Temporal Modulation of Resistive Elements for Frequency Response Engineering

This thesis studies time-varying resistive elements, and it shows how they can be used to engineer a multifrequency perfect absorber. The aim was to briefly review the literature and explore the potential of time-varying resistive elements in providing control over the frequency response of electromagnetic systems, which is an essential characteristic in bandwidth enhancement applications. The performed brief literature review shows that not much attention has been devoted to studies of how time-varying resistive elements can control interference between multiple waves. Consequently, the thesis studied the frequency response of a temporally varying resistive termination illuminated by multiple waves. It was found that by properly designing the time modulation, it is possible to engineer and control interference phenomena, giving rise to a possibility of inducing virtual reactive response from a purely resistive termination. This characteristic is then used to design a multifrequency perfect absorber that fully absorbs incident radiation at multiple frequencies simultaneously, overcoming the absorption limit for static linear thin absorbers