[SciPy-User] Problem with complex bandpass filter

Benno Meier meier.benno@googlemail....
Sat Feb 25 08:53:15 CST 2012

Dear all,

I'm trying to implement a complex bandpass for IQ data in python using scipy.signal

I first create a lowpass using irdesign (giving b and a) and then I transform the taps (b to b2). 

However, the filtered spectrum looks exactly the same as before.

import scipy.signal.filter_design as ssfd
from scipy.signal import lfilter

[b, a] = ssfd.iirdesign(wp,ws,1,120)
b2 = b*np.array(1j*2*np.pi*0.4*np.arange(len(b)))

Can anyone help or point me to a routine that does the job?


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