US Patent 7636747 Digital low-pass filter

A digital low-pass filter includes: a first subtracter that subtracts a first feedback term from an input; a first multiplier that multiplies an first subtracter output by a constant k1; a first delay unit that delays an input by a predetermined sampling time; a first adder that supplies, to the first delay unit, the input obtained by adding an first multiplier output to an first delay unit output; a second subtracter that subtracts the first feedback term from an first adder output; a second multiplier that multiplies an second subtracter output by a constant k2; a second delay unit that outputs, as the first feedback term, a signal obtained by delaying an input by a predetermined sampling time; and a second adder that supplies, to the second delay unit, a signal obtained by adding an second multiplier output to the second delay unit output.