Patent ID: 7432849

Claim:
A frequency modulation radar apparatus for vehicle use which sends a transmission signal the frequency of which is frequency modulated so as to linearly rise or fall in accordance with the elapse of time, receives the signal reflected by a target object, samples a beat signal that is obtained by mixing the reception signal thus received with said transmission signal, performs a discrete frequency analysis by using a predetermined window function, extracts a peak signal from a spectrum of said beat signal obtained, and calculates a distance or a relative speed to said target object based on a frequency (f n ) of said peak signal, said apparatus comprising: a frequency correction section that adds an amount of frequency correction (δ) to said frequency (f n ) of said peak signal thereby to calculate a corrected frequency (f n +δ); and a CPU that calculates the distance or relative speed to said target object based on said corrected frequency (f n +δ); wherein by using a strength (a n ) of said peak signal, a strength (a n−1 ) of a signal of which a discrete frequency is smaller by one than that of said peak signal, a strength (a n+1 ) of a signal of which a discrete frequency is larger by one than that of said peak signal, and a strength (a max ) of one of said strength (a n−1 ) and said strength (a n+1 ) which is not smaller than the other, said frequency correction section calculates said amount of frequency correction (δ) based on the strength (a n ) of said peak signal, said strength (a max ) and a characteristic of said window function; and when said strength (a n−1 ) is larger than said strength (a n+1 ) and said amount of frequency correction (δ) is positive, or when said strength (a n−1 ) is less than or equal to said strength (a n+1 ) and said amount of frequency correction (δ) is negative, said frequency correction section correctively sets said amount of frequency correction (δ) to zero (δ=0).