Beacon interrogator beamwidth control using sidelobe signal integration

Abstract

A method for inhibiting responses by transponders to interrogation signals originating in the side lobes of an interrogating radar of a secondary radar system. The interrogating radar first transmits a reference signal with the highest power level of the reference signal being directed into a zone of interest to the interrogating radar. The interrogating radar then transmits a control signal having a higher power level than the reference signal in all regions of space except within the zone of interest. The control signal is of substantially longer duration than the reference signal. A transponder receives, detects and measures the peak amplitude of the reference signal and establishes a minimum trigger level (MTL) at a predetermined level below the reference signal peak. The control signal is received, detected and integrated. The peak amplitude of the integrated control signal is compared with the MTL. A transponder response is inhibited if the peak amplitude of the integrated control signal is greater than the MTL. The peak amplitude of the integrated control signal may be amplified before comparison with the MTL to increase the amount of synthetic beam sharpening provided by the method and the amount of synthetic beam sharpening provided may be controlled by the interrogating radar by delaying the start of transmission of the control signal.