Patent ID: 7660369

Claim:
A radio-controlled device for measuring time, the radio-controlled device comprising: a reference signal generator configured to generate a cyclic reference signal; a time measuring unit configured to measure a time based on a frequency of the generated cyclic reference signal; a receiving unit configured to receive, as a target electric signal, a target radio wave on which time information indicative of an official time standard is superimposed, the target radio wave being generated by amplitude modulating a target carrier wave with the time information; a quadrature detector configured to extract an in-phase component and a quadrature-phase component of the target radio wave from the received target electric signal every a period of time corresponding to at least one cycle of the reference signal; a demodulating unit configured to demodulate the time information from the received electric signal based on amplitude information of the target radio wave, the amplitude information being obtained from the in-phase component and the quadrature-phase component of the target radio wave; a phase calculator configured to calculate phase data associated with a phase of the target radio wave based on the in-phase component and the quadrature-phase component calculated every the period of time; a variability calculator configured to calculate a variability of the calculated phase data of the target radio wave relative to a reference phase, the reference phase changing at a constant rate in time according to a frequency error, the frequency error being contained in the reference signal relative to a frequency of the target carrier wave; and a reception determining unit configured to determine whether reception of the radio-controlled device is good based on the calculated variability.