Yasuharu Nakai

Smaller surface acoustic wave duplexer for US personal communication service having good temperature characteristics

Using a flattened SiO2/Cu electrode/36–48° LiTaO3 structure, a small (5×5 mm2) surface acoustic wave (SAW) duplexer with a good temperature coefficient of frequency (TCF) for US personal communication services (PCS) was realized by the authors. However, a smaller duplexer is strongly required. Using the flip-chip bonding process of SAW chips and a Rayleigh SAW propagating on a flattened SiO2/Cu electrode/126–128° YX-LiNbO3 structure, which has a larger coupling factor than the above-mentioned substrate, a smaller (3×2.5 mm2) SAW duplexer with a good TCF was realized.

Surface Acoustic Wave Duplexer Composed of SiO2/Cu Electrode/LiNbO3 Structure Having Convex and Concave Portions

The transition bandwidth of 20 MHz between the transmission (Tx: 1850–1910 MHz) and the receiving (Rx: 1930–1990 MHz) bands of personal communication service (PCS) handy phones in the United States (US) is very narrow compared with those of other systems. We have already realized surface acoustic wave (SAW) duplexers with sizes of 5.0×5.0×1.7 and 3.0×2.5×1.2 mm3 for PCS handy phones in the US with an excellent temperature coefficient of frequency (TCF) by using a shear horizontal (SH) wave on a flattened SiO2/Cu electrode/36–48° YX-LiTaO3 structure and a Rayleigh wave on a SiO2/Cu electrode/120–128° YX-LiNbO3 structure. Although the surface of the above-mentioned structures is flattened SiO2, we have also studied the shape of the SiO2 surface. As a result, in addition to increasing the stop-band width, which corresponds to the reflection coefficient, the TCF and power durability have been improved by forming convex portions on the surface of the SiO2 over the interdigital transducer (IDT) gaps.

Surface acoustic wave duplexer composed of SiO 2 film with convex and concave on Cu-electrodes/LiNbO 3 structure

Authors have already realized 3.0times2.5times1.2 or 2.5times2.0times0.48 mm3 size SAW duplexers for personal communication services in US with an excellent temperature coefficient of frequency (TCF) by using the Rayleigh wave on the SiO2/Cu-electrode/ 120deg-128degYX-LiNbO3 and 36deg-48degYX-LiTaO3 structures. This time, authors intentionally attempted to make the convex portions on the SiO2 film over the gap of interdigital transducers (IDTs). As the results, the calculated and measured results showed the increase of the reflection coefficient and the improvement of the TCF. In addition to them, the measured results showed that a power durability have been drastically improved without any deterioration in the frequency characteristics by making the convex portions on the SiO2 film over the gap of the IDTs.

Miniature surface acoustic wave devices with excellent temperature stability using high density metal electrodes and SiO 2 film

Currently, miniature surface acoustic wave (SAW) devices (filters and duplexers) with a good temperature stability are strongly required. In order to realize its requirement, various SAW substrates combining a high density metal electrode, a SiO 2 film, and LiTaO 3 or LiNbO 3 substrate were researched. Their combinations offer excellent properties such as large electrode reflection coefficient, large mechanical coupling factor, low velocity, and good temperature stability. This paper reviews realization of miniature SAW devices with low insertion loss and good temperature stability, such as SAW duplexers for personal communication service system in the United States (US-PCS) and wide band code division multiple access system (W-CDMA) using thier combinatios.

P2H-5 Small 3x2.5mm² Sized Surface Acoustic Wave Duplexer for US-PCS with Excellent Temperature and Frequency Characteristics

Using flattened-SiO₂/Cu-electrode/36~48deg LiTaO₃ structure, small size (5 x5mm²) surface acoustic wave (SAW) duplexer with a good temperature coefficient of frequency (TCF) for US-PCS was realized by authors. However, a smaller duplexer has been strongly required. Using flip-chip bonding process of SAW chips and Rayleigh SAW propagating on the flattened-SiO₂/Cu- electrode/126~128degYX-LiNbO₃, which has larger cou pling factor than above-mentioned substrate, a smaller sized (3x2.5mm²) SAW duplexer with a good TCF has been realized.