Novel power circulation methods for a surface acoustic wave motor

This paper describes two novel power circulation methods which can increase the efficiency of surface acoustic wave (SAW) motors by 7 times. One method requires two driving interdigital transducers (IDTs) and two unidirectional IDTs to circulate power mechanically in a piezoelectric substrate. Another method requires two unidirectional IDTs and an electrical combiner to circulate power electrically. A traveling wave has been successfully excited at the driving frequency of 14.5 MHz by these two methods. The experimental result shows that the driving performance of the SAW motors with the power circulation methods was equivalent to the conventional non-circulation method. As the input power is one seventh, the efficiency of the SAW motor has been increased by 7 times by using the power circulation methods.