| 摘要 |
<p>PURPOSE:To obtain the accurate reference phase at all times by supplying an AC signal to a reference resonance circuit which is resonating at the constant frequency at all times and detecting the phase difference between the AC signal obtained from the reference resonance circuit and the formed AC signal to make it the reference phase. CONSTITUTION:A reference resonance circuit 3 consists of a ceramic vibrator 301 turning the frequency f0 to the peculiar vibrating frequency and resistances 302 and 303. The both ends are connected to a selection circuit 4 like loop coils 2-1 to 2-n. A phase detection circuit 10 consists of the phase detecting device and a low-pass filter with the shielding frequency lower enough than the frequency f0, and outputs an AC signal generated in one loop coil or the reference resonance circuit 3 and amplified by a reception amplifier 8 and a DC signal with the level according to the phase difference of the sine wave signal of the frequency f0. The AC signal is supplied for the constant time to the reference resonance circuit 3, then the phase difference between the AC signal obtained from the circuit 3 and the former AC signal is detected to make it the reference phase.</p> |
