Investigation of basic physics of non-Foster negative capacitance in time domain

Possible application of non-Foster elements such as negative capacitors and negative inductors in broadband matching of small antennas has been a subject of many research studies for a number of years. Unfortunately, due to serious stability problems, there have been a very few practical examples of real-world engineering implementations. Recent examples of inclusion of negative capacitors into metamaterial structures have renewed research interests in non-Foster elements. At the same time, it has been shown that the physical interpretation of operation of negative capacitors and inductors, which is extremely important for stability analysis, is still not completely clear. This paper attempts to explain some basic physical issues of a negative capacitor by time-domain measurements on the low-frequency laboratory prototype.