Third order modal degeneracy in waveguids: Features and application in amplifiers

We investigate a particular degeneracy condition in the dispersion of coupled periodic structures causing three eigenmodes to coalesce under proper coupling between eigenmodes supported by the system. This condition is referred to as a stationary inflection point (SIP) which is a third order degener...

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Published in2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) pp. 109 - 110
Main Authors Yazdi, Farshad, Othman, Mohamed A. K., Veysi, Mehdi, Capolino, Filippo, Figotin, Alexander
Format Conference Proceeding
LanguageEnglish
Published IEEE 01.07.2017
Subjects
Couplings
Dispersion
Electromagnetic waveguides
Electron beams
Gain
Impedance
Periodic structures
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Summary:We investigate a particular degeneracy condition in the dispersion of coupled periodic structures causing three eigenmodes to coalesce under proper coupling between eigenmodes supported by the system. This condition is referred to as a stationary inflection point (SIP) which is a third order degeneracy. We also show that by tuning the coupling parameters in the coupled periodic structure, the dispersion can be engineered to exhibit a slight positive or negative group velocity around the SIP frequency rather than zero group velocity. In particular, such regime provides a three-mode synchronous operation with an electron beam which is potentially beneficial for enhancing the efficiency of the traveling wave tubes (TWTs). Therefore, we use the proposed regime to design a SIP-based TWT where we show a gigantic gain enhancement compared to conventional single-mode Pierce-like TWTs.
DOI:10.1109/USNC-URSI.2017.8074921