A synthesis of low-sensitivity digital filters using T-cascade connection

Digital filter response is degraded from the desired one. when the filter is implemented using finite wordlength multipliers. To avoid such degradation, low-sensitivity filter structures such as wave digital filters (WDF's) are used. On the other hand, the pipeline processing would be preferable for the fast operation of filters. A pipeline approach is not applicable for WDF's. though. This paper proposes new low-sensitivity filter structures which are also suited for the pipeline proces sing. The fundamental idea to obtain low-sensitivity structures is to synthesize digital 2-port circuits with 'structurally induced losslessness'. The losslessness of a digital 2-port circuits is characterized by a para-unitary scattering matrix. WDF's also satisfy this losslessness. Then the proposed structures are synthesized by factoring such scattering matrices, and constructed using T-cascade connection of new basic sections. Each section is also characterized by a para-unitary scattering matrix.