Ibis simulation versus Measurement

     Hello,
     
     lately I have been using an Ibis model of a clock. As I use a Quad
     simulator, the Ibis model is converted to a Quad model. Although a V-T
     table is included to describe the waveform, there is a distinct
     difference between the rising and falling edge in simulation and
     measurement. Even when taking into account probe loading and
     oscilloscope filtering, the simulated edges cannot match the
     measurement. The step in the clock output (caused by transmission line
     loading and reflected wave effects), visible in the simulation, is not
     seen on the oscilloscope screen. I tried to modify the waveform, which
     by the way is normalised in Quad, but with unsatisfactory results.
     
     Tested are:
     
     - the waveform supplied with the clock model
     - a straight line
     - a sinusoidal form
     - no waveform at all (deleted)
     
     Especially the straight line shows a sharp step, the worst of all. The
     last one (no waveform at all) shows the least visible step, and thus
     is the best (with respect to the rising/falling edge form). Thus one
     would ask oneself, why taking the trouble of including those
     waveforms?
     
     Is there someone with a similar experience?
     Or does someone have some recommendations?
     
     
     Best Regards
     
     Alex Hilbers
     ahilbers@tulip.nl
     
 
Received on Fri Feb 28 02:39:53 1997