The interesting thing about the compensation networks being used in transmitters and receivers today, is that the actual driver or receiver sits on a high impedance node formed by mutual inductance cancellation of the two 50 ohm line and termination ports. A transient pulse response of the actual circuit will give the right answer. But if, as I suspect many do, frequency domain techniques are used to derive the impulse response, and the network termination and receiver/driver are considered lumped at the same point, the resulting impulse response will be off by 10% and include additional pulse distortion, which is significant for a die. The conclusion I made for all impulse response generation methods is that the receiver/driver needs to be modeled at a minimum as a 3-port network per SE port, using a high impedance receiver/driver port whenever necessary, and the impedance deviation from 50 ohms needs to part of the modeling. Otherwise, the resulting impulse response, or derived waveforms passed to the AMI DLL will be incorrect. There are also some numerical issues that need to be addressed for s-parameters with mixed 50 ohm/10K ohm ports.
On 5/28/2010 4:52 AM, Mike Steinberger wrote:
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