Image Number 3 for United States Patent #5432519.
An antenna system comprising two similar radiation antenna elements with a single monopulse feed system is scanned while transmitting in-phase radio waves from the two elements. Reflected radio waves are received by the two elements and fed to a hybrid circuit which in turn produces a sum signal .SIGMA. and a difference signal .DELTA.. After detection is performed by a detector, a signal processing unit subtracts the difference signal .DELTA. from the sum signal .SIGMA.. In this processing step, the output signal produced by the above subtraction process is actually output only if the receiving pattern waveform associated with the sum signal .SIGMA. has an upwardly convex form, that is, its double differential coefficient is negative and further if the receiving pattern waveform associated with the difference signal .DELTA. has a downwardly convex form, that is, its double differential coefficient is positive, whereby an antenna pattern with beam compression is provided.