Signal growth in a pure time-modulated transmission line and the loss effect

Author's Department

Electronics & Communications Engineering Department

Third Author's Department

Electronics & Communications Engineering Department

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https://doi.org/10.1098/rsos.240569

All Authors

Mohamed F. Hagag, Thomas R. Jones, Karim Seddik, Dimitrios Peroulis

Document Type

Research Article

Publication Title

Royal Society Open Science

Publication Date

11-13-2024

doi

10.1098/rsos.240569

Abstract

We present the first comprehensive study for signal growth in transmission lines (TL) with purely time-modulated characteristic impedance Zo (infinite superluminality). This study pioneers the investigation into the effects of varying the cell’s electrical length and the impact of loss on momentum bandgaps and amplification levels. It also thoroughly examines how time-modulated transmission line truncation by a static load influences the sensitivity of amplification gain to the relative phase between the incoming signal and modulation, comparing these findings with the case of parametric amplification. Varying Zo is accomplished by loading TLs with a sinusoidally time-modulated capacitor (TMC). The study starts with a simple lumped model cell to facilitate understanding of the phenomena. Following this, transmission lines are introduced, and the effects of incorporating loss are examined. To accomplish this, three models are investigated: a lossless L-C TL lumped model loaded with a shunt lossless TMC and a TL loaded with a shunt lossless and lossy TMC. Dispersion diagrams are plotted and momentum bandgaps are identified at a modulation frequency double the signal frequency. Within the momentum bandgap, only imaginary frequencies are found and correlated to momentum bandgap width and signal growth level. Signal growth is confirmed using harmonic balance and transient simulations, and the results are consistent with the dispersion diagram outcomes.

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Article. Record derived from SCOPUS.

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