Main Page | Namespace List | Class Hierarchy | Class List | File List | Namespace Members | Class Members | File Members | Related Pages

GrCostasLoop.h

Go to the documentation of this file.
00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2002 Free Software Foundation, Inc. 00004 * 00005 * This file is part of GNU Radio 00006 * 00007 * GNU Radio is free software; you can redistribute it and/or modify 00008 * it under the terms of the GNU General Public License as published by 00009 * the Free Software Foundation; either version 2, or (at your option) 00010 * any later version. 00011 * 00012 * GNU Radio is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00015 * GNU General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU General Public License 00018 * along with GNU Radio; see the file COPYING. If not, write to 00019 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, 00020 * Boston, MA 02111-1307, USA. 00021 */ 00022 00023 #ifndef _GRCOSTASLOOP_H_ 00024 #define _GRCOSTASLOOP_H_ 00025 00026 #include <VrSigProc.h> 00027 #include <gr_fir.h> 00028 #include <gr_iir.h> 00029 #include <gr_firdes.h> 00030 #include <gr_nco.h> 00031 00032 template<class iType,class oType> 00033 class GrCostasLoop : public VrSigProc 00034 { 00035 protected: 00036 gr_fir<iType,iType,float> *ifilter; 00037 gr_fir<iType,iType,float> *qfilter; 00038 gr_iir<double,double,double> *loopfilter; 00039 vector<double>fftaps; 00040 vector<double>fbtaps; 00041 gr_nco<iType,oType> *nco; 00042 unsigned int decimate; 00043 double sensitivity; 00044 double freq; 00045 double Fc; 00046 double arg; 00047 double argInc; 00048 double phi; 00049 double phase; 00050 virtual void initialize(); 00051 public: 00052 virtual const char *name() { return "GrCostasLoop"; } 00053 virtual int work(VrSampleRange output, void *ao[], 00054 VrSampleRange inputs[], void *ai[]); 00055 virtual ~GrCostasLoop() 00056 { 00057 delete ifilter; 00058 delete qfilter; 00059 delete loopfilter; 00060 delete nco; 00061 } 00062 GrCostasLoop(int d, double f,double s,double Fc) 00063 : VrSigProc(1,sizeof(iType),sizeof(oType)), 00064 decimate(d),sensitivity(s),freq(f),Fc(Fc),arg(0) { } 00065 }; 00066 00067 template<class iType,class oType> void 00068 GrCostasLoop<iType,oType>::initialize() 00069 { 00070 // Create all three filters 00071 double Fs = getInputSamplingFrequencyN (0); 00072 vector<float> lpf_coeffs = 00073 gr_firdes::low_pass (1.0, Fs, Fc, Fc/10,gr_firdes::WIN_HAMMING,0); 00074 ifilter = new gr_fir<iType,iType,float>(lpf_coeffs); 00075 qfilter = new gr_fir<iType,iType,float>(lpf_coeffs); 00076 loopfilter = new gr_iir<double,double,double>(fftaps,fbtaps); 00077 nco = new gr_nco<float,float>(); 00078 argInc = 2*M_PI*freq*(1 / (double)getInputSamplingFrequencyN(0)); 00079 } 00080 00081 template<class iType,class oType> int 00082 GrCostasLoop<iType,oType>::work(VrSampleRange output, void *ao[], 00083 VrSampleRange inputs[], void *ai[]) 00084 { 00085 iType **i = (iType**)ai; 00086 oType **o = (iType**)ao; 00087 int size = output.size/decimate; 00088 00089 float alpha=0.01; 00090 float beta=0.01; 00091 iType i_path_fifo[size]; 00092 iType q_path_fifo[size]; 00093 iType i_filtered[size]; 00094 iType q_filtered[size]; 00095 iType phase_det_out[size]; 00096 VrComplex phase_corr; 00097 00098 for (int j = 0; j < size; j++) 00099 { 00100 //mix incoming signal with cos and -sin of NCO 00101 for(int k = 0; k<decimate;k++) 00102 { 00103 i_path_fifo[j*decimate+k] = i[0][j*decimate+k] * nco->get_phase().real(); 00104 q_path_fifo[j*decimate+k] = i[0][j*decimate+k] * -nco->get_phase().imag(); 00105 nco->step(); 00106 } 00107 // Call both FIR filters. 00108 i_filtered[j]=ifilter->filter (i_path_fifo); 00109 q_filtered[j]=qfilter->filter (q_path_fifo); 00110 // Then do multiply or ATAN 00111 phase_det_out[j] = atan2(q_filtered[j],i_filtered[j]); 00112 // Call IIR filter for Loop filter 00113 // loopfilter.filter(nco_control,phase_det_out,size,decimate); 00114 // Adjust phase and frequency 00115 phase_corr.real(cos(alpha*phase_det_out[j])); 00116 phase_corr.imag(sin(alpha*phase_det_out[j])); 00117 nco->rotate_phase(phase_corr); 00118 nco->delta_freq(beta*phase_det_out[j]); 00119 o[0][j] = 0; 00120 } 00121 // Write output info, store state if necessary 00122 return output.size; 00123 } 00124 00125 #endif

Generated on Wed Aug 4 02:22:04 2004 for GNU Radio by doxygen 1.3.8