A novel weighted method for layered SAW filters using slanted finger interdigital transducers

Abstract

In this paper, we propose a novel weighted method to improve the inclined pass-band problem that is intrinsic to surface acoustic wave (SAW) filters with slanted finger interdigital transducers (SFITs). By the dispersive characteristics of SAW in layered piezoelectric substrates, the present method could make the inclined pass-band flatter or the bandwidth wider. We derived a coupling-of-modes model for the calculation of the frequency responses of layered SAW devices with SFITs and calculated the dispersive characteristics of an AlN/silicon layered piezoelectric substrate, such as the phase velocity and the electromechanical coupling coefficient. Then we utilized the dispersive electromechanical coupling coefficient to flatten the inclined pass-band and the dispersive phase velocity to widen the bandwidth. Two designed examples of wide-band layered SAW filters using SFITs on AlN/silicon substrates are presented to prove the validity of the proposed method: one is designed to flatten the inclination of the pass-band; the other, to widen the bandwidth. Results show that the dispersions of layered piezoelectric media are favourable for improving the performance of SFIT-based SAW filters.

Surface acoustic wave devices on AlN/3C–SiC/Si multilayer structures

“…SAW propagation properties in various multilayer substrates including an AlN thin film have been well investigated and employed in various designs of layered SAW filters [30][31][32]. In this work, for the first time, the comprehensive theoretical analysis of SAW propagation characteristics in an AlN (0 0 0 2)/3C-SiC (1 0 0)/Si (1 0 0) multilayer structure is investigated.…”

“…While the thickness of the piezoelectric thin film is comparable to the wavelength, the acoustic wave propagation properties are dispersive with respect to the thickness of the piezoelectric layer in the multilayer structure. In general, the dispersion behavior is often observed in layered SAW devices [30][31][32] and Lamb wave devices [35][36][37]. As a result, in the AlN/3C-SiC/Si multilayer structure, SAW propagation properties would be dispersive with respect to the AlN film thickness normalized to wavelength (h AlN /λ) and the 3C-SiC layer thickness normalized to wavelength (h 3C-SiC /λ).…”

AlN/3C–SiC Composite Plate Enabling High‐Frequency and High‐Q Micromechanical Resonators

“…Piezoelectric thin films, such as aluminum nitride (AlN) and zinc oxide (ZnO), have been utilized in the various designs of nano/micro electroacoustic resonators because of the efficient electromechanical transduction 25–29. The properties of acoustic waves propagating in various piezoelectric media have been well studied and employed in many electroacoustic resonator designs, including surface acoustic waves (SAW),25–27 bulk acoustic waves (BAW),28 and plate acoustic waves (Lamb waves) 29. Recently, Lamb waves propagating in piezoelectric thin plates have attracted great attention for the designs of electroacoustic resonators since it combines the advantages of BAW and SAW: ultra‐high phase velocities ( V p ) and multiple frequencies excitation by interdigital transducers (IDT).…”

Dispersion characteristics of high-order lamb wave modes in an AlN/3C-SiC layered plate

“…iezoelectric thin films, such as aluminum nitride (AlN) and zinc oxide (ZnO), have been utilized in the various designs for electroacoustic resonators because they have the efficient electromechanical transduction and complementary metaloxide semiconductor (CMOS) compatibility [1][2][3][4][5]. The properties of acoustic waves propagating in various piezoelectric media have been well studied and employed in many electroacoustic resonators, including surface acoustic wave (SAW) devices [1,2], film bulk acoustic wave resonators (FBAR) [3], and plate acoustic wave (Lamb wave) resonators [4,5].…”

“…The properties of acoustic waves propagating in various piezoelectric media have been well studied and employed in many electroacoustic resonators, including surface acoustic wave (SAW) devices [1,2], film bulk acoustic wave resonators (FBAR) [3], and plate acoustic wave (Lamb wave) resonators [4,5].…”