Unbalanced device comprised of FBAR resonators

A splitbar is comprised of two identical thin film bulk acoustic (FEAR) resonators, whose electrodes are cross connected such that the C-axes of the piezoelectric films are parallel/anti-parallel to an applied electric field stimulus. The RF response of a splitbar is near identical to that of a single resonator, but unlike the single resonator, because the resonators are cross wired, their H2 responses annihilate one another enabling the splitbar to have extremely low harmonic emissions. If, however, the series resonances of the two resonators are placed at slightly different frequencies, a narrow LC resonance, whose center frequency is in between the series resonance frequencies, is formed, and the splitbar now exhibits a large H2 response at twice the center frequency of the LC resonance. To study this resonance, we vary the frequency spacing by biasing the splitbar with a dc voltage. We explain why the H2 power emitted by the splitbar is: (1) is proportional to its stored energy, (2) increases strongly with resonator frequency separation, and (3) increases as resonator Q is increased. We also analyze the powerbar, which is the dual of the splitbar, and which exhibits analogous behavior.