All-pass filter implementation in numpy I'm playing with Python &amp; numpy to filter audio. It is relatively straightforward to design and us low-high-bandpass/stop FIR and IIR filters, stuff can be done in a couple of lines.

I'm implementing a small software defined radio software, and I need an all-pass filter that has 90 degrees phase shift everywhere, and is flat (as much as possible).

Unfortunately I was unable to find any quick solution for this.

Please share your thoughts on this.

Thank you,

Tamás.
The Hibert transform will produce a signal with 90 degree phase shift.  Look in Numpy documentation at scipy.signal.hilbert as a start.

I'm not sure what you are actually trying to do, but you mentioned 90 degree phase shift and radio in the same post, so you may find the following article of use:

http://home.comcast.net/~szemengtan/LinearSystems/hilbert.pdf