Patent ID: 7391361

Claim:
A signal processing method for an FM-CW radar which determines relative distance and relative velocity with respect to a target from peak frequencies occurring in an upsweep and downsweep sections of a triangular FM-CW wave wherein, when said target is a target that has previously been detected, predicted values for the peak frequencies currently detected in the upsweep and downsweep sections are computed from the relative distance and relative velocity previously detected with respect to said target, and it is determined whether any of said predicted values exceeds a detection frequency range and, if there is a peak frequency that exceeds said detection frequency range, said frequency is folded and said folded frequency is taken as one of said predicted values, said method then proceeding to search the currently detected peak frequencies to determine whether there are upsweep and downsweep peak frequencies approximately equal to said predicted values and, if said upsweep and downsweep peak frequencies are found, said peak frequencies approximately equal to said folded predicted value are folded and said folded peak frequencies are used, wherein, when said target is not a target that has previously been detected, relative distance (r a ) and relative velocity (v a ) are obtained based on said peak frequencies occurring in said upsweep and downsweep sections, relative distance (r b ) and relative velocity (v b ) are computed by folding one or the other of said peak frequencies occurring in said upsweep and downsweep sections, when said relative velocity (v b ) is within a prescribed range, and when the value of said relative distance (r b ) is outside a prescribed range, instantaneous errors (Δr a and Δr b ) for said relative distances (r a and r b ) are obtained, integrated values (ΣΔr a and ΣΔr b ) are obtained for said respective instantaneous errors, and when neither Δr b ≧Δr a nor ΣΔr b ≧ΣΔr a holds, said relative distance (r b ) and said relative velocity (v b ) computed by folding said peak frequencies are employed.