| 摘要 |
PURPOSE:To improve the discriminating property of a signal from noises by receiving an electromagnetic induction signal with two coils to amplify a difference of signals received with the coils by an amplification circuit. CONSTITUTION:Receiving coils 21a and 21b provided on a wrist watch are wound in such a direction that electromagnetic induction currents (received signal currents) Ia and Ib and generated respectively when a transmitting coil 17 provided on a shirt generates an electromagnetic induction signal in the direction Z0. Voltages developed at both ends of capacitors Ca and Cb by the received signal currents Ia and Ib generated in the receiving coils 21a and 21b are inputted into differential amplifiers OP1 and OP2, respectively, and amplified. Then, outputs of the differntial amplifiers OP1 and OP2 are outputted into input terminals on the negative and positive sides of the differential amplifiers. Thus, the differential amplifiers amplify the difference of the received signals and the received signal amplified is outputted to a waveform shaping circuit 23 thereby enabling the reducing of the amplification factor of a noise generated with the amplification circuit as compared with that of the signal. |
