Embodiments of a method for tuning the resonant frequency of an antenna in a wireless communication device are disclosed, along with embodiments of a wireless communication device using such a method. Embodiments sense the out-of-band impedance of the antenna, which comprises an antenna element and selectively adjustable impedance disposed between the antenna element and a ground plane of the wireless device, and adjust the selectively adjustable impedance to achieve a desired resonant frequency of the antenna. Embodiments separate an antenna signal into an in-band signal and out-of-band impedance, generate an error signal related to the out-of-band impedance, apply the error signal to a controller circuit configurable to generate an impedance error signal representing the change in antenna impedance, and apply the impedance error signal to the selectively adjustable impedance. Embodiments of a method and electronic circuit for determining the change in impedance of an antenna are also disclosed.