As engineers keep abreast of the times for technology development, the specification requirements are more precise and rigid. In order to achieve higher data rate, lower loss material is widely adopted in PCB industry. In addition to impedance measurement for quality control, material loss is also a key factor affecting high-speed transmission. Therefore, measurement stability and repeatability are of paramount importance. The impedance measurement by Time-Domain Reflectometer (TDR) is widely used in the conventional PCB inspection method for high-speed application [1]. Besides the impedance monitor, the channel loss is more critical when the operation speed is going higher. Delta-L method is applied to measure PCB material loss property of the test coupon for the electrical requirements check [2]. How to characterize in-board channel accurately and efficiently is very challenging.