Patent ID: 7019684

Claim:
In a semiactive radar guidance system for a guided missile, such system including a heterodyne receiver wherein the frequency of a first local oscillator is required to be rendered coherent with the frequency of echo signals from a target being tracked by a frequency control signal from automatic frequency control circuitry, such circuitry being susceptible to vibration during flight to assume one of two stable conditions, the first of such conditions being one in which the frequency control signal has the proper amplitude and polarity to maintain coherency and the second of such conditions being one in which the polarity of the frequency control signal has an incorrect polarity, the improvement comprising: (a) first means, responsive to vibration-induced changes in the automatic frequency control circuitry from one stable condition to the other, for generating a control signal indicative of such change; and (b) second means, responsive to the control signal, for correcting the polarity of the frequency control signal.