Using Non-Foster Circuits and Characteristic Modes to Improve Small Half Loop Antenna Performance

Traditionally, electrically small wire antennas (ESAs) have a high-quality factor and low radiation resistance. This implies that ESAs are narrow band and have poorly realized gain. In this paper, we present an efficient way to improve the performance of an electrically small wire half loop antenna by loading it with a non-Foster circuit (NFC). The use of the theory of Characteristic Modes (CMs) provides important physical insight in the design of this load to improve the antenna performance. The loaded antenna shows remarkable improvement in antenna gain and signal to noise ratio compared to the antenna without the NFC. Furthermore, by loading the antenna the omnidirectional pattern (TE mode) is maintaining up to a higher frequency range.