| 摘要 |
PROBLEM TO BE SOLVED: To provide an arithmetic unit used for an ultrasonic flowmeter, or the like, and which keeps the operation amount to be small, while computing the propagation time difference with high accuracy. SOLUTION: The arithmetic unit includes first and second Fourier transform portions 121 and 122, which perform respectively Fourier transformation on two input signals; a complex-conjugate deriving portion 123, which derives complex conjugate of an output value of the first Fourier transform portion 121; a multiplier 124, which outputs a value after multiplication of the complex conjugate and an output value of the second Fourier transform portion 122; a Hilbert transform portion 130 which performs Hilbert transformation on the value, after multiplication, first and second inverse-Fourier transform portions 125 and 140 which perform respectively inverse-Fourier transformation on the value, after multiplication and an output value of the Hilbert transform portion; a phase relation deriving portion 150 which derives the phase relation between the two input signals, based on the output values of the first and second inverse-Fourier transform portions 125 and 140, and a time difference-deriving portion 160 which derives a time difference between the two input signals, based on the phase relation. COPYRIGHT: (C)2011,JPO&INPIT |
