fm.py 文件源码

def symbol_recovery_24(xdi, xdq):
    angles = numpy.where(xdi >= 0, numpy.arctan2(xdq, xdi), numpy.arctan2(-xdq, -xdi))
    theta = (signal.convolve(angles, smooth)) [-len(xdi):]

    xr = (xdi + 1j * xdq) * numpy.exp(-1j * theta)
    bi = (numpy.real(xr) >= 0) + 0
    # pll parameters
    period = 24
    halfPeriod = period / 2
    corr = period / 24.
    phase = 0

    res = []
    pin = 0

    stats = {0: 0, 1: 1}
    oddity = 0

    latestXrSquared = [0]*8
    lxsIndex = 0
    theta = [0]
    shift = 0

    # pll, system model, error calculation, estimate update
    for i in range(1, len(bi)):
        if bi[i-1] != bi[i]:
            if phase < halfPeriod-2:
                phase += corr
            elif phase > halfPeriod+2:
                phase -= corr
        if phase >= period:
            phase -= period
            latestXrSquared[lxsIndex] = (xdi[i] + 1j * xdq[i])**2
            lxsIndex += 1
            if lxsIndex >= len(latestXrSquared):
                lxsIndex = 0
            th = shift + cmath.phase(sum(latestXrSquared)) / 2
            if abs(th - theta[-1]) > 2:
                if th < theta[-1]:
                    shift += math.pi
                    th += math.pi
                else:
                    shift -= math.pi
                    th -= math.pi
            theta.append(th)
            oddity += 1
            if oddity == 2:
                oddity = 0
                yp = (xdi[i] + 1j * xdq[i])
                ypp = cmath.exp(-1j * th) * yp
                # bit decode
                nin = 1 * (ypp.real > 0)
                stats[nin] += 1
                res.append(pin ^ nin)
                pin = nin
        phase += 1
    return res