[SI-LIST] Re: (no subject)
- From: "D G" <dgun@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 17 Dec 2002 02:59:32 +0800
Sandor,
You may have already seen Glen Walpert's e-mail. I'll copy the
pertinent URL below:
http://www.picosecond.com/objects/AN-13.pdf
You are correct that this is not the dispersion with respect to
dielectrics (PCB material in particular) that was asked about. I
brought it up as a specific example of what Jim Knighten mentioned:
"Rounding of edges: If a dispersive medium propagates high
frequencies faster than low frequencies, it is quite possible to see
edges in a time domain pulse sharpened, rather than rounded
(degraded)."
- Daniel
From: "Sandor" <sandor@xxxxxxxxxx>
> A selfgratifying thought experiment: Let's pass a wave through a
> dispersive medium. For simplicity's sake, take a perfect square wave.
> The wave will be distorted (rounded in the practical sense, unless
> having some really wacky dispersion characteristics) at the other end -
> on both rising and falling edges. Now we pass the distorted wave
> through a dispersive medium with (exactly) the inverse dispersion
> characteristics. We should get our original square wave back - perfect
> on both rising and falling edges.
>
> In Daniel's example, if the sharpening/rounding happens asymmetrically
> on the rising and falling edges, then that must be because the wave
> wasn't perfectly symmetrical on the rising and falling edges in the
> first place. Again, a simple example: if the rising edge nicely rounded
> but the falling edge is perfectly square, a medium that propagates high
> frequencies faster, depending on the actual characteristics, can sharpen
> the rising edge but it will smear the falling one.
>
> Daniel, could you provide me with some pointers about what you were
> referring to when you mentioned sampling technology? If it's about
> shifting sampled points in some fashion, it doesn't seem analogous to
> dispersion in the sense this discussion thread was using this
> terminology.
>
> Regards,
>
> Sandor
>
> ------------------------------------------------------------------
> Sandor Daranyi
> Senior Design Engineer
> Aristocrat Technologies Australia Pty Limited
>
>
> > -----Original Message-----
> > From: D G [mailto:dgun@xxxxxxxxxx]
> > Sent: Thursday, 12 December 2002 5:32
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: (no subject)
> >
> >
> >
> > Jim,
> >
> > This is true, and is used to good effect in sampling
> > technology. However, if I'm not mistaken, the sharpening of
> > the rising edge comes at the expense of the falling edge,
> > which becomes more "rounded".
> >
> > - Daniel
> >
> > From: "Knighten, Jim L" <JK100005@xxxxxxxxxxxxxxxx>
> > >
> > > Jeff,
> > >
> > > Here's one for the dead horse:
> > >
> > > Rounding of edges: If a dispersive medium propagates high
> > frequencies
> > > faster than low frequencies, it is quite possible to see
> > edges in a time
> > > domain pulse sharpened, rather than rounded (degraded).
> > >
> > > Jim
> > >
> > >
> > > Jim Knighten, Ph.D.
> > > Teradata, a Division of NCR http://www.ncr.com
> > > 17095 Via Del Campo
> > > San Diego, CA 92127
> > > USA
> > > Tel: 858-485-2537
> > > Fax: 858-485-3788
> > > jim.knighten@xxxxxxx
> > >
> _____________________________________________________________
>
>
--
Daniel
ZZZ-dgun-ZZZ-@xxxxxxxxxxxxxxx
(remove the Z-'s to reply--they're what I do when I read spam)
--
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