Coupled-cavity TWT Research Articles

High-power linear-beam tubes

High-power klystrons, coupled-cavity traveling-wave tubes (TWT's), and hybrid tubes, all of which utilize the microwave cavity as the basic circuit element, are described. These amplifiers are used in communications, radars, electronic countermeasures, and other applications at power levels from a few hundred watts to megawatts, at frequencies from ultrahigh frequency on up, and are particularly suited for high average powers. High gain, 30 to 60 dB, is normally achieved, and bandwidth usually lies in the 1-30-percent range. Elementary theory of operation is described, together with design considerations and systems interface information. Typical tube designs and data are presented. Recent developments are discussed, including high-efficiency techniques (to 75 percent), improvements in bandwidth, periodic focusing, and beam control electrodes. Most of the basic design techniques are well developed, and emphasis is being shifted to improvements in the detailed performance characteristics such as gain and phase resolution ripples, noise, and the sensitivities to operating voltages and currents.

High power TWT for satellite communication

Performance characteristics are presented for an 8-kw CW coupled cavity traveling wave tube along with some unique design techniques employed in achieving this performance. The tube is designed and will be shown to meet or exceed the stringent requirements of commercial ground satellite communication systems.

Circuit Considerations for the Reduction of Intermodulation Distortion in High Power Travelling-wave Tubes†

ABSTRACT A circuit analysis has been conducted on the reduction of intermodulation distortion generated in high power coupled cavity travelling-wave tubes for single sideband frequency division multiplex transmitters. Distortion-efficiency trade-off parameters have been considered through the use of two known techniques : (1) depressed collector tube operation ; and (2) direct narrow-band negative r.f. feedback around the travelling-wave tube. Because of the tube's non-linear properties when saturated, tube operation must be well below saturation and, hence, will be inefficient. Collector depression will improve the efficiency considerably. By using feedback, the distortion level will be reduced by the amount of loop gain, provided the system is stable. Circuit considerations and limitations of these two improvement techniques facilitate a more efficient operation of tow distortion travelling-wave-tube amplifiers.

High power broadband coupled-cavity traveling-wave tubes

This paper describes the extension of the cold circuit bandwidth to 60 per cent and the operating bandwidth for high power traveling-wave tubes to 45 per cent. A new liquid cooled coupled-cavity circuit fulfills the bandwidth requirements and has high average power capability. In the process of increasing the bandwidth, a number of new problems required solution. The major difficulties encountered in wide-band operation are the spurious interaction at higher order modes, band edge oscillations, interaction impedance variation across the pass band and general operational instability because of regeneration. All of the above mentioned problems are magnified at higher operation voltages because of the merging of the fundamental and a particular higher order mode.