Thin Film Resonators and Filters 1

This and the following paper deal with resonators and filters for use in wireless systems. The trend in wireless systems is to push for higher frequencies and wider bandwidths. System architectures are increasingly using digital signal processing which moves DSP towards the higher frequencies. There is always a push for miniaturization and acoustic devices offer fundamental size reductions in wavelength scaled devices. Manufacturing of filters and resonators requires high precision because of the small fractional bandwidths allowed in frequency control devices. To overcome fabrication limits stiffer structures or faster wave propagation modes are used at higher frequency. The first part of these papers will deal with resonators and resonator fundamentals and the second primarily with filters. Manufacturing and packaging issues will also be addressed. The BVD lumped element equivalent circuit model gives an accurate representation of the resonator compared to the 1D results, excepts at harmonics. The BVD model can be extended to include other losses and spurious resonances.