The V-band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for inter-satellite communications. In a recent program sponsored by NASA Lewis Research Center, Hughes Aircraft Company developed a successful 70-Watt, 20 kV, V-band ferruled coupled-cavity travelling-wave tube (TWT), designated as Model 961 HA With a 4-stage depressed collector, the 961 HA has an overall efficiency of 27.4%. In an effort to develop a V-band TWT with higher efficiency that is also easier and less expensive to manufacture, we are investigating the ring-plane slow-wave circuit as an alternative to the more conventional ferruled coupled-cavity circuit of the 961 HA The prototype ring-plane circuit as conceived by White et al., shows promise because of its advantages of higher impedance and a larger beam aperture. However it has disadvantages of high voltage operation and narrow bandwidth. We are incorporating geometric variations such as slotted support planes and vane loading to alleviate these disadvantages. In order to compare ring-plane circuit variations to the 961 HA ferruled coupled-cavity circuit, computational procedures involving the combined use of three-dimensional, small-signal, and large-signal simulation codes were developed. The three-dimensional simulation code MAFIA is used to model the cavity designs and to accurately simulate the cold-test parameters (dispersion, impedance, and attenuation).
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