Non-foster circuit for wideband matching of high frequency helical antenna

This paper adopts normalized determined function (NDF) to analyze the stability of a non-Foster matched antenna. A -40 pF negative capacitor is achieved at high frequency (HF). The negative capacitor is connected to the input of a 2-meter height helical antenna for wideband cancellation of the large input reactance of the antenna at HF. Nyquist plots of NDFs are used to evaluate the stability of the non-Foster system with and without the stabilization resistor. The performance of input matching and efficiency improvement by non-Foster matching circuit is measured. The received signal power level can be increased by 20-30 dB from 3 to 13 MHz compared to without matching case, and about 15 dB improvement compared to a commercial well-matched HF antenna.