Precession period extraction of high-rate rotating projectile

Precession is conical motion that projectile axes rotate around the projectile velocity direction in flight. Precession is one of micro-motions in addition to the translation. Precession produces frequency modulation on the returned radar signal and induces additional Doppler shifts to the Doppler frequency shift caused by translation, called micro-Doppler effect. The mathematics of micro-Doppler signatures shows that the reflector radial velocity is the sum of the mass center radial velocity and the micro velocity. The reflector radial velocity contains the information about precession, which can be obtained by using the short time Fourier transform(STFT). The mass center radial velocity can be derived from polynomial expressions. The velocity subtracted from the reflector radial velocity gives the micro velocity.Time-domain and frequency-domain analyses were jointly adopted. The sliding window autocorrelation of the micro velocity was also used to measure precession period. Both computer simulation and the experimental results demonstrate the validity.