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From: markt on 6 May 2008 16:05
>3. Does anyone have a link where I can read up on all of this myself?
>The standard DSP books don't seem too helpful...

I would recommend any application notes from companies that design A/D
converters. Analog Devices, National Semiconductor, Atmel, Maxim, TI,
etc., all have good app notes as I recall. I think I've read Tim's papers
as well at one time or another.

Mark
From: PRCalDude on 6 May 2008 16:53
>On Tue, 06 May 2008 07:32:34 -0500, PRCalDude wrote:
>
>> Hi all,
>>
>> I'm new to this board and need some steering in the right direction.
>>
>> I've been trying to understand spec sheets for high speed digitizers
and
>> had several questions:
>>
>> 1. What does "form factor" tell you?
>
>Usually that means the physical form of the card; it's often taken to
>mean what the card is compatible with (ISA, VME, etc).
>
>> 2. What is the relationship
>> between MSPS (mega samples/s) and bandwidth? For example, I saw one
card
>> that touted a 250 MHz BW, but only supported 105 MSPS signal capture
>> rate. Shouldn't the signal capture rate be much higher?
>
>Not necessarily. You're assuming that the card should do anti-aliasing.

>But if you're going to use the card to sub-sample bandlimited data (as is

>done in radios) or to sample non-stationary or non-Gaussian data with
>high signal-to-noise ratios then you want the most bandwidth you can
>get. I have a paper that touches on this: http://www.wescottdesign.com/
>articles/Sampling/sampling.html.
>
>Note that the sampler's window duration and jitter performance will limit

>a data acquisition system's high-frequency performance just as easily as

>the bandwidth will. Since these specifications will be buried (or
>nonexistent), and possibly hard to interpret, you'll have to dig for
them.
>
>> 3. Does anyone have a link where I can read up on all of this myself?
>> The standard DSP books don't seem too helpful...
>
>Not that I know of, although hopeful titles would be like "analog to
>digital conversion applications" or "data acquisition applications". If

>there is a book I'd like to hear about it; in the mean time this is
>something that one absorbs with experience (and by asking questions in
>newsgroups).
>
>"Standard DSP" books teach theory, and do so very well. _Applying_ the
>theory is left as an exercise to the reader.
>
>--
>Tim Wescott
>Control systems and communications consulting
>http://www.wescottdesign.com
>
>Need to learn how to apply control theory in your embedded system?
>"Applied Control Theory for Embedded Systems" by Tim Wescott
>Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
>
Mark, Tim,

Thanks a lot.

Tim,

I'll try to digest some of your papers and then post some follow up
questions on this thread.
From: markt on 6 May 2008 17:38
Oh, I should add, Pentek (www.pentek.com) has some stuff on their website
that may be of interest as well. They would be particularly useful if
you're purchasing some sort of receiver board (if you aren't already
looking at theirs in particular). I say that because you mentioned "form
factor," which implies you may not be delving directly into an ADC itself,
but a product that uses an ADC in some fashion. Their stuff tends to be a
bit adverty for their own products, but just about any app note is. You
get used to that. :)

I don't own any stock in Pentek, but I am doing a system design with one
of their boards at the moment, hehe.

Mark
From: Jerry Avins on 6 May 2008 17:47
PRCalDude wrote:
> Hi all,

...

> I've been trying to understand spec sheets for high speed digitizers and
> had several questions:

...

> The standard DSP books don't seem too helpful...

That's because analog-to-digital converters are primarily analog gizmos.
You need to be conversant with analog specs to understand them. Data
sheets and application notes from (of all people) Analog Devices Inc.
can be very helpful. Other makers also produce nifty and informative
literature.

Jerry
--
Engineering is the art of making what you want from things you can get.
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