling-wave interaction devices (parametric amplifiers and masers) is noted.