Automatic antenna tuning unit for software-defined and cognitive radio

In this paper, we propose a new architecture for a closed-loop controlled antenna tuning unit (ATU) system (only transmitting path is shown). In contrast to previous work, no analog-to-digital converters (ADCs) are used. Using the ATU, the narrow instantaneous bandwidth of an electrically small antenna (ESA) is automatically tuned over a much wider frequency range by the ATU. This matching scheme ensures that the narrowband antenna is automatically matched to any desired frequency under all environmental conditions using circuits with practical component values and tolerances. It is imperative that the entire tuning process be completed rapidly using efficient algorithms and fast hardware, and for these algorithms and hardware to consume as little power as possible.