An X band voltage tunable magnetron using a θ mode interdigital structure

Circuit coupling considerations make conventional pi mode VTM operation above C band an increasingly difficult task. This paper reviews a program, sponsored under U. S. Army Electronics Command Contract No. DA- 36-039-AMC-02199E, in which many of the restraints on higher frequency VTM operation have been relaxed through the use of the N/2±1 modes of an interdigital structure. Among the principal advantages of this higher order mode operation are: (a) circuit sizes in band comparable to conventional S band devices; (b) the opportunity for heavy coupling, and (c) a reduction in cathode radiation. The major complicating factor is that mode separation is not equivalent to the pi mode ease and that the two null field patterns of the N/2±1 modes are spatially degenerate. These problems, though, have been overcome by careful choice of vane number and by the use of mode positioners.