In this paper, we analyze possible sources of dissipation in aluminium nitride (AlN) contour mode resonators for three different resonance frequency devices (f r ) (220 MHz, 370 MHz, and 1.05 GHz). For this purpose, anchors of different widths (W a ) and lengths (L a ) proportional to the acoustic wavelength (λ) are designed as supports for resonators in which the dimensions of the vibrating body are kept fixed. The Q extracted experimentally confirms that anchor losses are the dominant source of damping for most anchor designs when f r is equal to 220 and 370 MHz. For specific anchor dimensions (W a /λ is in the range of 1/4-1/2) that mitigate energy leakage through the supports, a temperature-dependent dissipation mechanism dominates as seen in higher f r resonators operating close to 1.05 GHz. To describe the Q due to anchor losses, we use a finite-element method with absorbing boundary conditions. We also propose a simple analytical formulation for describing the dependence of the temperature-dependent damping mechanism on frequency. In this way, we are able to quantitatively predict Q due to anchor losses and qualitatively describe the trends observed experimentally.[ 2014-0232]Index Terms-AlN contour mode resonators, quality factor, anchor losses, temperature dependent dissipation, finite element analysis, perfectly matched layer. 1057-7157

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The performance of inductors at high frequencies and small sizes is one of the largest limiting factors in the continued miniaturization of dc-dc converters. Piezoelectric resonators can have a very high quality factor and provide an inductive impedance between their series and parallel resonant frequencies, making them a promising technology for further miniaturizing dc-dc converters. In this paper we analyze the impact of resonator parameters on the performance of the piezoelectric resonator based dc-dc converter, derive the optimal load impedance and efficiency limits, and analyze the impacts of varying conversion ratio and load impedance. This work is accompanied by a prototype dc-dc converter using a piezoelectric resonator fabricated from lithium niobate. The piezoelectric resonator has a quality factor of 4178 and a coupling coefficient, k 2 t , of 29%. The converter is able to achieve high efficiency zero voltage switching and a continuously variable conversion ratio without the use of any discrete inductors. It achieves a maximum power output of 30.9 W at an efficiency of 95.2% with a power density of 6.76 W cm 3 .

In this paper, we analyze the origin of elastic nonlinearities in aluminium nitride contour mode resonators (CMRs). Our study highlights that the nonlinear behavior is due to thermal effects when the resonators are electrically excited and the input is slowly (slow with respect to the device thermal time constant) swept through the excitation frequencies close to the main resonance. An analytical expression that relates the nonlinear behavior of the device to its geometry and material properties is derived. Amplitude-frequency (A-f) and third-order intermodulation (IMD3) measurements on 1-GHz AlN CMRs are employed to demonstrate the theoretical reasoning. The two experiments confirm the validity of the analytical derivation when the system is dominated by thermally induced nonlinearities. In the case of large frequency difference between the modulation frequencies, purely elastic nonlinearity can also be extracted from the IMD3 measurements.[ 2012-0264]Index Terms-Amplitude-frequency, contour mode AlN resonator, duffing equation, lumped electrical mode, thermal nonlinear effect, third-order intermodulation distortion.

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