| 摘要 |
PURPOSE:To make it possible to simplify and miniaturize constitution and to provide the fail-safe function by detecting a beat frequency after mixing AC signals differing in frequency and by making a decision by the existence of it. CONSTITUTION:Alternating-current signals differing in frequency, generated by oscillators OSC1 and OSC2, are mixed by mixer MIX and after envelope detection is carried out by detector DET, its beat frequency component is detected by LPF. When the outputs of oscillators disappear, the envelope detection output is a mere alternating current. Therefore, when the detection output of OUT disappears, it is possible to detect either output of OSC1 and OSC2 disappearing. Namely, even when only one oscillator generates an AC signal output, it can be judged that no beat frequency component is generated. |
