A SAW Resonator With Two-Dimensional Reflectors

TriQuint Semiconductor, Apopka, FL, USA.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control (Impact Factor: 1.51). 01/2010; 57(1):30-7. DOI: 10.1109/TUFFC.2010.1375
Source: PubMed


It is known that a part of the loss of leaky SAW resonators is due to radiation of acoustic energy in the bus-bars. Many researchers are working on so-called phononic crystals. A 2-D grating of very strong reflectors allows these devices to fully reflect, for a given frequency band, any incoming wave. A new device based on the superposition of a regular SAW resonator and a 2-D periodic grating of reflectors is proposed. Several arrangements and geometries of the reflectors were studied and compared experimentally on 48 degrees rotated Y-cut lithium tantalate. In particular, a very narrow aperture (7.5 lambda) resonator was manufactured in the 900 MHz range. Because of its small size, this resonator has a resonance Q of only 575 when using the standard technology, whereas a resonance Q of 1100 was obtained for the new device without degradation of the other characteristics. Because of the narrow aperture, the admittance of the standard resonator showed a very strong parasitic above the resonance frequency, whereas this effect is drastically reduced for the new device. These results demonstrate the feasibility of the new approach.

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    • "On the other hand, classical 1D SAW resonators alleviate this problem by using transducers and reflectors of the same topology. As shown earlier by M. Solal [10] this also can be achieved in 2D periodic arrays employing planar technology. Here we further investigate this type of topology in view of both achieving a complete bandgap characteristics as well as design of novel transducer topologies without analog in the 1D design. "
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    ABSTRACT: 2D composite grating building blocks with hexagonal symmetry are proposed and analyzed as efficient reflectors and transducers in the design of low loss surface acoustic wave (SAW) resonators. Eigen-frequency and frequency response finite element analyses (FEA) are used to study the propagation and excitation characteristics of SAWs in the 2D composite structures. The proposed structures have the advantage of being compatible with the planar SAW technology, while exhibiting a complete frequency bandgap. Three distinct types SAW phononic transducers are here invented and their operation confirmed both analytically and experimentally. The proposed research paves the way for subsequent implementation of the phononic bandgap technology in high performance micro-acoustic RF components.
    2014 IEEE International Frequency Control Symposium (FCS); 05/2014
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    ABSTRACT: It is well known than transverse effects like radiation in busbars are an important contribution in the loss of Leaky SAW resonators. Due to the complex nature of the wave and to the presence of several modes, scalar models are not sufficient to predict these effects. It is also known that the electrode gap has a strong impact on these effects. A periodic FEM/BEM model is presented and used to simulate the effect of the gap. Test devices are measured and compared with the simulation with a good agreement. The results show that smaller gaps are favorable.
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 10/2010; 60(11):175-180. DOI:10.1109/ULTSYM.2010.5935439 · 1.51 Impact Factor
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    ABSTRACT: A concept is demonstrated for the development of a phononic surface acoustic wave interdigital transducer (IDT) able to excite acoustic waves in a transverse manner with respect to the applied electric field. The basic principles of the design and fabrication of the transversely coupled phononic transducer are presented. More specifically, the IDT consists of a regular interdigital electrode configuration on which a 2D array of low profile masses is superimposed. The transversely coupled mode of excitation is explained in terms of the specific localization of the elastic energy along with the operation within the complete frequency bandgap of the composite transducer grating. The experimental results provide solid evidence for the suggested mode of operation.
    Applied Physics Letters 03/2014; 104(10) 103503. DOI:10.1063/1.4868409 · 3.30 Impact Factor
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