Results 1 to 13 of 13
  1. #1
    karthikbalaguru
    Guest
    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



    See More: sinusoidal carrier




  2. #2
    Jeff Liebermann
    Guest

    Re: sinusoidal carrier

    karthikbalaguru <[email protected]> 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 [email protected]
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558



  3. #3
    karthikbalaguru
    Guest

    Re: sinusoidal carrier

    On Jan 1, 5:08 am, Jeff Liebermann <[email protected]> wrote:
    > karthikbalaguru <[email protected]> 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





  4. #4
    karthikbalaguru
    Guest

    Re: sinusoidal carrier

    On Jan 2, 12:19*am, karthikbalaguru <[email protected]>
    wrote:
    > On Jan 1, 5:08 am, Jeff Liebermann <[email protected]> wrote:> karthikbalaguru <[email protected]> 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




  5. #5

    Re: sinusoidal carrier

    On Jan 1, 11:22 am, karthikbalaguru <[email protected]>
    wrote:
    > On Jan 2, 12:19 am, karthikbalaguru <[email protected]>
    > wrote:
    >
    >
    >
    > > On Jan 1, 5:08 am, Jeff Liebermann <[email protected]> wrote:> karthikbalaguru <[email protected]> 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.



  6. #6
    Jeff Liebermann
    Guest

    Re: sinusoidal carrier

    karthikbalaguru <[email protected]> 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 [email protected]
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558



  7. #7
    Larry
    Guest

    Re: sinusoidal carrier

    Jeff Liebermann <[email protected]> wrote in
    news:[email protected]:

    > 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;



  8. #8
    Jeff Liebermann
    Guest

    Re: sinusoidal carrier

    Larry <[email protected]> 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=uwJALBsAAABrIaFW2rR1mZdU36XjShcYHL6ZsB4DzFwc97yAjR_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 [email protected]
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558



  9. #9
    Larry
    Guest

    Re: sinusoidal carrier

    Jeff Liebermann <[email protected]> wrote in
    news:[email protected]:

    > 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.
    >
    >


    Hee hee....You'd make a great 75 meter guy. Mean and nasty is the only way
    to get bandwidth!...(c;

    I was gonna call on Skype to say hello, but now I'm afraid.

    Larry
    --
    Next time some broker tells you what a great investment he's selling,
    ask him about Rhodium, a shiny metal used in Catalytic Converters.
    Jan 1st 2004 2005 2006 2007 2008
    Rhodium $452 $1341 $3006 $5339 $6775 PER OUNCE!
    How much longer can we pay for new cars at this rate?
    Feb '97 it was $182/oz



  10. #10
    DTC
    Guest

    Re: sinusoidal carrier

    [email protected] wrote:
    > It's an analog world!


    And an exponential one at that.

    For most people, if it sounds TWICE as loud, its TEN times
    greater sound pressure level.



  11. #11
    Larry
    Guest

    Re: sinusoidal carrier

    DTC <[email protected]> wrote in news:kqPej.33406$lD6.14340
    @newssvr27.news.prodigy.net:

    > [email protected] wrote:
    >> It's an analog world!

    >
    > And an exponential one at that.
    >
    > For most people, if it sounds TWICE as loud, its TEN times
    > greater sound pressure level.
    >


    Wouldn't that be logarithmic?....(c;

    Larry
    --
    Next time some broker tells you what a great investment he's selling,
    ask him about Rhodium, a shiny metal used in Catalytic Converters.
    Jan 1st 2004 2005 2006 2007 2008
    Rhodium $452 $1341 $3006 $5339 $6775 PER OUNCE!
    How much longer can we pay for new cars at this rate?
    Feb '97 it was $182/oz



  12. #12
    DTC
    Guest

    Re: sinusoidal carrier

    Larry wrote:
    > DTC <[email protected]> wrote in news:kqPej.33406$lD6.14340
    >> For most people, if it sounds TWICE as loud, its TEN times
    >> greater sound pressure level.
    >>

    >
    > Wouldn't that be logarithmic?....(c;


    Sounds like a (ahem)... *natural* answer to me.



  13. #13
    karthikbalaguru
    Guest

    Re: sinusoidal carrier

    On Jan 2, 1:18*am, [email protected] wrote:
    > On Jan 1, 11:22 am, karthikbalaguru <[email protected]>
    > wrote:
    >
    >
    >
    >
    >
    > > On Jan 2, 12:19 am, karthikbalaguru <[email protected]>
    > > wrote:

    >
    > > > On Jan 1, 5:08 am, Jeff Liebermann <[email protected]> wrote:> karthikbalaguru <[email protected]> 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.



    Interesting to know that real life sine wave has distortion

    Thx,
    Karthik Balaguru




  • Similar Threads