High-Performance SAW Resonator on New Multilayered Substrate Using LiTaO₃Crystal

Abstract

To develop the high-performance filters and duplexers required for recent long-term evolution frequency bands in mobile handsets, a surface acoustic wave (SAW) resonator is needed that has a higher quality (Q) and a lower temperature coefficient of frequency (TCF). To achieve this, the authors focused on acoustic energy confinement in the depth direction for a rotated Y-X LiTaO (LT) substrate. Characteristics of multilayered substrates with low-impedance and high-impedance layers under LT layer were studied numerically in terms of acoustic energy distribution, phase velocity, coupling coefficient, and temperature characteristics employing a finite-element method simulation. After several calculations, a novel multilayered structure was developed that uses SiO for a low-impedance layer and AlN for a high-impedance layer under the thin LT layer. A one-port resonator using the new substrate was fabricated, and its experimental results showed that the developed resonator had a Bode-Q over 4000 and TCF of -8 ppm/°C, which are four times higher than and one-fifth as small as those of a conventional 4° YX-LT SAW resonator, respectively. By applying this technology, a band 25 duplexer with very narrow duplex gap was successfully developed, which shows extremely low insertion loss, steep cutoff characteristics, and stable temperature characteristics.

Surface Acoustic Wave Devices Using Lithium Niobate on Silicon Carbide

“…A comparison between the above resonator and other mounted acoustic resonators [3], [4], [49], [50] is shown in Table IV. Although more optimizations are still required for transverse mode suppression and electrical loss, the device in this work has already demonstrated a quite high k 2 and Bode-Q.…”

“…One of the most exciting advances in recent years is the acoustic devices based on transferred lithium niobate thin films, which were first enabled by the ion slicing technique developed for integrated photonics in the 90s [1]. These LiNbO 3 thin-film devices so far have taken various forms (suspended [2] or solidly mounted [3]) and employed a diversity of modes (SAW [4], shear horizontal (SH0) [5], [6], S0 [7], [8], and A1 [9], [10]) over a wide range of frequencies from kHz to 30 GHz. They all have their unique merits and can be compared and rationalized based on how one categorizes them.…”

“…However, the latter is still debatable as Q depends on the design as well as fabrication in an interleaved and complex fashion. On the other hand, solidly mounted or unreleased LiNbO 3 devices [3], [11], [12] can feature a more straightforward process, lower cost, larger power handling, and better linearity. In terms of the material stacks for both types of devices, they typically use a transferred LiNbO 3 thin film on either a LiNbO 3 or Si substrate, occasionally with an intermediate layer of SiO 2 for film transfer, device release, or temperature compensation purpose.…”

Low-Loss and Wideband Acoustic Delay Lines

“…With properly designed electrode pitch, polarity, and electrode sections in the ADL, the frequencies, phases, and relative amplitudes of the terms in the Fourier series can be varied to obtain a quasi-arbitrarily configurable filter response. Because of such addressability in their response, transversal filters understandably have been favored over filters based on coupled resonators, such as those based on surface acoustic waves (SAW) [14], lamb waves [15], or thickness modes [16], for certain applications.…”

A Low Temperature Drifting Acoustic Wave Pressure Sensor with an Integrated Vacuum Cavity for Absolute Pressure Sensing

“…Experimental results show the sensor can measure the absolute pressure in the range of 0 to 0.4 MPa, while the temperature range is from 20 • C to 220 • C with a TCF of −14.4 ppm/ • C. Such a TCF is only about half of that of previously reported works.acoustic waves (SAWs) and Lamb waves. Acoustic wave devices have gained much more attention in the last few decades because of their low cost, small size, low power consumption and wireless operation [15][16][17][18][19][20]. However acoustic wave pressure sensors still suffer an unavoidable frequency shift vs. temperature, and this will result in inaccurate pressure readouts.…”