A closed-loop controlled antenna tuning unit (ATU) system includes a return loss detector connected to sample an RF signal generated by a signal source to provide a return loss signal. A matching state searching circuit is connected to receive the return loss signal and, in response, selectively store a return loss value and an impedance matching state. A central controller is connected to provide a switch control signal and apply an optimum matching state to the impedance synthesizer at the conclusion of the matching state search. An impedance synthesizer is responsive to the switch control signal for coupling a radio frequency signal and matching the impedance of an antenna to a signal source.