METHOD AND DEVICE FOR REDUCING THE DISTANCE DOPPLER AMBIGUITIES IN PULSE DOPPLER RADAR DEVICES

摘要

A method and apparatus for resolving Doppler frequency shift ambiguities in pulse Doppler radar systems provides a radiated signal that is modulated with a periodic waveform having a plurality of pulses within a period, the interpulse intervals between pulses in the period being unequal. Radar target returns are autocorrelated for a plurality of lags, which may include the interpulse intervals and linear combinations thereof. The calculated arguments theta Ci of the autocorrelation function are unwrapped by adding 2k pi , k=0, +/-1, +/-2, . . . , to the phase theta C1 obtained for the shortest lag T1 and determining an integer mk2 from |( theta C2+2mk2 pi )-(T2/T1) theta C1| pi and then setting theta 2= theta C2+2mk2 pi . Phase angles theta 3, theta 4, . . . , theta m are unwrapped in a similar manner, the integer mki being determined from |( theta Ci+2mki pi )-(Ti/Ti-1) theta Ci| pi . The unwrapped phase angles and the point (0,0) are least mean square fitted to lines of phase angle vs lag for each value of k. The root mean square error of the phase angle offset from each line is determined and the slope of the line with the minimum RMS error is chosen as the Doppler frequency shift from which the velocity of the target is extracted.