Filter quality “Q” and Filter types“Q” - Quality factor“Q” ExamplesSlide 4Filter types2/19/2004 BAE 5413 1 of 4Filter quality “Q” and Filter types2/19/2004 BAE 5413 2 of 4“Q” - Quality factor•Consider a band pass filter12121)(2222ssAsssAssGcc21Q121211)(2222sQfsfAssQsAssG2/19/2004 BAE 5413 3 of 4“Q” Examples•Q=1, 1100021100021)(22ssAssG10-1100101102103104-100-500Frequency (rad/sec)Gain dB10-1100101102103104-90090Frequency (rad/sec)Phase deg2/19/2004 BAE 5413 4 of 4“Q” Examples•Q=10,11000021100021)(22ssAssG10-1100101102103104-100-500Frequency (rad/sec)Gain dB10-1100101102103104-90090Frequency (rad/sec)Phase deg2/19/2004 BAE 5413 5 of 4Filter types•Butterworth - Ripple-free passband and a smooth stop band. Butterworth has least distortion due to almost linear phase. •Chebyshev - Predetermined passband ripple and requires smaller order than a Butterworth filter for a desired response. Superior for applications where passband includes only one frequency of interest •Elliptical - Equiripple pass- and stop-band, Predetermined amount of passband ripple along with ripple in the stop band. Elliptic filters require smallest order for a desired magnitude response•Bessel -constant propagation delay across the input frequency spectrum•Gaussian -the most gradual pass band roll-off and the lowest group delay. Low distortion across the
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