I don't have any problem with going on the Net with this.
     
     This is more of a theoretical issue than anything else.  Not really 
     related to IPC.  With all the talk about too much mail, I decided to 
     throw the issue on the net with the option to email direct.
     
     So without any further talk, here goes:
     
     I am trying to write a technical paper for my company on what I have 
     found.
     
     My basic model was based on a lumped parameter model of a one inch 
     copper trace with one end terminated with a signal source, the trace 
     lumped with trace resistance and trace inductance in series, to a 
     termination of a resistor (load) and capacitor (dielectric) in 
     parallel.
     
     I drop into the frequency domain with Laplace and write my system 
     response.  
     
     Up to this point, I am still in line with any cross check of a similar 
     circuit in any circuit analysis book.  If anyone is into it, I'm 
     following the basic derivation of telegraph/telephone equations for 
     transmission line signal analysis.  OK, so big deal.
     
     Now, I plug in "standard" values for the lumped parameters of copper 
     trace resistance per inch, copper trace inductance per inch...
     
     I DERIVE the impedance of the trace using IPC impedance relation for a 
     stripline trace.  From this, I derive capacitance per inch.  This is 
     where I'm a little skittish about what I'm doing.
     
     If I set the load resistance to infinity, I get a large resonant spike 
     at about 800 MHz.  If I adjust the load resistance to below 150 ohms, 
     the spike goes away.  To anyone interested, I'm playing around with 
     the system damping factor from my second order system response 
     equation.  Alright, so what???
     
     No matter what I do with the load resistance, there is a large 
     roll-off above 800 MHz.  Like 40 dB!!!
     
     I'm using MathCad for printable output.  I have Word, Wordperfect, 
     Excel, and MathCad software on an IBM compatible 486/66 MHz machine.
     
     So far, I have had two people say that they are interested, a third 
     has had no problem with boards (ECL based circuitry - I was sort of 
     expecting that), a fourth has seen designers wrestle with running 
     simulations - looking at results - do a little adjusting - run 
     simulation again and so on for a couple of weeks (Spice based).
     
     Doug McKean
     ADC Video Systems
     
     Tel: 203-630-5788
     email: [log in to unmask]