diff options
| -rw-r--r-- | gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc | 15 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h | 25 |
2 files changed, 38 insertions, 2 deletions
diff --git a/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc b/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc index e13a933ea..824a78dd9 100644 --- a/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc +++ b/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.cc @@ -49,6 +49,17 @@ gr_pfb_channelizer_ccf::gr_pfb_channelizer_ccf (unsigned int numchans, gr_make_io_signature (1, 1, numchans*sizeof(gr_complex))), d_updated (false), d_numchans(numchans), d_oversample_rate(oversample_rate) { + // The over sampling rate must be rationally related to the number of channels + // in that it must be N/i for i in [1,N], which gives an outputsample rate + // of [fs/N, fs] where fs is the input sample rate. + // This tests the specified input sample rate to see if it conforms to this + // requirement within a few significant figures. + double intp = 0; + double x = (10000.0*rint(numchans / oversample_rate)) / 10000.0; + double fltp = modf(numchans / oversample_rate, &intp); + if(fltp != 0.0) + throw std::invalid_argument("gr_pfb_channelizer: oversample rate must be N/i for i in [1, N]"); + d_filters = std::vector<gr_fir_ccf*>(d_numchans); // Create an FIR filter for each channel and zero out the taps @@ -68,7 +79,7 @@ gr_pfb_channelizer_ccf::gr_pfb_channelizer_ccf (unsigned int numchans, // performs the FFT shift operation on every other turn. d_rate_ratio = (int)rintf(d_numchans / d_oversample_rate); d_idxlut = new int[d_numchans]; - for(int i = 0; i < d_numchans; i++) { + for(unsigned int i = 0; i < d_numchans; i++) { d_idxlut[i] = d_numchans - ((i + d_rate_ratio) % d_numchans) - 1; } @@ -175,7 +186,7 @@ gr_pfb_channelizer_ccf::general_work (int noutput_items, i--; } - n += (i+d_rate_ratio) >= d_numchans; + n += (i+d_rate_ratio) >= (int)d_numchans; // despin through FFT d_fft->execute(); diff --git a/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h b/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h index e33e1938e..d56ccdbc6 100644 --- a/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h +++ b/gnuradio-core/src/lib/filter/gr_pfb_channelizer_ccf.h @@ -89,6 +89,19 @@ class gri_fft_complex; * <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 filter output can also be overs ampled. The over sampling rate + * is the ratio of the the actual output sampling rate to the normal + * output sampling rate. It must be rationally related to the number + * of channels as N/i for i in [1,N], which gives an outputsample rate + * of [fs/N, fs] where fs is the input sample rate and N is the number + * of channels. + * + * For example, for 6 channels with fs = 6000 Hz, the normal rate is + * 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4, + * 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample + * ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2, + * so the output rate would be 1200 Hz. + * * The theory behind this block can be found in Chapter 6 of * the following book. * @@ -104,6 +117,18 @@ class gr_pfb_channelizer_ccf : public gr_block * 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. + * \param oversample_rate (float) The over sampling rate is the ratio of the the actual + * output sampling rate to the normal output sampling rate. + * It must be rationally related to the number of channels + * as N/i for i in [1,N], which gives an outputsample rate + * of [fs/N, fs] where fs is the input sample rate and N is + * the number of channels. + * + * For example, for 6 channels with fs = 6000 Hz, the normal + * rate is 6000/6 = 1000 Hz. Allowable oversampling rates + * are 6/6, 6/5, 6/4, 6/3, 6/2, and 6/1 where the output + * sample rate of a 6/1 oversample ratio is 6000 Hz, or + * 6 times the normal 1000 Hz. */ friend gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int numchans, const std::vector<float> &taps, |