Study the Mechanism and Suppression of AM/PM Conversion of Traveling-Wave Tubes Using Eulerian Hydrodynamic Analysis

In this paper, the fourth-order analytic solution of amplitude modulation to phase modulation (AM/PM) conversion is first derived from an Eulerian nonlinear analytic model. The analytic relationships between electron phases, detuning parameter b, and AM/PM conversion are also found. Then, the mechan...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2018-11, Vol.65 (11), p.5062-5067
Main Authors: Qiu, Hai-Jian, Hu, Yu-Lu, Hu, Quan, Zhu, Xiao-Fang, Li, Bin
Format: Article
Language:English
Subjects:
AM/PM conversion
Amplitude modulation
analytic solution
Analytical models
Conversion
Digital modulation
Electron beams
Electron tubes
Eulerian analysis
Exact solutions
Harmonic analysis
Mathematical models
mechanism
Nonlinear analysis
Phase distortion
Phase modulation
Power generation
Traveling wave tubes
traveling-wave tube (TWT)
Wave interaction
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Summary:In this paper, the fourth-order analytic solution of amplitude modulation to phase modulation (AM/PM) conversion is first derived from an Eulerian nonlinear analytic model. The analytic relationships between electron phases, detuning parameter b, and AM/PM conversion are also found. Then, the mechanism of AM/PM conversion is studied. It is found that the generation of the harmonics in the dc component of the electron phase in the nonlinear beam-wave interaction region is the main mechanism of AM/PM conversion. Next, a series of AM/PM conversion suppression schemes is discussed by using the mechanism. The Eulerian formations are validated by an in-house code based on the Lagrangian theory. Results show that the fourth-order analytic solution of normalized axial electric field and AM/PM conversion agree well with the Lagrangian theory in the nonlinear region. In addition, the suppression schemes are applied to a high-efficiency Ku-band space traveling-wave tube (TWT). The AM/PM conversion distortion is greatly reduced by approximately 50% with a slight drop of output power. We hope that our efforts will help the nonlinear design of TWT in the future.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2018.2868855