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[Commit-gnuradio] r3935 - gnuradio/branches/developers/trondeau/digital-
From: |
trondeau |
Subject: |
[Commit-gnuradio] r3935 - gnuradio/branches/developers/trondeau/digital-wip/gnuradio-core/src/python/gnuradio/blksimpl |
Date: |
Sat, 4 Nov 2006 14:26:29 -0700 (MST) |
Author: trondeau
Date: 2006-11-04 14:26:29 -0700 (Sat, 04 Nov 2006)
New Revision: 3935
Modified:
gnuradio/branches/developers/trondeau/digital-wip/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
Log:
Changed how Costas loop is handled in QPSK -- slightly overdamping for improved
performance; might need more tweaking
Modified:
gnuradio/branches/developers/trondeau/digital-wip/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
===================================================================
---
gnuradio/branches/developers/trondeau/digital-wip/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
2006-11-04 21:25:35 UTC (rev 3934)
+++
gnuradio/branches/developers/trondeau/digital-wip/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
2006-11-04 21:26:29 UTC (rev 3935)
@@ -238,10 +238,10 @@
self.agc = gr.feedforward_agc_cc(16, 1.0)
# Costas loop (carrier tracking)
- # FIXME: need to decide how to handle this more generally; do we pull
it from higher layer?
costas_order = 4
- beta = .25 * self._costas_alpha * self._costas_alpha
- #self.costas_loop = gr.costas_loop_cc(self._costas_alpha, beta, 0.1,
-0.1, costas_order)
+ # The value of beta is now set to be overdamped; this value can have a
huge impact on the
+ # performance of QPSK. Set to 0.25 for critically damped or higher for
underdamped responses.
+ beta = .10 * self._costas_alpha * self._costas_alpha
self.costas_loop = gr.costas_loop_cc(self._costas_alpha, beta, 0.002,
-0.002, costas_order)
# RRC data filter
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