typedef struct fm_mod { double samplerate; /* sample rate of in and out */ double offset; /* offset to calculated center frequency */ double amplitude; /* how much amplitude to add to the buff */ double phase; /* current phase of FM (used to shift and modulate ) */ double *sin_tab; /* sine/cosine table for modulation */ } fm_mod_t; void fm_mod_init(fm_mod_t *mod, double samplerate, double offset, double amplitude); void fm_modulate(fm_mod_t *mod, sample_t *samples, int num, float *buff); typedef struct fm_demod { double samplerate; /* sample rate of in and out */ double phase; /* current rotation phase (used to shift) */ double rot; /* rotation step per sample to shift rx frequency (used to shift) */ double last_phase; /* last phase of FM (used to demodulate) */ iir_filter_t lp[2]; /* filters received IQ signal */ double *sin_tab; /* sine/cosine table rotation */ } fm_demod_t; void fm_demod_init(fm_demod_t *demod, double samplerate, double offset, double bandwidth); void fm_demodulate(fm_demod_t *demod, sample_t *samples, int num, float *buff);