Hughes Electronics Corporation

Other

Hughes Aircraft Company

John Fraschilla

David A Whelan

Brian M Pierce

Steve K Panaretos

Brian T McWhirter

Lonny Richard Walker

Jay L Edie

An array of thick flared notch radiators, wherein the separation distance between adjacent pairs of flared notch sticks is set to be less than one-half wavelength at the highest frequency of concern. The separation distance suppresses the propagation of higher order modes along the length of the sticks, which would degrade the array performance. The separation distance is achieved by fabricating the sticks with an increased thickness, thereby reducing the stick-to-stick channel width.

Thick flared notch radiator array

Ferro-electric frequency selective surface radomes that have dielectric layers that comprise voltage controlled material, and the electrical properties of the dielectric layers are voltage controlled. By varying the dielectric properties, the passband frequency of the radomes can be shifted to optimize frequency and angular response of the frequency selective surface. The radomes comprise grating screens having a plurality of printed radiating elements. Inner and outer voltage controlled dielectric layers are disposed on the grating screens. Relatively high ohms per square resistive films are disposed on exposed surfaces of the voltage controlled dielectric layers. In one embodiment, voltage control circuitry is coupled to the respective resistive films for controlling the voltages applied to the respective voltage controlled dielectric layers by actively varying the dielectric permittivity of the resistive films around a small percentage of its nominal value to provide a ground on outer surfaces of the dielectric layers. In another embodiment, the ferro-electric frequency selective surface radome may comprise voltage controlled dielectric layers disposed on one surface of the grating screens. Voltage control circuitry is coupled to the first and second grating screens for controlling the voltages applied thereto and thus the performance of the radome.

Ferro-electric frequency selective surface radome

An impregnated carbon film expanded into a honeycomb structure is employed in a tapered notch phased array antenna and is used to absorb cross-polarized incident fields to reduce the reflections from shorted TEM parallel plate modes existing between radiator elements of the antenna. The carbon loading used to achieve this absorption may comprise a resistive taper, or analog circuit or anisotropic elements having a predetermined tapering resistive profile. The honeycomb cross-polarized load of the present invention provides the electrical performance necessary to meet tapered notch phased array antenna electrical requirements while reducing the weight and cost of antennas in which it is employed.

Honeycomb cross-polarized load

An asymmetrical notch radiating element comprising a metal or metal-clad dielectric substrate into which a tapered slot or notch is disposed. The direction of the axis of the tapered slot lies along any preselected axis and is not constrained to be collinear with the normal to the aperture of the element. An asymmetrical antenna array comprises a plurality of asymmetrical notch radiating elements as described above. Each of the plurality of radiating elements is disposed such that the apertures of each of the elements are substantially coplanar and are at an angle relative to the notch axis. The present antenna uses asymmetric slot lines to control the antenna's electrical performance. The precise slot dimensions are chosen to optimize radiation and reduce scattering. The asymmetric flared notch allows optimization of the transmit gain in a direction that is not necessarily normal to the array surface. The asymmetrical notch radiator is designed for use in phased array antennas where reduced radar cross section and wide bandwidth are essential, or in conformal arrays, where the surface normal and array axis are not collinear. The normally high specular radar reflection from the antenna radiators, that lies along the array normal, no longer points in the same direction as the peak antenna gain. This allows the design of a low radar cross section array antenna that does not suffer poor gain due to its reduced cross section.

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Redondo Beach, CA, United States of America

John Fraschilla