> 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?
>
> Mark
Not 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
Reply by Mark●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 commengr●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 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
>
C'mon Vlad... I'm waiting for your answer/views on this, since you seem to
be good at "digital career"
Reply by Jerry Avins●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 glen herrmannsfeldt●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 Jerry Avins●September 29, 20092009-09-29
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.
�����������������������������������������������������������������������
Reply by commengr●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
>>>
>>
>>
>> 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
>
-------------------------------------------------------------
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
Reply by Michael Plante●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
>
>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.
>
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