Constricted Passband Equiripple

Chebyshev I and Elliptic filters are famous for their flat equiripple passbands.  However, many applications require a flat equiripple effect only for frequencies nearer to the cutoff frequency.  In these situations, a totally flat equiripple passband is detrimental in that it unnecessarily reduces the rate of attenuation at the band edge and possibly requires a higher order filter.

Filter Solutions removes this potential waste of quality by optionally constricting the equiripple effect to a percentage of the passband.  For example, if the quality of a low pass passband is not an issue for the lower 50%, the equiripple may be constricted to the upper 50%.  The rate of attenuation at the band edge is then increased, and the order of the filter could possibly be reduced.  Likewise, ff the stop band attenuation is fixed for an Elliptic filter, the stop band ratio could be increased slightly and possibly reduce the required order.

Filter Solutions supports constricted equiripple passbands for both odd order and even order filters and for any user-entered percent restriction.