diff options
Diffstat (limited to 'gnuradio-core/src/lib/general')
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_fll_band_edge_cc.cc | 104 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_fll_band_edge_cc.h | 40 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_fll_band_edge_cc.i | 1 |
3 files changed, 90 insertions, 55 deletions
diff --git a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.cc b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.cc index 0f3d85c83..030e45ddf 100644 --- a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.cc +++ b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.cc @@ -53,11 +53,13 @@ gr_fll_band_edge_cc_sptr gr_make_fll_band_edge_cc (float samps_per_sym, float ro } +static int ios[] = {sizeof(gr_complex), sizeof(float), sizeof(float), sizeof(float)}; +static std::vector<int> iosig(ios, ios+sizeof(ios)/sizeof(int)); gr_fll_band_edge_cc::gr_fll_band_edge_cc (float samps_per_sym, float rolloff, int filter_size, float alpha, float beta) : gr_sync_block ("fll_band_edge_cc", gr_make_io_signature (1, 1, sizeof(gr_complex)), - gr_make_io_signature (1, 1, sizeof(gr_complex))), + gr_make_io_signaturev (1, 4, iosig)), d_alpha(alpha), d_beta(beta), d_updated (false) { // base this on the number of samples per symbol @@ -67,6 +69,29 @@ gr_fll_band_edge_cc::gr_fll_band_edge_cc (float samps_per_sym, float rolloff, d_freq = 0; d_phase = 0; + set_alpha(alpha); + + design_filter(samps_per_sym, rolloff, filter_size); +} + +gr_fll_band_edge_cc::~gr_fll_band_edge_cc () +{ + delete d_filter_lower; + delete d_filter_upper; +} + +void +gr_fll_band_edge_cc::set_alpha(float alpha) +{ + float eta = sqrt(2.0)/2.0; + float theta = alpha; + d_alpha = (4*eta*theta) / (1.0 + 2.0*eta*theta + theta*theta); + d_beta = (4*theta*theta) / (1.0 + 2.0*eta*theta + theta*theta); +} + +void +gr_fll_band_edge_cc::design_filter(float samps_per_sym, float rolloff, int filter_size) +{ int M = rint(filter_size / samps_per_sym); float power = 0; std::vector<float> bb_taps; @@ -81,11 +106,11 @@ gr_fll_band_edge_cc::gr_fll_band_edge_cc (float samps_per_sym, float rolloff, int N = (bb_taps.size() - 1.0)/2.0; std::vector<gr_complex> taps_lower; std::vector<gr_complex> taps_upper; - for(int i = 0; i < bb_taps.size(); i++) { + for(unsigned int i = 0; i < bb_taps.size(); i++) { float tap = bb_taps[i] / power; - float k = (-N + i)/(2.0*samps_per_sym); //rng = scipy.arange(-nn2, nn2+1) / (2*spb); - + float k = (-N + (int)i)/(2.0*samps_per_sym); + gr_complex t1 = tap * gr_expj(-2*M_PI*(1+rolloff)*k); gr_complex t2 = tap * gr_expj(2*M_PI*(1+rolloff)*k); @@ -97,61 +122,32 @@ gr_fll_band_edge_cc::gr_fll_band_edge_cc (float samps_per_sym, float rolloff, d_filter_upper = gr_fir_util::create_gr_fir_ccc(vtaps); d_filter_lower = gr_fir_util::create_gr_fir_ccc(vtaps); - set_taps_lower(taps_lower); - set_taps_upper(taps_upper); -} - -gr_fll_band_edge_cc::~gr_fll_band_edge_cc () -{ -} - -void -gr_fll_band_edge_cc::set_taps_lower (const std::vector<gr_complex> &taps) -{ - unsigned int i; - - for(i = 0; i < taps.size(); i++) { - d_taps_lower.push_back(taps[i]); - } - - d_filter_lower->set_taps(d_taps_lower); - - // Set the history to ensure enough input items for each filter - set_history(d_taps_lower.size()+1); + d_filter_lower->set_taps(taps_lower); + d_filter_upper->set_taps(taps_upper); d_updated = true; -} - -void -gr_fll_band_edge_cc::set_taps_upper (const std::vector<gr_complex> &taps) -{ - unsigned int i; - - for(i = 0; i < taps.size(); i++) { - d_taps_upper.push_back(taps[i]); - } - - d_filter_upper->set_taps(d_taps_upper); // Set the history to ensure enough input items for each filter - set_history(d_taps_upper.size()+1); + set_history(filter_size+1); - d_updated = true; } void gr_fll_band_edge_cc::print_taps() { unsigned int i; + std::vector<gr_complex> taps_upper = d_filter_upper->get_taps(); + std::vector<gr_complex> taps_lower = d_filter_lower->get_taps(); + printf("Upper Band-edge: ["); - for(i = 0; i < d_taps_upper.size(); i++) { - printf(" %.4e + %.4ej,", d_taps_upper[i].real(), d_taps_upper[i].imag()); + for(i = 0; i < taps_upper.size(); i++) { + printf(" %.4e + %.4ej,", taps_upper[i].real(), taps_upper[i].imag()); } printf("]\n\n"); printf("Lower Band-edge: ["); - for(i = 0; i < d_taps_lower.size(); i++) { - printf(" %.4e + %.4ej,", d_taps_lower[i].real(), d_taps_lower[i].imag()); + for(i = 0; i < taps_lower.size(); i++) { + printf(" %.4e + %.4ej,", taps_lower[i].real(), taps_lower[i].imag()); } printf("]\n\n"); } @@ -164,6 +160,13 @@ gr_fll_band_edge_cc::work (int noutput_items, const gr_complex *in = (const gr_complex *) input_items[0]; gr_complex *out = (gr_complex *) output_items[0]; + float *frq, *phs, *err; + if(output_items.size() > 2) { + frq = (float *) output_items[1]; + phs = (float *) output_items[2]; + err = (float *) output_items[3]; + } + if (d_updated) { d_updated = false; return 0; // history requirements may have changed. @@ -180,21 +183,28 @@ gr_fll_band_edge_cc::work (int noutput_items, out_upper = norm(d_filter_upper->filter(&out[i])); out_lower = norm(d_filter_lower->filter(&out[i])); error = out_lower - out_upper; - d_error = 0.1*error + 0.9*d_error; // average error + d_error = 0.01*error + 0.99*d_error; // average error - d_freq = d_freq + d_beta * error; - d_phase = d_phase + d_freq + d_alpha * error; + d_freq = d_freq + d_beta * d_error; + d_phase = d_phase + d_freq + d_alpha * d_error; if(d_phase > M_PI) d_phase -= M_TWOPI; else if(d_phase < -M_PI) d_phase += M_TWOPI; - + if (d_freq > d_max_freq) d_freq = d_max_freq; else if (d_freq < d_min_freq) d_freq = d_min_freq; + + if(output_items.size() > 2) { + frq[i] = d_freq; + phs[i] = d_phase; + err[i] = d_error; + } } + return noutput_items; } diff --git a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.h b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.h index 86e69df16..09baf7fde 100644 --- a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.h +++ b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.h @@ -39,6 +39,26 @@ class gri_fft_complex; * \brief Frequency Lock Loop using band-edge filters * * \ingroup general + * + * The frequency lock loop derives a band-edge filter that covers the upper and lower bandwidths + * of a digitally-modulated signal. The bandwidth range is determined by the excess bandwidth + * (e.g., rolloff factor) of the modulated signal. The placement in frequency of the band-edges + * is determined by the oversampling ratio (number of samples per symbol) and the excess bandwidth. + * The size of the filters should be fairly large so as to average over a number of symbols. + * The FLL works by calculating the power in both the upper and lower bands and comparing them. The + * difference in power between the filters is proportional to the frequency offset. + * + * In theory, the band-edge filter is the derivative of the matched filter in frequency, + * (H_be(f) = \frac{H(f)}{df}. In practice, this comes down to a quarter sine wave at the point + * of the matched filter's rolloff (if it's a raised-cosine, the derivative of a cosine is a sine). + * Extend this sine by another quarter wave to make a half wave around the band-edges is equivalent + * in time to the sum of two sinc functions. The baseband filter fot the band edges is therefore + * derived from this sum of sincs. The band edge filters are then just the baseband signal + * modulated to the correct place in frequency. All of these calculations are done in the + * 'design_filter' function. + * + * Note: We use FIR filters here because the filters have to have a flat phase response over the + * entire frequency range to allow their comparisons to be valid. */ class gr_fll_band_edge_cc : public gr_sync_block @@ -46,7 +66,11 @@ class gr_fll_band_edge_cc : public gr_sync_block private: /*! * Build the FLL - * \param taps (vector/list of gr_complex) The taps of the band-edge filter + * \param samps_per_sym (float) Number of samples per symbol of signal + * \param rolloff (float) Rolloff factor of signal + * \param filter_size (int) Size (in taps) of the filter + * \param alpha (float) Loop gain 1 + * \param beta (float) Loop gain 2 */ friend gr_fll_band_edge_cc_sptr gr_make_fll_band_edge_cc (float samps_per_sym, float rolloff, int filter_size, float alpha, float beta); @@ -58,8 +82,6 @@ class gr_fll_band_edge_cc : public gr_sync_block gr_fir_ccc* d_filter_upper; gr_fir_ccc* d_filter_lower; - std::vector<gr_complex> d_taps_upper; - std::vector<gr_complex> d_taps_lower; bool d_updated; float d_error; float d_freq; @@ -76,17 +98,19 @@ public: ~gr_fll_band_edge_cc (); /*! - * Resets the filter taps with the new prototype filter - * \param taps (vector/list of gr_complex) The band-edge filter + * Design the band-edge filter based on the number of samples per symbol, + * filter rolloff factor, and the filter size + * \param samps_per_sym (float) Number of samples per symbol of signal + * \param rolloff (float) Rolloff factor of signal + * \param filter_size (int) Size (in taps) of the filter */ - void set_taps_lower (const std::vector<gr_complex> &taps); - void set_taps_upper (const std::vector<gr_complex> &taps); + void design_filter(float samps_per_sym, float rolloff, int filter_size); /*! * Set the alpha gainvalue * \param alpha (float) new gain value */ - void set_alpha(float alpha) { d_alpha = alpha; } + void set_alpha(float alpha); /*! * Set the beta gain value diff --git a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.i b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.i index 545bad4f6..c9c792c8a 100644 --- a/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.i +++ b/gnuradio-core/src/lib/general/gr_fll_band_edge_cc.i @@ -36,5 +36,6 @@ class gr_fll_band_edge_cc : public gr_sync_block void set_alpha (float alpha); void set_beta (float beta); + void design_filter(float samps_per_sym, float rolloff, int filter_size); void print_taps(); }; |