A New Method for Tuning Transistor-Based Non-Foster Negative Impedance Circuits for Low-Frequency Antennas

In this paper, a new method for tuning a transistor-based non-Foster circuit is introduced. Traditional non-Foster circuits invert a load impedance to create a negative impedance slope. Adjustments are made by modifying the load impedance. Previous work has added tunability by replacing the load with a varactor. This paper presents a new method of creating a tunable non-Foster circuit that does not rely on modifying the load.