Crossed-field backward-wave oscillators above X-band

The extension of crossed-field, or M-type, backward-wave oscillators into frequency ranges above X-band is described. Two tube types cover ranges of 10.8 to 15 Gc and 14.9 to 18.1 Gc, respectively, with minimum power outputs of 120 and 80 watts being achieved across these respective bands. Design criteria usually applied to such tubes were not practical in a number of important respects. For example, operation at 18.1 Gc takes place with a magnetic field substantially less than critical value. Basic dimensions of a representative X-band device in terms of wavelengths are compared with these two higher frequency models. New approaches to optics, output, and gun mount designs are described which are also applicable to lower frequency tubes. For example, the interdigital delay line structure converts to a single ridge waveguide output instead of the coax used in the aforementioned X-band device.