Reply by DSP_student November 3, 20082008-11-03
Hi all,

I'm trying to find an even lengthed sequence of FIR coefficients where
every coefficient will be one of the five: 1, -1, 0, j, -j.
I'm looking for a sequence whose FFT will have one notch (or at least a
20dB attenuation relative to other frequency samples) at a certain
frequency. I'm hoping to find different sequences so that each sequence
will have a notch (or attenuation) at a different frequency sample.

I know that the literature is full with articles about low-correlation
frequencies, some of them (e.g. Legendre sequences) have notch at DC
frequency. This is good, but i'm looking for the ability to have notches at
all frequency samples, not just the DC (besides, Legendre sequences have
odd length).

Could anyone help me with relevant information about this subject?

Thank you in advance,