Ooops. Too hasty!
2^ (roof(log_2(N)) + 1) long FFT. Sorry. Bob N4HY -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Robert McGwier Sent: Saturday, February 19, 2005 3:54 PM To: Alberto di Bene; [email protected] Subject: RE: [Discuss-gnuradio] Resampling in the frequency domain Alberto: Glad to know you are here. I would not revert to the time domain. "Rename" the complex bins of your fft by performing a simple circular shift until the right bin is on zero. Apply the low pass filter in the frequency domain, IFFT and then downsample. Since these frequencies or bins are discrete, you might need to retune BUT this can now be done on the decimated signal. REMEMBER, fft is a circular convolution. So if you use a N tap filter, you will probably want to use an roof(log_2(N))+1 long FFT and then do overlap save or add to turn it into a linear convolution. If this was not clear, please say so. Cheers, Bob Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
