Auxiliary antenna interference canceller

Abstract

A high gain, primary receiving antenna and a single scannable auxiliary lar antenna array are utilized. The auxiliary linear array is coupled to means for forming multiple directive narrow receiving beams simultaneously on the auxiliary array, each of which are scanned over an assigned segment of space to locate and isolate a respective one of a plurality of interfering or jamming signals which are also contained in the signal received by the primary antenna. The interfering signals are cancelled by separately adjusting the phase and amplitude of each one of the interfering signals received and then feeding them to a respective signal subtractor coupled to the output of a receiver connected to the primary antenna.

I claim: 
     
       1. An interference cancelling system, comprising: primary receiving antenna means including an output for providing a first output signal including a desired signal and all interfering signals;   steerable auxiliary receiving antenna means including means for simultaneously forming and scanning a plurality of relatively narrow receiving beams respectively directed to a predetermined number of individual sources of interfering signals for providing a respective number of second output signals; and   means connected to the output of said primary antenna means and said auxiliary antenna means for subtracting said second output signals from said first output signal.   
     
     
       2. The system of claim 1 wherein said subtracting means includes means for subtracting each of said second output signals individually from said first output signal and generating control output signal. 
     
     
       3. The system of claim 2 and additionally including means for adjusting the amplitude and phase of said second output signals to match corresponding intefering signals in said first output signal from said primary antenna means. 
     
     
       4. The system of claim 3 and additionally including means for adjusting the amplitude and phase of said second output signals in response to the control output signal of said subtractor 
     
     
       5. The system of claim 4 wherein said means for adjusting the amplitude and phase of said second output signals comprises null detector means. 
     
     
       6. The system of claim 5 wherein said subtracting means includes a respective number of linear subtractor means connected in series for subtracting each of said second output signals individually from said first output signal. 
     
     
       7. The system of claim 2 wherein said auxiliary receiving antenna means comprises a linear array including a plurality of antenna elements. 
     
     
       8. The system of claim 7 wherein said means for forming and scanning a plurality of relatively narrow receiving beams includes a respective number of scanning control loops, each said control loop including: a phasing network for adjusting the phases of each said antenna element and providing intermediate output signals therefrom; signal adder means for summing said intermediate output signals; and beam scanning control means responsive to the summed intermediate output signals to control said phasing network to direct a receiving beam pattern to a selected source of interfering signals. 
     
     
       9. The system of claim 8 and additionally including a threshold detector coupled between each said signal adder and each said beam scanning control circuit. 
     
     
       10. The system of claim 9 and wherein each phasing network includes a respective phase shifter coupled to each antenna element of said auxiliary antenna means.