engleski

Metamaterials based on Non-Foster Elements

It is well known that any passive metamaterial must satisfy basic dispersion constraints.This fundamental issue is a cause of inherent narrowband behavior of all metamaterials (SNG, DNG, SNZ, DNZ). In [1], a possibility of going around the basic dispersion constrains by the use of non-Foster active elements such as negative capacitors and negative inductors, was predicted theoretically. Very recent experimental studies [2, 3] showed that is indeed possible to build active (almost) dispersionless ENZ and MNZ metamaterials. Here, the basic physics of non-Foster metamaterials will be reviewed and several illustrative examples of practical prototypes developed at University of Zagreb will be presented. These include a 2D ENZ unit cell for broadband 2D electromagnetic cloak (Fig. 1) and a broadband ENZ RF transmission line with superluminal phase and group velocities (Fig. 2). Finally, currently investigated novel concepts of matched ‘EM nihility’ and frequency independent active transmission lines will be highlighted.

active metamaterial; negative capacitor; superluminal

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