Analysis of thin-film Bragg structures and piezoelectric microwave resonators on their basis

A number of regularities inherent in acoustic Bragg structures and microwave resonators manufactured on their basis are revealed. It is found out that, even in the case of a relatively small number of structure layers, the width of the forbidden gap is the same as for an infinite number of layers. The resonator eigenfrequencies are found to be dependent on not only the resonance frequency of the intrinsic resonator, which is determined by only the resonator thickness and the sound velocity, but also on the position of this resonance frequency in the forbidden gap. The existence of additional quasi-harmonic modes whose frequencies are close to harmonics of the calculated frequency and are nonlinearly dependent on this frequency is shown.