sinusoidal carrier

Hi,
Is there any specific reason for most of the modulation technique to
use sinusoidal carrier for modulation in wireless communication ? I
searched the internet, but, did not get any specific link for this ?
Any ideas / links ?

Thx in advans,
Karthik Balaguru

karthikbalaguru <(E-Mail Removed)> hath wroth:

>Is there any specific reason for most of the modulation technique to
>use sinusoidal carrier for modulation in wireless communication ?

Yep. By definition, a sinusodial waveform is one that doesn't have
any harmonics or distortion. It consists only of the fundamental
frequency. If you want to minimize interference to other services on
other frequencies, a low distortion sine wave carrier is a must.

>I
>searched the internet, but, did not get any specific link for this ?
>Any ideas / links ?
>
>Thx in advans,
>Karthik Balaguru

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Jan 1, 5:08 am, Jeff Liebermann <je...@cruzio.com> wrote:
> karthikbalaguru <karthikbalagur...@gmail.com> hath wroth:
>
> >Is there any specific reason for most of the modulation technique to
> >use sinusoidal carrier for modulation in wireless communication ?
>
> Yep. By definition, a sinusodial waveform is one that doesn't have
> any harmonics or distortion. It consists only of the fundamental
> frequency. If you want to minimize interference to other services on
> other frequencies, a low distortion sine wave carrier is a must.
>
Yeah, i find that sawtooth wave of constant period contains odd and
even harmonics that fall off at -6 dB/octave.
Square wave of constant period contains odd harmonics that fall off
at -6 dB/octave.
Triangle wave, (an integral of square wave) contains odd harmonics
that fall off at -12 dB/octave.
But, Sine wave does not contain any harmonics or distortion.

Karthik Balaguru

On Jan 2, 12:19*am, karthikbalaguru <karthikbalagur...@gmail.com>
wrote:
> On Jan 1, 5:08 am, Jeff Liebermann <je...@cruzio.com> wrote:> karthikbalaguru <karthikbalagur...@gmail.com> hath wroth:
>
> > >Is there any specific reason for most of the modulation technique to
> > >use sinusoidal carrier for modulation in wireless communication ?
>
> > Yep. *By definition, a sinusodial waveform is one that doesn't have
> > any harmonics or distortion. *It consists only of the fundamental
> > frequency. *If you want to minimize interference to other services on
> > other frequencies, a low distortion sine wave carrier is a must.
>
> Yeah, i find that sawtooth wave of constant period contains odd and
> even harmonics that fall off at -6 dB/octave.
> Square wave of constant period *contains odd harmonics that fall off
> at -6 dB/octave.
> Triangle wave, (an integral of square wave) contains odd harmonics
> that fall off at -12 dB/octave.
> But, Sine wave does not contain any harmonics or distortion.
>

Thx for your info.
Thinking over this, i have a strange query
How is it possible that a sinusodial waveform alone doesn't have
any harmonics or distortion ?

Thx in advans,
Karthik Balaguru

On Jan 1, 11:22 am, karthikbalaguru <karthikbalagur...@gmail.com>
wrote:
> On Jan 2, 12:19 am, karthikbalaguru <karthikbalagur...@gmail.com>
> wrote:
>
>
>
> > On Jan 1, 5:08 am, Jeff Liebermann <je...@cruzio.com> wrote:> karthikbalaguru <karthikbalagur...@gmail.com> hath wroth:
>
> > > >Is there any specific reason for most of the modulation technique to
> > > >use sinusoidal carrier for modulation in wireless communication ?
>
> > > Yep. By definition, a sinusodial waveform is one that doesn't have
> > > any harmonics or distortion. It consists only of the fundamental
> > > frequency. If you want to minimize interference to other services on
> > > other frequencies, a low distortion sine wave carrier is a must.
>
> > Yeah, i find that sawtooth wave of constant period contains odd and
> > even harmonics that fall off at -6 dB/octave.
> > Square wave of constant period contains odd harmonics that fall off
> > at -6 dB/octave.
> > Triangle wave, (an integral of square wave) contains odd harmonics
> > that fall off at -12 dB/octave.
> > But, Sine wave does not contain any harmonics or distortion.
>
> Thx for your info.
> Thinking over this, i have a strange query
> How is it possible that a sinusodial waveform alone doesn't have
> any harmonics or distortion ?
>
> Thx in advans,
> Karthik Balaguru

An ideal sine wave has no harmonic distortion by definition. That is,
the equation a*sin(wt) only has the fundamental frequency. A real life
sine wave has distortion, but you need hardware to detect it.

Regarding the fall off of harmonics, there is some rule of thumb no
longer in my brain that relates the harmonic fall off with the number
of continuous derivatives of the function. This is the closest I could
find on google to the rule of thumb:
http://www.me.rochester.edu/courses/...es/movies.html
Generally the smoother the function, the lower the harmonic levels.

My recollection is the square wave falls off as the 1/n where n is the
harmonic. Also the 3rd harmonic of a square wave is stronger than the
fundamental. You would need to google fourier series to get reality.

karthikbalaguru <(E-Mail Removed)> hath wroth:

>Is there any specific reason for most of the modulation technique to
>use sinusoidal carrier for modulation in wireless communication ? I
>searched the internet, but, did not get any specific link for this ?

I seem to be doing your homework. This is also the wrong newsgroup
for basic communications questions. Any book on basic communications
theory will have a page on waveform analysis.

You start with a sine wave. It's strictly the fundamental with no
harmonics.

If you add distorition (harmonics), if the harmonics are odd order
(3,5,7,9,11,etc), then the waveform will be symmetrical.

If you add distortion (harmonics), if the harmonics are even order
(2,4,6,8,10, etc), then the waveform will by asymmetrical.

Exmaples:
http://en.wikipedia.org/wiki/Sine_wave
http://en.wikipedia.org/wiki/Triangle_wave
http://en.wikipedia.org/wiki/Sawtooth_wave
http://en.wikipedia.org/wiki/Square_wave

If you spend some time with a function generator and spectrum
analyzer, you can see the effects of odd and even harmonics on
spectra.

If you want to use a computer to see how it works, I suggest you
download Sillanumsoft Visual Analyzer. This is a very handy audio
oscilloscope, spectrum analyzer, and function generator. You can
internally generate a waveform, and see the resulting spectra.
<http://www.sillanumsoft.org>
Don't forget to click the "ON" button in the upper left corner.

There are lots of other reasons to use a sine wave to drive a cell
phone. In order to get sufficient bits per baud, most modulation
methods involve both FM and AM. FM modulation doesn't care about the
harmonic content of the synthesizer. AM modulators care and will
produce distorted and non-linear garbage if overdriven by harmonic.

In addition, the FCC and other regulatory agencies fail to appreciate
harmonics and spurious signals being belched by cell phones. If you
remove the modulation, the remaining RF carrier needs to be about
clean down to about 0.0001% (about -60dB below peak power) in order to
placate the regulatory agency. If you can see the distortion, it will
fail.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> There are lots of other reasons to use a sine wave to drive a cell
> phone. In order to get sufficient bits per baud, most modulation
> methods involve both FM and AM. FM modulation doesn't care about the
> harmonic content of the synthesizer. AM modulators care and will
> produce distorted and non-linear garbage if overdriven by harmonic.
>

Isn't it amazing the number of "digital generation" people you meet that
have no concept that you cannot transmit data, directly, over-the-air or
over long distances, without converting it into the analog world as
modulation. I've even had college kids in electronic engineering question
me about why data was "encoded" by some kind of modem for transmission.

They're ALL convinced their digital SELLphones are all data, not converted
into 8K or 11K samples for the phase modulated transmitters...

73 DE W4CSC

Jeff, I noticed your sig on usenet with all your Skype and phone numbers on
it. Doesn't that create a storm of crank/hate calls from the nutcases on
here? If not, I'm amazed. I know the spambots will storm email. I had to
get rid of myhamcall@myisp over it.

Larry
--
One of my neighbors is a very-well-educated person. He thinks TV DATA
comes in over the new DIGITAL TV antenna....(c; How broadband would that
be??....(c;

On Jan 1, 4:52 pm, Larry <no...@home.com> wrote:
> Jeff Liebermann <je...@cruzio.com> wrote innews:(E-Mail Removed):
>
> > There are lots of other reasons to use a sine wave to drive a cell
> > phone. In order to get sufficient bits per baud, most modulation
> > methods involve both FM and AM. FM modulation doesn't care about the
> > harmonic content of the synthesizer. AM modulators care and will
> > produce distorted and non-linear garbage if overdriven by harmonic.
>
> Isn't it amazing the number of "digital generation" people you meet that
> have no concept that you cannot transmit data, directly, over-the-air or
> over long distances, without converting it into the analog world as
> modulation. I've even had college kids in electronic engineering question
> me about why data was "encoded" by some kind of modem for transmission.
>
> They're ALL convinced their digital SELLphones are all data, not converted
> into 8K or 11K samples for the phase modulated transmitters...
>
> 73 DE W4CSC
>
> Jeff, I noticed your sig on usenet with all your Skype and phone numbers on
> it. Doesn't that create a storm of crank/hate calls from the nutcases on
> here? If not, I'm amazed. I know the spambots will storm email. I had to
> get rid of myhamcall@myisp over it.
>
> Larry
> --
> One of my neighbors is a very-well-educated person. He thinks TV DATA
> comes in over the new DIGITAL TV antenna....(c; How broadband would that
> be??....(c;

It's an analog world!

Larry <(E-Mail Removed)> hath wroth:

>Isn't it amazing the number of "digital generation" people you meet that
>have no concept that you cannot transmit data, directly, over-the-air or
>over long distances, without converting it into the analog world as
>modulation. I've even had college kids in electronic engineering question
>me about why data was "encoded" by some kind of modem for transmission.

The author is apparently somewhere in India. I've discussed their
educational methodology with some of the survivors. It's largely
self-study, which is often interpreted as "get the answers any way you
can". If they can trick someone into doing your homework, all the
better. That's excerbated by the lack of availability in their skools
to get anyone to answer their questions. In addition, it's considered
a capital crime to admit that one doesn't know the answer. It's a
rotten situation and we're seeing the desperate few that are looking
to usenet largely in desperation.

The problem is that if you feed the pigeons, you get more pigeons. If
we continue to do their homework and reports, the only result will be
more students asking for us to do their homework and reports.

I try to give them just enough information to get them kick started,
but not enough to submit to an instructor for an assignment or quiz.

Also, the original author is NOT a dummy. See what he's posted in
other newsgroups:
<http://groups.google.com/groups/profile?hl=en&enc_user=uwJALBsAAABrIaFW2rR1mZdU36X jShcYHL6ZsB4DzFwc97yAjR_7iw>
My guess is that he's having trouble with communications fundamentals,
is in a hurry, or is totally lost. Simply because he's clueless in
communications theory doesn't mean he's also clueless in other topics.

>They're ALL convinced their digital SELLphones are all data, not converted
>into 8K or 11K samples for the phase modulated transmitters...

I've been reading how the various 3G protocols operate and frankly,
I'm lost. Worse, the more I read, the more confused I get.

>Jeff, I noticed your sig on usenet with all your Skype and phone numbers on
>it. Doesn't that create a storm of crank/hate calls from the nutcases on
>here? If not, I'm amazed. I know the spambots will storm email. I had to
>get rid of myhamcall@myisp over it.

Nope. Hardly anyone calls. Probably because I have a reputation for
being mean and nasty.

I have both Skype and GizmoProject set to only accept calls from
people in my address book. They can send me an instant message (chat)
to ask if I'm busy. Most people are considerate. I guess a small
number of Nigerian scammers and people trying to sell me something,
but those usually get a fast disconnect followed by an abuse report.
The only time calls are a problem is when I'm using Skype on my cell
phone (XV6700 running WM5) via Wi-Fi. I have that set for outgoing
calls only.

Incidentally, I've had the same few email addresses for perhaps 15+
years. I've never changed them. I spend my time improving my spam
filtering and mail reading technique. Some spam still gets through,
but nothing intolerable.

As for the nut cases, most will use email instead of a phone call as
they don't want to deal with my mean and nasty bad attitude in real
time. I don't blame them.

What does happen is I get considerable email asking for personalized
help. I try to answer those when possible, but usually I reply that
I'm busy and don't particularly want to deal with their problems. If
they post their question in a newsgroup, various people will answer,
and everyone learns. If they just ask me to solve their problem, I
consider that billable consulting. A few have actually paid for my
advice which helps support my decadent and lavish lifestyle.



--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In <(E-Mail Removed)> Jeff Liebermann <(E-Mail Removed)> writes:

>Nope. Hardly anyone calls. Probably because I have a reputation for
>being mean and nasty.

You are Carl J. Lydick and I claim my two-fifty.

--
__________________________________________________ ___
Knowledge may be power, but communications is the key
(E-Mail Removed)
[to foil spammers, my address has been double rot-13 encoded]