Stability of Non-Foster Reactive Elements for Use in Active Metamaterials and Antennas

During the last couple years there have been lot of attempts to use negative non-Foster reactive elements for improving the bandwidth of electrically small antennas (ESAs) or metamaterial-based structures. However, negative non-Foster reactive elements are actually electronic circuits that are not absolutely stable, which could impose serious problems in practical applications. This communication studies the stability of several networks with non-Foster reactive elements by using a time domain approach. This will help to model more realistic situations for antenna and metamaterial technology.