Impulse radar guidance apparatus and method for use with guided projectiles

Abstract

An impulse radar guidance system and method for use with a spinning projectile. The system and method tracks the flight of the spinning projectile using an all-weather radar or tracker. A linearly polarized asymmetric waveform is transmitted at the projectile that comprises a series of repeating pulses having a relatively strong, short, positive electric field pulse followed by a relatively weak, long, negative electric-field baseline. The projectile contains a dipole antenna having a switching diode disposed between respective halves thereof. The waveform is reflected from the antenna which spins with the projectile and reflects a relatively strong signal when the electric field pulse of the asymmetric waveform is aligned along a conduction direction of the diode, a relatively weak reflected signal when the antenna and diode are aligned orthogonal to the electric field pulse, and a small, non-zero, signal when the diode is aligned anti-parallel to the electric field pulse and the diode is back-biased so that respective halves of the antenna are disconnected. The radar or tracker measures the instantaneous roll angle of the spinning projectile during its flight as a function of the state of the reflected signal. The projectile has a maneuvering device, and a receiver that receives commands that causes the maneuvering device to actuate at one or more specific roll-angles to deflect the flight direction of the projectile at a target.