Multiple notch filters

[falkpl]

I am no DSP expert but am trying to realize a filter that will notch 60 Hz and a specified number of harmoinics from a signal.  I have routed my signal through muiltple notch filters (one for each harmonic) with a decreasing Bandstop Attenuation.  This works except the attenuation increases with harmonics and not the other way around.  I dont think my aproach is correct.  How do I cascade IIR filters in labview (8.21)

[johnsold]

What you are looking for is called a comb filter. The name comes from the comb-like appearance of the attenuation curve.

I am not sure how to implement one in LV. Especially with a requirement to be able to specify the number of harmonics. Probably use a combination of an adjustable low pass filter and the comb filter.

None of my filter books list comb filters in their indexes, so I will have to think about it a bit.

I am pretty sure that a synchronous filter filters harmonics, so maybe I can come up with something.

Lynn

[falkpl]

There is a comb filter in the digital filter design but it made a comb using all harmonics over the sampleing frequency.  This is not good since I am notching out a few harmonics and the Fs is 500k/sec.  If a can combine this with a low pass filter it might work but I dont want to use the addon toolkit if possible since the client doen not have the toolkit and wants all source code.  Thanks for any advice all will help.

Paul