#define PI 3.141592654

int generate_tone(float *samples, float freq, int len);
float dc_level(float *x, float length);
float max_abs(float *x, int length);
void complex_base_band(float *x, int length, float freq, float phase, float *yi, float *yq);
float get_gain(float dc_i, float dc_q);
float get_phase(float dc_i, float dc_q);