Study of power efficiency of non-foster impedance matching for electrically small antenna

Summary form only given. Electrically small antenna has attracted much attention because of its potential application in compact wireless communication and sensing systems. Matching is needed before any practical application for an electrically small antenna (ka <; 1, k - wavelength number, a - radius of the smallest sphere that can surround the antenna) because it has an input impedance consisting of large reactance and small radiation resistance. An electrically small antenna matched by a lossless passive matching network, according to the Bode-Fano limit, has a narrow bandwidth limitation determined by the high-Q-factor property. A non-Foster element provides a negative reactance slope versus frequency which can cancel the corresponding positive reactance slope of the input impedance of an electrically small antenna. Thus by adding an active matching circuit properly designed with non-Foster element, the electrically small antenna may have a larger impedance bandwidth. Other than the antenna bandwidth, the power efficiency involving DC power dissipation of the antenna system can also be important.In this work, the power efficiency of an electrically small antenna matched by a lossless passive matching network and a non-Foster circuit are compared. The average power efficiency is defined as the radiated power over total supplied power averaged over a given frequency band. A passive non-Foster matching circuit with 100% loss compensation by active devices is studied to theoretically evaluate the power efficiency of any electrically small antenna matched by a nonFoster circuit. The power efficiency of an electrically small antenna with no matching, lossless passive matching and passive non-Foster matching with 100% active loss compensation are compared considering the same frequency band. Our preliminary results indicate that careful tradeoff analysis is necessary to evaluate the power efficiency performance of various electrically small antenna matching approaches.