Free space link budget evaluation of UWB-IR systems

Ultra wideband impulse radio (UWB-IR) technology is an ideal candidate for wireless networks that can be utilized for short-range, high-speed, low power, and low cost indoor applications. The link budget of the free space propagation loss is usually estimated by using Friis´ transmission formula. However, it is not directly applicable to ultra wideband impulse radio transmission systems, in particular the single band impulse radio, as the formula is expressed as a function of the frequency. Moreover, the waveform may be distorted due to the frequency characteristics of the antenna, and the comparison between Tx and Rx waveforms is not straightforward. The paper discusses the free space link budget evaluation of UWB-IR systems based on the extended Friis´ transmission formula. The matched filter is considered at the receiver side to maximize the SNR for evaluation. An experimental evaluation of the antenna transfer function needs the three-antenna method for the calibration of the reference antenna. The technique gives very accurate results and is very useful for design and evaluation of UWB impulse radio transmission systems, especially for the evaluation of waveform distortion effects.