AM Broadcast Signal-of-Opportunity Location Device

Q-Track has identified the AM broadcast band as the most promising choice for a signal-of-opportunity to improve navigation in GPS denied areas.  We propose an asynchronous time-difference-of-arrival (TDOA) architecture using classical direction finding (DF) to resolve the integer ambiguity in phase comparison between AM band broadcast signals. This architecture will also be able to support a high accuracy location system using cooperative low-power beacons using Near-Field Electromagnetic Ranging (NFER). We will develop a preliminary RF and system architecture as well as DF and TDOA algorithms. In Phase I, Q-Track will assess the feasibility of the architecture and the accuracy of the algorithms in the context of real-world measurements of noise and propagation of AM broadcast signals in urban environments. Finally, Q-Track will figure out how our existing AM-band Locator-Receivers might be modified to implement an asynchronous TDOA and DF signal-of-opportunity handheld location device for Phase II. Q-Tracks extensive experience in developing high precision AM-broadcast band Locator-Receivers and in developing compact, high-efficiency antenna systems for handheld and body-mounted applications, helps reduce technical risk and ensure that the project is well-positioned for a successful Phase II prototype system. BENEFITS: The Global Positioning System (GPS) uses 24-32 Medium Earth Orbit (MEO) satellites to provide location and navigation information to benefit not only our military but also the private sector.  GPS signals, however, are not available indoors, in urban canyons, and in dense foliage.  This proposal envisions an ancillary navigation and system to provide location capability in GPS-denied areas.  Beyond the military benefit (including redundancy), the civilian sector can also benefit from such technology.  Examples include firefighters, SWAT teams, sewer workers, and urban vehicles.