On the class of linear filters attainable with charge routing networks

A general theory of Charge Routing Networks (CRN) has been published previously by Gersho and Gopinath (1979). A p-phase CRN consists of a collection of storage cells divided into p subgroups and a routing procedure controlled by a p-phase clock. During a particular clock phase, charge is routed from a particular subgroup of storage cells into another subgroup. This simple mechanism allows a wide range of electronic functions including image sensing, data storage, signal processing or logic operations. An outline of CRN's modus operandi is first given and their input-output relationship is derived. The main result of the paper is the determination of the class of filters realizable as CRNs. The proof is constructive, so that a procedure for the implementation of a filter of this class can be easily set up as shown in a worked example.