Apodization design technique for layered structure SAW devices

Design approaches are presented for layered structures based on the k-x domain analysis. Two design methods for a flat band filter are modified using this method and compared with the non velocity dispersion case. A compensation method is also presented which yield the desired filter response with velocity dispersion

SAW dispersive equivalent circuit modeling for diamond layered structures

A dispersive equivalent circuit (DEC) model including velocity dispersion of layered structures based on Smith\u27s equivalent circuit model is presented. Assuming the velocity dispersion is very small near the center frequency, the impedance term of Smith\u27s equivalent circuit has been separated. The modified equivalent circuit is given by an extension of the original Smith\u27s equivalent circuit model by cascading a velocity dispersion impedance term to the acoustic port and parallel to the longitudinal port. The frequency response of ZnO/diamond/Si layered structures, including velocity dispersion is calculated in the case of the modified equivalent circuit model and compared with the equivalent circuit including the velocity dispersion directly within the model parameters

Characteristics of IIDT on ZnO/diamond/Si structures

Characteristics of interdigitated interdigital transducer (IIDT) structure on ZnO/diamond/Si structures are discussed including velocity dispersion. The pass band width and the null frequency band width of the IIDT structure are narrower than that of non dispersive surface acoustic wave (SAW) velocity because of the velocity dispersion. A comparison of the velocity dispersive case with the non velocity dispersive case for sidelobe reduction for the IIDT structure will be presented

Characteristics of ZnO/diamond/Si SAW resonators

The surface acoustic wave (SAW) resonator response of ZnO/diamond/Si layered structures are calculated and discussed including velocity dispersion. Smith\u27s second equivalent circuit including energy storage effects is used to calculate the resonator response. The effect of velocity dispersion appears for the shift of resonant frequency to the expected center frequency, and appears for the band width of resonator becomes narrower than that of non dispersive case. The coupling of modes equation is modified for the velocity dispersion to explain these effects. The reflection coefficients of gratings are calculated for velocity dispersive case and the non velocity dispersive case. These results agree with the response calculated by the equivalent circuit model. With assuming the deviation of velocity dispersive be small neighboring the resonance area, the effect of velocity dispersion is explained in theoretically. The ZnO/diamond/Si SAW resonators provide high frequency operation and the high quality factor (Q) SAW resonators due to the velocity dispersion

Zno/Diamond/Si Saw Filter Properties Including Velocity Dispersion

The surface acoustic wave (SAW) filter properties of ZnO/diamond/Si structure are calculated including velocity dispersion. It is well known that the pole width of a SAW filter response and the number of electrodes have a reciprocal relation for bulk piezoelectric materials. However, the pole width of layered structures tends to be narrower than that of expected bulk SAW devices and the reason is due to the velocity dispersion of layered structures. The pole width of layered structures was calculated by the delta function model including the velocity dispersion and was compared with the experimental results. The dispersion effect is also calculated by using the Smith\u27s equivalent circuit model. The results of this analysis are presented and agree well with the experimental results

New ab initio based pair potential for accurate simulation of phase transitions in ZnO

A set of interatomic pair potentials is developed for ZnO based on the partially charged rigid ion model (PCRIM). The derivation of the potentials combines lattice inversion, empirical fitting, and ab initio energy surface fitting. We show that, despite the low number of parameters in this model (8), a wide range of physical properties is accurately reproduced using the new potential model. The calculated lattice parameters and elastic constants of ZnO in the wurtzite (WZ) phase, as well as the lattice parameters and stabilities of ZnO in other high-pressure and metastable phases, agree well with experiments and with density functional theory (DFT) calculations. The calculated transition pressure of the wurtzite-to-rocksalt (WZ-to-RS) transition is 12.3 GPa. A wurtzite-to-honeycomb (WZ-to-HC) phase transition induced by uniaxial pressure along the c-axis is simulated by means of molecular dynamics (MD) simulations. The WZ-to-HC transition takes place at an uniaxial pressure of 8.8 GPa while the reverse transition takes place at 2.9 GPa, which is consistent with DFT calculations. Other physical properties, including phonon dispersion, phonon density of states, and melting point calculated using our ZnO potential model are in good agreement with experimental and DFT data. Limitations of the novel ZnO potential model are also discussed