Patent ID: 7952520

Claim:
A Doppler very high frequency omnidirectional range (DVOR) monitoring apparatus, comprising: a receiver which receives radio waves from a DVOR apparatus, the radio waves including a modulated carrier and a modulated subcarrier; a first signal extractor which extracts a signal of a carrier component from a reception signal obtained by the receiver; a second signal extractor which extracts a signal of a subcarrier component from the reception signal obtained by the receiver and shifts a phase of the signal of the subcarrier component by a phase difference equivalent to a prescribed distance away from the DVOR apparatus relative to the signal of the carrier component; a combiner which combines each output from the first and the second signal extractors; a demodulator which demodulates an output signal from the combiner; and a monitor unit which performs operation confirmation of the DVOR apparatus based on the signal obtained by the demodulator, wherein: the first signal extractor comprises a frequency converter to perform frequency-converting of the reception signal obtained by the receiver into a reception intermediate frequency signal including a local frequency which is lower than the carrier component and the subcarrier component, and a first bandpass filter through which the reception intermediate frequency signal is passed; and the second signal extractor comprises a frequency converter to perform frequency-converting of the reception signal obtained by the receiver into a reception intermediate frequency signal, a phase shifter to shift a phase of the reception intermediate frequency signal by the phase difference, and a second bandpass filter differing in a passing band from the first bandpass filter and through which the reception intermediate frequency signal is passed.