Microwave Imaging

CHAPTER NINE

Microwave Imaging Apparatuses and Systems

9.1 INTRODUCTION

As far as instrumentation for microwave imaging is concerned, it should be mentioned that illuminating–receiving systems are essentially based on two different approaches. The first one concerns the use of one or more probes (linear or circular arrays) operating in a real or synthetic mode. Usually, probes are constituted by dipoles or small horns. The second approach involves the use of passive probes that are sequentially modulated. Clearly, the imaging apparatuses must be suitable for use in the measurement configurations described in Chapter 4.

9.2 SCANNING SYSTEMS FOR MICROWAVE TOMOGRAPHY

Scanning systems for tomography are often composed of circular arrays of antennas. Typically, one antenna transmits and the other antennas (or a subset of thereof) are used to receive the signal scattered by the body to be inspected. As mentioned previously, the geometric positions of the transmitting and receiving antennas with respect to the body to be inspected in the various configurations have been described in Chapter 4. To illustrate this approach, we consider the configuration of one of the first proposed imaging systems working at microwaves, namely, the scanning system developed for medical purposes at the Polytechnic University of Catalunya, Barcelona, Spain (Jofre et al. 1990). It consists of a ring of antennas positioned around a tank in which the object to be inspected is placed (see Fig. 9.1). In tomographic ...