A technique for estimating signal waveforms at inaccessible points in high speed digital circuits

There is a large difference between the waveforms of high speed digital signals measured on a printed circuit board and those at the receiving terminals of LSI chips. In order to ensure that the high speed digital signal is correctly transferred, one of the major issues is how to estimate the waveform at the receiving terminal, where the waveform cannot be directly measured. Therefore, we have developed a new technique for estimating the waveform at the receiving terminal from the waveform measured at an accessible test point, based on the input impedance and transmission characteristics of the traces. By comparing the estimated waveform and the measured waveform in a Blu-ray Disc recorder system, it was confirmed that it is possible to estimate the waveform with high accuracy. Furthermore, it was confirmed that the estimated waveform has good correlation with the timing margin for correct data transfer.