Southwest Research Institute 2001 Annual Report, Signal Exploitation and Geolocation

The Institute continues to provide support to the U.S. and friendly foreign governments and government prime contractors in the areas of signal intelligence, communications, tagging/tracking, and surveillance systems. Recognized as a world leader in shipboard radiolocation and signal acquisition systems, the Institute provides hardware and software solutions that meet the challenging operational requirements of clients worldwide.

SwRI continues to develop innovative wideband signal acquisition and direction finding (DF) systems. These special purpose systems, with sophisticated capabilities in small and cost-effective packages, are being fielded around the world. The third generation of VHF/UHF frequency hop processing systems is under development, and systems that address the entire high-frequency (HF) spectrum -- detection, acquisition, recognition, DF, demodulation/decoding, and reporting -- are being fielded.

SwRI's numerical electromagnetic modeling capabilities are expanding and currently lead the industry. Antenna pattern databases previously collected using full-scale or scale model platforms can now be numerically generated. This technology has been applied to ships, aircraft, and even body-worn antennas to optimize both antenna design and platform installation for best DF results. Numerical modeling has been successful in predicting HF-DF performance on both U.S. and Canadian warships.

The Institute maintains a leadership role in the advancement of beacon tracking technology. SwRI's transportable satellite downlink terminal, used with SwRI-developed miniature, low-powered, global positioning system (GPS) based beacons, provides the capability to track the location of vehicles, personnel, and materials worldwide. The SwRI-developed RS-8 SILO Signal Intercept from Low Orbit™ is the latest in a series of smart beacons that conserve power by only transmitting to low-Earth orbit satellites when the beacon's position, as determined by its internal GPS receiver, is within the satellite's footprint.

The Institute remains at the forefront of DF networking. SwRI systems can be operated locally or remotely, with confidence measures being reported automatically. SwRI DF systems can be integrated into DF networks and tasked using existing command and control systems.

Institute engineers are developing techniques that use the existing cellular telephone communications infrastructure for tracking and locating the source of a call. In one technique analogous to GPS, but entirely terrestrial, the differences in the arrival times of cellular messages from different cellular base stations are used to estimate the location of the receiver. This entirely passive method (patent-pending) requires no participation by the cellular provider and shows potential for use in emergency (911) reporting and for other commercial and law enforcement tracking and locating missions.

Because of their unique designs, SwRI antennas are the only ones available that permit the installation of other antennas above the DF antenna. On single mast warships, the mast top is reserved for mission-critical systems such as tactical air navigation or DF antennas. SwRI-designed and produced antennas, such as the AS-420A, allow the U.S. Navy to have both tactical air navigation and DF antennas installed at or near the top of the mast, a prime location that offers optimum communication, DF, and radar performance. Although lightweight, these antennas are made of high-strength materials that withstand the severe shock and vibration-induced stresses associated with a vessel operating in severe weather or combat conditions.

SwRI's Model AS-506 shipboard antenna provides HF/VHF/UHF DF capability for patrol or attack craft and is designed to support additional sensors weighing up to 60 pounds. In addition to mast-mounted DF antennas, the Institute has developed the AS-141 HF-DF antenna specifically for future applications requiring a low-radar cross section. This antenna is designed to meet the severe shipboard physical environment and can be mounted on decks or on ship bulkheads.

Copyright© 2002 by Southwest Research Institute. All rights reserved under U.S. Copyright Law and International Conventions. No part of this publication may be reproduced in any form or by any means, electronic or mechanical, including photocopying, without permission in writing from the publisher. All inquiries should be addressed to Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, phone (210) 522-2257, fax (210) 522-3547.