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Chebyshev I Filter offers a steeper roll-off than Butterworth by allowing controlled ripples in the passband while maintaining a flat stopband. Suitable when sharper cutoff is needed and small passband variation is acceptable. This filter requires the definition of the band type, order, the critical frequencies (in Hertz) and the max ripple (in dBa).
The Chebyshev I filter is a common filter used to clean up signals. Compared to the Butterworth, it has a sharper cutoff — meaning it more quickly separates the frequencies the users want from those they don’t. The trade-off is that in the useful frequency range (the passband), the amplitude is not perfectly flat. Instead, it has small ripples — tiny ups and downs in the signal strength. These ripples are controlled by a setting the user choose.
Chebyshev I filter may be used for several reasons including:
•Sharper cutoff than Butterworth: Useful when you want to strongly reject noise outside the frequency band.
•Acceptable trade-off: If a little unevenness in the kept frequencies is okay, you get better blocking power.
•Efficient: You can achieve the same cutoff sharpness with a lower filter order than Butterworth, meaning less computational effort.
When applying a Chebyshev I filter, the following parameters should be defined:
•Band type (low-pass, high-pass, band-pass, or band-stop).
•Order (integer, e.g., 2, 4, 6): Higher order = sharper cutoff.
•Critical frequencies (Hz): where the filtering begins (cutoff points).
•Maximum ripple (in dB): This controls how much unevenness is allowed in the passband. Example: ripple = 1 dB means the passband amplitude may vary by ±1 dB. Lower ripple = smoother passband but slower cutoff.
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Figure: Chebyshev I filter dialog
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Figure: FFT Spectrum of B-ICC record before (red) and after (blue) applying Chebyshev I filter
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