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two identical filter in series

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tarkyss

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in order to filter the noise, the low pass filter is replaced with two same filter in series, how much about the difference, thanks
 

Kral

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Re: two same filter in series

Tarkyss,
Please give more details of your specific filter application. In general, the ultimate slope of a low pass filter is 6n dB/octave (20n dB/decade), where n is the number of poles. The more filters you cascade, the sharper the filter. However, keep in mind that cascading 2 identical filters will usually not be the optimal solution. For example, a 2 pole Butterworth filter will out perform 2 cascaded lag filters, if stopband attenuation for a given cutoff frequency is your figure of merit.
Regards,
Kral
 

tarkyss

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two same filter in series

Kral, thanks, now I am studying a RTL code, In the code, two identical filters are in series, I dont know why, so i guess it may be for s/n, what do you think about the reason?
 

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