From: email@example.com (Mike Monett)
Subject: Re: Aylward, Engelhardt: Noise in a transient sim?
Date: 25 Oct 2002 16:12:50 -0700
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NNTP-Posting-Date: 25 Oct 2002 23:12:51 GMT
"Kevin Aylward" wrote in message news:...
> > Kevin, I don't know how you got so far off track. I'm talking about
> > sampling a repetitive waveform, the same as a conventional Tek or HP
> > sampling scope.
> I know you are.
> >The signal is any waveform that can be viewed on a
> > conventional scope, including eye patterns. The signal can be anything
> > from dc to 7GHz, although dc is somewhat difficult due to thermal
> > drift. Even so, the binary sampler is far better than a diode sampling
> > bridge.
> No problem here. I am taking issue with the claim that the signal has a
> (noise) BW of 7GHz. It most certainly does not.
What's your problem. The instantaneous bandwidth and noise bandwidth
are the same.
> > Conventional sampling scopes have so much noise it is difficult to
> > measure signals below 1mV. With the binary sampler, detecting a 10uV
> > signal is easy, 1uV is difficult, and below 1uV looks unreachable at
> > the moment. This is far better performance than can be obtained with
> > conventional sampling technology.
> > Does this help?
> Ahmm.. I understand all of this very well indeed, this is all very
> elementary. However, it seems that the subtleties I am pointing out are
> not really being appreciated.
That is a good possibility. I have the feeling you are inventing
definitions to suit your arguments. These definitions change depending
on your position. Give me some equations that express your viewpoint,
then we can discuss.
> Yes, the signal can vary from DC to 7 GHz, but this is *not* the same as
> saying that the signal has a *BW* of 7Ghz. The signal is not varying in
> a continuous manner, such that while it is varying, you are extracting
> its information content. You are sampling a fixed repetitive signal,
> therefore it has a very limited BW, therefore you can filter out the
> noise without filtering out the signal.
Not exactly. The signal risetime defines the bandwidth needed to
preserve the frequency components. All I need to know is the
fundamental frequency, then I can give you the waveshape which means
the harmonic content and phase relationship. The same as any
conventional sampling system is defined.
> In summary, you are not measuring a 1uv, 7 GHz BW signal, you are
> measuring a signal that varies from DC to 7Ghz, that has a very limited
> BW. You are confusing signal frequency, with signal BW, they are not the
No, Kevin. Any sampling scope has a defined bandwidth. I am using the
Thank you for realizing the binary sampler has performance advantages
that cannot be achieved with current sampling technology.
Since there is no new information or insight in this thread, there is
little need to continue this discussion.