A system comprises: a radio frequency (RF) resonator comprising a cavity and a tuning element, the cavity having at least one port, and the tuning element having a length inside the cavity; a processor; a spectrum analyzer coupled to the at least one port, the spectrum analyzer to provide to the processor values of a resonance parameter, the resonance parameter indicative of a resonant wavelength of the RF resonator; and an automotive steering mechanism coupled to the tuning element.