From: Tom Rondeau <trondeau@vt.edu>
Date: Tue, 28 Dec 2010 17:48:18 +0000 (-0500)
Subject: PFB channelizer can be specified without external taps. Uses optfir to generate an... 
X-Git-Url: https://git.gag.com/?a=commitdiff_plain;h=3751671d1b596113e441ca326280bdcc94fdcc6f;p=debian%2Fgnuradio

PFB channelizer can be specified without external taps. Uses optfir to generate an internal filter to cover the channel bandwidth; user can specify the attenuation of this filter if desired.
---

diff --git a/gnuradio-core/src/python/gnuradio/blks2impl/pfb_channelizer.py b/gnuradio-core/src/python/gnuradio/blks2impl/pfb_channelizer.py
index a479ed48..ecbdd204 100644
--- a/gnuradio-core/src/python/gnuradio/blks2impl/pfb_channelizer.py
+++ b/gnuradio-core/src/python/gnuradio/blks2impl/pfb_channelizer.py
@@ -20,7 +20,7 @@
 # Boston, MA 02110-1301, USA.
 # 
 
-from gnuradio import gr
+from gnuradio import gr, optfir
 
 class pfb_channelizer_ccf(gr.hier_block2):
     '''
@@ -29,15 +29,31 @@ class pfb_channelizer_ccf(gr.hier_block2):
     This simplifies the interface by allowing a single input stream to connect to this block.
     It will then output a stream for each channel.
     '''
-    def __init__(self, numchans, taps, oversample_rate=1):
+    def __init__(self, numchans, taps=None, oversample_rate=1, atten=100):
 	gr.hier_block2.__init__(self, "pfb_channelizer_ccf",
 				gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
 				gr.io_signature(numchans, numchans, gr.sizeof_gr_complex)) # Output signature
 
         self._numchans = numchans
-        self._taps = taps
         self._oversample_rate = oversample_rate
 
+        if taps is not None:
+            self._taps = taps
+        else:
+            # Create a filter that covers the full bandwidth of the input signal
+            bw = 0.4
+            tb = 0.2
+            ripple = 0.1
+            made = False
+            while not made:
+                try:
+                    self._taps = optfir.low_pass(1, self._numchans, bw, bw+tb, ripple, atten)
+                    made = True
+                except RuntimeError:
+                    ripple += 0.01
+                    made = False
+                    print("Warning: set ripple to %.4f dB. If this is a problem, adjust the attenuation or create your own filter taps." % (ripple))
+
         self.s2ss = gr.stream_to_streams(gr.sizeof_gr_complex, self._numchans)
         self.pfb = gr.pfb_channelizer_ccf(self._numchans, self._taps,
                                           self._oversample_rate)
diff --git a/gnuradio-examples/python/pfb/channelize.py b/gnuradio-examples/python/pfb/channelize.py
index 27d87e55..f845c05c 100755
--- a/gnuradio-examples/python/pfb/channelize.py
+++ b/gnuradio-examples/python/pfb/channelize.py
@@ -36,7 +36,7 @@ class pfb_top_block(gr.top_block):
 
         # Create a set of taps for the PFB channelizer
         self._taps = gr.firdes.low_pass_2(1, self._fs, 475.50, 50, 
-                                          attenuation_dB=10, window=gr.firdes.WIN_BLACKMAN_hARRIS)
+                                          attenuation_dB=100, window=gr.firdes.WIN_BLACKMAN_hARRIS)
 
         # Calculate the number of taps per channel for our own information
         tpc = scipy.ceil(float(len(self._taps)) /  float(self._M))