On Sep 28, 3:25�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:> commengr wrote: > >>On 11-09-2009 at 13:37:34 arun <arunkumar...@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 Consultanthttp://www.abvolt.comThe God of DSP has spoken! Rick
Digital modulation - In digital domain or analog..?
Started by ●September 11, 2009
Reply by ●September 28, 20092009-09-28
Reply by ●September 28, 20092009-09-28
rickman wrote:> On Sep 28, 3:25 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: >> commengr wrote: >>>> On 11-09-2009 at 13:37:34 arun <arunkumar...@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 Consultanthttp://www.abvolt.com > > The God of DSP has spoken!Let's not get carried away. Not god; oracle, Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●September 29, 20092009-09-29
>rickman wrote: >> On Sep 28, 3:25 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: >>> commengr wrote: >>>>> On 11-09-2009 at 13:37:34 arun <arunkumar...@gmail.com> wrote: >>>>>> We modulate the carrier frequency based on the digital inputvalues...>>>>> 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 islimited.>>>> However, in theory there can be one, tough in practice it wouldnever>>>> 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 Consultanthttp://www.abvolt.com >> >> The God of DSP has spoken! > >Let's not get carried away. Not god; oracle, > >Jerry >-- >Engineering is the art of making what you want from things you can get. >����������������������������������������������������������������������� >Vlad, correct me. Why can't we call a spreading sequence a digital carrier? Carrier is something on which we modulate data on (I know the definition ain't that simple); when we spread a signal, we modulate our data onto the carrier.
Reply by ●September 29, 20092009-09-29
On 9/28/2009 10:08 PM, commengr wrote:>> rickman wrote: >>> On Sep 28, 3:25 pm, Vladimir Vassilevsky<nos...@nowhere.com> wrote: >>>> commengr wrote: >>>>>> On 11-09-2009 at 13:37:34 arun<arunkumar...@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 Consultanthttp://www.abvolt.com >>> The God of DSP has spoken! >> Let's not get carried away. Not god; oracle, >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ����������������������������������������������������������������������� >> > > > Vlad, correct me. Why can't we call a spreading sequence a digital > carrier? > > Carrier is something on which we modulate data on (I know the definition > ain't that simple); when we spread a signal, we modulate our data onto the > carrier.I've not previously heard a spreading sequence referred to as a carrier, and I'd argue it's the opposite. Typically an unmodulated carrier can be described as CW (continuous wave), and once the modulation is applied the bandwidth spreads out to match the modulation. e.g., applying a stream of PSK symbols to the otherwise unmodulated carrier spreads the bandwidth out to the symbol rate. Applying a spreading sequence to the modulated PSK sequence spreads the bandwidth out further, to the chip rate of the spreading sequence, which seems to me the equivalent of adding more modulation, not a "digital carrier". I'm still trying to sort out what a "digital carrier" might be. I don't think I've ever heard the term before this week, so I don't think it's a common term. Is the idea that different spreading codes can be isolated (i.e., CDMA), so each code is considered a "carrier"? That seems to me to be a strange way to think of it, but I suppose some may choose to think of it that way. The whole concept of a carrier gets muddied by the fact that many popular modulation types can be described as "suppressed carrier", where the "carrier" isn't really identifiable within the signal, anyway. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
Reply by ●September 29, 20092009-09-29
On 24 Sep, 23:45, Clay <c...@claysturner.com> wrote:> 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 ;-)I looked up the word the first time you mentioned it. I couldn't find 'obtuNed', but instead found 'obtuSed'. With the background story it seems that the word might be a word play between 'tune' and 'obtuse'? A change - tuning - to the brain that causes the personality to take a turn for the obtuse? Rune
Reply by ●September 29, 20092009-09-29
>I looked up the word the first time you mentioned it. I couldn't >find 'obtuNed', but instead found 'obtuSed'. With the background >story it seems that the word might be a word play between 'tune' >and 'obtuse'? A change - tuning - to the brain that causes the >personality to take a turn for the obtuse?Try looking at the original messages again. The word is OBTUNDED. You missed a D. Steve
Reply by ●September 29, 20092009-09-29
On 29 Sep, 10:00, "steveu" <ste...@coppice.org> wrote:> >I looked up the word the first time you mentioned it. I couldn't > >find 'obtuNed', but instead found 'obtuSed'. With the background > >story it seems that the word might be a word play between 'tune' > >and 'obtuse'? A change - tuning - to the brain that causes the > >personality to take a turn for the obtuse? > > Try looking at the original messages again. The word is OBTUNDED. You > missed a D.Even with the D, it's still not in my dictionary. Rune
Reply by ●September 29, 20092009-09-29
>On 29 Sep, 10:00, "steveu" <ste...@coppice.org> wrote: >> >I looked up the word the first time you mentioned it. I couldn't >> >find 'obtuNed', but instead found 'obtuSed'. With the background >> >story it seems that the word might be a word play between 'tune' >> >and 'obtuse'? A change - tuning - to the brain that causes the >> >personality to take a turn for the obtuse? >> >> Try looking at the original messages again. The word is OBTUNDED. You >> missed a D. > >Even with the D, it's still not in my dictionary. >Try a medical dictionary, like http://www.medterms.com/script/main/art.asp?articlekey=4614
Reply by ●September 29, 20092009-09-29
>>On 29 Sep, 10:00, "steveu" <ste...@coppice.org> wrote: >>> >I looked up the word the first time you mentioned it. I couldn't >>> >find 'obtuNed', but instead found 'obtuSed'. With the background >>> >story it seems that the word might be a word play between 'tune' >>> >and 'obtuse'? A change - tuning - to the brain that causes the >>> >personality to take a turn for the obtuse? >>> >>> Try looking at the original messages again. The word is OBTUNDED. You >>> missed a D. >> >>Even with the D, it's still not in my dictionary. >> >Try a medical dictionary, like >http://www.medterms.com/script/main/art.asp?articlekey=4614 >It's also in Webster's: http://www.merriam-webster.com/dictionary/obtund
Reply by ●September 29, 20092009-09-29
>On 9/28/2009 10:08 PM, commengr wrote: >>> rickman wrote: >>>> On Sep 28, 3:25 pm, Vladimir Vassilevsky<nos...@nowhere.com> wrote: >>>>> commengr wrote: >>>>>>> On 11-09-2009 at 13:37:34 arun<arunkumar...@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 fromthat,>> 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 regardingthis,>>>>>> Vlad? >>>>> If you don't understand digital carrier, you shouldn't pursuedigital>>>>> career. >>>>> >>>>> Vladimir Vassilevsky >>>>> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com >>>> The God of DSP has spoken! >>> Let's not get carried away. Not god; oracle, >>> >>> Jerry >>> -- >>> Engineering is the art of making what you want from things you canget.>>>�����������������������������������������������������������������������>>> >> >> >> Vlad, correct me. Why can't we call a spreading sequence a digital >> carrier? >> >> Carrier is something on which we modulate data on (I know thedefinition>> ain't that simple); when we spread a signal, we modulate our data ontothe>> carrier. > >I've not previously heard a spreading sequence referred to as a carrier,>and I'd argue it's the opposite. Typically an unmodulated carrier can >be described as CW (continuous wave), and once the modulation is applied>the bandwidth spreads out to match the modulation. > >e.g., applying a stream of PSK symbols to the otherwise unmodulated >carrier spreads the bandwidth out to the symbol rate. > >Applying a spreading sequence to the modulated PSK sequence spreads the >bandwidth out further, to the chip rate of the spreading sequence, which>seems to me the equivalent of adding more modulation, not a "digital >carrier". > >I'm still trying to sort out what a "digital carrier" might be. I >don't think I've ever heard the term before this week, so I don't think >it's a common term. Is the idea that different spreading codes can be >isolated (i.e., CDMA), so each code is considered a "carrier"? That >seems to me to be a strange way to think of it, but I suppose some may >choose to think of it that way. > >The whole concept of a carrier gets muddied by the fact that many >popular modulation types can be described as "suppressed carrier", where>the "carrier" isn't really identifiable within the signal, anyway. > >-- >Eric Jacobsen >Minister of Algorithms >Abineau Communications >http://www.abineau.com >------------------------------------------------------------- Thanks Eric, for first thinking about what I wrote rather than having prejudice against the 'out-of-norm' propositions, unlike someone. Vlad might be the best, he most definitely ain't GOD (may GOD forgive us for even thinking like that)>and I'd argue it's the opposite. Typically an unmodulated carrier can >be described as CW (continuous wave), and once the modulation is applied>the bandwidth spreads out to match the modulation.I understand typically a carrier is supposed to be CT signal, but a DT signal will do the same i.e. when we spread a DT signal (data, low bit-rate) by another DT (data, but at a higher bit-rate), the information on the low bit-rate signal will be transferred (data-modulated) on the high bit-rate signal. The bandwidth requirements would be exactly same as those for high bit-rate signal>Applying a spreading sequence to the modulated PSK sequence spreads the >bandwidth out further, to the chip rate of the spreading sequence, which>seems to me the equivalent of adding more modulation, not a "digital >carrier".I agree, the reason for doing so is to make sure we can transmit the 'spread signal' onto a channel which is not suitable for transmission of a digital signal (strict bandwidth constraints). If there were no limitations, I believe we could have, theoretically, transmitted a digital signal over wireless link. If we have a baseband link, we can transmit the 'spread' signal onto it, no problem. Its just that it can support the chip-rate Further, we don't seem to mind this too much, CDMA systems are so widely implemented I believe the hindrance in accepting a digital carrier is the decades old notion that carriers can only be analog. Carrier should be a signal onto which some signal can be modulated. I am not an expert in 'digital carrier', I shall, however, continue to propose/discuss things that I think about
