Ultrawide band sensor for rangefinding and communication

Ultra-wideband sensor for range-fmding and communicationRobert D. JamesJeffrey B. MendolaVirginia Polytechnic Institute and State UniversityCenter for Transportation Research1700 Kraft Drive, Suite 2000Blacksburg, VA 24061ABSTRACTUltra-wideband (UWB) communications is a new field oftechnology that has a wide range of applications from rangefinding to wide bandwidth communications. Ultra-wideband signals are unusual because their bandwidth to centerfrequency ratio is not small and can be greater than 100%. Recent developments of integrating this technology on a chiphave made it versatile and low cost. A number of areas especially those in ITS can benefit by this technology includingAutomatic Vehicle Identification (AVI), Advanced Traveler Information Systems (ATIS), Advanced Traffic ManagementSystems (ATMS), Transportation Planning, Collision Avoidance, and Automated Highway Systems (AHS). This paperdescribes the basics of UWB technology, describes its features, provides background on the technology, and provides somepossible applications of UWB to ITS. This paper is not intended to be overly detailed in any one area, but, to provideinformation about a technology to a wide audience.Keywords: Ultra-wideband technology, range-fmding, multi-access communications, collision avoidance, advanced trafficmanagement systems, automatic vehicle identification, advanced traveler information systems, automated highway systems,transportation planning1. INTRODUCTIONUltra-wideband technology is a new field of communications and radar that uses ultra-short pulses of energy and complexpulse trains for location and communication. Ultra-wideband signals are characterized by the ratio oftheir bandwidth totheir center frequency. Normal narrowband signals have bandwidth-to-center-frequency ratios that are 0.0 1 or less.Wideband and spread spectrum signals have bandwidth-to-center-frequency ratios that are 0.01 to 0.25. However, ultra-wideband signals have bandwidth-to-center-frequency ratios that are 0.25 to 2.0. Since the bandwidth is so large thesesignals lose their sinusoidal nature and take on a whole new set of properties. An ultra-wideband signal is produced bygenerating an ultra-short pulse that is in many cases less than a nanosecond in duration. This makes the pulse duration on thesame order as the RF cycle. To some, the pulses are so different than conventional RF that they are referred to as non-sinusoidal impulse technology. However, without some kind ofvariation in the signal it cannot be radiated from an antenna.Work is currently underway to develop a large current radiator that will not require oscillations.In addition to the short duration pulses, these devices can be made with very high pulse repetition frequencies (pro. Thepulses can be repeated on the order ofmicroseconds. With very fme variations ofthe spacings ofthese trains of pulses,sophisticated messages can be communicated with the device. With correlation technology, a significant quantity ofinformation can be transmitted. Therefore, these devices can be joined together to communicate as well as co-locate eachother.With current technology, these capabilities are possible with solid state electronics. Low cost chips can be made to perform awide range of applications. UWB offers accurate location and sophisticated communication at a very low price.2. FEATURES OF UWB TECHNOLOGY2.1. Range finding66