An FM-CW radar detects at least one of the relative distance and the relative speed of a predetermined object based on the frequencies of projection portions observed in the frequency spectrums of beat signals in an ascending-modulation section and a descending-modulation section, where the projection portions are generated by one and the same object. The radar determines the moving speed of a predetermined moving object such as a vehicle or the like having the radar mounted thereon, and the frequency difference between the projection portions observed in the frequency spectrums of the beat signals in the ascending-modulation section and the descending-modulation section is inversely calculated, where the frequency difference corresponds to the stationary object, and a predetermined pair corresponding to the frequency difference is extracted on a priority basis.
A radar wherein, in accordance with a peak frequency f1[t-nT] of a first projecting portion at a predetermined timing t-nT, a center frequency fr[t] of peak frequencies of first and second projecting portions at a current measurement timing t is predicted, and f1[t] and f2[t] in which (f1[t]+f2[t])/2 approximates the predicted fr[t] is extracted as a pair candidate. In addition, f1[t] and f2[t] in which Doppler shift frequency is substantially equal to a Doppler shift frequency calculated from the peak frequency f1[t-nT] of the first projecting portion and the peak frequency f2[t-nT] of the second projecting portion are selected.
