Re: Continuous-time DSP with no sampling

in article 1131463050.523957.145500@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, Yannis at
ytctdsp@xxxxxxxxx wrote on 11/08/2005 10:17:

>
> robert bristow-johnson wrote:
>> in article 1131399617.730331.219850@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, Yannis at
>> ytctdsp@xxxxxxxxx wrote on 11/07/2005 16:40:
>>
>>> Robert,
>>>
>>> You are beating the wrong horse.
>>
>> i'm sure he deserves it for some other reason i'm not aware of yet.

that was typed tongue-in-cheek.

> No, I meant that your comments in your previous message, which could
> have some validity in some cases, are targeting the wrong person (me).
> You even gave a URL in which somebody is ranting about academics in
> general, making some blanket statements like "they pretend to teach",
> etc. This is an insult to me.

if you're not in that group, the criticism (or "insult") is not directed
toward you.

> See
> http://www.ieee.org/organizations/pubs/newsletters/sscs/oct04/tsividis.html

i'm glad to read that you're a good teacher. i probably hadn't emphasized
the other salient complaint of Anderson: "They represent their research and
writing as important and relevant when much of it is not." i understand
that you sincerely believe this CT DSP to be important and relevant
research, but i can believe that only if there is some reasonable hope that
it will be feasible someday. i do not.

....
>>
>>> if I had let myself be convinced by several people back then that what I was
>>> trying to do was impossible, I would not have tried.
>>
>> then build us a faster-than-light transportation device, because this is
>> sorta similar.
>
> No, there is a better way. It just sounds impossible to you, based on
> the picture you have in mind. The paper you read is two years old. We
> haven't quite sitting since then.

i admire your optimism. but i don't share it.

>>> Fortunately, I did not take their advice, and in the end I was proven right.
>>> I hope history will repeat itself with this work.
>>>
>>> Being relevant in university research does not mean you do not jump
>>> into difficult territory.
>>
>> it should also have promise. and the promise of something better than what
>> is existing technology. that's where i also remain skeptical.
>
> Yes, but you are missing an important point. Sometimes, the promise is
> not evident before solutions are found. And, solutions cannot be found
> unless one tries.

and sometimes the "solution" is hopelessly unfeasible. i doubt, with
sampling rates as high as they are getting, that a CT DSP system as you
describe will ever be preferable, in terms of price/performance, to
sampled-data (at those high frequencies). the noise, due to glitches will
be broadbanded, or in the high frequencies, and if you limit your
application of CT DSP to lower frequency signals, you'll have trouble making
it more feasible than sampled-data. if the unlimited "sampling-rate" is the
selling point for higher frequencies, then the glitches will kill you. it's
unavoidable.

> Thus, if one needs to be 100% sure that something
> works before starting to work on it, they would not even begin.

that is what we call a "strawman argument". i'm not requiring 100%
certainty, only something better than 0%. (and that's where the kernel of
the disagreement is.)

> Again, this was the case with my work with the first fully-integrated MOS op
> amp in the early seventies. So, the best one can do is follow one's intuition.

well, someone's paying for your intuition. the question is whether or not
that's a good investment in this particular case of CT DSP.

> For me, CT DSP has the following promise: no aliasing;

neither does sampled-data for finite BW signals (if the sample rate is high
enough, often that is quite feasible). what infinite BW signals are you
planning to use this technology on (if it were to work).

> no quantization noise at non-harmonic frequencies (for a sine test signal;
> for more general inputs, better spectral properties for the
> quantization error than classical techniques);

certainly, even in the perfect circumstances, you get broadbanded
quantization noise, because you do not have infinite bits.

> and power dissipation that goes down when the input activity is slow or low.

given the same application, say a simple digital filter, i cannot imagine
the power requirement of this CT DSP to be competitive with sampled-data.

> This is enough promise for me; the fact that there are significant problems
> to be solved before this promise can be fulfilled is a *necessary* condition
> for me to be willing to do research.

good, knock yourself out!

> Enough said for now... I do not plan to continue this discussion. But I
> will get back when we have a chip, which may take a year or two.

we'll be waiting with bated breath.


--

r b-j rbj@xxxxxxxxxxxxxxxxxxxx

"Imagination is more important than knowledge."


.

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