Evaluation of an Ultra-Wideband Propagation Channel

This paper describes the results of an ultrawideband (UWB) propagation study in which arrays of propagation measurements were made. After a description of the propagation measurement technique, an approach to the spatial and temporal decomposition of an array of measurements into wavefronts impinging on the receiving array is presented. Based on a modification of the CLEAN algorithm, this approach provides estimates of time-of-arrival, angle of arrival, and waveform shape. This technique is applied to 14 arrays of indoor propagation measurements made in an office/laboratory building. Statistical description of the results is presented, based on a clustering model for multipath effects. The parameters of these statistical models are compared to results derived for narrowband signal propagation in the indoor environment. I. Ultra-Wideband Radio An ultra-wideband (UWB) radio signal is one whose fractional bandwidth (i.e., its 3 dB bandwidth divided its center frequency) is large, typically over 0.25. Such signals are generated by driving an antenna with very short electrical pulses (on the order of a few nanoseconds to fractions of a nanosecond in duration). Hence these radio systems often are referred to as short-pulse or impulse radio systems. Typically the radiated pulse signals are generated without the use of local oscillators or mixers. The antennas in UWB systems are significant pulseshaping filters. In addition, many environments provide a wealth of resolvable multipath. As a result, the received signal often bears little resemblance to the signal driving the transmitter’s antenna. If the result of an impulse transmission in free space is a received waveform p(t), then in a typical environment, a typical multipath model for the signal r(t) received over an indoor propagation channel is