4.5. Elliptic filters: the Cauer approximation – Digital Filters Design for Signal and Image Processing

4.5. Elliptic filters: the Cauer approximation

The Chebyshev approximation that distributes error in one of the bands allows for filtering performances equivalent to those of Butterworth filters, and at lower orders. We can distribute the approximation error at the same time in the passband and the attenuated band. This theory, which is called elliptic approximation, leads to the development of Cauer filters. In this text, we will not discuss this type of filter in detail.