Forums

Name that modulation...

Started by John E. Hadstate July 16, 2008
dbd <dbd@ieee.org> writes:

> I would say it -is- bipolar Gaussian frequency shift keying, but I > wouldn't say it in public.
Er, Dale, I think you just did. ;-) -- "And he sees the vision splendid of the sunlit plains extended And at night the wondrous glory of the everlasting stars."
On Jul 16, 6:03 pm, p.kootsoo...@remove.ieee.org (Peter K.) wrote:
> dbd <d...@ieee.org> writes: > > I would say it -is- bipolar Gaussian frequency shift keying, but I
> > wouldn't say it in public.
> Er, Dale, I think you just did. ;-)
Did you see my lips move? Dale B. Dalrymple
"John E. Hadstate" <jh113355@hotmail.com> wrote in message 
news:T_mdnfOEwsd__ePVnZ2dnUVZ_g-dnZ2d@supernews.com...
> Start with logic 0s and 1s. Convert them to pulses that look > roughly like Gaussian bell curves each going from near-zero > to maximum to near-zero in one bit time, 0s going negative, > 1s going positive. Use said negative-and-positive-going > pulses to frequency-modulate a carrier. > > What is the name of this type of modulation? If my > description of the mechanics of this modulation scheme is not > quite right, what is the name of the modulation that would > produce the same apparent result as described above? >
I can see how this signal could also be generated by starting with a sine wave whose frequency is one-half of the bit rate with its zero-crossings sync'ed to the bit transitions. This sine wave would then be squared and BPSK modulated by the bit stream. The result could then have been used to frequency-modulate a higher-frequency subcarrier. I was looking for an acronym to google. My thanks to everyone who responded.
"dbd" <dbd@ieee.org> wrote in message 
news:4fd74a7c-6dec-49e3-8005-9ea6cab91a93@x35g2000hsb.googlegroups.com...
> On Jul 16, 6:03 pm, p.kootsoo...@remove.ieee.org (Peter K.) wrote: >> dbd <d...@ieee.org> writes: >> > I would say it -is- bipolar Gaussian frequency shift keying, but I > >> > wouldn't say it in public. > >> Er, Dale, I think you just did. ;-) > > Did you see my lips move? > > Dale B. Dalrymple
Perhaps you are a ventriloquist... --Phil Martel
On Jul 16, 4:57 pm, "John E. Hadstate" <jh113...@hotmail.com> wrote:
> Start with logic 0s and 1s. Convert them to pulses that look > roughly like Gaussian bell curves each going from near-zero to > maximum to near-zero in one bit time, 0s going negative, 1s > going positive. Use said negative-and-positive-going pulses to > frequency-modulate a carrier. > > What is the name of this type of modulation? If my description > of the mechanics of this modulation scheme is not quite right, > what is the name of the modulation that would produce the same > apparent result as described above?
John, The other answers are good, but i would be a bit more general. In my mind what you describe is a subset of the CPM continuous phase modulation family. Assuming that the 0s and 1s you describe are actually being mapped to a binary +/-1, which is evident when you describe negative and positive going pulses, then all that remains is for you to describe exactly the frequency pulse g(t) which for CPM can be GMSK, Raised cosine, shaped raised cosine (which all give you the Gaussian shape-like curve you describe). You then drive the output (with suitable scaling) through a freq modulator. The resultant for single h is s(t,a) = exp(j * phi(t,a) ) where phi(t,a) = 2 pi h sum_i a_i q(t-iT) and q(t) = int_{-infty}^t g(b) db and a_i are the binary mapped symbols I guess all i would do is define the freq pulse shape g(t) that you observe, and you have everything else. col
On Jul 17, 9:06&#2013266080;am, cb...@hotmail.com wrote:
> On Jul 16, 4:57 pm, "John E. Hadstate" <jh113...@hotmail.com> wrote: > > > Start with logic 0s and 1s. &#2013266080;Convert them to pulses that look > > roughly like Gaussian bell curves each going from near-zero to > > maximum to near-zero in one bit time, 0s going negative, 1s > > going positive. &#2013266080;Use said negative-and-positive-going pulses to > > frequency-modulate a carrier. > > > What is the name of this type of modulation? &#2013266080;If my description > > of the mechanics of this modulation scheme is not quite right, > > what is the name of the modulation that would produce the same > > apparent result as described above? > > John, > > The other answers are good, but i would be a bit more general. &#2013266080;In my > mind what you describe is > a subset of the CPM continuous phase modulation family. &#2013266080;Assuming that > the 0s and 1s you describe are actually being mapped to a binary +/-1, > which is evident when you describe negative and positive going pulses, > then all that remains is for you to describe exactly the frequency > pulse g(t) which for CPM can be GMSK, Raised cosine, shaped raised > cosine (which all give you the Gaussian shape-like curve you > describe). &#2013266080;You then drive the output (with suitable scaling) through > a freq modulator. > > The resultant for single h is > > s(t,a) = exp(j * phi(t,a) ) > > where > > phi(t,a) = 2 pi h sum_i a_i q(t-iT) and q(t) = int_{-infty}^t g(b) db > > and a_i are the binary mapped symbols > > I guess all i would do is define the freq pulse shape g(t) that you > observe, and you have everything else. > > col
Thanks. Given the noise and distortion, I can't really tell whether the original frequency-modulating pulses are Gaussian, sine-squared, or some other similar shape. Mainly, I was looking for acronyms like GMSK, SFSK, etc. that point in the right general direction.
John Hadstate wrote:
> On Jul 17, 9:06 am, cb...@hotmail.com wrote: >> On Jul 16, 4:57 pm, "John E. Hadstate" <jh113...@hotmail.com> wrote: >> >>> Start with logic 0s and 1s. Convert them to pulses that look >>> roughly like Gaussian bell curves each going from near-zero to >>> maximum to near-zero in one bit time, 0s going negative, 1s >>> going positive. Use said negative-and-positive-going pulses to >>> frequency-modulate a carrier. >>> What is the name of this type of modulation? If my description >>> of the mechanics of this modulation scheme is not quite right, >>> what is the name of the modulation that would produce the same >>> apparent result as described above? >> John, >> >> The other answers are good, but i would be a bit more general. In my >> mind what you describe is >> a subset of the CPM continuous phase modulation family. Assuming that >> the 0s and 1s you describe are actually being mapped to a binary +/-1, >> which is evident when you describe negative and positive going pulses, >> then all that remains is for you to describe exactly the frequency >> pulse g(t) which for CPM can be GMSK, Raised cosine, shaped raised >> cosine (which all give you the Gaussian shape-like curve you >> describe). You then drive the output (with suitable scaling) through >> a freq modulator. >> >> The resultant for single h is >> >> s(t,a) = exp(j * phi(t,a) ) >> >> where >> >> phi(t,a) = 2 pi h sum_i a_i q(t-iT) and q(t) = int_{-infty}^t g(b) db >> >> and a_i are the binary mapped symbols >> >> I guess all i would do is define the freq pulse shape g(t) that you >> observe, and you have everything else. >> >> col > > Thanks. Given the noise and distortion, I can't really tell whether > the original frequency-modulating pulses are Gaussian, sine-squared, > or some other similar shape. Mainly, I was looking for acronyms like > GMSK, SFSK, etc. that point in the right general direction.
The positive and negative fixed-amplitude modulation would be ordinary FSK if the transitions were abrupt. Slowing the frequency transitions by shaping the pulses reduces out-of-band splatter. Modulating with square pulses and bandpass filtering the modulated carrier will produce the rounded pulses you observe upon demodulation. Make the bandpass filter narrow enough and you have MSK. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
On Jul 17, 2:38 am, "John E. Hadstate" <jh113...@hotmail.com> wrote:
> "John E. Hadstate" <jh113...@hotmail.com> wrote in messagenews:T_mdnfOEwsd__ePVnZ2dnUVZ_g-dnZ2d@supernews.com... > ...
> > What is the name of this type of modulation?
>... > I was looking for an acronym to google. My thanks to everyone > who responded.
Then how about: PDGMSK bipolar RTZ at: http://www.argreenhouse.com/society/TacCom/papers98/15_01i.pdf Dale B. Dalrymple
dbd wrote:
> On Jul 17, 2:38 am, "John E. Hadstate" <jh113...@hotmail.com> wrote: >> "John E. Hadstate" <jh113...@hotmail.com> wrote in messagenews:T_mdnfOEwsd__ePVnZ2dnUVZ_g-dnZ2d@supernews.com... >> ... > >>> What is the name of this type of modulation? > >> ... >> I was looking for an acronym to google. My thanks to everyone >> who responded. > > Then how about: > PDGMSK bipolar RTZ > > at: > http://www.argreenhouse.com/society/TacCom/papers98/15_01i.pdf > > Dale B. Dalrymple
Pretty Damn Good Minimum-Shift Keying? Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
On Jul 17, 10:31 am, Jerry Avins <j...@ieee.org> wrote:
> John Hadstate wrote:
> > Thanks. Given the noise and distortion, I can't really tell whether > > the original frequency-modulating pulses are Gaussian, sine-squared, > > or some other similar shape. Mainly, I was looking for acronyms like > > GMSK, SFSK, etc. that point in the right general direction. > > The positive and negative fixed-amplitude modulation would be ordinary > FSK if the transitions were abrupt. Slowing the frequency transitions by > shaping the pulses reduces out-of-band splatter. Modulating with square > pulses and bandpass filtering the modulated carrier will produce the > rounded pulses you observe upon demodulation. Make the bandpass filter > narrow enough and you have MSK.
Yes, and it might be informative for him to take a look at this signal in the frequency domain to see this, as well as perhaps synthesizing/ simulating some similar ones and seeing what those look like in frequency.