Patent ID: 7366619

Claim:
A signal processing unit for processing a periodic detection signal output from a fluxgate magnetometer excited by a periodic excitation signal with a predetermined first frequency, the detection signal having a second frequency double of the predetermined first frequency and a magnitude of a magnetic field to be measured, the signal processing unit comprising: an integrating unit composed of a plurality of digital elements and operative to integrate the detection signal over every quarter of one cycle of the detection signal to generate an integration value, the integration values to be generated being represented as S 1 , S 2 , S 3 , S 4 , . . . ; a calculating unit composed of a plurality of digital elements and configured to perform addition and subtraction on the generated integration values in accordance with the following equations to calculate an in-phase component and a quadrature-phase component: I p =S 4p−3 +S 4p−2 −S 4p−1 −S 4p Q p =S 4p−3 −S 4p−2 −S 4p−1 +S 4p where I p represents the in-phase component, Q p represents the quadrature-phase component, and p=1, 2, 3, . . . ; and an amplitude obtaining unit configured to obtain an amplitude of the detection signal based on the obtained in-phase component and the quadrature-phase component.