Patent ID: 7271761

Claim:
A method of calculating a prediction distance from a reference object to a target after predetermined constant time from a current state that the reference object and the target have a positional relationship therebetween, said method comprising: frequency-modulating a radar wave signal within a predetermined frequency modulation range so that a frequency of the frequency modulated radar ware changes in time, a rate of frequency change of said radar wave signal in time being set to F 0 /Tf, said F 0 representing a center frequency in the frequency modulation range, said Tf representing the predetermined constant time; mixing the frequency-modulated radar wave signal transmitted from the reference object and a reflection signal to obtain a beat signal, said reflection signal being based on the transmitted radar wave signal reflected from the target, said beat signal being based on a frequency difference between a frequency of the transmitted radar wave signal and that of the reflection signal; sweeping the beat signal within the frequency modulation range from on of the bottom of the frequency modulation range and the top of the frequency modulation range to the other thereof to obtain a frequency component of the beat signal; and obtaining the prediction distance based on the frequency component of the beat signal.