// Helper function to keep code base small
void resamp_crcf_bench(struct rusage * _start,
struct rusage * _finish,
unsigned long int * _num_iterations,
unsigned int _P,
unsigned int _Q)
{
// adjust number of iterations: cycles/trial ~ 500 + 100 Q
*_num_iterations /= (500 + 100*_Q);
// create resampling object; irrational rate is just less than Q/P
float rate = (float)_Q/(float)_P*sqrt(3301.0f/3302.0f);
unsigned int m = 12; // filter semi-length
float bw = 0.45f; // filter bandwidth
float As = 60.0f; // stop-band attenuation [dB]
unsigned int npfb = 64; // number of polyphase filters
resamp_crcf q = resamp_crcf_create(rate,m,bw,As,npfb);
// buffering
float complex buf_0[_P];
float complex buf_1[_Q*4];
unsigned int num_written;
unsigned long int i;
for (i=0; i<_P; i++)
buf_0[i] = i % 7 ? 1 : -1;
// start trials
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
resamp_crcf_execute_block(q, buf_0, _P, buf_1, &num_written);
resamp_crcf_execute_block(q, buf_0, _P, buf_1, &num_written);
resamp_crcf_execute_block(q, buf_0, _P, buf_1, &num_written);
resamp_crcf_execute_block(q, buf_0, _P, buf_1, &num_written);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 4;
// destroy object
resamp_crcf_destroy(q);
}
int main(int argc, char*argv[])
{
// options
float r = 1.1f; // resampling rate (output/input)
unsigned int m = 13; // resampling filter semi-length (filter delay)
float As = 60.0f; // resampling filter stop-band attenuation [dB]
float bw = 0.45f; // resampling filter bandwidth
unsigned int npfb = 64; // number of filters in bank (timing resolution)
unsigned int n = 400; // number of input samples
float fc = 0.044f; // complex sinusoid frequency
int dopt;
while ((dopt = getopt(argc,argv,"hr:m:b:s:p:n:f:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'r': r = atof(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': bw = atof(optarg); break;
case 's': As = atof(optarg); break;
case 'p': npfb = atoi(optarg); break;
case 'n': n = atoi(optarg); break;
case 'f': fc = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (r <= 0.0f) {
fprintf(stderr,"error: %s, resampling rate must be greater than zero\n", argv[0]);
exit(1);
} else if (m == 0) {
fprintf(stderr,"error: %s, filter semi-length must be greater than zero\n", argv[0]);
exit(1);
} else if (bw == 0.0f || bw >= 0.5f) {
fprintf(stderr,"error: %s, filter bandwidth must be in (0,0.5)\n", argv[0]);
exit(1);
} else if (As < 0.0f) {
fprintf(stderr,"error: %s, filter stop-band attenuation must be greater than zero\n", argv[0]);
exit(1);
} else if (npfb == 0) {
fprintf(stderr,"error: %s, filter bank size must be greater than zero\n", argv[0]);
exit(1);
} else if (n == 0) {
fprintf(stderr,"error: %s, number of input samples must be greater than zero\n", argv[0]);
exit(1);
}
unsigned int i;
// number of input samples (zero-padded)
unsigned int nx = n + m;
// output buffer with extra padding for good measure
unsigned int y_len = (unsigned int) ceilf(1.1 * nx * r) + 4;
// arrays
float complex x[nx];
float complex y[y_len];
// create resampler
resamp_crcf q = resamp_crcf_create(r,m,bw,As,npfb);
// generate input signal
float wsum = 0.0f;
for (i=0; i<nx; i++) {
// compute window
float w = i < n ? kaiser(i, n, 10.0f, 0.0f) : 0.0f;
// apply window to complex sinusoid
x[i] = cexpf(_Complex_I*2*M_PI*fc*i) * w;
// accumulate window
wsum += w;
}
// resample
unsigned int ny=0;
#if 0
// execute one sample at a time
unsigned int nw;
for (i=0; i<nx; i++) {
// execute resampler, storing in output buffer
resamp_crcf_execute(q, x[i], &y[ny], &nw);
// increment output size
ny += nw;
}
#else
// execute on block of samples
resamp_crcf_execute_block(q, x, nx, y, &ny);
#endif
// clean up allocated objects
resamp_crcf_destroy(q);
//
// analyze resulting signal
//
// check that the actual resampling rate is close to the target
float r_actual = (float)ny / (float)nx;
float fy = fc / r; // expected output frequency
// run FFT and ensure that carrier has moved and that image
// frequencies and distortion have been adequately suppressed
unsigned int nfft = 1 << liquid_nextpow2(ny);
float complex yfft[nfft]; // fft input
float complex Yfft[nfft]; // fft output
for (i=0; i<nfft; i++)
yfft[i] = i < ny ? y[i] : 0.0f;
fft_run(nfft, yfft, Yfft, LIQUID_FFT_FORWARD, 0);
fft_shift(Yfft, nfft); // run FFT shift
// find peak frequency
float Ypeak = 0.0f;
float fpeak = 0.0f;
float max_sidelobe = -1e9f; // maximum side-lobe [dB]
float main_lobe_width = 0.07f; // TODO: figure this out from Kaiser's equations
for (i=0; i<nfft; i++) {
// normalized output frequency
float f = (float)i/(float)nfft - 0.5f;
// scale FFT output appropriately
float Ymag = 20*log10f( cabsf(Yfft[i] / (r * wsum)) );
// find frequency location of maximum magnitude
if (Ymag > Ypeak || i==0) {
Ypeak = Ymag;
fpeak = f;
}
// find peak side-lobe value, ignoring frequencies
// within a certain range of signal frequency
if ( fabsf(f-fy) > main_lobe_width )
max_sidelobe = Ymag > max_sidelobe ? Ymag : max_sidelobe;
}
// print results and check frequency location
printf(" desired resampling rate : %12.8f\n", r);
printf(" measured resampling rate : %12.8f (%u/%u)\n", r_actual, ny, nx);
printf(" peak spectrum : %12.8f dB (expected 0.0 dB)\n", Ypeak);
printf(" peak frequency : %12.8f (expected %-12.8f)\n", fpeak, fy);
printf(" max sidelobe : %12.8f dB (expected at least %.2f dB)\n", max_sidelobe, -As);
//
// export results
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n",OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"m=%u;\n", m);
fprintf(fid,"npfb=%u;\n", npfb);
fprintf(fid,"r=%12.8f;\n", r);
fprintf(fid,"nx = %u;\n", nx);
fprintf(fid,"x = zeros(1,nx);\n");
for (i=0; i<nx; i++)
fprintf(fid,"x(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"ny = %u;\n", ny);
fprintf(fid,"y = zeros(1,ny);\n");
for (i=0; i<ny; i++)
fprintf(fid,"y(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"\n\n");
fprintf(fid,"%% plot frequency-domain result\n");
fprintf(fid,"nfft=2^nextpow2(max(nx,ny));\n");
fprintf(fid,"%% estimate PSD, normalize by array length\n");
fprintf(fid,"X=20*log10(abs(fftshift(fft(x,nfft)/length(x))));\n");
fprintf(fid,"Y=20*log10(abs(fftshift(fft(y,nfft)/length(y))));\n");
fprintf(fid,"G=max(X);\n");
fprintf(fid,"X=X-G;\n");
fprintf(fid,"Y=Y-G;\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"if r>1, fx = f/r; fy = f; %% interpolated\n");
fprintf(fid,"else, fx = f; fy = f*r; %% decimated\n");
fprintf(fid,"end;\n");
fprintf(fid,"plot(fx,X,'Color',[0.5 0.5 0.5],fy,Y,'LineWidth',2);\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('normalized frequency');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"legend('original','resampled','location','northeast');");
fprintf(fid,"axis([-0.5 0.5 -120 20]);\n");
fprintf(fid,"\n\n");
fprintf(fid,"%% plot time-domain result\n");
fprintf(fid,"tx=[0:(length(x)-1)];\n");
fprintf(fid,"ty=[0:(length(y)-1)]/r-m;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(tx,real(x),'-s','Color',[0.5 0.5 0.5],'MarkerSize',1,...\n");
fprintf(fid," ty,real(y),'-s','Color',[0.5 0 0], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(tx,imag(x),'-s','Color',[0.5 0.5 0.5],'MarkerSize',1,...\n");
fprintf(fid," ty,imag(y),'-s','Color',[0 0.5 0], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('imag');\n");
fclose(fid);
printf("results written to %s\n",OUTPUT_FILENAME);
printf("done.\n");
return 0;
}