Scientific-atlanta, Inc.

John R Jones

Doren W Hess, Jr

Circular open ended waveguide feeds for compact ranges. Feeds according to the present invention employ smaller apertures for a given frequency of operation than a standard compact range feed. According to a first embodiment of the invention, a circular open ended waveguide feed is constructed to operate with its lowest desired frequency of operation at approximately 1.01 times the cutoff frequency. A second embodiment includes a circular open-ended waveguide loaded with ridges to lower the cutoff frequency further and thus further reduce aperture size for a given bandwidth to radiate a broader beamwidth.

Feeds for compact ranges

Method for measuring polarization of antennas utilizing three-antenna methods and far-field scanning techniques where the measured data is processed via digital Fourier transform. In one method, the normalized received phasor voltage for transmission between each of three antennas measured pairwise is digitally recorded as a continuously sampled function of relative roll angle between the antennas as one of the antennas is rolled in a continuous manner. The recorded data is digitally processed via a one-dimensional Discrete Fourier Transform to yield transformed quantities relating to the polarization of the antennas under test. From these quantities, standard polarization parameters including the circular polarization ratio, axial ratio, tilt angle and sense of the electric field polarization ellipse of each antenna may be obtained. In another method, the antenna in each pair which is not continuously rotated is rotated in incremental fashion while the normalized received phasor voltage for transmission between each pair of antennas is digitally recorded. The recorded data for this second method is digitally processed via a two-dimensional Fast, Discrete or other Fourier transform. This step/scan procedure further compensates for test range ambient and reflected noise and for transmitter and receiver RF path variations compared to the single scan procedure of the first method.

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Lawrenceville, GA, United States of America

John R Jones