Advances in 3‐D electromagnetic focusing: Optimized time reversal and optimal constrained power focusing

Abstract

In this paper, we show how to successfully deal with the problem of focusing a vector field in a 3‐D scenario, by properly extending two recently introduced procedures developed with respect to 2‐D fields. In particular, to address this problem relevant in many applications, we describe an improved version of the well‐known time reversal technique, the optimized time reversal, and a procedure able to provide an optimal focusing in the presence of arbitrary upper bounds for the field intensity, the optimal constrained power focusing. The two approaches are presented, discussed, and comparatively assessed in two different scenarios representative of realistic working conditions. The results confirm the possibility of tackling the problem of focusing a 3‐D vector field in an efficient way and that the optimal constrained power focusing, while computationally heavier, provides the best possible focusing performance.

A Novel Approach on Microwave Hyperthermia

“…FMs are easy to comprehend and apply during the treatment as opposed to complicated focusing algorithms [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Those algorithms need to be run before the treatment, and the user has no control over the program, and since they are patient-specific, the patient also needs to wait for the algorithm to converge.…”

“…In general, the breast is placed in a cavity encircled by a number of antennas; next, the amplitude and the phase are optimized in a patient-specific manner for each antenna. Two-dimensional specific absorption rate (SAR) focusing algorithms have been developed by Iero et al [ 3 , 4 ], which is then extended to 3D and named as optimal constrained power focusing (FOCO) [ 5 ]. In previously reported works, simple or semi-realistic phantoms have been used.…”

Space-Time Plasma-Steering Source: Control of Microwave Plasmas in Overmoded Cavities

“…Furthermore, field polarization has also been shown to have a significant impact on microwave breakdown dynamics and pattern [60]. Although it was not discussed in this paper, TR allows the control of the focusing field polarization [61,62]. Thus, this Space-Time Plasma Steering Source could lead to the development of methods allowing the space-time sculpture of microwave breakdown, with the microwave energy that would "accompany" the breakdown dynamics and pattern.…”

Wireless Power Transfer Through Simultaneous Near-Field Focusing and Far-Field Synthesis

“…If more focal points have to be accounted for, for example due to the presence of a set of devices that have to be included in the wireless link (WPT or WPIT are good examples of this situation), specific synthesis strategies have to be followed. Some methodologies used to overcome these limitations involve multiple-feed reflectarrays [13], ad-hoc microwave designs [16], [17], artificial neural networks [18], optimization approaches [19]- [22] or time-reversal techniques [21]- [23]. While the first two mentioned alternatives involve specific hardware design, optimization approaches have been shown to be an effective method for solving such problems from an algorithmic point of view, allowing the design of solutions for different radiating structures (arrays, reflectarrays, transmittarrays, etc.)…”