iir_theory.py 文件源码

def tf_inputfilter(self, inputfilter=None, frequencies=None):  # input
        # anti aliasing filter and additional delay model
        # delay comes from latency in fpga + on average half sampling time
        moduledelay = self.moduledelay + self.loops / 2.0
        if inputfilter is None:
            inputfilter = self.inputfilter
        if frequencies is None:
            frequencies = self.frequencies
        frequencies = np.asarray(frequencies, dtype=np.complex)
        try:
            len(inputfilter)
        except:
            inputfilter = [inputfilter]  # make it iterable
        tf = frequencies*0 + 1.0
        for f in inputfilter:
            if f > 0:  # lowpass
                tf /= (1.0 + 1j * frequencies / f)
                moduledelay += 1
            elif f < 0:  # highpass
                tf /= (1.0 + 1j * f / frequencies)
                moduledelay += 2
        # add delay
        delay = moduledelay * self.dt  # + extradelay
        tf *= np.exp(-1j*delay*frequencies*2*np.pi)
        return tf