RADAR CROSS-SECTION REDUCTION TECHNIQUES APPLICABLE TO IN-BAND ANTENNA SCATTERING

THE RADARS EMBEDDED IN VERY LOW OBSERABLE PLATFORMS MUST NOT COMPROMISE "STEALTHINESS" BY THE RADAR CROSS-SECTION (RCS) OF THEIR ANTENNAS. SUCH ANTENNAS CAN BE COVERED WITH A METALLIC RADOME THAT MINIMIZES THE RCS TO OUT-OF-BAND THREAT RADAR SIGNALS. BUT IT CANNOT SIMILARLY SUPPRESS INBAND SIGNALS. SUCH SIGNALS WILL PASS THROUGH THE RADOME AND BE SUBJECTED TO SCATTER BY THE ANTENNA BEHIND IT. THIS SCATTER IS A PRESENT-DAY LIMITATION TO THE PRESERVATION OF VERY LOW PLATFORM OBSERVABILITY. THIS PROPOSAL DESCRIBES A PHASED ARRAY DESIGN THAT SOLVES THIS REMAINING PROBLEM. IT RESULTS IN AN ANTENNA SYSTEM WITH A VERY LOW RCS OVER VIRTUALLY ALL ASPECT ANGLES AND POLARIZATIONS IN-BAND, AND A SIGNIFICANT RCS REDUCTION OVER THE ENTIRE THREAT RADAR BAND. MOREOVER, THE PROPOSED IN-BAND RCS REDUCTION TECHNIQUE WILL IMPOSE NO PENALTY IN RADAR PERFORMANCE. THE TECHNIQUE FOR DOING THIS INVOLVES AN ARRAY GROUND PLANE THAT IS BOTH POLARIZATION DEPENDENT AND FREQUENCY DEPENDENT. FOR CROSS-POLARIZED INCIDENT WAVES OF ALL FREQUENCIES, THE ARRAY APPEARS TO BE A GOOD MICROWAVE ABSORBER WHILE FOR CO-POLARIZED INCIDENT WAVES ABOVE-BAND, IT BECOMES VERY LOSSY. ARRAY ELEMENTS RECEIVING CO-POLARIZED SIGNALS IN-BAND ARE CONJUGATE MATCHED TO MINIMIZE SPECULAR SCATTER.