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Backward wave oscillation (BWO) and other parasitic oscillation are encountered in the process of manufacturing W-band TWT. In order to eliminate the oscillation, a kind of attenuation material is coated to the folded waveguide wall. This method presents a good performance to enable stable working of the TWT and increase the output power to 15W at the same drive level.
This paper gives the recent progress of a W-band 10 W CW TWT, describes the basic design and test results. The prototype has a 10 W output power with 2 GHz bandwidth.
A dynamic velocity taper (DVT) characterized by exponential taper pitch have been designed for high efficiency millimetre wave TWT. Design result in K and Ka band shows a great improvement of electron efficiency. The experimental results can reach 23% in Ka band and 25% in K band TWT.
The lossy ceramics can improve the output characteristics of the Gryo-TWT. In the paper, a Gyro-TWT based on lossy ceramics is introduced, the operation frequency 34 GHz, peak power 160Kw, bandwidth 2.4GHz, has been obtained with 65Kv beam voltage and 8A beam current.
The linearity of a Ku-band TWT is improved with AM/PM les 3.43deg/dB, IM3/C les -44.43 dBc, and it's output power has increased to 55.84 dBm by optimizing electron beam radius and helix structure.
The self-consistent nonlinear equations for beam-wave interaction and the equations of electronic are built up for Gyro-TWT in wave-guide with helical corrugation, numerical calculations of the equations above have been performed. The simulation results show: Among the center frequency 9.5 GHz, when the gain falls to 3dB the corresponding bandwidth is 19%.
Attenuator has been designed to meet the strict requirements in W-band for folded waveguide TWT. Synthetical analysis of parameters is carried out, and using microwave studio simulation results show design has good performances. Fabrication technology and test system are in progress to develop the practical attenuator.
An attenuator structure for FWGTWT was designed and optimized for a good match to the folded waveguide circuit, SII<-20 dB from 90 GHz to 98 GHz for single port system. The equivalent relationship between dielectric loss and conductivity loss was described and discussed in this paper, in order to load the attenuators in beam/wave interaction simulation using MAFIA.
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