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How does PCM-Demodulation work?

Started by Green Xenon [Radium] April 25, 2008
Hi:

How does a PCM-demodulator work?


Thanks,

Radium
"Green Xenon [Radium]" <glucegen1@excite.com> writes:

> Hi: > > How does a PCM-demodulator work? > > > Thanks, > > Radium
Lookup A/D and D/A conversion. -- % Randy Yates % "...the answer lies within your soul %% Fuquay-Varina, NC % 'cause no one knows which side %%% 919-577-9882 % the coin will fall." %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO http://www.digitalsignallabs.com
Randy Yates wrote:
> "Green Xenon [Radium]" <glucegen1@excite.com> writes: > >> Hi: >> >> How does a PCM-demodulator work? >> >> >> Thanks, >> >> Radium > > Lookup A/D and D/A conversion.
So a PCM-demodulator is the same thing as a DAC?
"Green Xenon [Radium]" <glucegen1@excite.com> writes:

> Randy Yates wrote: >> "Green Xenon [Radium]" <glucegen1@excite.com> writes: >> >>> Hi: >>> >>> How does a PCM-demodulator work? >>> >>> >>> Thanks, >>> >>> Radium >> >> Lookup A/D and D/A conversion. > > > So a PCM-demodulator is the same thing as a DAC?
I'm guessing so. In almost 30 years, I've never heard of a PCM-demodulator, but I am getting old and senile. Where did you come across this term? -- % Randy Yates % "I met someone who looks alot like you, %% Fuquay-Varina, NC % she does the things you do, %%% 919-577-9882 % but she is an IBM." %%%% <yates@ieee.org> % 'Yours Truly, 2095', *Time*, ELO http://www.digitalsignallabs.com
On Apr 25, 1:01&#2013266080;am, "Green Xenon [Radium]" <gluceg...@excite.com>
wrote:
> Hi: > > How does a PCM-demodulator work? > > Thanks, > > Radium
Like Randy I have have never seen the exact term "PCM Demodulator" and I expect it is some kind of marking speak for a simple D/A process. But google is a freind and offers up this site: http://www.sunequipco.com/LABS/DCL-10300/DCL-10300.htm They will teach you all about such named devices. IHTH, Clay
Green Xenon [Radium] wrote:
> Hi: > > How does a PCM-demodulator work? > > > Thanks, > > Radium
Here is analog methodology. But you still have to synchronize to the beginning of a symbol (called pulse group here). http://www.tpub.com/content/neets/14184/css/14184_178.htm PCM is somewhat broad. You need a way to synchronize correctly (depends on the specifics). In a digital implementation, it is a matter of clocking in the serial pulse state (present or not) into something that will generate the digital sample value (i.e. serial-to-parallel register). This can then be clocked to the DAC. Cheers, J.Elms
On Apr 25, 12:01 am, "Green Xenon [Radium]" <gluceg...@excite.com>
wrote:
> Hi: > > How does a PCM-demodulator work? > > Thanks, > > Radium
Your question is very broad. Once an analog signal has been sampled and put into PCM form (e.g., A/D samples), the resulting PCM bits can then be used to modulate a carrier in a variety of ways (QPSK, FSK, BPSK, etc). Thus, a PCM demodulator would require, for example, a QPSK or FSK demodulator. This demodulator would output a stream of PCM bits which represent samples of an analog signal. This technique is sometimes used when conveying analog channels in a time-division multiplexed scheme. Darol Klawetter
Randy Yates wrote:
(snip)

> I'm guessing so. In almost 30 years, I've never heard of a > PCM-demodulator, but I am getting old and senile. Where did you come > across this term?
Well, the M is for modulation, but I agree using the term "demodulator" in that case is unusual. In the past, other modulation methods such as PWM (pulse width modulation) were used. In that case, a real demodulator makes some sense. Compare to demodulating an AM-SC (Amplitude modulation - suppressed carrier) signal like the stereo subcarrier. For PWM, even as a 'digital' signal, the demodulation is somewhat analog. For PWM, you might have a PLL to lock onto the bit stream (such as that coming off a CD), but the actual demodulation is the D/A converter. -- glen
Randy Yates wrote:
> "Green Xenon [Radium]" <glucegen1@excite.com> writes: > >> Randy Yates wrote: >>> "Green Xenon [Radium]" <glucegen1@excite.com> writes: >>> >>>> Hi: >>>> >>>> How does a PCM-demodulator work? >>>> >>>> >>>> Thanks, >>>> >>>> Radium >>> Lookup A/D and D/A conversion. >> >> So a PCM-demodulator is the same thing as a DAC? > > I'm guessing so. In almost 30 years, I've never heard of a > PCM-demodulator, but I am getting old and senile. Where did you come > across this term?
There is AM-demodulation and FM-demodulation. So why not PCM-demodulation?
glen herrmannsfeldt wrote:
> Randy Yates wrote: > (snip) > >> I'm guessing so. In almost 30 years, I've never heard of a >> PCM-demodulator, but I am getting old and senile. Where did you come >> across this term? > > Well, the M is for modulation, but I agree using the term > "demodulator" in that case is unusual. > > In the past, other modulation methods such as PWM (pulse width > modulation) were used. In that case, a real demodulator makes > some sense. Compare to demodulating an AM-SC (Amplitude > modulation - suppressed carrier) signal like the stereo > subcarrier. > > For PWM, even as a 'digital' signal, the demodulation is > somewhat analog. For PWM, you might have a PLL to lock onto > the bit stream (such as that coming off a CD), but the actual > demodulation is the D/A converter. > > -- glen >
A PCM-demodulator does to a PCM-signal what an AM-demodulator does to an AM-signal which is also what an FM-demodulator does to an FM-signal. I know how AM/FM demodulation work. I am just curious as to how PCM-demodulation works. From that start, I've also believed that PCM-demodulation has nothing to do the DAC conversion at all.