Local Polynomial Regression as Adaptive Windowing Function in Complex-Valued Reflection Coefficient Measurements

This article discusses some features of the digital processing of the measurement results of the complex-valued reflection coefficient based on the usage of the time-domain gating methods. Particular attention is paid to the cases when the design of the device under test implies the presence of several discontinuities distributed along its length, i.e., it has a group response in time-domain. The local polynomial regression algorithm, known as the Savitzky-Golay filter, is proposed as an adaptive window function for the time-domain gating. The advantages and the disadvantages of this algorithm are considered comparing to the symmetric gating windows and the notch windows usage.