常见窗函数C 实现_c语言有hann函数

窗函数的作用

在信号处理中，我们通常对信号进行截断分析，如果信号截断为非周期截断，那么频谱将发生泄露。通过加窗，可以减少频谱的泄露。我们可以这么想象，窗函数可以将一个非周期的信号，强行变成一个周期的信号。

1.blackman 窗函数实现

void dsps_wind_blackman_f32(float *window, int len)
{
    const float a0 = 0.42;
    const float a1 = 0.5;
    const float a2 = 0.08;
 
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = a0 - a1 * cosf(i * 2 * M_PI * len_mult) + a2 * cosf(i * 4 * M_PI * len_mult);
    }
}

2.Blackman-Harris window

 
void dsps_wind_blackman_harris_f32(float *window, int len)
{
    const float a0=0.35875; 
    const float a1=0.48829;
    const float a2=0.14128;
    const float a3=0.01168;
    
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = a0 
                    - a1 * cosf(i * 2 * M_PI * len_mult) 
                    + a2 * cosf(i * 4 * M_PI * len_mult) 
                    - a3 * cosf(i * 6 * M_PI * len_mult);
    }
}

3.Blackman-Nuttall window

void dsps_wind_blackman_nuttall_f32(float *window, int len)
{
    const float a0=0.3635819; 
    const float a1=0.4891775;
    const float a2=0.1365995;
    const float a3=0.0106411;
    
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = a0 
                    - a1 * cosf(i * 2 * M_PI * len_mult) 
                    + a2 * cosf(i * 4 * M_PI * len_mult) 
                    - a3 * cosf(i * 6 * M_PI * len_mult);
    }
}

4.Flat-Top window

void dsps_wind_flat_top_f32(float *window, int len)
{
    const float a0=0.21557895; 
    const float a1=0.41663158; 
    const float a2=0.277263158; 
    const float a3=0.083578947; 
    const float a4=0.006947368;    
 
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = a0 
                    - a1 * cosf(i * 2 * M_PI * len_mult) 
                    + a2 * cosf(i * 4 * M_PI * len_mult)
                    - a3 * cosf(i * 6 * M_PI * len_mult)
                    + a4 * cosf(i * 8 * M_PI * len_mult);
    }
}

5.Hann window

void dsps_wind_hann_f32(float *window, int len)
{
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = 0.5 * (1 - cosf(i * 2 * M_PI * len_mult));
    }
}

6. Nuttall window

void dsps_wind_nuttall_f32(float *window, int len)
{
    const float a0=0.355768; 
    const float a1=0.487396;
    const float a2=0.144232;
    const float a3=0.012604;
 
    float len_mult = 1/(float)(len-1);
    for (int i = 0; i < len; i++) {
        window[i] = a0 
                    - a1 * cosf(i * 2 * M_PI * len_mult) 
                    + a2 * cosf(i * 4 * M_PI * len_mult) 
                    - a3 * cosf(i * 6 * M_PI * len_mult);
    }
}