[SI-LIST] Re: Propagation speed of a stripline trace in PCB

Mani,
TDR measures the round-trip delay, i.e. the time it takes for the signal 
to arrive at the end of the line plus the time it takes for the reflection 
to travel back. In a ideal, loss-less transmission line this is thus 
exactly twice the propagation delay of the line. In a lossy line or when 
there are parastics it's only approximately a factor of 2 (because the 
propagation speed will depend on the frequency content of the signa, which 
changes due to frequency dependent losses); but in most practical cases 
the deviation from 2 will be smaller than your other measurement 
uncertainties.

Wolfgang






Mani Ganesan <signal.integrity2@xxxxxxxxx> 
Sent by: si-list-bounce@xxxxxxxxxxxxx
09/03/2010 11:27 AM

To
si-list@xxxxxxxxxxxxx
cc

Subject
[SI-LIST] Propagation speed of a stripline trace in PCB






Hi All
can you anyone confirm me whether the propagation speed of a stripline 
trace
in PCB is correct?

propagation speed (stripline) = 11.8/sqrt(epslon_r)   inches/ns

epslon_r = relative dielectric permittivity.

So for my rogers 4350 material i am having DK = 3.66

speed = 6.16 in/ns

my trace length os 2.47 inches. so the signla propogation time = 400 ps.

But my TDR measurement data both simulated and measured is showing around
800 pico seconds. Please see the attached plot.

Can anyone let me know what is the reason on that.

Thank You
SI



------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at: 
                                 http://www.freelists.org/archives/si-list
 
Old (prior to June 6, 2001) list archives are viewable at:
                                 http://www.qsl.net/wb6tpu
 




------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: