std::complex <double> FmFunction::calc (const double &inpt)
{
liquid_float_complex res{0.0f, 0.0f};
freqmod_modulate(_mod, (float)inpt, &res);
return std::complex<double> ((double)res.real, (double)res.imag);
}
// Help function to keep code base small
// _kf : modulation factor
// _type : demodulation type {LIQUID_FREQDEM_DELAYCONJ, LIQUID_FREQDEM_PLL}
void freqmodem_test(float _kf,
liquid_freqdem_type _type)
{
// options
unsigned int num_samples = 1024;
//float tol = 1e-2f;
unsigned int i;
// create mod/demod objects
freqmod mod = freqmod_create(_kf); // modulator
freqdem dem = freqdem_create(_kf,_type); // demodulator
// allocate arrays
float m[num_samples]; // message signal
float complex r[num_samples]; // received signal (complex baseband)
float y[num_samples]; // demodulator output
// generate message signal (single-frequency sine)
for (i=0; i<num_samples; i++)
m[i] = 0.7f*cosf(2*M_PI*0.013f*i + 0.0f);
// modulate/demodulate signal
for (i=0; i<num_samples; i++) {
// modulate
freqmod_modulate(mod, m[i], &r[i]);
// demodulate
freqdem_demodulate(dem, r[i], &y[i]);
}
// delete modem objects
freqmod_destroy(mod);
freqdem_destroy(dem);
#if 0
// compute power spectral densities and compare
float complex mcf[num_samples];
float complex ycf[num_samples];
float complex M[num_samples];
float complex Y[num_samples];
for (i=0; i<num_samples; i++) {
mcf[i] = m[i] * hamming(i,num_samples);
ycf[i] = y[i] * hamming(i,num_samples);
}
fft_run(num_samples, mcf, M, LIQUID_FFT_FORWARD, 0);
fft_run(num_samples, ycf, Y, LIQUID_FFT_FORWARD, 0);
// run test: compare spectral magnitude
for (i=0; i<num_samples; i++)
CONTEND_DELTA( cabsf(Y[i]), cabsf(M[i]), tol );
#endif
}