Propagation Constant Measurement Based on a Single Transmission Line Standard Using a Two-Port VNA

Area of Science:

• Electrical Engineering
• Electromagnetics
• Metrology

Background:

• Accurate measurement of transmission line characteristics is crucial for high-frequency applications.
• Traditional methods often require complex calibration procedures and multiple standards.
• Vector network analyzers (VNAs) are standard tools, but their calibration can introduce errors.

Purpose of the Study:

• To develop a simplified and accurate method for measuring the propagation constant of transmission lines.
• To reduce measurement errors associated with VNA calibration and connector repeatability.
• To achieve improved broadband traceability to SI units.

Main Methods:

• A new measurement technique using a single line standard is proposed.
• The method emulates multiple line standards from the multiline calibration technique.
• Each standard is realized by sweeping an unknown network along a transmission line, requiring only transmission and reflection capabilities.

Main Results:

• Measurements were performed on a slab coaxial airline using three different VNAs.
• The propagation constant measurements were nearly identical across all VNAs.
• The method successfully avoids disconnecting or moving cables, minimizing connector repeatability errors.

Conclusions:

• The proposed method offers accurate and repeatable measurements of transmission line propagation constants.
• It simplifies the measurement process by requiring only a single line standard and no VNA pre-calibration.
• The technique enhances traceability to SI units by reducing systematic errors.