Rocky Mountain Chapter EMC Society |
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Our last meeting was .. Practical
Analysis of Lossy Transmission Lines Presenter: Dr. Eric Bogatin, Chief Technical Officer, Giga Test Labs. What we saw: : Dr Bogatin took
time from his busy schedule visit us and " take the
lid off" the mysteries of transmitting high
frequency signals acoss backplanes. The basic problem is
that transmission lines begin to attenuate signals at
high frequency, some more than others. In this lecture we
looked at what design and material factors influence the
signal losses and how to measure, model and simulate
these effects. Eric started the talk with the obvious
question...Why worry about lossy lines.?? The answer is
that losses in the transmission line attenuate the signal
resulting in collapse of the eye diagram. After showing
the frequency effects in the time domain, a frightning
detail was presented - for high frequency signalling 1ns
rise time becomes a show stopper. Eric then presented the
physics behind the losses in a transmission line both DC
and AC as well as some practical approximations for
modeling the effects of the conductance and the
resistance. The next part of the talk addressed the
impact on signal integrity from the losses.Using clear
and simple charts Eric demonstrated how the amplitude of
a clock is affected by varing dissipation factors and
then posulated the obvious question - How does one
measure dissipation factor? In the last segment, Eric
discussed how dissipation factors may be measured
utilizing specialized equipment. Eric also discussed some
surprising results of measurements of transmission lines
including vias. In conclusion, the largest limiting
factor of transmitting high frequency signals is the
attenuation in the laminate. Accurate determination of
the disspation factor is vital for proper simulation of
the effects. 37 people came to the Chapter meeting of
which 12 or so were new attendees. Biography: Eric is the Chief Technical Officer at GigaTest Labs, specializing in the accessories for optimizing high bandwidth, Signal Integrity Measurements. GiaTest also provides help for customers designs, and provides services for the measurement , characterizantion and troubleshooting for high bandwidth products. They also provide comprehensive Signal Integrity training, emphasizing practical engineering techniques. In addition to private and public short courses from fundamental to advanced levels, Dr. Bogatin publishes many papers on Signal Integrity topics. A number of them are available for free download from the GigaTest Labs web site. Differential Impedance Finally Made Simple - Dr. Bogatins previous presentation to the RMCEMC is also available. Click here to download. ************************************** Contact Information: Eric Bogatin
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