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Aluminum nitride (AlN) Lamb wave resonators (LWRs) utilizing the lowest symmetric (S0) mode have attracted much interests since they have high frequencies, low motional impedances, and capability of multiple frequencies on a single chip. However, the transverse spurious modes are often strong in AlN LWR, and largely degrade the performance in application, so suppression the transverse mode is highly...
Diamond has the highest sound velocity among all materials and has been applied in high frequency surface acoustic wave (SAW) devices in the gigahertz range. To date, numerous researches have reported that the SAW devices built on a diamond wafer can work in the frequency range from 2 GHz to 10 GHz. S. Fujii et al. reported that the one-port resonator with an interdigital transducer (IDT)/AlN/single...
Amorphous thin films are used as components of acoustic resonators because they could control temperature coefficient of resonator. Because elastic constants of thin films are often different from those of bulk materials, the direct measurement of sound velocity and temperature coefficient of velocity (TCV) for individual thin films becomes important in designing resonators. Because The TCV of amorphous...
The constantly rising demand for higher data rates is addressed by advanced communication standards like carrier aggregation (CA) in combination with LTE. The increased complexity of the RF frontend has put tremendous pressure on improving linear performance of BAW filters over the last years. On top of that a large number of intermodulation (IMD) specification have been added to safeguard all CA...
Partial substitution of Al by Sc in AlN wurtzite films leads to a strong enhancement of the piezoelectric properties as long as the wurtzite phase is maintained. This is very promising for improving piezoelectric MEMS devices and enlarging their application range. Nucleation of (0001)-AlScN works particularly well on Pt (111) thin films. However, in some applications, the growth on insulating substrates...
Coupling between surface acoustic waves (SAW) and arrays of mechanical resonators has appeared early in SAW history as a potential means to slow down wave propagation through mass-loading, in particular by creating corrugations on the substrate surface. This concept has been revisited over the past few years in the context of locally-resonant phononic crystals where pillars deposited on a homogeneous...
Over the course of accelerated failure testing of 2-port SAW delay line resonators on quartz, periodic acoustomigration damage patterns with acoustic apertures of less than 6 wavelengths were observed across the fully metalized region between the transducers, while typical electrode stress damage was observed over the acoustic aperture in the transducer gratings. This suggested the power density had...
Lithium niobate (LN) based thin film piezoelectrics have being extensively explored [1-3] for the making of high coupling and high performance resonators. The most important bottleneck for the use of LN film is related to fabrication process and it is particularly challenging when a bottom electrode is included in the stack to increase the film capacitance per unit area. We have explored Y-cut LN...
Temperature stability is critical for commercial oscillators and many methods have been explored such as: a) constant-resistance-based control methods; b) DTCMs with look-up tables; c) phase-lock-loop based control methods. Whereas exemplary results have been attained with these techniques, to be effective they require: a) accurate knowledge of the source of temperature fluctuations; (b) the use of...
RF filtering technologies based on piezoelectric MEMS resonators have been successfully developed and commercialized in the past decade thanks to their size and outstanding performance. The challenge to enhance filter's performance in terms of lower insertion losses and wider bandwidth still makes for an active research topic, especially spurring the interest for new classes of materials such as doped-AlN...
I.H.P. SAW (Incredible High-Performance SAW) has a novel multi-layered structure to confine SAW energy in substrate surface area, and it shows extremely high quality (Q) factor, low temperature coefficient of frequency (TCF) and improved electromechanical coupling coefficient (K2). This paper introduces its mechanism of the high acoustic Q factor, both theoretically and experimentally, and its applications...
Transmit filters comprising piezoelectric resonators are fabricated in a Thin Film Bulk Acoustic Resonator (FBAR) technology. A filter's 2nd harmonic emissions (H2), generated by the resonators in the filter's output stage must be sufficiently small to prevent the filter from desensitizing a nearby receiver. Anti-parallel and anti-series connected resonator configurations, in which the H2 emissions...
Analog signal processing techniques based on surface acoustic wave (SAW) devices have been commercialized in the past 50 years. Delay lines [1] and resonators [2] have been implemented for a wide range of applications [3]. The use of small scale resonators has boomed because of the continuous growth of the cell phone business, whereas components such as delay lines have been relegated to smaller markets...
Spurious modes (SMs) result in in-band ripples and degrade the out-of-band rejection of filters, thus impeding the synthesis of high performance filters with MEMS resonators. Therefore, the ability to predict the presence of SMs in specific resonator geometries is highly desired and different techniques have been explored such as: 1-D/2-D analytic models, and 2-D/3-D finite element methods (FEM)....
In order to achieve better performance of bulk and surface acoustic wave resonators operating at several GHz, it is crucial to dispose of advanced techniques and methods to provide information about the elastic constants of the constituent layered materials and to image the spatial profile of the acoustic field, both inside and outside the resonator.
The SAW on rotated “leaky” Y-cuts LiTaO3 and LiNbO3 is a dominantly localized near surface slow shear-horizontal wave, which is weakly coupled to the fast shear bulk wave. Any surface perturbation can lead to radiation of bulk-acoustic waves from the device, increasing losses. To minimize this radiation, LSAW resonators are typically synchronous, with all electrodes in the IDT and in the reflectors...
Mobile filters are required to process increasing RF power levels, driven by the need for higher data-rates and improved cell-edge coverage. This results in more demanding filter specifications for loss, rejection, isolation, linearity and reliability, while, at the same time, handset OEMs require smaller filter footprints.
Filters operated at high power levels and comprising BAW resonators produce 2nd harmonic emissions. To model the emissions of a BAW resonator, Feld and Shim constructed a nonlinear Mason model, which implements an “extended” pair of piezoelectric constitutive equations containing arbitrary 2nd order terms: T = cES − eE + [1/2δ3cES2 − δ1eSE + 1/2δ2εSE2] D = eS + εSE + [1/2δ1eS2 − δ2εSSE +1/2δ4εSeE2...
Factors limiting the isolation of conventional miniaturized filters and duplexers have been considered in the literature. They can be classified into two types of signal leakage: one occurs via the main signal path due to the finite impedance of the RX filter in the TX band in a duplexer; the second one is due to electromagnetic feedthrough (EMF), electromagnetic couplings or imperfect grounding....
Topological Insulators (TI) have been the subject of intense research by condensed matter physicists over the last decade for many reasons. One of which is the existence of helical edge modes, which can occur even when wave propagation through the bulk of the material is impossible. Eager to engineer devices that support these helical modes, researchers have invented classical systems analogous to...
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