Showing papers by "Roozbeh Tabrizian published in 2009"

Effect of phonon interactions on limiting the f.Q product of micromechanical resonators

Abstract: We discuss the contribution of phonon interactions in determining the upper limit of f.Q product in micromechanical resonators. There is a perception in the MEMS community that the maximum f.Q product of a microresonator is limited to a “frequency-independent constant” determined by the material properties of the resonator [1]. In this paper, we discuss that for frequencies higher than ω τ = 1/τ, where τ is the phonon relaxation time, the f.Q product is no longer constant but a linear function of frequency. This makes it possible to reach very high Qs in GHz micromechanical resonators. Moreover, we show that 〈100〉 is the preferred crystalline orientation for obtaining very high Q in bulk-acoustic-mode silicon resonators above ∼750 MHz, while 〈100〉 is the preferred direction for achieving high-Q at lower frequencies.

Low-loss MEMS band-pass filters with improved out-of-band rejection by exploiting inductive parasitics

Abstract: This paper reports on a new implementation of integrated lumped filters with improved out-of-band rejection and passband loss. Inductive parasitics are exploited to provide additional transmission zeros at the high frequency end, which can improve both the out-of-band rejection and roll-off. Thick silver is electroplated to reduce the insertion loss and achieve high quality factor. An insertion loss of better than 3dB has been achieved for filters across 220MHz to 640MHz with unloaded Q as high as 50. The out-of-band rejection of filters is as high as 60dB. These are believed to be the highest performing integrated filters in terms of out-of-band attenuation and spurious-free response implemented on silicon substrate.