Modeling Deformed Transmission Lines for Continuous Strain Sensing Applications

TL;DR

This paper presents a numerical framework based on Maxwell's equations and finite-difference methods to model how mechanical deformations affect transmission line impedance, enabling continuous strain sensing applications.

Contribution

The authors develop a novel finite-difference Yee method-based numerical framework to accurately simulate deformation effects on transmission lines over a wide frequency range.

Findings

Framework accurately captures experimentally observed deformation effects.

Simulation results agree with analytical predictions and experimental data.

Framework can model complex material arrangements in transmission lines.

Abstract

Transmission lines are essential components in various signal and power distribution systems. In addition to their main use as connecting elements, transmission lines can also be employed as continuous sensors for the measurement and detection of external influences such as mechanical strains and deformations. The measuring principle is based on deformation-induced changes of the characteristic impedance. Reflections of an injected test signal at resulting impedance mismatches can be used to infer applied deformations. To determine the effect of deformations on the characteristic impedance, we develop a numerical framework that allows us to solve Maxwell's equations for any desired transmission-line geometry over a wide frequency range. The proposed framework utilizes a staggered finite-difference Yee method on non-uniform grids to efficiently solve a set of decoupled partial differential equations that we derive from the frequency domain Maxwell equations. To test our framework, we compare simulation results with analytical predictions and corresponding experimental data. Our results suggest that the proposed numerical framework is able to capture experimentally observed deformation effects and may therefore be used in transmission-line-based deformation and strain sensing applications. Furthermore, our framework can also be utilized to simulate and study the electromagnetic properties of complex arrangements of conductor, insulator, and shielding materials.