Comparison between ST-cut quartz 25 degree and -60 degree NSPUDT propagation directions

This paper discusses directivity and other propagation properties of natural single phase unidirectional transducer (NSPUDT) propagation directions on ST-cut quartz. The work focuses on the comparison of surface acoustic wave (SAW) directivity and propagation properties between the ST-cut quartz -60...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2002-06, Vol.49 (6), p.820-826
Main Authors: Da Cunha, Mauricio Pereira, Nakano, Alberto Yoshihiro
Format: Article
Language:English
Subjects:
Directivity
Euler angles
Noise levels
Quartz
Reflection coefficient
Surface acoustic waves
Transducers
Wave propagation
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Summary:This paper discusses directivity and other propagation properties of natural single phase unidirectional transducer (NSPUDT) propagation directions on ST-cut quartz. The work focuses on the comparison of surface acoustic wave (SAW) directivity and propagation properties between the ST-cut quartz -60 degree , Euler angles: (0 degree , 132.75 degree , -60 degree ), and the ST-cut quartz 25 degree , Euler angles: (0 degree 132.75 degree , 25 degree ), NSPUDT propagation directions, including predicted and measured directivity responses for both propagation directions. The well-known SAW 25 degree propagation direction is used for low loss, high performance SAW filter designs for consumer products and communications Applications. The ST-cut quartz -60 degree propagation direction has been predicted to have a reflection coefficient 2.5 times larger than ST-cut quartz 25 degree . In addition the ST-cut quartz -60 degree satisfied the NSPUDT 90 degree reflection coefficient phase condition much more closely, resulting in an improved directivity response. For the delay line structures used in the experiments, the measured directivity is 10.1 dB for the -60 degree propagation direction. For the same structures, the measured directivity along the 25 degree propagation direction is about 5.0 dB. The experimental results given in this paper verify that indeed ST-cut quartz -60 degree has a higher directivity than ST-cut quartz 25 degree , confirming the theoretical predictions. In addition, this work compares other propagation properties for both directions, namely, phase velocities, electromechanical couplings, temperature coefficients of delay, power flow angles, and metallic strip reflection coefficient amplitudes and phases.
ISSN:0885-3010
DOI:10.1109/TUFFC.2002.1009342