PC-based reflectometer for microwave applications using three probe algorithm

This paper describes a technique for measurement of complex reflection coefficients (/spl Gamma/) using a slotted line for microwave applications such as estimation of water quality and power absorbed in human skin in vivo. In order to carry out precise calculations of magnitude and phase of reflection coefficient from measured standing wave voltages at a frequency, the three-probe reflectometer (TPR) algorithm has been used (which was implemented on a notebook computer using Visual Basic 6.0 programming). This system provides a real-time measurement of complex reflection coefficient of loads such as lossy liquids and open-ended waveguides radiating into free-space. To test for different reflection coefficients, open-ended waveguides and different lossy liquids are used as loads. Also, reflection coefficients were measured using a vector network analyzer (VNA). There is a close match in reflection coefficient values measured by the TPR system and VNA.