Linear System Approach to Ultrawideband Antenna Distortion Analysis

Since the federal communications commission (FCC) approved rules for the commercial use of ultrawideband (UWB) radio applications, UWB antenna structures have been an intensive research field in order to satisfy the spectrum requirements of this technology. There are some differences between narrowband and UWB antennas. First of all, the design process in UWB antennas is more difficult than in narrowband cases since the antenna has to radiate in an extreme bandwidth. Because of this fact, UWB antennas may distort waveforms, in contrast to narrowband systems. The contribution to distortion comes from two different points: radiation patterns and mismatch. In this paper, the distortion introduced by UWB antennas is analysed using a linear system approach which takes into account both contributions. In order to compare two antennas and show the method suitability, measured transfer functions obtained from to UWB geometries are used, computing metrics dependent on the communication direction.