A new triply rotated quartz cut for the fabrication of low loss SAW filters

The dramatic expansion of the cellular phone market has led to a very stron g interest in the development of SAW devices devoted to frequency filtering . For intermediate frequency applications (50-500 MHz) and narrow frequency bandwidth (less than 2% of the filter central frequency f(0)), the (ST,X) cut of quartz has been the industrial standard for the design of SAW filter s for a long time Nevertheless, a deeper analysis of the quartz properties shows the existence of unexplored angular domains for which Rayleigh waves can be efficiently excited, exhibiting physical characteristics better than the ones of the (ST,X) cut. This paper presents a family of quartz allowin g significant improvements of SAW devices on quartz, A larger number of exp eriments have been performed confirming the above mentioned theoretical pre dictions. A filter bunt on this cut is presented showing the interest of th e proposed crystal orientations.