ELECTRONICALLY STEERABLE FIELD REFLECTOR ANTENNA TECHNIQUES.
Final rept. 25 Jan 65-25 Mar 66,
AIRBORNE INSTRUMENTS LAB DEER PARK NY
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Antenna systems consisting of two concave reflectors illuminated by a planar feed cluster were investigated. The primary reflector was a segment of a rotationally symmetrical paraboloid the secondary reflector was on the opposite side of the primary focus and concave toward the primary focus. Its contour and size were variable the planar feed cluster was normal to the axis of the primary reflector and located near its focus. These reflectors and feed were arranged in an offset configuration so the aperture blocking, usually caused by the secondary reflector, was eliminated. A computer study of the system geometry was extended to three dimensions pervious work had studied the two-dimensional geometry and a model antenna system was built and tested. The size, contour, and position of the secondary reflector were investigated in relation to the systems ability to scan, zoom, and correct for distortion. A model of this antenna system demonstrated good scanning and zooming ability as a result of linear and second-order phasing across the feed. The two-reflector geometry was too complex to permit any correlation of results from three-dimensional systems with results from two-dimensional or cylindrical calculations, even though the correlation has been demonstrated to be excellent for simpler cluster-feed systems. However, the extended analysis three dimensional led to a simple antenna design that provided the optimum results in both scanning and distortion correction the simpler two-dimensional analysis had previously led to more complex geometries resulting in different antenna designs for each capability.
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