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Discussion Groups | Comp.DSP | Difference between Digital and Discrete Signal


There are 27 messages in this thread.

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Difference between Digital and Discrete Signal - Ranga - 2004-10-12 02:45:00

Hi,

Can anyone correct the difference between Digital and Discrete signal?

I feel, digital signals can be one and zero.

But discrete signal can be any numeral, say one, two or ten.

The difference between Analog and Discrete/Digital signal is that
signals are periodic in Digital, while analog signals are continuous.

Please guide me.

Regards,
Ranga.


Re: Difference between Digital and Discrete Signal - Gerard Lyonnaz - 2004-10-12 02:58:00

Ranga wrote:

> Hi,
>
> Can anyone correct the difference between Digital and Discrete signal?
>
> I feel, digital signals can be one and zero.
>
> But discrete signal can be any numeral, say one, two or ten.
>
> The difference between Analog and Discrete/Digital signal is that
> signals are periodic in Digital, while analog signals are continuous.
>
> Please guide me.
>
> Regards,
> Ranga.

A digitized signal is otained most of the time by sampling a discrete
signal,
 once sampled, the signal is digitized (using ADC). For example,
 in telephony, the signal  is sampled at a 8Khz rate, digitized on
13bits,
 and after digitally compressed  using mulaw or alaw.
  Gerard


Re: Difference between Digital and Discrete Signal - Fred Marshall - 2004-10-12 03:42:00

"Gerard Lyonnaz" <g...@hp.com> wrote in message 
news:4...@hp.com...
> Ranga wrote:
>
>> Hi,
>>
>> Can anyone correct the difference between Digital and Discrete signal?
>>
>> I feel, digital signals can be one and zero.
>>
>> But discrete signal can be any numeral, say one, two or ten.
>>
>> The difference between Analog and Discrete/Digital signal is that
>> signals are periodic in Digital, while analog signals are continuous.
>>
>> Please guide me.
>>
>> Regards,
>> Ranga.
>
> A digitized signal is otained most of the time by sampling a discrete
> signal,
> once sampled, the signal is digitized (using ADC). For example,
> in telephony, the signal  is sampled at a 8Khz rate, digitized on
> 13bits,
> and after digitally compressed  using mulaw or alaw.
>  Gerard
>

Hmmmmm.....

I'd say that a discrete signal is a sequence of samples - no matter how 
those samples occur or how they are represented.  They could be generated by 
a mathematical expression, etc.  There's lots of analysis and texts on 
discrete systems - without mention of how the representation of the values 
of the samples is implemented.  There are also lots of examples of discrete 
systems that use "analog" storage mechanisms - like charge-coupled devices, 
bucket-brigade or switched capacitor filters, etc.

A digital signal is necessarily discrete.  To make it digital as well means 
the values are described using finite precision arithmetic.

The sample rate or interval, uniform or nonuniform has nothing to do with 
it.

I don't agree that: "A digitized signal is otained most of the time by 
sampling a discrete signal"

That's because sampling is the process that might be used to generate the 
discrete signal in the first place.  Then you need to talk about 
representation and storage.

Rather, I'd say that "A digitized signal is obtained most of the time by 
sampling a continuous signal (as with a sample-hold) and storing the result 
using finite precision arithmetic (as out of an ADC) - as would be found in 
a digital computer."  The latter is where the term "analog to digital 
converter" takes its meaning.

Fred


Re: Difference between Digital and Discrete Signal - mk - 2004-10-12 04:10:00

On 11 Oct 2004 23:45:45 -0700, r...@rediffmail.com (Ranga)
wrote:

>Hi,
>
>Can anyone correct the difference between Digital and Discrete signal?

In this context, signals can be quantized and sampled. Not all sampled
signals are quantized (ie signals in a switched capacitor filter) and
not all quantized signals are sampled (output of an analog
comparator). A discrete signal is one which is sampled but not
necessarily quantized. A digital signal is one which is sampled and
quantized. So all discrete signals are digital but not vice versa.
An analog to digital converter is a good example of a system where all
domains appear at once and shows how processing can be done at all
domains. The analog signal is conditioned (possibly with a low pass
and/or an analog matched filter) at the input, applied to a
sample-hold filter with analog values and then quantized with
comparators set at different thresholds (in a flash converter). These
blocks can be ordered differently based on your requirements.

hth.


Re: Difference between Digital and Discrete Signal - 2004-10-12 10:18:00

Hi,

   Read the First chapter in the book " Digital Signal Processing" A
Computer based approach by SK Mithra, TMH.

  Sathish

"Ranga" <r...@rediffmail.com> wrote in message
news:6...@posting.google.com...
> Hi,
>
> Can anyone correct the difference between Digital and Discrete signal?
>
> I feel, digital signals can be one and zero.
>
> But discrete signal can be any numeral, say one, two or ten.
>
> The difference between Analog and Discrete/Digital signal is that
> signals are periodic in Digital, while analog signals are continuous.
>
> Please guide me.
>
> Regards,
> Ranga.


Re: Difference between Digital and Discrete Signal - Sandeep Chikkerur - 2004-10-12 23:29:00

"Sathish" <s...@de.bosch.com> wrote in message news:<ckgp47$gt6$1...@ns2.fe.internet.bosch.com>...
> Hi,
> 
>    Read the First chapter in the book " Digital Signal Processing" A
> Computer based approach by SK Mithra, TMH.
> 
>   Sathish
> 
> "Ranga" <r...@rediffmail.com> wrote in message
> news:6...@posting.google.com...
> > Hi,
> >
> > Can anyone correct the difference between Digital and Discrete signal?
> >
> > I feel, digital signals can be one and zero.
> >
> > But discrete signal can be any numeral, say one, two or ten.
> >
> > The difference between Analog and Discrete/Digital signal is that
> > signals are periodic in Digital, while analog signals are continuous.
> >
> > Please guide me.
> >
> > Regards,
> > Ranga.

Hi,

Discrete Signals : 
Obtained by sampling the analog signal at disctrete instants of time.
However the magnitude of the discrete signals is same as that of the
analog signal at that point in time.
(Discrete only in time)

Digital Signal :
When the magnitude of the discrete signal is quantized to the the
nearest integer, we get a digital signal.
(Which is both discrete in magnitude & time)

Example:
Say, after sampling the analog signal, we get discrete signal as below
x[0] = 0
x[1] = 0.9
x[2] = 1.8
x[3] = 2.6
x[4] = 2.1
x[5] = 1.8 ....

When you want to digitize this signal, you pass it through the ADC &
the output
would be as below.
x[0] = 0
x[1] = 1
x[2] = 2
x[3] = 3
x[4] = 2
x[5] = 2...

The above output depends upon the resolution of the ADC .
More the resolution, less the quantization error.

I hope this helps your question.

Regards
Sandeep


Re: Difference between Digital and Discrete Signal - Rick Lyons - 2004-10-13 08:46:00

On 12 Oct 2004 20:29:41 -0700, s...@yahoo.com (Sandeep
Chikkerur) wrote:

  (snipped)
>
>Hi,
>
>Discrete Signals : 
>Obtained by sampling the analog signal at disctrete instants of time.
>However the magnitude of the discrete signals is same as that of the
>analog signal at that point in time.
>(Discrete only in time)
>
>Digital Signal :
>When the magnitude of the discrete signal is quantized to the the
>nearest integer, we get a digital signal.
>(Which is both discrete in magnitude & time)
>
>Example:
>Say, after sampling the analog signal, we get discrete signal as below
>x[0] = 0
>x[1] = 0.9
>x[2] = 1.8
>x[3] = 2.6
>x[4] = 2.1
>x[5] = 1.8 ....
>
>When you want to digitize this signal, you pass it through the ADC &
>the output
>would be as below.
>x[0] = 0
>x[1] = 1
>x[2] = 2
>x[3] = 3
>x[4] = 2
>x[5] = 2...
>
>The above output depends upon the resolution of the ADC .
>More the resolution, less the quantization error.
>
>I hope this helps your question.
>
>Regards
>Sandeep

Hi,

  very nice explanation!  This is good.

[-Rick-]


Re: Difference between Digital and Discrete Signal - Jerry Avins - 2004-10-13 16:49:00

Rick Lyons wrote:

> On 12 Oct 2004 20:29:41 -0700, s...@yahoo.com (Sandeep
> Chikkerur) wrote:
> 
>   (snipped)
> 
>>Hi,
>>
>>Discrete Signals : 
>>Obtained by sampling the analog signal at disctrete instants of time.
>>However the magnitude of the discrete signals is same as that of the
>>analog signal at that point in time.
>>(Discrete only in time)
>>
>>Digital Signal :
>>When the magnitude of the discrete signal is quantized to the the
>>nearest integer, we get a digital signal.
>>(Which is both discrete in magnitude & time)
>>
>>Example:
>>Say, after sampling the analog signal, we get discrete signal as below
>>x[0] = 0
>>x[1] = 0.9
>>x[2] = 1.8
>>x[3] = 2.6
>>x[4] = 2.1
>>x[5] = 1.8 ....
>>
>>When you want to digitize this signal, you pass it through the ADC &
>>the output
>>would be as below.
>>x[0] = 0
>>x[1] = 1
>>x[2] = 2
>>x[3] = 3
>>x[4] = 2
>>x[5] = 2...
>>
>>The above output depends upon the resolution of the ADC .
>>More the resolution, less the quantization error.
>>
>>I hope this helps your question.
>>
>>Regards
>>Sandeep
> 
> 
> Hi,
> 
>   very nice explanation!  This is good.

Except, to pick a nit, digital signals can also be, and sometimes are,
generated by computation.

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


Re: Difference between Digital and Discrete Signal - glen herrmannsfeldt - 2004-10-13 17:23:00

Jerry Avins wrote:

(snip on discretizing, digitizing and sampling)

> Except, to pick a nit, digital signals can also be,
 >  and sometimes are, generated by computation.

I have a whole CD of audio test signals that I believe
was generated by computation.   If you want a sine wave
it is most accurate to compute it than digitize an
analog wave.

For a philosophy question, is it sampling and digitizing
a virtual analog signal?

-- glen


Re: Difference between Digital and Discrete Signal - Jerry Avins - 2004-10-13 17:48:00

glen herrmannsfeldt wrote:

> 
> 
> Jerry Avins wrote:
> 
> (snip on discretizing, digitizing and sampling)
> 
>> Except, to pick a nit, digital signals can also be,
> 
>>  and sometimes are, generated by computation.
> 
> I have a whole CD of audio test signals that I believe
> was generated by computation.   If you want a sine wave
> it is most accurate to compute it than digitize an
> analog wave.
> 
> For a philosophy question, is it sampling and digitizing
> a virtual analog signal?

I guess that to some extent, it depends on the actual code.

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


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