Patent ID: 6993545

Claim:
A digital filter having a plurality of digital filter elements which are connected to each other in series, each digital filter element comprising: at least one forward coefficient multiplication circuit; at least one backward coefficient multiplication circuit; an adder logic circuit which performs an addition operation of an input signal and an output signal of said backward coefficient multiplication circuit; a storage circuit which serves to store an output signal of said adder logic circuit; an overflow detecting circuit which receives the output signal of said backward coefficient multiplication circuit, an output signal of the forward coefficient multiplication circuit in the preceding stage and all of the carry signals to the MSB(most significant bit)s from adjacent lower bits in summation of the output signals of said backward and forward coefficient multiplication circuits in the current and preceding stages respectively and which serves to detect an overflow occurring in the output signal of said adder logic circuit; and a clipping circuit connected to said storage circuit in order to clip an output signal of said storage circuit to either a positive or negative predetermined fixed value and output the clipped value in accordance with an output signal of said overflow detecting circuit.