Tomohisa Komura

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 for US personal communication services with good temperature characteristics

The transmission (Tx) and receiving (Rx) passbands of the Personal Communication Services (PCS) mobile phone system in the US are 1850–1910 MHz and 1930–1990 MHz, respectively. The transition bandwidth between Tx and Rx is very narrow, 20 MHz. A duplexer for the US-PCS employing surface acoustic waves (SAWs) requires a substrate which has good temperature stability, an optimum electromechanical coupling factor, a large reflection coefficient, and a good resonant mechanical Q value. Previously, there did not exist any substrate suitable for the US-PCS SAW duplexer. In this paper, we describe a new substrate that is suitable for the US-PCS SAW duplexer and a US-PCS SAW duplexer constructed with this new substrate.

SAW substrate, with coupling factor and excellent temperature stability suitable for duplexer of PCS in US

The pass-bands of a transmission (Tx) and a receiving (Rx) of the Personal Communication Services (PCS) Handy-phone in US are 1850-1910 MHz and 1930-1990 MHz, respectively. The transition bandwidth between the Tx and the Rx is very narrow as 20 MHz compared with other systems. A duplexer for the PCS using surface acoustic wave (SAW) requires a SAW substrate, which has a the good temperature stability, an optimum electromechanical coupling factor, and a large reflection coefficient. Some Rayleigh waves and leaky SAW (LSAW) on various substrate or structures have a good temperature characteristic, but almost all of them have not an optimum coupling factor and a large reflection coefficient for the US-PCS duplexer. In 2003, the authors reported a US-PCS SAW duplexer having good temperature stability, a steep frequency characteristic in transition band, a low loss, and a large out-of-band suppression. This paper describes the detail of the new substrate having the good temperature stability, the optimum electromechanical coupling factor, and sufficient reflection coefficient.

SAW substrate for Duplexer with Excellent Temperature Characteristics and Large Reflection Coefficient realized by using Flattened SiO2 Film and Thick Heavy Metal Film

Authors previously proposed a SAW PCS-duplexer with an excellent temperature coefficient of frequency (TCF) and a good frequency characteristic composed of a thick-SiO2/thin-Au-electrodes/LiTaO3 structure. However, a sheet resistance of thin Au electrode is large, compared with thick Al-electrode, so thin Au-electrode is not suitable for filters requiring low loss. Authors tried to use thick Cu electrodes with small resistance. By flattening large convex portions on the SiO2 surface, a SAW substrate suitable for US-PCS duplexer with low insertion loss and an excellent TCF was realized

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.