On Sep 14, 11:58�am, Rune Allnor <all...@tele.ntnu.no> wrote:> On 14 Sep, 17:33, Jerry Avins <j...@ieee.org> wrote: > > > Maybe Matlab isn't a drug after all! :-) > > Depends on what you mean by 'drug.' If something-that- > blunts-down-intellectual-skills-and-advances-lethargy > qualifies, it certainly is. > > RuneThe word is "obtunds" Clay
Digital modulation - In digital domain or analog..?
Started by ●September 11, 2009
Reply by ●September 17, 20092009-09-17
Reply by ●September 17, 20092009-09-17
On 17 Sep, 17:46, Clay <c...@claysturner.com> wrote:> On Sep 14, 11:58�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > On 14 Sep, 17:33, Jerry Avins <j...@ieee.org> wrote: > > > > Maybe Matlab isn't a drug after all! :-) > > > Depends on what you mean by 'drug.' If something-that- > > blunts-down-intellectual-skills-and-advances-lethargy > > qualifies, it certainly is. > > > Rune > > The word is "obtunds"Thanks! If my mind wasn't already so obtused, I might actually start using it... Rune
Reply by ●September 17, 20092009-09-17
Clay wrote:> On Sep 14, 11:58 am, Rune Allnor <all...@tele.ntnu.no> wrote: >> On 14 Sep, 17:33, Jerry Avins <j...@ieee.org> wrote: >> >>> Maybe Matlab isn't a drug after all! :-) >> Depends on what you mean by 'drug.' If something-that- >> blunts-down-intellectual-skills-and-advances-lethargy >> qualifies, it certainly is. >> >> Rune > > The word is "obtunds"Clay, I know a lot of words. Thanks for a new one. It's much better than "de-enhances". Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●September 17, 20092009-09-17
Rune Allnor <allnor@tele.ntnu.no> writes:> On 12 Sep, 00:13, Randy Yates <ya...@ieee.org> wrote: >> arun <arunkumar...@gmail.com> writes: >> > HI, >> >> > I am new to this group. I have very basic doubt about >> > digital modulation. >> > We modulate the carrier frequency based on the digital input values... >> > So is the output of modulator block a digital signal with samples >> > representing the modulated carried signal or is it a modulated >> > continous (analog) signal.. >> >> arun, >> >> The output of any real-world modulator is always going to be >> analog. Even in the theoretical world, the purpose of the modulator is >> to transform from discrete-time to continuous-time. > > Wouldn't this conversion be the task of the DAC?Hi Rune, Sorry for the delay - I just now noticed your post. You could do it with a DAC (and associated preprocessing), of course. But the operation is more generic than that of a DAC. Think of a "device" that takes N = log_2(M) bits in (for an M-ary modulation) and generates M (distinct) analog waveforms. That's a modulator. A DAC, OTOH, simply converts a natural or signed binary number into a DC level. example, the pulse shaping used for simple binary PAM is performed in the modulator. At least this is Proakis's presentation. -- Randy Yates % "Though you ride on the wheels of tomorrow, Digital Signal Labs % you still wander the fields of your mailto://yates@ieee.org % sorrow." http://www.digitalsignallabs.com % '21st Century Man', *Time*, ELO
Reply by ●September 18, 20092009-09-18
On 17 Sep, 23:17, Randy Yates <ya...@ieee.org> wrote:> Rune Allnor <all...@tele.ntnu.no> writes: > > On 12 Sep, 00:13, Randy Yates <ya...@ieee.org> wrote: > >> arun <arunkumar...@gmail.com> writes: > >> > HI, > > >> > =A0 =A0I am new to this group. I have very basic doubt about > >> > digital modulation. > >> > We modulate the carrier frequency based on the digital input values.=..> >> > So is the output of modulator block a digital signal with samples > >> > representing the modulated carried signal or is it a modulated > >> > continous (analog) signal.. > > >> arun, > > >> The output of any real-world modulator is always going to be > >> analog. Even in the theoretical world, the purpose of the modulator is > >> to transform from discrete-time to continuous-time. =A0 > > > Wouldn't this conversion be the task of the DAC? > > Hi Rune, > > Sorry for the delay - I just now noticed your post. > > You could do it with a DAC (and associated preprocessing), of > course. But the operation is more generic than that of a DAC. Think of a > "device" that takes N =3D log_2(M) bits in (for an M-ary modulation) and > generates M (distinct) analog waveforms. That's a modulator. > > A DAC, OTOH, simply converts a natural or signed binary number into a DC > level. =A0example, the pulse shaping used for simple binary PAM is > performed in the modulator. > > At least this is Proakis's presentation.That question was the first of a couple of posts in this thread I posted the same day. The next post made me think through the system in some more detail, and you are right. The DAC takes the digitized signal to an intermediate analog signal, which is not strictly needed in a digital system. Rune
Reply by ●September 24, 20092009-09-24
On Sep 17, 3:42�pm, Jerry Avins <j...@ieee.org> wrote:> Claywrote: > > On Sep 14, 11:58 am, Rune Allnor <all...@tele.ntnu.no> wrote: > >> On 14 Sep, 17:33, Jerry Avins <j...@ieee.org> wrote: > > >>> Maybe Matlab isn't a drug after all! :-) > >> Depends on what you mean by 'drug.' If something-that- > >> blunts-down-intellectual-skills-and-advances-lethargy > >> qualifies, it certainly is. > > >> Rune > > > The word is "obtunds" > > Clay, I know a lot of words. Thanks for a new one. It's much better than > "de-enhances". > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������Hello Jerry, I'm quite sure you know more words than most people. I first came across this term while reading about "pumphead syndrome." This happens to people on heart lung machines where the machine damages some blood cells and/or perfuses micro airbubbles that reduce blodd flow to the brain. The patient suffers reduced cognitive ability for awhile - maybe up to a year. Also the medical literature discribes patients who suffered brain trauma as being "obtunded." I thought this term perfectly fitted what Rune described even if the cause is different ;-) Clay
Reply by ●September 27, 20092009-09-27
>HI, > > I am new to this group. I have very basic doubt about >digital modulation. >We modulate the carrier frequency based on the digital input values... >So is the output of modulator block a digital signal with samples >representing the modulated carried signal or is it a modulated >continous (analog) signal.. > > > >Thanks in advance, >arun >Hi Arun, If we are talking about the signal that gets transmitted ultimately then that has to be analog. I guess you meant 'discrete-time domain' rather than 'digital domain' and 'continuous-time domain' rather than 'analog domain'. The implementation of the modulator mentioned by you can be in 'discrete-time domain' or 'continuous-time domain'. If it is in discrete-time domain, then we operate on samples. Now the practical implementation using digital electronics will convert these discrete-time signals to digital signal, where the samples are represented as a sequence of bits. Then we need to convert the output digital signal to continuous-time analog signal by using a digital-to-analog converter (DAC). This is what happens in all digital communications systems that use digital electronics. In short, in discrete-time digital implementation, we 'sample' signals (sampled signals are still analog) and then use digital electronics to actually implement the functionality. In continuous-time implementation, the continuous-time digital modulating signal will modulate the continuous-time analog carrier, giving out a continuous-time analog signal. Cheers, Nikhil
Reply by ●September 27, 20092009-09-27
Nikhil A D <nikhil2385@gmail.com> wrote: <> I am new to this group. I have very basic doubt about <>digital modulation. <>We modulate the carrier frequency based on the digital input values... <>So is the output of modulator block a digital signal with samples <>representing the modulated carried signal or is it a modulated <>continous (analog) signal.. (snip) < If we are talking about the signal that gets transmitted < ultimately then that has to be analog. This reminds me of the discussion about modulation and modems, with the suggestion that the device used to connect up DSL is not a modem because the output is digital and not analog. Continuing on, what do we mean when we say "digital signal?" Anyway, yes the device needed for DSL is a modem. (Some may argue a difference between baseband and non-baseband, but that doesn't seem so significant in most cases.) The names for the modulation methods are often different (even for the same physics), but yes in the end the result is an analog signal. -- glen
Reply by ●September 28, 20092009-09-28
>On 11-09-2009 at 13:37:34 arun <arunkumar.us@gmail.com> wrote: > >(...) >> We modulate the carrier frequency based on the digital input values... >(...) > >Is your carrier digital? > > > >-- >Mikolaj >I call a spreading sequence a digital carrier, but apart from that, I can't think of any other digital carrier. Digital carriers are only for baseband and so their usage is limited. However, in theory there can be one, tough in practice it would never exist It would be interesting to read the views of experts regarding this, Vlad?
Reply by ●September 28, 20092009-09-28
commengr wrote:>>On 11-09-2009 at 13:37:34 arun <arunkumar.us@gmail.com> wrote: >>>>>We modulate the carrier frequency based on the digital input values... >> >> >>Is your carrier digital? >> >> >>Mikolaj > > > I call a spreading sequence a digital carrier, but apart from that, I > can't think of any other digital carrier. > > Digital carriers are only for baseband and so their usage is limited. > However, in theory there can be one, tough in practice it would never > exist > > It would be interesting to read the views of experts regarding this, > Vlad?If you don't understand digital carrier, you shouldn't pursue digital career. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
