Shear Mode Transducers for High Q Bulk Microwave Resonators

Parameter characterization of high-overtone bulk acoustic resonators by resonant spectrum method

“…It was reported that the Q-frequency product exhibited by the types of VHF BAW and UHF SAW resonators is often used on the order of 12 · 10 12 and 6 · 10 12 , respectively [1]. On the other hand, high-overtone bulk acoustic resonator (HBAR) consisting of a piezo-film with two electrodes on a substrate with a very high Q value, exhibits a Q-Frequency product more than 10 14 [2][3][4].…”

Characteristics of the unique modes in HBARs

“…It is intuitive that the thicker the substrate, the higher the Q-value of the HBAR if the mechanical quality of the substrate is much higher than that of the film (one to two orders higher than that of the piezo-film, such as ZnO-film on spinal, YAG, and boule [1,4]). However, when the thickness ratio of the substrate to the film goes to larger, the spacing of the modes will get narrower and other parameters may get worse.…”

“…, we deduced the parameters, ) 4) Changing n-value (thickness of the substrate) but taking it always an integer, we obtained the quantitative relationship of the Q-value and other parameters of the unique mode with the thickness of the HBAR. Because only the substrate thickness is changed, it can be found from Eq.…”

“…However, highovertone bulk acoustic resonator (HBAR) consisting of a piezoelectric thin film on a very high-Q substrate, which needs not exhibit piezoelectricity, exhibited a Q-f product more than 14 10 . HBAR is an attractive candidate for very high-stability frequency control/selection [1][2][3][4].…”

“…How to chose the operating mode properly? High Q-value of the HBAR comes from the extremely high Q-value of the substrate material (one to two orders high than that of the piezo-film), such as spinal, YAG, and boule [1,4], with enough thickness. It was described in [3] that the thicker the substrate the more the energy stored (increase Q-value), but at the same time the narrower the spacing of the resonance frequencies (SRF).…”