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Scattering Parameters Representing Imperfections in Precision Coaxial Air Lines
1National Institute of Standards and Technology, Boulder, CO 80303.
Summary
This study presents scattering parameter models for coaxial air lines, accounting for conductor imperfections and losses. Accuracy is mainly limited by precise measurements of conductor dimensions.
Area of Science:
- Electrical Engineering
- Electromagnetics
- Transmission Line Theory
Background:
- Coaxial transmission lines are critical components in RF and microwave systems.
- Accurate modeling of scattering parameters is essential for system performance analysis.
- Existing models often simplify conductor geometry and loss mechanisms.
Purpose of the Study:
- To develop advanced scattering parameter expressions for the principal mode of a coaxial air line.
- To incorporate skin-effect loss and dimensional variations of conductors into the model.
- To analyze the impact of non-circular conductor cross-sections on scattering parameters.
Main Methods:
- Derivation of scattering parameter expressions for the principal mode.
- Inclusion of skin-effect loss calculations.
- Application of the Bergman kernel technique for conformal mapping of conductor cross-section deviations.
- Numerical simulations for a 7 mm air line.
Main Results:
- Validated scattering parameter expressions considering conductor imperfections and losses.
- Demonstrated numerical results for a practical 7 mm air line.
- Identified conductor radii measurement precision as the primary limitation on scattering parameter accuracy.
Conclusions:
- The developed model provides a more accurate representation of coaxial air line behavior.
- Precise dimensional metrology of conductors is crucial for high-accuracy scattering parameter extraction.
- The Bergman kernel technique effectively models geometric deviations in conductors.
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