Investigation of an adaptively-tuned digital non-Foster approach for impedance matching of electrically-small antennas

An adaptively-tuned digital non-Foster negative capacitor is investigated for impedance matching of electrically-small antennas. Such a digital non-Foster approach has the potential to address difficult design challenges such as stability and tolerance issues in analog non-Foster circuits. Furthermore, the digital non-Foster approach is tunable in software. The required negative capacitance is implemented using an ADC (analog-to-digital converter), DAC (digital-to-analog converter), and signal processing. In addition, the proposed adaptive approach uses the DAC and ADC to excite the antenna with a signal, and determine the antenna capacitance and resistance using impulse response and/or ARMA modeling. The digital non-Foster negative capacitance is then used to cancel the observed undesired reactance of the antenna. Results are given for an RC model of an electrically-short antenna that show effective estimation of impedance, and successful cancellation of most of the undesired reactance.