|
From: | Tim Meehan |
Subject: | Re: [Discuss-gnuradio] CPM timing recovery |
Date: | Wed, 6 Jun 2007 19:43:56 -0400 |
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Nothing that modulates data has constant envelope. Plot the amplitude of
a BPSK or GMSK signal (after transmission, not simulation) sometime.
- -Dan
Achilleas Anastasopoulos wrote:
> Bob,
>
> this is not correct.
>
> The CPM signal is by definition constant envelope.
> It is defined as
> s(t)=exp(j phi(t))
> where
> phi(t)= 2 pi int_0^t f(t') dt'
> where
> f(t)= h sum_k a_k p(t-kT).
> Selecting the approprate pulse shape p(t) shapes the spectrum of CPM,
> but regardless of the selection it has continuous phase
> (not abrupt transitions) as the name suggests ;-) and constant envelope.
> Thus the method you suggested (looking at the envelope variations)
> will not work.
>
> Achilleas
>
>
> ======================
> Since the signal will not really have infinite bandwidth (instantaneous
> transitions from one state to the next), the envelope will not be of
> constant modulus. The signal will be amplitude modulated with a
> component due to the data transitions. Looking at the modulus or
> modulus squared will reveal a line in the fft due to this amplitude
> modulation.
>
> Bob
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iD8DBQFGZue7y9GYuuMoUJ4RAtJ0AJwNEeom3VXahGVfdCYX6Sw536RtSACgw5vF
ntNgOm89dQPZkBHQyHTh6zk=
=eu2i
-----END PGP SIGNATURE-----
_______________________________________________
Discuss-gnuradio mailing list
address@hidden
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Prev in Thread] | Current Thread | [Next in Thread] |