[SI-LIST] Re: Transmission Line + Jitter
- From: "Zabinski, Patrick J." <zabinski.patrick@xxxxxxxx>
- To: andyk@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 26 Nov 2004 06:39:27 -0600
Andy,
I believe the answer is yes; you will see added
jitter (the real questions are how much, what type,
and do you care).
Specific to random jitter (which most often
follows Gaussian distributions), jitter is the result
of voltage noise on the signal. Accordingly, any
resistive element (i.e., lossy element) will
inject some (usually small, inconsequential)
amount of random noise on the signal, which
presents itself as random jitter. My understanding
is that this jitter is usually small enough that
you don't care, so this is more of a theoretical
discussion that practical (until we see 100's of
GHz signals or data being transmitted over very-lossy
lines).
Specific to deterministic jitter, the discussion
needs to be specific to the type of signal
you're passing through it. In brief, transmission
line losses are frequency dependent, which will
shifts data transitions (i.e., rising and falling
edges) differently depending upon the frequency
content of the edge.
If the signal is a clock that is exactly
repetative (i.e., same exact duty cycle
throughout with no change in phase, frequency,
etc.), then the effective frequency content of
each pulse is the same. Accordingly, each
transition will be delayed by the same amount.
As a result, you will not see any added
deterministic jitter.
If the signal is a data pattern where the pulses
changes in width, then the effective frequency
content of each pulse will vary, which in turn
will shift the edges by varying amounts, which will
manifest itself as deterministic jitter (i.e.,
data dependent jitter, or intersymbol interference).
Depending upon several factors, this type of
jitter can be significant.
Pat
> -----Original Message-----
> From: Andy Kuo [mailto:andyk@xxxxxxxxxx]
> Sent: Thursday, November 25, 2004 7:57 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Transmission Line + Jitter
>
>
> Hi All,
>
> I have a basic question to ask:
>
> Assuming I have one single transmission line and it is
> perfectly matched
> and properly terminated. This transmission line is lossy. I
> am applying
> a square signal through the transmission line
>
> Will I see any jitter in the edge crossing?
>
> Regards,
> Andy
>
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