filtering.py 文件源码

def fir1(n, wn):
    # Variables definition :
    nbands = len(wn) + 1
    ff = np.array((0, wn[0], wn[0], wn[1], wn[1], 1))

    f0 = np.mean(ff[2:4])
    l = n + 1

    mags = np.array(range(nbands)) % 2
    aa = np.ravel(np.matlib.repmat(mags, 2, 1), order='F')

    # Get filter coefficients :
    h = firls(l - 1, ff, aa)

    # Apply a window to coefficients :
    wind = np.hamming(l)
    b = np.matrix(h.T * wind)
    c = np.matrix(np.exp(-1j * 2 * np.pi * (f0 / 2) * np.array(range(l))))
    b = b / abs(c * b.T)

    return np.squeeze(np.array(b)), 1