A new approach is proposed to reduce the length requirements for the measurement of transmission line S-parameters in printed circuit boards (PCBs). In addition, the approach improves the accuracy of measurements. We demonstrate that guided-wave multiple reflections of the transmission lines in the signal propagation direction limits use of short transmission lines samples. The elimination of the guided-wave multiple reflections is introduced to overcome the coupon length limit for accurate measurements of transmission lines S-parameters. We introduce implementations of the proposed approach in the time and frequency domains. For time-domain measurements, we do corrections to remove the reflection noise signals from received signals: the first is the waveform manipulation for removing the internal reflections, and the second is the novel manipulation of S-parameters to compensate for reflected and transmitted losses. For native frequency-domain measurements, that manipulation of the S-parameters is used as a de- embedding correction method to remove the reflected and transmitted signals’ contributions from the S-parameters. Simulation results are presented to demonstrate the efficiency and accuracy of the new approach. Results show that the new approach can reduce the minimum length of high-speed transmission lines from 8 inches in traditional industry standards to only 0.5 inch for both 4-port TDR/VNA measurements and 2-port SET2DIL.