Frequency-Dependent Per-Port Renormalization

Abstract

A frequency-dependent and per-port (FDPP) channel termination and renormalization method is presented as a more accurate substitute for the traditional method that uses frequency independent, uniform impedance as the serialization/deserialization transmit (TX)/receive (RX) termination impedances. Although the traditional method is employed in practically all the existing high-speed interface standards, the assumption of the constant, uniform termination impedance at TX and RX is not exactly correct and will lead to inaccuracy. The new method characterizes the mismatch conditions at the TX and the RX terminations on a per frequency point and per-port basis and, thus, produces more accurate results during the channel characterization and performance assessment. The mathematical computation procedure of the FDPP approach is introduced. Two representative TX/RX terminations and three typical channels representing mid/high/ultra-high losses are used to demonstrate the effects of the FDPP renormalization method. The obtained S -parameters, eye-diagrams, as well as the channel operational margin (COM) figure of merits are compared to that generated using the traditional method. The comparison shows that the FDPP method produces more realistic and accurate results than the traditional approach. In the end, a proposal of expanding the [Reference] section in the current Touchstone 2.0 format is presented.