Some issues regarding field synthesis in complex environments
O.M. Bucci, M. D'Urso, T. Isernia
Classical synthesis methods and techniques exploit simplifying assumptions about the environment, such as for instance free space assumptions or the esistence of a common element pattern in array synthesis. These hypotheses are far from true in a number of applications wherein the antenna has to operate in a complex environment where a number of objects act as 'obstacles' for the different radiating elements. Also, synthesis problems exist, such as for instance the synthesis of fields for microwave diagnostics or hyperthermic applications, wherein the synthesis has to be performed in a non homogeneous and eventually partially known medium.
The aim of the talk is to fix some facts which can be indeed exploited in a number of situations, and stimulate discussions about the open challenges, and the possible ways to tackle them.
Known results include the fact that whenever the scenario is perfectly known, the optimal focusing of a scalar field can be reduced to a relatively simple Convex Programming problem by taking into account the scenario into the field radiated by each elementary radiating source. Also, the optimal focusing of scalar far fields in the presence of near fields obstacles can be dealt with in a similar fashion by including in the overall synthesis near field constraints, which still turn out to be convex constraints.
Open challenges include the synthesis of shaped beams under the same conditions, and, last but not least, the synthesis of (near) fields under volumetric design goals and constraints and in the presence of some uncertainty about the scenario. Such a last issue seems to be of particular interest for the actual success of microwave quantitative imaging in biomedical applications.