Hi,
I am new to filter design. I would like to design FIR Band Pass filters with
lower cutoff frequency 0.1Hz and upper cutoff frequency 5Hz (sampling frequency
is 12800Hz). I tried with FDATOOL to design band pass filter (FIR with various
combinations like equiripple, Least Squares Windowing (Kaiser, Blackman etc) .
but results are not satisfactory
Can anybody guide in this Regard.
Thanks in Advance.
Regards,
svs
Bandpass FIR Filter Design
Started by ●January 9, 2007
Reply by ●January 9, 20072007-01-09
Hi svs,
the problem is not the filter design algorithm, but the numerical
representaion of coefficients and the filter order. Using such an extreme
ratio of sampling frequency to cutoff frequency will result in very large
filters and very small coefficients.
You should use some decimation stages first to reduce the sampling
frequency and then run your filter with a low sampling frequency.
Regards,
A.Klemenz
At 20:43 08.01.2007 -0800, SVS wrote:
>Hi,
>I am new to filter design. I would like to design FIR Band Pass filters
>with lower cutoff frequency 0.1Hz and upper cutoff frequency 5Hz (sampling
>frequency is 12800Hz). I tried with FDATOOL to design band pass filter
>(FIR with various combinations like equiripple, Least Squares Windowing
>(Kaiser, Blackman etc) . but results are not satisfactory
>Can anybody guide in this Regard.
>Thanks in Advance.
>Regards,
>svs
the problem is not the filter design algorithm, but the numerical
representaion of coefficients and the filter order. Using such an extreme
ratio of sampling frequency to cutoff frequency will result in very large
filters and very small coefficients.
You should use some decimation stages first to reduce the sampling
frequency and then run your filter with a low sampling frequency.
Regards,
A.Klemenz
At 20:43 08.01.2007 -0800, SVS wrote:
>Hi,
>I am new to filter design. I would like to design FIR Band Pass filters
>with lower cutoff frequency 0.1Hz and upper cutoff frequency 5Hz (sampling
>frequency is 12800Hz). I tried with FDATOOL to design band pass filter
>(FIR with various combinations like equiripple, Least Squares Windowing
>(Kaiser, Blackman etc) . but results are not satisfactory
>Can anybody guide in this Regard.
>Thanks in Advance.
>Regards,
>svs
Reply by ●January 10, 20072007-01-10
Sita-
> I am new to filter design. I would like to design FIR Band Pass filters with
> lower cutoff frequency 0.1Hz and upper cutoff frequency 5Hz (sampling frequency
> is 12800Hz). I tried with FDATOOL to design band pass filter (FIR with various
> combinations like equiripple, Least Squares Windowing (Kaiser, Blackman etc) .
> but results are not satisfactory
Your specifications are going to require a really long FIR filter (many taps) to get
some amount of stopband attenuation. You might try an IIR filter instead.
If you do end up using IIR filter for this, and intend to implement on a fixed-point
DSP device, then you will likely need at least 32-bit coefficients.
-Jeff
> I am new to filter design. I would like to design FIR Band Pass filters with
> lower cutoff frequency 0.1Hz and upper cutoff frequency 5Hz (sampling frequency
> is 12800Hz). I tried with FDATOOL to design band pass filter (FIR with various
> combinations like equiripple, Least Squares Windowing (Kaiser, Blackman etc) .
> but results are not satisfactory
Your specifications are going to require a really long FIR filter (many taps) to get
some amount of stopband attenuation. You might try an IIR filter instead.
If you do end up using IIR filter for this, and intend to implement on a fixed-point
DSP device, then you will likely need at least 32-bit coefficients.
-Jeff
