A synthesis procedure and performance results for an offset dual reflector with perfect focusing at \pm 8\deg of beam scan are presented. This bifocal antenna extends the theory of the previously reported symmetric system to an offset design. Approximations, such as the smearing of focal points into a "focal ring," are eliminated, as is blockage. The offset design affords greater design flexibility, although the synthesis is more complex. Computed and experimental results demonstrate the improved beam-scanning performance of this antenna.

An offset bifocal reflector antenna design for wide-angle beam scanning

The design principle and construction of an offset bifocal reflector are discussed and some test results are presented. the reflector surface is designed in a three-dimensional configuration, and four typical bifocal reflector antennas characterized by the vertical and horizontal cross sections of the subreflector are derived. Mapping of the coordinate system set up on the horn feeder is accomplished with a geometrical optics technique, and it is found that an antenna with low distortion cross-polarization degradation attributable to asymmetry is possible.



A 1.3 m bifocal reflector antenna at 14/11 GHz with a beam separation of 9° was designed and fabricated, and its radiation properties were measured with offset feeding, which is useful in constructing a multibeam antenna. the radiation properties within this beam separation angle are equivalent to those of a single pencil-beam antenna such as the Cassegrainian; the cross-polarization level is less than -30 dB in the worst case.

Offset bifocal reflector antenna

Design and operational performance features of a NASA planned 30/30 GHz flight experiment communications system multiple-beam antenna (MBA) are described. The MBA is a shared aperture offset Cassegrain type with a main reflector diameter of 3 m and physically separated transmit and receive feeds. A planar frequency selective surface is employed which is transmissive to the receive signals and reflective to the transmit signals. Trade-offs and constraints in the MBA feed design are explored, noting the higher feed loss and complexity due to choosing variable power dividers for the beam forming network. Doublet beam coverage of the east coast of the continental U.S. is shown to be possible with a triangular lattice array of feed horns with aperture diameters and element spacings of two wavelengths. The doublet configuration requires ten times the components as a singlet array.

A multiple beam antenna concept for a 30/20 GHz satellite communications system

A multiple beam antenna concept for a 30/20 GHz satellite communications systems

http://ieeexplore.ieee.org/iel6/8250/25855/01148261.pdf

D. Chang

Papers

A scan-corrected offset dual reflector antenna system