NOVEL FIBER OPTIC MULTIMODE FEED FOR MONOPULSE LIDAR ANTENNA APPLICATION

A NOVEL MULTIMODE FEED FOR A COHERENT AMPLITUDE MONOPULSE LIDAR IS PROPOSED. THE HEART OF THIS FEED CONFIGURATION IS A MULTIMODE GRADIENT INDEX (SLAB) FIBER COUPLED TO THE SECOND FIBER IDENTICAL WITH THE FIRST TO FORM A MULTIMODE DIRECTIONAL COUPLER WITH SPECIALIZED PERFORMANCE. THE SIGNAL (BEACON OR LIDAR RETURN) IS FOCUSSED BY THE ANTENNA OBJECTIVE ONTO THE PLANE END OF ONE FIBER. THE SPOT DISPLACEMENT IS THEN PROPORTIONAL TO THE ANGULAR DEVIATION OF THE TARGET. WITH PROPER DESIGN OF THE COUPLING REGION, A SIGNAL PROPORTIONAL TO THE ANGULAR DEVIATION IS COUPLED INTO THE SECOND FIBER (DIFFERENCE SIGNAL) LEAVING IN THE FIRST FIBER A CENTERED GAUSSIAN BEAM (THE SUM SIGNAL). FOR COMPLETENESS, A SCHEMATIC FIBER OPTICAL RECEIVER (NOT PROPOSED HERE) WHICH AFTER AMPLIFICATION DERIVES AN ERROR SIGNAL FROM THESE SUM AND DIFFERENCE SIGNALS IS DESCRIBED. WE PROPOSE TO: DESIGN A PLANAR INTEGRATED-OPTIC SLAB-COUPLER FOR A 2DIMENSIONAL LIDAR FEED SYSTEM; SUPERVISE FABRICATION AND EVALUATION OF THE APPROXIMATE ACTUAL REALIZATION OF THIS DESIGN; COMPUTE PERFORMANCE PARAMETERS OF THE ACTUAL FEED COMPONENT; DEVELOP AND CARRY OUT TESTS TO VERIFY THE PERFORMANCE OF THE FEED COMPONENT.