[sdiy] Is everything digital?

[Aaron Lanterman]

On Sat, 14 May 2005, The Old Crow wrote:

>  My only other comment on this topic is how I perceive digital vs.
> analog:
>
>  discrete time domain = digital
>
>  continuous time domain = analog

I think really you need a matrix with "value" along one axis and "time" 
across the other to describe the cases, like this:

discrete-time, discrete-value      discrete-time, continuous-value
continuous-time, discrete-value    continuous-time, continuous-value

When I teach about FIR and IIR filters and such in ECE2025, Introduction 
to Signal Processing, and make kids do homework assignments, it's 
discrete-time, continuous-value. When the kids implement things in MATLAB, 
it winds up discrete-time, discrete-value, but that's incidental. We don't 
really discuss finite word length effects until ECE4270, which is our 
Oppenheim and Schafer course. The text we use is called "Discrete-Time 
Signal Processing," since it's the discrete-time part - giving you 
z-transforms, etc., dealing with sampling effects, aliasing, etc. - that 
really gives the field it's character, even though it's more often called 
"digital signal processing."

BBD's would be discrete-time, continuous-valued processing. BDD's are 
sampled data systems but they're certainly not digital. ;)

- Aaron

-----------------------------------------------------------------------------

Dr. Aaron Lanterman, Asst. Prof.       Voice:  404-385-2548
School of Electrical and Comp. Eng.    Fax:    404-894-8363
Georgia Institute of Technology        E-mail: lanterma at ece.gatech.edu
Mail Code 0250                         Web:    users.ece.gatech.edu/~lanterma
Atlanta, GA 30332                      Office: GCATT 334B