Analysis and Modeling of Near-Field Effects on the Link Budget for UWB-WPAN Channels

Wireless personal area networks applications may benefit from the use of ultra-wideband (UWB) technology. In these applications transmit and receive antennas are very close to each other and the far-field condition assumed in most of the link budget models may not be satisfied. Under near- field conditions, variations in the link budget and pulse shape compared to the far-field can be observed. In this work, a new UWB link budget model for very short distances is proposed and validated with measurements using different types of antennas. The measurements have been performed in the time domain by exciting the antenna with very short pulse of 35 ps width covering a large frequency band. The proposed model, which includes frequency, antenna size and orientation as parameters, shows a good agreement with the simulations and the measurements.