[Commit-gnuradio] r11576 - gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter

[trondeau]

Author: trondeau
Date: 2009-08-11 16:56:56 -0600 (Tue, 11 Aug 2009)
New Revision: 11576

Modified:
   
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc
   
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h
Log:
Bug fixes for PFB channelizer and added documenation of its behavior.

Modified: 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc
===================================================================
--- 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc
    2009-08-11 22:55:57 UTC (rev 11575)
+++ 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc
    2009-08-11 22:56:56 UTC (rev 11576)
@@ -76,18 +76,26 @@
   d_taps_per_filter = (unsigned int)ceil((double)ntaps/(double)d_numchans);
 
   // Create d_numchan vectors to store each channel's taps
-  std::vector< std::vector<float> > vtaps(d_numchans);
+  d_taps.resize(d_numchans);
 
+  // Make a vector of the taps plus fill it out with 0's to fill
+  // each polyphase filter with exactly d_taps_per_filter
+  std::vector<float> tmp_taps;
+  tmp_taps = taps;
+  while((float)(tmp_taps.size()) < d_numchans*d_taps_per_filter) {
+    tmp_taps.push_back(0.0);
+  }
+ 
   // Partition the filter
   for(i = 0; i < d_numchans; i++) {
     // Each channel uses all d_taps_per_filter with 0's if not enough taps to 
fill out
-    vtaps[i] = std::vector<float>(d_taps_per_filter, 0);
+    d_taps[i] = std::vector<float>(d_taps_per_filter, 0);
     for(j = 0; j < d_taps_per_filter; j++) {
-      vtaps[i][j] = taps[i + j*d_numchans];  // add taps to channels in 
reverse order
+      d_taps[i][j] = tmp_taps[i + j*d_numchans];  // add taps to channels in 
reverse order
     }
     
     // Build a filter for each channel and add it's taps to it
-    d_filters[i]->set_taps(vtaps[i]);
+    d_filters[i]->set_taps(d_taps[i]);
   }
 
   // Set the history to ensure enough input items for each filter
@@ -96,6 +104,20 @@
   d_updated = true;
 }
 
+void
+gr_pfb_channelizer_ccf::print_taps()
+{
+  unsigned int i, j;
+  for(i = 0; i < d_numchans; i++) {
+    printf("filter[%d]: [", i);
+    for(j = 0; j < d_taps_per_filter; j++) {
+      printf(" %.4e", d_taps[i][j]);
+    }
+    printf("]\n\n");
+  }
+}
+
+
 int
 gr_pfb_channelizer_ccf::work (int noutput_items,
                              gr_vector_const_void_star &input_items,

Modified: 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h
===================================================================
--- 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h
     2009-08-11 22:55:57 UTC (rev 11575)
+++ 
gnuradio/branches/developers/trondeau/pfb/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h
     2009-08-11 22:56:56 UTC (rev 11576)
@@ -34,25 +34,90 @@
 class gr_fir_ccf;
 class gri_fft_complex;
 
+
 /*!
- * \brief FIR filter with gr_complex input, gr_complex output and float taps
+ * \class gr_pfb_channelizer_ccf
+ *
+ * \brief Polyphase filterbank channelizer with 
+ *        gr_complex input, gr_complex output and float taps
+ *
  * \ingroup filter_blk
+ *
+ * This block takes in complex inputs and channelizes it to <EM>M</EM>
+ * channels of equal bandwidth. Each of the resulting channels is
+ * decimated to the new rate that is the input sampling rate
+ * <EM>fs</EM> divided by the number of channels, <EM>M</EM>.
+ *
+ * The PFB channelizer code takes the taps generated above and builds
+ * a set of filters. The set contains <EM>M</EM> number of filters
+ * and each filter contains ceil(taps.size()/decim) number of taps.
+ * Each tap from the filter prototype is sequentially inserted into
+ * the next filter. When all of the input taps are used, the remaining
+ * filters in the filterbank are filled out with 0's to make sure each
+ * filter has the same number of taps.
+ *
+ * Each filter operates using the gr_fir filter classs of GNU Radio,
+ * which takes the input stream at <EM>i</EM> and performs the inner
+ * product calculation to <EM>i+(n-1)</EM> where <EM>n</EM> is the
+ * number of filter taps. To efficiently handle this in the GNU Radio
+ * structure, each filter input must come from its own input
+ * stream. So the channelizer must be provided with <EM>M</EM> streams
+ * where the input stream has been deinterleaved. This is most easily
+ * done using the gr_stream_to_streams block.
+ *
+ * The output is then produced as a vector, where index <EM>i</EM> in
+ * the vector is the next sample from the <EM>i</EM>th channel. This
+ * is most easily handled by sending the output to a
+ * gr_vector_to_streams block to handle the conversion and passing
+ * <EM>M</EM> streams out.
+ *
+ * The input and output formatting is done using a hier_block2 called
+ * pfb_channelizer_ccf. This can take in a single stream and outputs
+ * <EM>M</EM> streams based on the behavior described above.
+ *
+ * The filter's taps should be based on the input sampling rate.
+ *
+ * For example, using the GNU Radio's firdes utility to building
+ * filters, we build a low-pass filter with a sampling rate of 
+ * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
+ * bandwidth of <EM>TB</EM>. We can also specify the out-of-band
+ * attenuation to use, <EM>ATT</EM>, and the filter window
+ * function (a Blackman-harris window in this case). The first input
+ *  is the gain of the filter, which we specify here as unity.
+ *
+ *      <B><EM>self._taps = gr.firdes.low_pass_2(1, fs, BW, TB, 
+ *           attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
+ *
+ * The theory behind this block can be found in Chapter 6 of 
+ * the following book.
+ *
+ *    <B><EM>f. harris, Multirate Signal Processing for Communication 
+ *       Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.
+ *
  */
+
 class gr_pfb_channelizer_ccf : public gr_sync_block
 {
  private:
+  /*!
+   * Build the polyphase filterbank decimator.
+   * \param numchans (unsigned integer) Specifies the number of channels 
<EM>M</EM>
+   * \param taps    (vector/list of floats) The prototype filter to populate 
the filterbank.
+   */
   friend gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int 
numchans,
                                                                  const 
std::vector<float> &taps);
 
   std::vector<gr_fir_ccf*> d_filters;
+  std::vector< std::vector<float> > d_taps;
   gri_fft_complex         *d_fft;
   unsigned int             d_numchans;
   unsigned int             d_taps_per_filter;
   bool                    d_updated;
 
   /*!
-   * Construct a Polyphase filterbank for channelization with the given 
-   * number of channels and taps
+   * Build the polyphase filterbank decimator.
+   * \param numchans (unsigned integer) Specifies the number of channels 
<EM>M</EM>
+   * \param taps    (vector/list of floats) The prototype filter to populate 
the filterbank.
    */
   gr_pfb_channelizer_ccf (unsigned int numchans, 
                          const std::vector<float> &taps);
@@ -60,7 +125,16 @@
 public:
   ~gr_pfb_channelizer_ccf ();
   
+  /*!
+   * Resets the filterbank's filter taps with the new prototype filter
+   * \param taps    (vector/list of floats) The prototype filter to populate 
the filterbank.
+   */
   void set_taps (const std::vector<float> &taps);
+
+  /*!
+   * Print all of the filterbank taps to screen.
+   */
+  void print_taps();
   
   int work (int noutput_items,
            gr_vector_const_void_star &input_items,