Hallo,
currently i'am working on a ecg bandpass. To design my filter i use mostly "filterDesigner"-Tool by Matlab.
What are the specifications?
- Band of choice is 0.05 Hz – 150 Hz (recommended by American Hearth Association)
- sample rate = 500 Hz
- Take a stopband between 40 dB – 60 dB
- group delay has to be minimal
What filter would i choose?
- Because of minimal group delay i would choose a FIR-Filter, BUT the first cut-off is 0.05 Hz (the transition band has to be very sharp for example 0.01 Hz- 0.05 Hz) -> the filter order is about 15.000 i think with Equiripple design
- Lets take IIR-Filter -> here Butterworth Bandpass because it has the best phase response and a smooth passband
- But huge group delay at cut-off frequencies
FilterDesign Example
- Method: IIR-Butterworth Bandpass
- Minimum Order
- Fs = 500
- Fstop 1 [0.01] – Fpass1 [0.05]
- Fpass2 [150] – Fstop2 [200]
- Astop [40] , Apass [1], Astop [60]
My question to the experts, can you recommend a better design? The result is okay but the huge group delay looks very bad.
Best regards!
Best Answer