Hi Dr. Novak,
Thanks. I would say it is to "replace" the nominal impedance w/ the actual
termination used in tx/rx circuits, rather than "add" :-)
On the rx side the termination has to be implemented. When the signal
passes the termination stage and comes to the Slicer, it will be seeing
Hi-Z of digital input impedance (for voltage type Slicer).
So it seems up to the rx termination the channel signal transmission is
still power-based - despite the power here can be the apparent power, and
not necessarily the effective power. Still, the sparam relation btw tx and
rx is power-based.
After the termination, it seems to be either voltage-based - if the Slicer
is a voltage type, or current-based, if the Slicer is a current type.
Make sense?
Best Regards,
Tramp
On Sun, Dec 8, 2019 at 10:37 AM Istvan Novak <istvan.novak@xxxxxxxxxxx>
wrote:
What can close the loop in your thoughts are the considerations that S
parameters are
steady-state frequency-domain linearized descriptors based on a chosen
reference
impedance. Moreover, we usually describe only the passive channel by S
parameters.
In the actual application, you have to consider also the terminations
instead of the
chosen normalization impedance, so you need to add the actual source
impedance
of the driver and the actual load impedance of receiver. The silicon
impedance tends
to be high compared to the typical 50-ohm reference impedance and
therefore by the
time you consider these impedances, what matters much more is voltage
(though
neither the reactive nor the dissipative power is going to be absolutely
zero in a real case).
Regards,
Istvan Novak
Samtec
On 12/8/2019 10:36 AM, Tramp wrote:
Hi experts,it
We all know sparam is power based. But when it comes to the RX sampler,
seems to be voltage based to me. This is bcs that the slicer doesnt careif
the voltage it is sampling is inphase w/ time, or out of phase since itcan
shift its time base to locate the peaks of incoming voltage. In other
words, what is cared for is the apparent power rather than the effective
power.
is my understanding correct?
Best Regards,
Tramp
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