Ideal versus realistic non-Foster elements in active metamaterials

The `parasitics´ of realistic non-Foster elements limit performance of recently introduced broadband active metamaterials and associated devices. Here, we present a very simple and clear explanation of this non-ideal behavior, based on the inevitable delay and frequency characteristic of used active component. Finally, it is shown that presented analysis can be used for the design of non-Foster elements with substantially decreased parasitics, which enables practical realization of stable superluminal transmission lines with many unit cells.