Impulse-radio ultra-wideband systems for vital-sign monitoring and short-range communications

Abstract

In recent years, regulation authorities from many countries have allowed unlicensed use of ultra-wideband (UWB) technology, e.g. between 3.1 - 10.6 GHz in the United States or 6 - 8.5 GHz in Europe. In order to not disturb the primary radio operation in these bands, the mean UWB power spectral density is limited to - 41.3 dBm/MHz only. One possible implementation of UWB technology is the so called impulse-radio ultra-wideband (IR-UWB) concept, which uses very short carrierless baseband impulses for communication or sensing applications. This thesis investigates the IR-UWB concept in component and system design. IR-UWB technology is introduced, followed by a discussion of some important figures of merit, suitable impulse shapes and basic system architectures. The potential of IR-UWB technology is shown by two example systems targeting the UWB spectral mask allocated in the United States. For this, two hardware demonstrators are presented using commercially available components and components tailored for UWB operation designed and manufactured in a SiGe HBT production technology. One IR-UWB system is a radar sensor for a precise movement determination and breath-rate sensing, applying a time-of-flight measurement technique with a correlation reception. A measurement precision in the millimeter to submillimeter range, as well as breathing measurements on male humans and a seven-week-old infant are presented. The other IR-UWB system is a novel short-range communication system, best suited for a transmission of analog information, like e.g. speech, music or sensor signals. It uses a frequency-modulated carrier as a trigger signal to generate a continuous position-modulated impulse train. In an additional chapter, advanced concepts are shown, which enhance the presented systems by a beam-steerable UWB antenna array or an impulse generator, addressing the European UWB regulation.