FAST FOURIER TRANSFORMER

PURPOSE:To correspond to a signal as well in which a dynamic characteristic is remarkable changed hourly by obtaining the self-correlation of an analog input signal beforehand and removing a noise component. CONSTITUTION:An analog input signal is inputted to a self-correlerating means 13 and the analog input signal is branched to two same analog signals in a branching connection 131 by the self-correlating means 13. A first analog input signal enters an A/D converter 132, is converted to a digital value, stored temporarily to a data memory 133 and the temporarily delayed digital value stored into a data memory 133 is inputted to a D/A converter 13. On the other hand, another branched and connected analog input signal, namely, a second analog input signal is inputted as the reference signal of a D/A converter 134, and in the internal part of the D/A converter 134, at the time of D/A conversion, the second analog input signal inputted to the reference voltage part of the D/A converter and the digital value outputted by the data memory 133 are multiplied.