[Commit-gnuradio] r4009 - gnuradio/trunk/gnuradio-core/src/python/gnuradio/blksimpl

[trondeau]

Author: trondeau
Date: 2006-11-21 10:21:15 -0700 (Tue, 21 Nov 2006)
New Revision: 4009

Modified:
   gnuradio/trunk/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
Log:
improved Costas loop gains for QPSK receiver

Modified: gnuradio/trunk/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py
===================================================================
--- gnuradio/trunk/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py  
2006-11-20 18:42:54 UTC (rev 4008)
+++ gnuradio/trunk/gnuradio-core/src/python/gnuradio/blksimpl/dqpsk.py  
2006-11-21 17:21:15 UTC (rev 4009)
@@ -239,13 +239,13 @@
        
         # Costas loop (carrier tracking)
         if self._costas_alpha is None:   # If no alpha value was specified by 
the user
-            alpha_dir = {2:0.075, 3:0.075, 4:0.105, 5:0.105, 6:0.125, 7:0.130}
+            alpha_dir = {2:0.075, 3:0.09, 4:0.09, 5:0.095, 6:0.10, 7:0.105}
             self._costas_alpha = alpha_dir[self._samples_per_symbol]
         
         costas_order = 4        
-        # The value of beta is now set to be overdamped; this value can have a 
huge impact on the
+        # The value of beta is now set to be underdamped; 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 = .15 * self._costas_alpha * self._costas_alpha
+        beta = .5 0 * self._costas_alpha * self._costas_alpha
         self.costas_loop = gr.costas_loop_cc(self._costas_alpha, beta, 0.02, 
-0.02, costas_order)
 
         # RRC data filter