Stabilizing non-foster-based tuning circuits for electrically small antennas

Although non-Foster circuits are very attractive for microwave and antenna applications because they are not restricted by the gain-bandwidth product, stability is a major issue with these circuits. This paper presents a systematic way to stabilize the widely used non-Foster circuit (NFC) topology originally introduced by Linvill [1]. As a case study, a NFC tuned electrically small antenna (ESA) is considered. The stability analysis approach is based on frequency domain method. The circuit is stabilized with conventional control techniques (CCTs).