A De-Embedding and Embedding Procedure for High-Speed Channel Eye Diagram Oscilloscope Measurement

Abstract

In this paper, a procedure is proposed based on general purpose transient circuit simulation tools instead of FFT/IFFT technique by most oscilloscope vendors for de-embedding the test fixture and embedding the channel part between the channel access point and the channel receiver input non-accessible test point. For de-embedding, a special technique based on inverting the T-Matrix is proposed to get a combination of a passive, S-parameter model and a linear amplifier of a de-embedding network compatible with most circuit transient simulation tools. In the de-embedding cable and other transmission line procedures, a prompt phase rotation is also applied to the de-embedding, S-parameter model so it becomes realistically physical and can be synthesized into a SPICE circuit model. A method for de-embedding a lumped resistor which acts as a attenuator at the sampling point to minimize the impact to the regular operation of the signal channel is also proposed. For embedding, the S-parameter model of the physical channel between test fixture and the receiver from either simulation or measurement is used. The directly measured oscilloscope waveform including the transmitter equalization is applied as the de-embedding procedure signal source in the de-embedding and embedding network transient circuit simulation to obtain the receiver input waveform followed by receiver numerical equalization. Finally, based on oscilloscope measurement on the accessible test point and the proposed de-embedding and embedding procedure, we will get the channel eye diagram accurately after transmitter and receiver equalizations.Several practical application examples including 16Gb/s and 32Gb/s cases are displayed. The application examples show easy usage and effectiveness of the procedure for high-speed channel eye diagram oscilloscope measurement