PURPOSE: To save the mounting space of a filter circuit by constituting two kinds of band-pass filters which have been made up of a coil, a resistor and a capacitor with a switched capacitor filter.

CONSTITUTION: The titled circuit consists of a modulation circuit 1 and a filter circuit 2, the filter circuit 2 consists of low-pass filters 21a, 21b, plural operational amplifiers and plural capacitors and band-pass filter circuits 22a, 22b comprising a switched capacitor filter passing a required frequency band of a signal inputted to change the capacitance of the capacitor by a high frequency sampling clock. Then the sent signal is modulated by the modulation circuit 1 to obtain high and low group carriers. The undesired band component of two kinds of carriers is eliminated by the low-pass filter 21a of the pre-stage, the band-pass filters 22a, 22b extract two kinds of the carriers and a reflected noise generated by the signal having a frequency near the sampling clock frequency is eliminated by the low-pass filter 21b of the post stage to save of the filter circuit.