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A study of efficiency of Ka-band TWTs with multistage depressed collectors (MDCs) ion-treated and untreated, respectively is reported. It was shown that efficiency of the TWT with ion-treated MDCs improved by as high as 7%, in comparison to that of one with untreated MDCs.
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.
A kind of broadband microwave window for W-band TWT is manufactured. The measurement result reveals that the pass bandwidth is more than 10 GHz in W-band which has met the requirements of the TWT.
Attenuators for W-band folded waveguide TWT have been successfully fabricated using BeO and Al2O3 respectively. And these samples could meet the strict dimension requirements based on former design after repetitious attempts. Test system of attenuator was developed to test them, and test results showed good performance that can meet the practical requirements in W-band folded waveguide TWT.
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.
A 140 GHz folded waveguide slow-wave circuit is designed using the Pierce theory and a three-dimensional (3D) particle-in-cell (PIC) code. Dispersion relation and interaction impedance of the circuit are calculated using Mafia code and theory model. A small-signal gain performance of the circuit is obtained from 3-D PIC simulation and the small-signal theory.
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