A mobile terminal can include a printed circuit board with a reference voltage conductor, an antenna coupled to the first side of the printed circuit board, and a parasitic resonator coupled to the second side of the printed circuit board. More particularly, the parasitic resonator can be connected to the printed circuit board by first and second couplings, which provide first and second impedances, respectively, between the parasitic resonator and the reference voltage conductor. The impedances can be of different values, and can be provided by discrete impedance components. The resonant frequency of the parasitic resonator can be adjusted by altering the impedances of the first and second couplings.