Use of a Digital Non-Foster Radio Architecture for Conventional Tuning of Electrically-Small Antennas

Abstract

Prior investigations of digital non-Foster antenna tuning have pointed out the similarity between these systems and SDR (software-defined radio) systems, where the SDR receiver ADC (analog-to-digital converter) and SDR DAC (digital-to-analog converter) can serve corresponding digital non-Foster circuit roles. In previous investigations, the particular focus has been on using digital non-Foster antenna impedance matching methods to overcome Wheeler-Chu limits of electrically-small antennas. However, the digital non-Foster radio architecture can also provide digital implementation of conventional impedance matching of electrically-small antennas. The advantage is that the impedance matching is accomplished in software without the need for external matching circuitry, allowing digital tuning of the antenna to desired frequency bands. Although such conventional impedance matching would not provide the bandwidth enhancement of non-Foster matching, it may be useful in providing some degree of preselection filtering for narrowband applications. Simulation results illustrate the proposed digital impedance-matching approach, and are compared to a conventional passively-matched electrically -small antenna at 75 MHz.