Emphasis mechanism of nonlinear responses caused by transverse modes in RF BAW devices

It is known that nonlinear responses by transverse resonances are more emphasized than those by the main resonance in radio frequency bulk acoustic wave devices. This paper investigates this mechanism using the LCR-based nonlinear equivalent circuit proposed by the authors. Here a number of acoustic branches are newly added to take multiple transverse resonances into account, and amplitudes of nonlinear voltage sources in the model are determined by summation of currents flowing to acoustic branches. Parameters necessary for the analysis are determined experimentally. It is shown that simulated second and third harmonic responses agree well with the measurement. Next, the magnification mechanism is discussed. It is shown that mth harmonics generated by transverse modes are magnified by m-times approximately, and the factor of m is originated to that at the production between field components of transverse and main modes.