> From: > John Malsbury > Subject: > [Discuss-gnuradio] Rectangular > Pulse Shape w/ PFB Clock Sync > Date: > Wed, 28 Sep 2016 00:07:46 -0700 > > ______________________________________________________________________ > I'm struggling with something pretty basic. I am trying to achieve > near theoretical performance detection of a rectangular (no RRC) QPSK > signal at 2 or 4 sps. I have an existing solution that uses a > discrete FIR filter followed by a Gardner timing recovery loop. The > taps of the FIR filter are a box car function. It works quite well > and implementation loss is negligible. > > > However, I'd like to achieve the same thing using the stock PFB clock > sync.
It won't work. The PFB clock recovery uses a derivative filter based on the matched pulse filter, and relies on a peaked match pulse filter shape. (Which has a derivative filter tap value of ideally 0 at the center of the matched pulse filter taps.) The derivative filter of a matched pulse filter for square pulses doesn't have the properties the PFB clock sync block needs. Regards, Andy > For the life of me I can't figure out the proper specification of > nfilts, and taps. > > > Given a signal with rectangular pulse shape at 'sps', can someone > spell out the taps and nfilt i need to enter into PFB clock sync for a > properly matched filter bank? > > > > -John > > > ______________________________________________________________________ > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
