parallel adaptive filters and filtering methods that enable processing of an input signal in a circuit that has an clock speed many times slower than the input rate of the input signal that is processed . a polyphase decimator structure processes a data stream requiring a low pass filtered bandlimited output that is used for high - rate output structures . the filters and methods break an input data stream into parallel paths that efficiently produce a bandlimited filtered output . each of the parallel paths is processed at a decimated rate to provide a filtered output signals corresponding to a filtered version of the input signal .