PURPOSE: To realize a highly precise, inexpensive correlation detecting processor that exercises automatic sweep control by using an analog circuit for the division and multiplication of two input signals and a digital signal for the arithmetic of a correlative function.

CONSTITUTION: When signals Xt and Yt are inputted to terminals 1 and 6, processor 12 generates output D of a digital signal expressing time difference (γ) between input signals and reciprocal arithmetic circuit 20 performs analog arithmetic for conversion into a frequency signal after conversion into an analog signal. The frequency signal proportional to the output signal of this reciprocal arithmetic circuit 20 is supplied to analog delay circuit 8 to vary the delay time linearly. Further, integration for obtaining a correlation function, detection of the maximum value of the function, sweep control, etc., are performed by digital processor 12. Therefore, advantages of both the analog system and digital system can be taken and the manufacture cost can be reduced with high precision.