Modulated, dual frequency, optical tracking link for a command guidance

Abstract

An optical tracking link for a command guidance missile system employing l frequency modulation of the optical signal transmitted from the missile beacon. Dual frequency encoding of the missile tracking beacon improves beacon-tracker performance in the presence of countermeasures or false signals. A solid state, missile beacon within the missile housing transmits alternate bursts of optical energy of first and second high frequencies during alternate half cycles of a low frequency modulating signal therefor. The optical, modulated signal is received by an optical tracker at the missile launch site, completing a link between the missile and the launch site. A visual tracker at the launch site provides line-of-sight contact with a target being tracked. A guidance control for the missile responds to output signals from the missile and visual tracker to develop an error signal between the longitudinal, line-of-sight axis and the missile trajectory. Any deviation of the missile from a course of impact with the target causes an error signal to be transmitted to the missile for flight course correction. The solid state beacon includes first and second clocks each having a high frequency output therefrom, which is modulated by a low frequency and coupled through a power driver to a GaAs diode array, which generates an optical signal in response to a square wave input signal. This alternately modulated signal is received by a detector preamplifier of the optical tracker. A diode array in the detector is activated by the impinging optical signal and generates an electrical signal in response to the input wave. This signal is filtered to retrieve the two high frequencies and demodulated to extract the lf modulating wave from each frequency. This low frequency is then combined in a differential amplifier and interfaced with error detection equipment for generating a command guidance signal to the missile for attitude control thereof.