Ultra Wide Band Antennas

Chapter 3

Representation, Characterization and Modeling of Ultra Wide Band Antennas ¹

3.1. Introduction

Ultra wide band (UWB) antennas have particular characteristics and constraints, in particular in impulse radio — which operates on signals with extremely broad instantaneous band — which do not exist or wave no object in the narrow band: their design is in general more delicate because it is subjected to more constraints and because their behavior is more difficult to understand and to qualify. Their experimental characterization is much more involved and appreciably more demanding. Finally, the additional dimension — time or frequency — confers onto the antenna a new functional role in the communication system. This is why we have adopted a functional approach to the UWB antenna, presented in section 3.2. The physics of the antenna — in particular its temporal behavior in impulse radio — must be correctly analyzed and interpreted using concepts, reference objects and suitable indicators: sections 3.3 and 3.4 are thus devoted to the signal distortion phenomenon and the concept of an ideal antenna. Because of the additional dimension, the significant amount of data (experimental or simulated) to be handled and analyzed very naturally results in the definition of various performance indicators synthesizing information, allowing us to better understand the behaviors, to qualify the imperfections quantitatively (but simply) and to more easily compare the antennas to one another: ...