Yosuke Hamaoka

Miniature Surface Acoustic Wave Duplexer with Wide Duplex Gap on SiO2/Al/LiNbO3 Structure

In this paper, we describe the development of a miniature surface acoustic wave (SAW) duplexer for a Band IV system in the universal mobile telecommunication system (UMTS). We employed the SiO2/Al electrode/5° YX-LiNbO3 structure, which has a high electromechanical coupling coefficient (K2) and a small temperature coefficient of frequency (TCF). It is necessary to suppress the Rayleigh mode spurious response to apply this structure to the duplexer. We clarified experimentally the relationship between the SiO2 shape and the thickness of the Al electrode in the SiO2/Al/LiNbO3 structure to suppress the spurious response. Furthermore, we determined the condition to reduce the bulk radiation for the transmitting band of the Band IV duplexer. The developed SAW duplexer has the optimum structure for the Band IV system. The SAW duplexer exhibits excellent performance for practical use. In addition, the TCF is about -30 ppm/°C. The SAW duplexer is 2.5×2.0×0.5 mm3. Additionally, the SAW duplexer has sufficient power durability owing to the use of multilayer electrodes of AlMgCu/Ti.

Zero Temperature Coefficient of Frequency Surface Acoustic Wave Resonator for Narrow-Duplex-Gap Application on SiO2/Al/LiNbO3 Structure

In this paper, we describe a zero temperature coefficient of frequency (TCF) surface acoustic wave (SAW) resonator on a SiO2/Al/LiNbO3 structure. We studied the dependence of TCF and electromechanical coupling factor (K2) of shear-horizontal (SH) SAW on SiO2 thickness, where the SiO2 shape control technique is applied to suppress spurious responses caused by the Rayleigh mode. As a result, we could realize a high performance SAW resonator having moderate K2 (8%) and zero TCF with complete suppression of the Rayleigh-mode spurious response. We demonstrated that the SiO2 shape control technique is effective for suppression of the Rayleigh-mode spurious response in the SAW resonator using the SiO2/Al/LiNbO3 structure for a wide range of SiO2 thicknesses. We also revealed the applicability of the SiO2/Al/LiNbO3 structure to SAW duplexers with a narrow duplex gap.

Transverse-Mode Spurious Suppression Technique for Surface Acoustic Wave Resonator with Zero Temperature Coefficient of Frequency on a SiO2/Al/LiNbO3 Structure

In this paper, we describe a suppression technique of transverse-mode spurious responses for a surface acoustic wave (SAW) resonator with a near zero temperature coefficient of frequency (TCF) on a SiO2/Al/LiNbO3 structure. We investigated the thinning of SiO2 on the dummy electrode region and studied how the transverse-mode responses change with remaining SiO2 thickness h on the dummy electrode region. As the results, we clarified that the remaining SiO2 thickness h on the dummy electrode region has an optimum value and could suppress the transverse-mode spurious responses completely when H and h are set at 0.35 λ and 0.20 λ, respectively. It was demonstrated that the selective SiO2 removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO2/Al/LiNbO3 structure for a wide range of SiO2 thicknesses, provided that the SiO2 thickness at the dummy electrode region is adjusted properly.

Good temperature coefficient of frequency SAW resonator on a SiO 2 /Al/LiNbO 3 structure

This paper describes a good temperature coefficient of frequency (TCF) surface acoustic wave (SAW) resonator on a SiO<inf>2</inf>/Al/LiNbO<inf>3</inf> structure. We studied the dependence of TCF and electromechanical coupling factor (K²) of shear-horizontal (SH) SAW on the SiO<inf>2</inf> thickness, where the SiO<inf>2</inf> shape control technique is applied to suppress spurious responses caused by Rayleigh-mode. As the results, we could realize high performance SAW resonator having moderate K² (8%) and zero TCF with complete suppression of the Rayleigh-mode spurious response. It was demonstrated that the SiO<inf>2</inf> shape control technique is effective for suppression of the Rayleigh-mode spurious response in the SAW resonator using the SiO<inf>2</inf>/Al/LiNbO<inf>3</inf> structure with wide range of SiO<inf>2</inf> thicknesses. We also revealed applicability of the SiO<inf>2</inf>/Al/LiNbO<inf>3</inf> structure to SAW duplexers with narrow duplex gap.

Small-sized SAW duplexers with wide duplex gap on a SiO 2 /Al/LiNbO 3 structure by using novel Rayleigh-mode spurious suppression technique

This paper describes the novel Rayleigh-mode spurious suppression technique for SAW duplexers with wide duplex gap on a SiO2/Al/LiNbO3 structure. We have cleared the optimum shape of SiO2 with taking account of the difference of the electrode thickness. The shape of SiO2 which can suppress the spurious depended on the thickness of Al electrode. By controlling the shape of SiO2, the Rayleigh-mode spurious of both Band I and Band IV duplexers can be suppressed. The small-sized SAW duplexers for Band I and Band IV systems were realized by employing this technology and optimizing the thickness of Al electrode. Our duplexers show the excellent performances for actually use. Insertion loss of transmitting band for Band I and for Band IV are 1.2 dB and 1.3 dB. And, the TCF is about -30 ppm/degC. The size of these duplexers is 2.5 mm times 2.0 mm. Additionally, the duplexers have sufficient power durability by using the multi-layer electrodes of AlMgCu/Ti.

Suppression of transverse-mode spurious responses for zero temperature coefficient of frequency SAW resonator on a SiO 2 /Al/LiNbO 3 structure

This paper describes a suppression of transverse-mode spurious responses for zero temperature coefficient of frequency (TCF) surface acoustic wave (SAW) resonator on a SiO₂/Al/LiNbO₃ structure. We investigated to use thinning of SiO₂ on the dummy electrodes and studied how the transverse-mode responses change with remaining SiO₂ thickness h on the dummy electrode region. As the results, we could realize high performance SAW resonator with complete suppression of the transverse-mode spurious responses when h is set at 0.20λ. It was demonstrated that the selective SiO₂ removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO₂/Al/LiNbO₃ structure for wide range of SiO₂ thicknesses, provided that the SiO₂ thickness at the dummy electrode region is adjusted properly.

Small-sized SAW duplexer on non-flat SiO 2 /Al/LiNbO 3 structure for UMTS Band I system

This paper describes the SiO2/Al/LiNbO3 structure for the SAW duplexer. Although this structure has large electromechanical coupling coefficient, it also supports unwanted spurious responses. They are categorized into two types of the Rayleigh-mode and transverse-mode. We have developed the novel spurious suppression techniques for these spurious; the SiO2 shape control technique for Rayleigh-mode and the scattered dummy electrode weighting for transverse-mode. We applied the proposed techniques to the balanced-type SAW duplexer for UMTS Band I system. The developed SAW duplexer was installed into a 2.5×2.0×0.5 mm3 package, and exhibited low insertion loss and high out-of-band rejection. The insertion losses in the Tx and Rx bands are 1.3dB and 2.0dB, respectively. The rejections in the Tx and Rx bands are 54 dB and 48 dB, respectively.

Study of Spurious Response near the Fast Shear Wave in SiO2/Al/LiNbO3 Structure

The shear horizontal (SH) mode on the SiO2/Al/LiNbO3 structure is studied because of its sufficient electromechanical coupling factor (K2) and good temperature coefficient of frequency (TCF). The authors proposed a method of suppressing the spurious response of the Rayleigh mode and the transverse mode for narrow duplex gap applications. For the narrow duplex gap application, the SiO2 thickness must be increased to achieve good TCF characteristics. However, another spurious response appears near the fast shear wave with increasing SiO2 thickness. In this paper, we discuss the suppression mechanism of the spurious response near the fast shear wave.

Suppression Technique of fast-shear-wave spurious responses in SAW resonators on SiO 2 /Al/LiNbO 3 structure

SH mode on SiO2/Al/LiNbO3 structure is studied because of their sufficient electromechanical coupling factor (K2) and good temperature coefficient of frequency (TCF). Authors proposed the suppression method of the spurious response of the Rayleigh mode and the transverse mode for the narrow duplex gap application. For the narrow duplex gap application, SiO2 thickness must be increased to achieve the good TCF characteristics. However, another spurious response is appeared near the fast-shear-wave as increasing the SiO2 thickness. This paper discusses the suppression mechanism of the spurious response near the fast-shear-wave.