Stability and implementation of Non-Foster circuits for antennas

In this work we discuss the subject of non-Foster networks realization. While the last years non-Foster design is revisited proposed circuits are very simple and they are usually employ the realization of a single negative element. This is because instability issues accompany active networks. Consequently, a general approach of multiple negative elements realization and the advantages that can offer is avoided. Here we introduce a non-Foster circuit with more than one element (four) that greatly enhances the operation of an antenna at very small circuits. To that end we test different non-Foster topologies and combination of them using stability criteria to verify that proposed circuit will not oscillate. While final behavior of antenna is worse than the ideally expected, still obtained antenna demonstrates a 10 db bandwidth from λ/30 × λ/30 to λ/13 × λ/13 aperture sizes.