Shunichi Seki

A novel temperature compensation method for SAW devices using direct bonding techniques

We have developed a novel temperature compensation method for SAW devices using a direct bonding technique. The SAW device applied this method was composed of a conventional piezoelectric substrate such as LiTaO/sub 3/ and LiNbO/sub 3/, directly bonded without any bonding agents to a glass substrate having a relatively low thermal expansion coefficient (TEC). The piezoelectric substrate and the glass substrate were bonded in an atomic scale and the interface was very uniform. Therefore, the thermal strain at the surface of the bonded substrate caused by the difference between the TECs of the substrates was quite uniform and stable. With this structure, the thermal expansion of the piezoelectric substrate was restrained and the elastic constant of the piezoelectric substrate was changed by the thermal strain. Using this technique, we have succeeded to improve the temperature coefficient of frequency (TCF) of the SAW devices without causing any deterioration in the frequency response. This novel temperature compensation method is very promising for RF-SAW device applications.

A new balanced-unbalanced type RF-band SAW filter

A new balanced-unbalanced type RF-band (950 MHz) surface acoustic wave (SAW) filter for use in portable telephones is presented. This SAW filter has unbalanced input and balanced output terminals. Balanced-unbalanced type SAW filters having a pass-band at 950 MHz were fabricated. The obtained results showed excellent characteristics such as low insertion loss, wide bandwidth, and small VSWR. Using the SAW filter, one can realize balanced-type RF circuits in portable telephones.

A new balanced-type RF-band SAW filter using SAW resonators

A new balanced-type RF-band (950 MHz) surface acoustic wave (SAW) filter using SAW resonators for use in portable telephones is presented. This SAW filter has balanced input and output terminals. Based on the computer simulation, balanced-type SAW filters having a pass-band at 950 MHz were fabricated. The obtained characteristics showed excellent characteristics such as low insertion loss, wide bandwidth, high attenuation at stopbands, and small VSWR. Using the SAW filter, one can realize balanced-type RF circuits in portable telephones.<<ETX>>