Yoshiro Fujiwara

Development of 800 MHz band SAW filters using weighting for the number of finger pairs

A surface acoustic wave (SAW) bandpass filter has been developed for pocket and mobile telephones for 800-MHz-band cellular radio systems. In developing this filter, it was found that the number of finger pairs suppressed the sidelobe. The number of finger pairs was varied for each input and output transducer which composed an interdigitated interdigital transducer (IIDT) structure. The proportion of weighting for the number of finger pairs was optimized using computer simulation. A transmitting filter for AMPS was constructed using this method. Sidelobe suppression improved to above 8 dB compared to no weighting. Absolute suppression was less than -24 dB. This filter has properties suitable for practical use in a temperature range from -30 to +70 degrees C.<<ETX>>

Wide frequency deviation and temperature stable VCO using SiO/sub 2//36 degrees Y-X LiTaO/sub 3/ resonator

An SiO/sub 2//36 degrees Y-X LiTaO/sub 3/ substrate which has an excellent temperature characteristic and a high electromechanical coupling coefficient has been prepared. The temperature coefficient of frequency (TCF) is zero, and the electromechanical coupling coefficient is 5.2% when the thickness of SiO/sub 2/(H/ lambda ) is 21%. An energy-trapped structure which is a one-port-type resonator connects a loading capacitance in series to a transducer. Using this resonator, a voltage-controlled oscillator (VCO) with an excellent temperature characteristic and a wide frequency deviation larger than 800 ppm/V is obtained.<<ETX>>