ELLIPTIC FILTER DESIGN FOR A CLASS OF GENERALIZED HALFBAND FILTERS

In multirate processing, symmetric finite impulse response halfband filters constitute an important class of filters that are useful for sampling rate alteration by a factor of two. Generalizing the notion of halfband filters to include infinite impulse response filters, a class of generalized halfband filters is examined and its properties are studied. The filters are efficient and have low roundoff noise. A filter design program has been developed to design a special class of elliptic filters taking into account restrictions due to the generalized halfband characteristics. The procedure adapts previous results for elliptic filter design to this special case. It is shown that if the passband and stopband edge frequencies are related, then these filters are computationally efficient even when no sampling rate change is needed.