Communications: directive radio wave systems and devices (e.g. – Directive – Including antenna pattern plotting
Patent
1993-11-22
1995-02-28
Blum, Theodore M.
Communications: directive radio wave systems and devices (e.g.,
Directive
Including antenna pattern plotting
342351, 343703, H01Q 300
Patent
active
053941578
ABSTRACT:
A method of identifying antenna-mode scattering centers in an aperture device or array from planar near field measurements. Antenna-mode scattering centers may be determined for aperture assemblies, phenomenological models of apertures, and antenna arrays comprising a feed and an array of antenna elements. The method uses a scanning probe and receiver for making near field measurements. A feed horn and signal source illuminates the device. An absorber is disposed between the device and the probe and this combination is illuminated. A first set of data is collected over a planar surface in a near field region of the device. The device is then illuminated with the absorber removed. A second set of data is collected over a planar surface in a near field region of the device. The difference between the first and second sets of data is determined to provide data indicative of the near field response of the probe to the near field scattered from the device. Data indicative of the scattered far field from the device is computed using a planar near-to-far-field transform. The computed far field data is then converted from probe coordinates to device coordinates. The converted far field data is equated to data corresponding to the far field of an array device whose excitation weights are a product of a reflection coefficient looking into the feed at a junction between an antenna element and the feed, and a horn-element coupling factor between the feed horn and an antenna element that is proportional to power received by an individual antenna element from the feed horn. A copolarized component of the far field is divided by a copolarized component of an embedded element pattern to produce a scalar array pattern. The excitation weights are determined using an inverse fast Fourier transform (FFT) of the scalar array pattern. The reflection coefficients are determined by dividing the excitation weights by the horn-element coupling factor. Finally the antenna-mode scattered far field may be computed for an arbitrary incident plane wave having the predetermined angle of arrival and polarization at a predetermined frequency, which antenna-mode scattered far field is indicative of the antenna-mode scattering centers in the device.
REFERENCES:
patent: 4453164 (1984-06-01), Patton
patent: 5119105 (1992-06-01), Ngai et al.
patent: 5278571 (1994-01-01), Helfrick
Alkov Leonard A.
Blum Theodore M.
Denson-Low Wanda K.
Hughes Aircraft Company
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