Origin of Second-Harmonic Signals in Octave Bandwidth Traveling-Wave Tubes

Wong, Patrick; Lau, Y. Y.; Chernin, D.; Hoff, Brad W.; Gilgenbach, R. M.

doi:10.1109/ted.2017.2785284

Cited by 6 publications

References 19 publications

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Two surface multipactor discharge with two-frequency rf fields and space-charge effects

2022

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This paper presents two-surface multipactor discharge with two-frequency rf fields using Monte Carlo simulations and Computer Simulation Technology (CST) Particle Studio. The effects of the relative strength and phase of the second carrier mode on multipactor susceptibility and time dependent physics are studied. Compared to single-frequency rf operation, shrinkage of multipactor susceptibility regions is observed for different configurations of two-frequency rf operation. The presence of a second carrier mode in the rf field results in mixed multipactor modes in which electrons take a fixed time period to complete a round trip between the two surfaces, while the time for electrons to traverse the gap in each direction is found to be different. CST simulation reveals that the space-charge effect reduces the electron growth rate and causes shrinkage of multipactor susceptibility bands.

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Two surface multipactor discharge with two-frequency rf fields and space-charge effects

2022

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Small-signal model for inhomogeneous helix traveling-wave tubes using transfer matrices

Marosi,

Rouhi,

Mealy

et al. 2024

Physics of Plasmas

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We introduce a practical method for modeling the small-signal behavior of frequency-dispersive and inhomogeneous helix-type traveling-wave tube (TWT) amplifiers based on a generalization of the one-dimensional (1D) Pierce model. Our model is applicable to both single-stage and multi-stage TWTs. Like the Pierce model, we assume that electrons flow linearly in one direction, parallel and in proximity to a slow-wave structure (SWS) that guides a single dominant electromagnetic mode. Realistic helix TWTs are modeled with position-dependent and frequency-dependent SWS characteristics, such as loss, phase velocity, plasma frequency reduction factor, interaction impedance, and the coupling factor that relates the SWS modal characteristic impedance to the interaction impedance. For the multi-stage helix TWTs, we provide a simple lumped element circuit model for combining the stages separated by a sever, or gap, which attenuates the guided circuit mode while allowing the space-charge wave on the beam to pass freely to the next stage. The dispersive SWS characteristics are accounted for using full-wave eigenmode simulations for a realistic helix SWS supported by dielectric rods in a metal barrel, all of which contribute to the distributed circuit loss. We compare our computed gain vs frequency, computed using transfer matrices, to results found through particle-in-cell simulations and the 1D TWT code LATTE to demonstrate the accuracy of our model. Furthermore, we demonstrate the ability of our model to reproduce gain ripple due to mismatches at the input and output ports of the TWT.

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Recent theory of traveling-wave tubes: a tutorial-review

Wong

Zhang

Luginsland

2020

Plasma Res. Express

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The traveling-wave tube (TWT), also known as the traveling-wave amplifier (TWA) or traveling-wave tube amplifier (TWTA), is a widely used amplifier in satellite communications and radar. An electromagnetic signal is inputted on one end of the device and is amplified over a distance until it is extracted downstream at the output. The physics behind this spatial amplification of an electromagnetic wave is predicated on the interaction of a linear DC electron beam with the surrounding circuit structure. Pierce, known as the ‘father of communications satellites,’ was the first to formulate the theory for this beam-circuit interaction, the basis of which has since been used to model other vacuum electronic devices such as free-electron lasers, gyrotrons, and Smith-Purcell radiators, just to name a few. In this paper, the traditional Pierce theory will first be briefly reviewed; the classic Pierce theory will then be extended in several directions: harmonic generation and the effect of high beam current on both the beam mode and circuit mode as well as ‘discrete effects’, giving a brief tutorial of recent theories of TWTs.

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Origin of Second-Harmonic Signals in Octave Bandwidth Traveling-Wave Tubes

Cited by 6 publications

References 19 publications

Two surface multipactor discharge with two-frequency rf fields and space-charge effects

Two surface multipactor discharge with two-frequency rf fields and space-charge effects

Small-signal model for inhomogeneous helix traveling-wave tubes using transfer matrices

Recent theory of traveling-wave tubes: a tutorial-review

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