Trw Limited

Northrop Grumman Systems Corporation

George H Simkins

Te-Kao Wu

Charles W Chandler

Ann L Peebles

Youn H Choung

John P Pacente

C Harry Chen

Benny Yee

A dual band high efficiency hybrid offset reflector antenna system ( ) that includes a low frequency antenna ( ) including a paraboloidal main offset reflector ( ) for reflecting a low frequency signal, as well as a high frequency antenna ( ) including both the main offset reflector ( ) and a hyperboloidal subreflector ( ) for reflecting a high frequency signal discrete from the low frequency signal. The hyperboloidal subreflector ( ) includes a frequency selective surface ( ) that passes the low frequency signal reflected by the paraboloidal main offset reflector ( ) with low subreflector diffraction loss, and that is highly reflective at the high frequency. Offset beam squint pointing error can be eliminated because the high and low frequency bands have separate feed focal locations ( ).

Dual band hybrid offset reflector antenna system

A multi-mode, multi-step feed horn (10) for a satellite antenna array that includes multiple transition steps (28-34) that provide control of the mode content of the signal, and the generation of substantially equal E-plane and H-plane beamwidths, with low cross-polarization and suppressed sidelobes. In one particular embodiment, two transition steps (32, 34) allow the E-plane to expand and generate the higher order TM.sub.11, propagation mode. The transition steps (32, 34) and a phase section (18) allow the mode content to be oriented relative to each other in the proper phase so that the useful bandwidth is on the order of 10%-15%. Two other transition steps (28, 30) provide impedance matching between a throat section (12) and the mode content transition steps (32, 34) to prevent or minimize reflections.

Multimode, multi-step antenna feed horn

The problem of reducing the size of a dual offset Cassegrain reflector type microwave antenna without adversely affecting performance while retaining the simplicity of the main reflector's (1) and subreflector's (3) traditional simple surface curvatures is solved by having the paraboloidal shaped main reflector's focal length, fm, and diameter, D, fulfil the criteria that the ratio of fm to D is less than 1.0; and in which the hyperboloidal shaped subreflector (3) is oriented so that its left foci, at which the microwave feed (5) aperture is placed, lies above the main reflector's focal axis. It's subreflector subtends an angular arc about the focal point that is slightly larger than the corresponding arc subtended by the main reflector. The elegance of the compact antenna is demonstrated by improved performance, attaining efficiencies in excess of seventy three percent.

Small volume dual offset reflector antenna

A travelling wave coupler autotracking system 10 controls the pointing of an antenna aboard an orbiting satellite by generating tracking signals covering a wideband frequency. The system 10 comprises a waveguide manifold 22 for exciting circular TE.sub.11 and TM.sub.01 modes covering a wideband frequency range, coupling arm waveguides 24, 26 for propagating signals having a phase velocity of TE.sub.10 mode that is the same as the phase velocity of TM.sub.01 mode, and couplers 30 for transforming microwave energy of the TM.sub.01 mode of the circularly polarized microwave signals into TE.sub.10 modes in the coupling waveguide. The system 10 can further comprise 180.degree.-hybrid 20 for combining the TE.sub.10 modes in the coupling waveguides in phase and for generating one or more error signals at different frequencies.

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Torrance, CA, United States of America

George H Simkins