MOVEMENT DISTANCE MEASURING DEVICE

摘要

A transmission antenna (12a) radiates a transmission signal onto a guide rail (2) as a radio wave. A reception antenna (12b) receives the radio wave which has been radiated from the transmission antenna (12a) onto a fixed surface and has been reflected from the fixed surface, and acquires said radio wave as a reflected signal. An IQ demodulator (14) subjects the reflected signal to quadrature detection using the transmission signal as a reference signal, and acquires an IQ signal representing coordinates of the reflected signal in an IQ plane. A phase rotation center detection circuit (15) detects the coordinates of a phase rotation center of the reflected signal in the IQ plane, on the basis of at least two IQ signals acquired by the IQ demodulator (14). A movement distance calculating circuit (16) calculates the phase difference of the reflected signal relative to the transmission signal, on the basis of the coordinates of the reflected signal and the coordinates of the phase rotation center in the IQ plane, and calculates the movement distance of a cage (3) on the basis of the phase difference.