PURPOSE: To widen the band with an excellent amplitude phase characteristic by using a shift register, a capacitor and an input output switch to operate a delay register for obtaining the constitution similar to an acyclic digital filter.

CONSTITUTION: When the output of the FF1 of a shift register means goes to an 'H' at first, switches 8-10 are turned on and an input signal is stored in capacitors 17-19 through a signal input line 7, the output of the FF1 goes to an 'L' and the switches 8-10 are turned on. Then a FF2 goes to an 'H', switches 26-28 are turned on and the signal stored in capacitors 17, 20, 23 is sent to multipliers 35-37 having a filter coefficient. When the output of the FF2 goes to an 'L', the switches 26-28 are turned off, the signals of the switches are added by an weighted adder 38, a clock is eliminated by an LPF 39 and outputted to a signal output line 40. Thus, since signals of one and two preceding clocks are weighted and added at present, the broad band processing is attained with excellent amplitude and phase characteristics.