Gated pseudonoise semi-active missile guidance system with improved illuminator leakage rejection

Claim 1

In a semi-active pseudonoise missile guidance system having a ground illuminator orientable to cause reflections of electromagnetic energy from a selected target, the combination comprising: first means within said ground illuminator for generating a repetitive pseudonoise code word having a predetermined bit duration; second means for repetitively selecting and transmitting a corresponding fraction of each bit of said code word to produce a gate pseudonoise transmitted sequence having a predetermined fractional duty cycle; front and rear receiving means within said missile, said rear receiving means being responsive to said transmitted sequence for establishing a local code and said front receiving means being responsive to said reflections, said front receiving means also being subject to undesired leakage signals of relatively high intensity from said ground illuminator; third means operating from the received signal output of said rear receiving means for producing a leakage gating signal having "on" and "off" times and for applying said gating signal to correspondingly gate the input of said front receiver "on" and "off", said third means being arranged to delay the beginning of said "on" time by a time increment at least equal to the radiation transit time of said transmitted second means output from said rear receiver to said front receiver as said leakage signals.