. Airborne radar. Airplanes; Guided missiles. 10-3] PARABOLOIDAL REFLECTOR AS TRACKING ANTENNA 517 exactly at the focal point of the paraboloid but rather is slightly displaced laterally and rotated in a circle of constant radius. This provides a motion of the radiated pattern conically about the antenna centerline — hence, the name, conical scan. The results of this are twofold. First, the signal, upon passing through the antenna, is modulated by the spinning feed for all targets except those on the centerline of the antenna. The phase of this modulation gives the direction in which the anten
. Airborne radar. Airplanes; Guided missiles. 10-3] PARABOLOIDAL REFLECTOR AS TRACKING ANTENNA 517 exactly at the focal point of the paraboloid but rather is slightly displaced laterally and rotated in a circle of constant radius. This provides a motion of the radiated pattern conically about the antenna centerline — hence, the name, conical scan. The results of this are twofold. First, the signal, upon passing through the antenna, is modulated by the spinning feed for all targets except those on the centerline of the antenna. The phase of this modulation gives the direction in which the antenna must move to bring the target onto the centerline. Second, angular resolution is increased so that a target can be located to a small fraction of the actual beamwidth. Adversely, however, the greater the feed offset, the greater the beam asymmetry and sidelobes that accompany the beam offset. For a typical antenna, however, with the beam offset so that extreme beam positions cross one another about 1^ db below the peak, these difficulties are not excessive. A typical antenna of this type is shown in Fig. 10-3. This has a ° beam from a 20-inch dish with a H db Fig. 10-3 A Typical Center-Fed Parabolic Tracking Antenna with a 4° Beam and a l^-db Crossover. (Courtesy, Westinghouse Electric Corporation). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Povejsil, Donald J. Princeton, N. J. , Van Nostrand
Size: 1484px × 1685px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversit, booksubjectairplanes
