Non-standard Antennas

Chapter 18Ultra-wideband Antenna Systems¹

 

 

 

18.1. Introduction

The abbreviation UWB (ultra-wideband) is widely used to describe electronic systems working with short-time electric pulses, base band transmission systems or without carrier, radar systems [IMM 02]. The latter are mainly military or have weak commercial potential in the civil field (archaeology, civil engineering, etc.). Several probationary means of UWB detection, designed by the laboratory XLIM of the University of Limoges (UMR 6172) are presented in this chapter. Through a brief description of some of them, the fundamental theoretical and technological aspects of the pulse UWB as well as the scientific approaches and the antenna systems proposed by the laboratory are presented.

18.2. The principles implemented through two applications

18.2.1. The radar cross-section measurement in UHF-VHF

The interest for the detection systems in bands UHF and VHF is that in this frequency domain, the reduction of signature of the materials by the use of the conventional passive techniques (shapes, materials) does not work. The major problem for the measurement of the radar cross-section (RCS) in the spectrum of the metric waves concerns the parasitic reflections of environment. It can turn out to be crippling even in the case of the anechoic measurement chambers. In the metric wave domain:

– the used large band antennas are characterized by a low directivity and high secondary lobes;

– absorbents which recover walls to avoid ...