PURPOSE: To obtain an original signal which is free from the folded noise, by using the noncyclic filters of an odd number of taps to both low and high band- pass filters within the band dividing and synthesizing filter blocks respectively.

CONSTITUTION: An input signal X(Z) of frequency fS is supplied to noncyclic filters 201 and 301 having odd number of taps with transmission functions H(Z) and H(-Z) within a band dividing filter block 100 via an input terminal 10. The outputs of the filters 201 and 301 are thinned to fS/2kHz respectively through sampling frequency thinning switches 401 and 402 and then fed to a band synthesizing filter block 200 via a signal processing circuit 300. Then 0 is inserted into each input with every second sample through sampling frequency interpolation switches 501 and 502 and then added by an adder 60 via noncyclic filters 202 and 302 having the same structure as the filters 201 and 301.