| 摘要 |
PROBLEM TO BE SOLVED: To provide a control technique that activates an oscillator, a counter, and an D/A converter that simultaneously conduct frequency down conversion, band-pass filtering and A/D conversion of an analog signal, including a carrier modulated by information by a known modulation technology. SOLUTION: A converter 30 employs a superconducting Josephson single fluxoid circuit acting as a voltage-controlled oscillator 34. The voltage-controlled oscillator receives an analog signal to be converted and generates a series of high-frequency pulses with a steep gradient, on the basis of a characteristic of a carrier signal. A series of pulses are fed to a gate circuit 36 in response to a gate control signal 42. When the gate circuit 36 passes through the pulses, a counter circuit 38 accumulates the pulses for a sampling period. Since the sampling period corresponds to a range of gate control pulses, a consecutive on/off period of the gate control signal is specified by the accumulation of the pulses.
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