A New Amplification Regime for Traveling Wave Tubes with Third Order Modal Degeneracy

Abstract

Engineering of the eigenmode dispersion of slow-wave structures (SWSs) to achieve desired modal characteristics, is an effective approach to enhance the performance of high power traveling wave tube (TWT) amplifiers or oscillators. We investigate here for the first time a new synchronization regime in TWTs based on SWSs operating near a third order degeneracy condition in their dispersion. This special three-eigenmode synchronization is associated with a stationary inflection point (SIP) that is manifested by the coalescence of three Floquet-Bloch eigenmodes in the SWS. We demonstrate the special features of "cold" (without electron beam) periodic SWSs with SIP modeled as coupled transmission lines (CTLs) and investigate resonances of SWSs of finite length. We also show that by tuning parameters of a periodic SWS one can achieve an SIP with nearly ideal flat dispersion relationship with zero group velocity or a slightly slanted one with a very small (positive or negative) group velocity leading to different operating schemes. When the SIP structure is synchronized with the electron beam potential benefits for amplification include (i) gain enhancement, (ii) gain-bandwidth product improvement, and (iii) higher power efficiency, when compared to conventional Pierce-like TWTs. The proposed theory paves the way for a new approach for potential improvements in gain, power efficiency and gain-bandwidth product in high power microwave amplifiers.

arXiv comment15 pages, 11 figures

References in corpus (11)

• Slow light in photonic crystals
• Giant Gain Enhancement in Photonic Crystals with a Degenerate Band Edge
• Active Negative Index Metamaterial Powered by an Electron Beam
• Experimental Demonstration of Degenerate Band Edge in Metallic Periodically-Loaded Circular Waveguide
• Theory of Exceptional Points of Degeneracy in Uniform Coupled-Waveguides and Balance of Gain and Loss
• Unidirectional Lasing Emerging from Frozen Light in Non-Reciprocal Cavities
• Giant Amplification in Degenerate Band Edge Slow-Wave Structures Interacting with an Electron Beam
• Wave Energy Amplification in a Metamaterial based Traveling Wave Structure
• Low Starting Electron Beam Current in Degenerate Band Edge Oscillators
• Multi-transmission-line-beam interactive system
• Theory of Double Ladder Lumped Circuits With Degenerate Band Edge

Cited by in corpus (8)

• General Conditions to Realize Exceptional Points of Degeneracy in Two Uniform Coupled Transmission Lines
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• Low-Threshold Lasing with Frozen Mode Regime and Stationary Inflection Point in Three Coupled Waveguide Structure
• Analytical Solution for Space-Charge Waves in a Two-Stream Cylindrical Electron Beam
• Frozen Mode Regime in an Optical Waveguide With Distributed Bragg Reflector
• Third Order Modal Exceptional Degeneracy in Waveguides with Glide-Time Symmetry
• Photonic emulation of two-dimensional materials with antiferromagnetic order
• Three-Way Serpentine Slow-Wave Structures with Stationary Inflection Point and Enhanced Interaction Impedance