Experimental comparison between ST-quartz 25/spl deg/ and 300/spl deg/ NSPUDT orientations

The work described reports on experimental directivity comparison between the ST-quartz 300° natural single phase unidirectional transducer (NSPUDT) orientation [Euler angles: 0° 132.75° 300°] and the ST-quartz 25° NSPUDT orientation [Euler angles: 0° 132.75° 25°]. The 25° NSPUDT orientation is a well-known quartz surface acoustic wave orientation, used for low loss, high performance SAW filter designs for consumer products and communications application. Using a search method for finding NSPUDT orientations, devised by one of the authors (MPdC) in a previous publication, ST-quartz 300° was predicted to have a reflection coefficient 2.5 times larger than the ST 25° orientation. In addition the 300 degree orientation satisfied the NSPUDT reflection coefficient 90° phase condition much more closely, resulting in an improved directivity response, and better NSPUDT performance. For the delay line structures used in the experiments, the measured directivity is 10.1 dB for the 300° orientation. For the same structures, the measured directivity along the 25° orientation is around 5.0 dB. The experimental results given in this paper verify that indeed ST-quartz 300° has a higher directivity than the 25° orientation, confirming the theoretical directivity predictions.