Non-foster circuits for small broadband antennas

As is well known antenna size implies limitations in bandwidth and gain characteristics. However, if non-Foster/negative circuits are employed such restrictions can be partially overcome. That is negative matching circuits can provide a way to construct very small efficient antennas. Non-Foster circuits have been considered since 1950´s when negative impedance converters (NIC) were proposed. NIC´s can be realized via a combination of active devices (transistors) as well as lumped capacitors and inductors. Still, inherent losses, noise issues and bandwidth limitations from available active elements have precluded their use except for narrow bandwidth applications. But, recent advancements in integrated circuits have renewed interest in non-Foster/negative matching.