Minh Tang

Development of a 45 GHz multiple-beam antenna for military satellite communications

Design and experimental results of a wide-angle coverage 45 GHz multiple-beam antenna for military satellite communications are presented in this paper. The high-gain spot beams with low sidelobe levels and efficient adjacent beam overlap are generated by employing an offset parabolic reflector with overlapping feed clusters. The beam shape can be adapted to cancel either single- or multiple-jammers by varying excitations within the feed cluster corresponding to the beam. Development of antenna components including Potter horn, polarizer, phase-amplitude controller, and beamforming network is discussed. Measured results of the demonstration antenna have shown that sidelobe and crosspolar levels of better than -25 dB are achieved for beams scanned over an eight-degree diameter circular coverage region. The adapted patterns of the antenna agree well with the computations, and null depths of better than 30 dB have been realized over a 4.5% bandwidth. >

Triangular ray-tube analysis of dielectric lens antennas

The dielectric lens is a viable alternative to the reflector as the main mission antenna to provide communication satellite services in the millimetre wave band. Of the various types of dielectric lenses available, the thin spherical lens is particularly suited for satellite usage. Its advantages are many, including low weight obtained through zoning, centre feeding with no blockage, circular symmetry for ease of fabrication and wide scanning capability with minimal gain loss. In addition, surface matching by means of circumferential slots is used to reduce weight further and minimise surface reflection loss. Most of the lens analyses published in the literature e.g. [1,2], are of the scalar ray tracing type where differentiation is not made between TE and TM incidences on the lens. Also, the effects of matching layers and zoning steps are not taken into consideration. In this paper, we are presenting an analysis approach that is valid for any type of dielectric lens where surface matching and zoning steps are correctly treated and the ray tracing contains both TE and TM components. As a result, we observe very good agreement between measurements and predictions of gain patterns for both thin spherical lens and thick shaped lens.

Dual-band multiple beam antenna system for satellite communications

This paper presents a dual-band antenna system that is suitable for satellite communications at K/Ka-band frequencies. It employs a minimum number of reflectors, each being fed with multiple feed horns. It is shown that the MBA performance in terms of coverage gain and co-polar isolation can be significantly improved by using optimal designs for the feed horn and the reflector. The performance results of this MBA are compared with conventional designs and the trade-offs are discussed.

Advanced antenna technologies for satellite communication payloads

A review of various antenna technologies suitable for satellite communications and applicable to fixed satellite, broadcast satellite, mobile communications, and personal communications services is presented. Antenna technologies suitable for generating contoured beam and multiple-beam antennas are reviewed. Design considerations for reflector antennas and feed assemblies and antenna performance in terms of coverage gain, sidelobe isolation, and cross-polar isolation are discussed. Current and future technological trends are presented in the above areas.

Dual-Band Multiple Beam Antenna System Using Hybrid-Cell Reuse Scheme for Non-Uniform Satellite Communications Traffic

An advanced dual-band antenna system suitable for broadband satellites that is capable of providing higher EIRP, higher G/T, and improved copolar isolation among frequency reuse beams is presented. The antenna system employs a hybrid-cell frequency reuse scheme instead of conventional fixed cell reuse (4-cell or 7-cell) in order to efficiently use spectrum based on traffic demands. It is shown that the advanced antenna employing high-efficiency horns and shaped reflectors provides about 1.0 dB EIRP improvement, 2.0 dB G/T improvement, and 3.0 dB improvement in C/I when compared to conventional antennas.