Doppler-type projectile velocity measurement and communication

Abstract

Projectile velocity measurement and communication apparatus comprises a microwave probe fixed to a projectile barrel near a muzzle end. An oscillator, having a reference frequency selected for exciting a fundamental electromagnetic mode in the barrel, is connected to the probe through a hybrid mixer configured for extracting, from moving projectile-reflected microwaves, a true Doppler signal having a varying frequency related to projectile barrel velocity. A processor, connected for receiving the Doppler signal, measures, by a clock oscillator, Doppler signal periods (half periods). A data presorter in the processor selects a last 'N' number of period measurements before the projectile reaches an interference position relative to the probe, to be fed to a fire control computer interface for determination therein of projectile barrel and muzzle velocities, calibration means being provided to update barrel diameter values used in such determination. An alternative, dual reference frequency variation is described, in which a dual hybrid mixer provides two independent Doppler signals, to eliminate dependency of projectile velocity determinations on barrel diameter. A reference frequency modulator and control means therefor are provided to enable microwave communication of information to the projectile, for example, of projectile target time of flight for fusing purposes. Corresponding methods for projectile velocity measurement and communication are provided.