Re: [Discuss-gnuradio] Comb filter generation

[Martin Dvh]

Marcus Leech wrote:
> I have a non-sinusoidal signal at frequency X, which is sampled at exactly 
> 100X, and I want to filter
> it so that only X, and its harmonics are present in the output signal. That 
> sounds to me like
> a comb filter--what's the most efficient way to express such using 
> gr_fir_filter_fff() ?
>
> [For the curious, this is part of my pulsar monitoring/detection software].
I would use an IIR filter for this.
(use multiple taps)

You could also use this little trick with a single_pole_iir:

block_size=100 #sample_freq/signal_freq
avg_alpha=0.01 #How much do you want to filter
s2p=gr.serial_to_parallel(gr_sizeof_gr_complex,block_size)
filter=gr_single_pole_iir_filter_cc(alpha,block_size)
p2s=gr.parallel_to_serial(gr_sizeof_gr_complex,block_size)
fg.connect(src,s2p,filter,p2s,dst)

This should give a nice comb filter without having too much computational 
requirements

Greetings,
Martin Dudok van Heel