Deposition of ZnO Films on Freestanding CVD Thick Diamond Films

For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.

Finite-element analysis of scattering parameters of surface acoustic wave bandpass filter formed on barium titanate thin film

The frequency dependence of scattering parameters of interdigital surface acoustic wave transducers placed on ferroelectric barium titanate(BaTiO_(3))epitaxial film in c-phase coated over magnesium oxide has been studied using the finite-element method(FEM)approach along with the perfectly matched layer(PML)technique.The interdigital transducer which has a comb-like structure with aluminum electrodes excites the mechanical wave.The distance between the fingers allows tuning the frequency properties of the wave propagation.The magnesium oxide is taken as the substrate.The two-dimensional model of two-port surface acoustic wave filter is created to calculate scattering parameters and to show how to design the fixture in COMSOL_(TM).Some practical computational challenges of finite element modeling of SAW devices in COMSOL_(TM)are shown.The effect of lattice misfit strain on acoustic properties of heterostructures of BaTiO_(3)epitaxial film in c-phase at room temperature is discussed in present article for two lowfrequency surface acoustic resonances.

Group delay and phase delay in GNSS systems

GNSS signals have previously been modulated using binary phase shift keying but this modulation scheme is being replaced by binary offset carrier(BOC)modulation.Research has considered how the BOC signals might be affected differently when passed through a surface acoustic wave(SAW)filter.The concern has been that because of the split spectrum nature of the BOC signals,the upper and lower side-lobes will be delayed significantly differently.This was suggested because SAW filters have nonlinear phase characteristics and therefore different frequencies are delayed differently.It was suggested that this difference in delay will result in greater distortion of the correlation triangle.A delay magnification effect was also mentioned when analyzing the delay of a BOC signal.It was not understood why the theoretical delay calculations did not match up with the actual results in both hardware and simulation.This paper clarifies some of the confusion and explains why the“delay magnification”applies to phase delay but not group delay.This paper also takes a look at how the code phase delay can vary with frequency and correlator spacing as a result of the SAW filter properties.