ADAPTIVE ARRAY NEAR FIELD MEASUREMENTS USING THE FRESNEL TRANSFORM APPROXIMATION

THIS PROPOSAL IS ADDRESSED TO THE TECHNICAL PROBLEM OF DETERMINING THE FAR-FIELD PERFORMANCE OF ADAPTIVE ARRAY ANTENNAS USING NEAR-FIELD MEASUREMENTS. THE INNOVATIVE CONCEPT PROPOSED IS TO FOCUS THE ARRAY IN THE NEAR FIELD BY THE FRESNEL TRANSFORM APPROXIMATION TO, IN EFFECT, MAKE PLANAR THE SPHERICAL WAVEFRONTS FROM NEAR-FIELD JAMMERS, SO THAT THEY APPEAR TO BE LOCATED IN THE FAR-FIELD WHEN THE ARRAY IS FOCUSED AT THE NEAR-FIELD RANGE OF THE JAMMERS. THE CONCEPT HAS THE POTENTIAL OF PROVIDING A HIGHLY ACCURATE AND EFFICIENT NEAR-FIELD MEASUREMENT TECHNIQUE FOR ADAPTIVE ARRAYS AT VERY LOW COST. IN ADDITION, THE CONCEPT ELIMINATES THE TRANSFORMATIONS GENERALLY NECESSARY TO OBTAIN THE FAR-FIELD PATTERN FROM NEAR-FIELD MEASUREMENTS. THE REQUIREMENTS FOR PROBE PATTERN COMPENSATION AND HIGH PROBE POSITION ACCURACY ARE OBVIATED SINCE THE FAR-FIELD PATTERN IS MEASURED DIRECTLY IN THE NEAR FIELD.