Multi-port Reflectometry Applied to a Varactor-Tuned Sampled-Line

This work applies multi-port reflectometry to a tunable sampled-line, demonstrating the ability to measure impedance when the parameters of the network are varied through varactor tuning. A theoretical model of the varactor-tuned sampled-line is presented and used to fit measured data in the plane of calibration constants used for impedance sensing. A 2-GHz demonstrator sampled-line is fabricated and characterized. Complex reflection coefficient measurements of the varying load are within 0.05 in magnitude and 5.7 degrees in phase over a 2.14:1 varactor tuning range.