Surface acoustic wave devices in telecommunications : modelling and simulation

330 p. : ill. ; 25 cm

Phase-sensitive and fast-scanning laser probe system for diagnosis of high frequency acoustic wave devices

AbstractThis paper describes a phase-sensitive and fast-scanning laser probe developed by the authors’ group for the diagnosis of acoustic wave devices used as a platform of highly sensitive sensors. Surface vibration is detected by the Sagnac interferometer, which is insensitive to low frequency vibration. From this feature, we can maximize the scanning speed without influence of low frequency vibration and sacrificing the signal-to-noise ratio of the measurement. It is demonstrated that high quality twodimensional (2D) image of acoustic wave field patterns can be captured in minutes order. Currently the maximum applicable frequency is 2.5 GHz. Because of the phase sensitivity, the measured field in the space domain is readily converted into the wavenumber domain by the 2D Fourier Transform. It is also demonstrated how effective the wavenumber domain analysis is for the purpose

Reem-Shape Phononic Crystal for Q Anchor Enhancement of Thin-Film-Piezoelectric-on-Si MEMS Resonator

This paper proposes a reem-shaped phononic crystal for the performance enhancement of TPoS resonators. The proposed phononic crystal offers an ultra-wide acoustic band gap that prevents energy leakage through the supporting substrate upon its placement at the anchoring boundary, resulting in significant improvements in the resonator quality factor. Simulated results show reem-shape phononic crystals generate a band gap up to 175 MHz with a BG of 90% and enhance the anchor quality factor from 180,000 to 6,000,000 and the unloaded quality factor from 133,000 to 160,000, representing 33.3-fold and 1.2-fold improvements, respectively

Higher-order surface acoustic wave modes of a finite elastic solid

The wave mode expressions of Rayleigh waves are given by two coordinates with one in exponentially decaying form as the signature of the distinct wave feature. Such expressions are hard to expand to include their higher-order modes because they could be in two coordinates without a fixed known form. For this reason, the higher-order modes of Rayleigh waves are hard to obtain with analytical solutions, as the past attempts shown through some studies. Fortunately, our recent efforts have been shown that the Rayleigh-Ritz method is an effective technique for the analysis of Rayleigh waves in elastic solids with complications. As a result, we want to utilize this powerful method for the finding and evaluation of higher-order modes for Rayleigh waves. The essential formulation of the method has been shown in our earlier papers, and we increased the order of basis functions for the computation and search of frequencies above the Rayleigh waves to locate the higher-order modes. The process is also validated with the finite element analysis

Figure of Merit Enhancement of Laterally Vibrating RF-MEMS Resonators via Energy-Preserving Addendum Frame

This paper examines a new technique to improve the figure of merit of laterally vibrating RF-MEMS resonators through an energy-preserving suspended addendum frame structure using finite element analysis. The proposed suspended addendum frame on the sides of the resonant plate helps as a mechanical vibration isolator from the supporting substrate. This enables the resonator to have a low acoustic energy loss, resulting in a higher quality factor. The simulated attenuation characteristics of the suspended addendum frame are up to an order of magnitude larger than those achieved with the conventional structure. Even though the deployed technique does not have a significant impact on increasing the effective electromechanical coupling coefficient, due to a gigantic improvement in the unloaded quality factor, from 4106 to 51,136, the resonator with the suspended frame achieved an 11-folds improvement in the figure of merit compared to that of the conventional resonator. Moreover, the insertion loss was improved from 5 dB down to a value as low as 0.7 dB. Furthermore, a method of suppressing spurious mode is demonstrated to remove the one incurred by the reflected waves due to the proposed energy-preserving structure

Q-Factor Enhancement of Thin-Film Piezoelectric-on-Silicon MEMS Resonator by Phononic Crystal-Reflector Composite Structure

Thin-film piezoelectric-on-silicon (TPoS) microelectromechanical (MEMS) resonators are required to have high Q-factor to offer satisfactory results in their application areas, such as oscillator, filter, and sensors. This paper proposed a phononic crystal (PnC)-reflector composite structure to improve the Q factor of TPoS resonators. A one-dimensional phononic crystal is designed and deployed on the tether aiming to suppress the acoustic leakage loss as the acoustic wave with frequency in the range of the PnC is not able to propagate through it, and a reflector is fixed on the anchoring boundaries to reflect the acoustic wave that lefts from the effect of the PnC. Several 10 MHz TPoS resonators are fabricated and tested from which the Q-factor of the proposed 10 MHz TPoS resonator which has PnC-reflector composite structure on the tether and anchoring boundaries achieved offers a loaded Q-factor of 4682 which is about a threefold improvement compared to that of the conventional resonator which is about 1570