This paper presents the parametric design and analysis of multiple-beam reflector-antenna systems employed for satellite communications. It is based on extending the earlier work of Rao (see IEEE Antennas and Propagation Magazine, vol.41, no.4, p.53-59,1999) by taking into account the efficiency of the horn and pointing error of the satellite in the design of the multiple-beam antennas (MBAs), and by analyzing the edge-of-coverage directivity and co-polar isolation (C/I) performance. Design and analysis equations are developed for the multiple-beam antennas using offset parabolic-reflector antennas by including various design parameters such as the number of reflectors, the number of frequency cells, the focal-length-to-diameter (F/D) ratio, the horn efficiency, and the pointing error. The analysis employs a quasi-Gaussian beam representation for the primary and secondary patterns in order to take into account the effect of the sidelobes. Results of the analysis given in this paper agree well with rigorous computations based on physical optics analysis of the antenna radiation. Design curves showing the impact of horn efficiency on the C/I performance of multiple-beam antennas are presented for various frequency-reuse schemes.

Parametric design and analysis of multiple-beam reflector antennas for satellite communications

Simplified design and analysis equations are presented for multiple-beam reflector antennas based on the Gaussian-beam analysis of the primary and secondary patterns. The derived equations are useful for the quick design and performance analysis in terms of the coverage-area directivity and the inter-beam isolation of multiple-beam antenna systems. Results of the analysis given in this paper agree well with rigorous computations based on physical-optics analysis of the reflector-antenna radiation patterns. Extension of the analysis to multiple-beam lens antennas, and to shaped/contoured-beam antennas, is also presented.

Design and analysis of multiple-beam reflector antennas

A modified template is proposed for shaped-beam satellite antenna patterns for use in orbit-planning studies of a fixed satellite service. Based on a previously discussed simple model, the template now includes the effects of beam scanning, aperture blockage, and surface errors. It is found to agree well with the measured data on current satellites and is a reasonable upper bound specification for future satellite antennas. >

A template for shaped-beam satellite antenna patterns

MIT LL is developing a small dual-polarized Ka-band monopulse antenna, which has very challenging specifications imposed on the radiator that require a sophisticated and efficient reflector antenna design. Reflector shaping is a technique that can be used to create a specific non-standard reflector profile to generate a desired aperture illumination that classical parabolic reflector surfaces cannot provide. A comparison with the classical Cassegrain parabolic reflector antenna will be reviewed and results discussed for the antenna design approach utilized at MIT LL. Measured data will be presented for the prototype antenna that was constructed.

A Ka-band Dual-Pol Monopulse Shaped Reflector Antenna

This article gives an overview of the activity in the areas of reflector antennas and feeds in Norway since 1978. The activity includes cylindrical, symmetrical, spherical, offset, single- and dual-reflectors, and primary dipole feeds, waveguide feeds, hybrid-mode feeds, lens feeds and microstrip antennas. The work has resulted in industrial applications and a number of articles in international journals.

Reflectors and feeds in Norway

The diffraction and blockage efficiencies of the conventional Cassegrain antenna are calculated by using the uniform geometrical theory of diffraction and physical optics. The various subefficiency terms corresponding to different diffraction fields are tabulated for a typical antenna and the results are discussed. Design curves that provide the aperture efficiency value as a function of main reflector diameter, subreflector diameter and the feed illumination taper are presented.

P. S. Kilkal

Papers

A study of the diffraction and blockage effects on the efficiency of the Cassegrain antenna