PAGE CONTENTS
Objectives
The main classes of antennas found in commercially available rescue transponders are vertical whips, wire, helical and patch antennas. Blade antennas are mentioned but don’t really apply to the applications we target. These antennas are most often integrated with a product and tend to operate on a single band (COSPAS or AIS-SART, for example). A few dual-band examples also operate on the COSPAS-SARSAT band and the 121.5 MHz aeronautical rescue frequency.
In this project, the goal is to develop a compact dual band 406/162MHz antenna for use in the latest generation of search and rescue beacons (to be possibly extended to special low-rate data-gathering applications). The focus will be on managing the complementary requirements of antenna size and electrical performance suitable for satellite and terrestrial service. Furthermore, a secondary objective is the development of a numerical model of the antenna (or antennas) studied as part of this project.
Challenges
The most significant challenge will be striking the right balance between physical size and electrical performance. Small antennas suffer severe constraints on bandwidth and efficiency that are defined by fundamental physical principles. Therefore, a significant part of this project is dedicated to managing these fundamental constraints while allowing us to satisfy, in some minimal sense, the requirements needed for reliable emergency beacon operation.
Plan
The project starts off with a preliminary study of the state of the art as well as understanding the special requirements and operational demands of the proposed dual-band antenna. An exploration of the combination of services that might best satisfy the “mission requirements” is carried out. This then allows the definition of a set of antenna requirements.
A prototype “breadboard” design will be carried out to test the proof of concept, satisfying as many of the electrical and mechanical constraints as needed. The test results are then used to verify and update the antenna model.
We then move on to producing a comprehensive design of the final antenna, taking into account all electrical, mechanical and environmental requirements. A full suite of electrical, mechanical and environmental tests, performed in the laboratory as well as under expected environmental conditions is carried out.
Current Status
At this point in the project, we have completed a market survey and a preliminary study of some candidate antenna designs. We are presently engaged in the preliminary design process. Numerous simulations and optimization cycles are being carried out in order to improve the simulation model as well as to settle on a set of antenna architectures to fabricate as part of the breadboard process. Once we clear the Preliminary Design Review process, we shall fabricate a set of antennas for extensive preliminary testing.
