[time-nuts] Transmission line question

Don Otknow donald.otknow at gmail.com
Wed Apr 6 22:05:21 UTC 2011


Just for the record I meant pin as in the metal contact of a device, not a
PIN diode. So I need the impedance the pin "see's" (that of the transmission
line(s)) to be the same as the output impedance of the pin.

Here's an extrapolation on the original question. If this is a high speed
digital signal, with frequency elements ranging from say 133 MHz to 1GHz,
then what I am really worried about, given the trace lengths (maybe 2 cm
each way) is the high frequency components getting reflected or not sent
down the line properly. If my source impedance from the the device is 50
ohms, the lines are each 100 ohms, and the terminations at each end are 100
ohms (probably AC terminated, but let's just say 100 ohms for simplicity),
am I setting myself up for the best possible signal integrity?

Here's a primitive diagram of the setup

                                 100 ohm line      100 ohm line
100 ohm term. to gnd _________________________100 ohm termination to gnd
                                                       |
                                                       |
                                                       | 50 ohm source
                                                       |


Donald


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