Rune Allnor wrote:> 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.What dictionary do you use? The very nice on-line Century Dictionary puts up page images of a comprehensive (but old) two-volume library tome. I keep a link to it on my browser tool bar, but you don't have to in order to use it. You should install the DjVu viewer, but that's free. To see what it's like, you can use the jpeg stopgap, but relatively speaking, that sucks! http://www.global-language.com/CENTURY/ Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Digital modulation - In digital domain or analog..?
Started by ●September 11, 2009
Reply by ●September 29, 20092009-09-29
Reply by ●September 29, 20092009-09-29
commengr <communications_engineer@yahoo.com> wrote: (big snip, and someone wrote) <>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 It would seem that a DT signal followed by the appropriate filter would be pretty much equivalent to a CT signal, so I probably agree. Say for discussion that we have a discrete time (digital) audio signal (such as a CD) and want to build a broadcast band AM or FM transmitter. Can the modulation be done entirely using DSP techniques, followed by the appropriate analog filter and out to the antenna? Most likely an analog amplifier on the way out. <>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. (snip) < 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 think it should be the other way. The carrier should be the signal that can be modulated by some signal. -- glen
Reply by ●September 29, 20092009-09-29
commengr wrote:> 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.What would the E and H fields in space be like on such a link? ... Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 1, 20092009-10-01
>commengr <communications_engineer@yahoo.com> wrote: >(big snip, and someone wrote) > ><>and I'd argue it's the opposite. Typically an unmodulated carrier can><>be described as CW (continuous wave), and once the modulation isapplied> ><>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), theinformation>< on the low bit-rate signal will be transferred (data-modulated) on thehigh>< bit-rate signal. The bandwidth requirements would be exactly same asthose>< for high bit-rate signal > >It would seem that a DT signal followed by the appropriate filter >would be pretty much equivalent to a CT signal, so I probably agree. > >Say for discussion that we have a discrete time (digital) audio >signal (such as a CD) and want to build a broadcast band AM or >FM transmitter. Can the modulation be done entirely using DSP >techniques, followed by the appropriate analog filter and out >to the antenna? Most likely an analog amplifier on the way out. > ><>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 transmissionof a>< digital signal (strict bandwidth constraints). If there were no >< limitations, I believe we could have, theoretically, transmitted adigital>< signal over wireless link. > >(snip) >< I believe the hindrance in accepting a digital carrier is the decadesold>< notion that carriers can only be analog. Carrier should be a signalonto>< which some signal can be modulated. > >I think it should be the other way. The carrier should be the signal >that can be modulated by some signal. > >-- glen >C'mon Vlad... I'm waiting for your answer/views on this, since you seem to be good at "digital career"
Reply by ●October 1, 20092009-10-01
On Sep 29, 12:15=A0pm, Jerry Avins <j...@ieee.org> wrote:> commengr wrote: > > 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 o=f a> > digital signal (strict bandwidth constraints). If there were no > > limitations, I believe we could have, theoretically, transmitted a digi=tal> > signal over wireless link. > > What would the E and H fields in space be like on such a link? > > =A0 =A0... >this is the essence of UWB is it not? Mark
Reply by ●October 1, 20092009-10-01
On 10/1/2009 8:37 AM, Mark wrote:> On Sep 29, 12:15 pm, Jerry Avins<j...@ieee.org> wrote: >> commengr wrote: >>> 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. >> What would the E and H fields in space be like on such a link? >> >> ... >> > > this is the essence of UWB is it not? > > MarkNot really. UWB tries to take up a lot of bandwidth so that the PSD stays very low to minimize interference with other devices and still be able to transport a high bit rate. The type of carrier or modulation used isn't anything magical to do that. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
