Nonlinear effects of non-Foster matching networks

Non-Foster circuits (NFCs) can overcome bandwidth and performance limitations of passive antennas and metamaterial structures. However, these active circuits have nonlinear transistors which can introduce undesirable effects at high signal power levels. A non-Foster matching network has been designed for a small loop antenna, and its broadband matching capability has been examined at varying signal power levels. It has been observed that the NFC impedance changes considerably as the signal power increases, thus reducing its matching capability as well as introducing stability problems.