🚀 go-pugleaf

Hi,

I hope this question belongs to this news group as I could not find a 
group which talks only about A/D conversion specifically.

PAM is a quite simple concept, yet, no two authors seems to agree on 
one thing. I have read several books and could not understand what 
the authors in general mean. 

I made the following two diagrams that I have not seen in any 
communication book. This is what I think about the PAM natural
sampling and flat-topped sampling. Please, if someone disagrees with
me send me an email, though, I will appreciate any comments.


1) The following is natural sampling PAM diagram that I made with a LPF
and an impulse train. What I have seen in almost every communication book
is a pulse train at the mixer. However, I modeled pulse train with an 
impulse train and a LPF. I think that in doing so one can understand 
flat-topped PAM better which is shown in the figure of #2.


                            Mixer 
                            
   Analog(message) ----------(X)------> PAM with natural sampling
    Signal input              |
                              |
                              |
                           -------
                           | LPF |
                           -------
                              |
                              |
         Impluse train--------|



2) All I did here is moved the LPF in the output branch from the input
branch. Since LPF transfer function is similar to an integrator, 
any product of the impulse and the analog-message siganal will be held. 
Thus, we will have sample and hold circuitry in the output branch.




                                   -------
Analog(message) ----------(X)------| LPF |----> Flat-topped PAM
 Signal input              |       -------
                           |
                           |
                           |
                           |
      Impluse train--------|


I have eliminated math as it is not possible to the summation 
signs and other symbols in ascii.

iqbal@sioux.eel.ufl.edu


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