Modeling and Design of Reconfigurable Point Actuated Aperture Antennas

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

0100246 Washington In order to meet the communication and broadcasting needs of the 21st century, aperture antennas are generally required to have shaped surfaces so that their radiation patterns efficiently match the geographical regions where the signals are to be transmitted and received. These antennas are, in general, rigid and consist of parabolic, paraboloidal, cylindrical, spherical, or hyperboloidal shapes. In terms of the current state of the art, beam shaping with these rigid structures is possible with multiple off-center feed arrays or asymmetric shaping of the reflector surface (contour beam reflector antennas). Beam steering can be accomplished electrically by utilizing the feed array or mechanically by using specially designed gimbals that tilt the whole reflector. In the case of spaceborne contoured beam reflector antennas, a major limitation is the fact that a rigid shaped reflector is optimized for coverage of a specific geographical area. Once the antenna is deployed on orbit, radiation pattern modification cannot be accomplished. As satellites become more reliable and their expected service life increase, the probability that the satellite service area and/or operator will change also increases. Mechanically active antennas have been proposed as a solution to this problem, but at time there are no commercially viable units. The main rationale of this stems from the following issues: 1. We have algorithms that can accurately predict reflector shapes based on user defined radiation patterns, but we have very few mechanisms that deal with real structures and even fewer for how to achieve these deflections for reflectors that will change their shape dynamically. 2. There is very little fundamental research on how many actuators to use, actuator placement, and optimal actuator deflections for active aperture antennas. 3. There is no fundamental mechanism for coupling the electromagnetics to the mechanics in a seamless fashion. The research proposed in this study seeks to effectively design, model and construct a mechanically reconfigurable antenna that addresses these issues. Since this type of antenna can be built at a fraction of the total cost of a traditional phased array antenna there is commercial significance as well. For example, a commercial manufacturer of phased array antennas claims that they can build phased array antennas at a cost of about $100.00 per element. The resolution needed for space based communications ranges from about 10,000 to 1,000,000 elements. This puts the total cost anywhere between ($1.0M-$100M). The system weight and complexity can also elevate this cost. A mechanically reconfigurable system can be built with off the shelf components today for less than $25,000. Presently there are roughly 600 satellites in commission throughout the world. By the year 2010, it is expected that up to 1000 new satellites will be launched, many with multiple antenna systems. Based on this fact it is easy to see the potential payoff. A fundamental approach to design and construction of these antennas will revolutionize the way these aperture antennas are built today!