Advanced technologies for ultra wideband system design

Abstract

AbstradThispaperpresents asummaryoftheultrawideband concept,clarifying its instantaneously large percent-bandwidth nature and the inseparability which results in its four-dimensional ambiguity function. In conventional design, this coupling is suppressed. However, evidence presented here suggests that there may be unique performance and EMC advantages to be gained from exploiting this coupling. The paper then explains why this improved performance is not attainable using switch-based transmitters.Although considerable effort has already been devoted to the analysis and development of ultrawideband (VWB) radar, there is yet some unexplored territory. Two of these unexplored approaches are the focus of this paper. The first is the use of a programmable function generator (e.g.. a direct digital synthesizer) to generate the nquired UWB waveform. The second relies on the first: the exploitation of localized wave solutions to Maxwell's equations for their contribution to improved resolution and reduced path loss. BackeroundTo take advantage of sinusoidal resonance effects, conventional radar waveform design methods utilize a small percent-bandwidth signal.Resonance allows frequency selectivity and increased antenna efficiency. Strictly speaking, a circuit or an antenna is only resonant at a single frequency, but near-resonance conditions persist in many designs at frequencies up to 10% from the resonant frequency. However, this percentage is still quite confining on the allowable combinations of signal center frequency and bandwidth. To avoid this percent-bandwidth limitation, some radar waveform designs incorporate multiple center frequencies (or a frequency sweep). However, the instantaneous percent bandwidth used in these designs still remains small.There are some radar applications which inherently require a larger percent bandwidth. The earliest known application was for detection of buried objects. Research reports on this topic date back to the early 1960's (e.g.. 111). A relatively long wavelength is required for propagation into the earth's surface, and a relatively large bandwidth is needed to get acceptable resolution of the measured depth of the buried object. The nominal set of parameters forthis application is acenter frequency of 1 GHz with a bandwidth of 1 GHz for a percent bandwidth of 100 46.At the time these requirements were emerging, there were a number of research and development activities which made it possible to test some of the theories of ultrawideband systems. One of these research activities is in the area of high-power baseband pulse radiation. High-power soums for very short pulses and radiators for these pulses were developed for simulating nuclear Electromagnetic Pulse (EMP) effects to test the susceptibility of electronic components and systems.Another research area was conwmed with the study of what has been called time-domain electromagnetics (e.g., 121-[5]). The main purpose of this work was to develop more thorough methods to characterize the reflection properties of radar target...

Multiuser Detection using IDMA Scheme in UWB Home Environment

“…Today, Ultra Wideband wireless communication technology has become a hot cake for researchers for transmitting a large amounts of digital data over a wide frequency spectrum using very short duration pulses, low powered radio signals [4], [7]. IR (Impulse radio), a form of UWB spread spectrum signalling technique is used for short-range applications in a dense multipath environment [5], [6].…”