Non-Foster antenna matching networks using reflection-mode negative-group-delay networks

Non-Foster networks provide a possible route for broad band matching of antennas. The major challenges when designing non-Foster elements using conventional Negative Impedance Converters (NICs) arise from the stability concerns, due to the existence of the feedback in the circuitry and the generation of negative impedance. Therefore, investigation of alternative means for designing non-Foster elements which are more stable is imperative. This paper presents a new perspective in designing non-Foster reactive elements based on negative group delay (NGD) networks. Firstly, a standalone NGD network in the reflection mode is designed, built and tested. Simulation and experimental results are introduced. Subsequently, a new technique which involves a negative resistance amplifier and a Lange coupler to compensate the inherent losses of the NGD network is proposed. The proposed technique is applicable to antenna matching where both transmit and receive capabilities are required. Simulation results of the resulting synthesised non-Foster element are presented.