Figure 4.

Illustration showing the volumetric strain profile of the 8th-order width-extensional vibration mode resonator. The distribution of strain polarities corresponds to that of displacement. The number of order is even. Insert provides the polarity and distribution of charge for this mode. Electrodes with the same amount were positioned on the corresponding strain regions. This DIDO configuration required a specific distribution of electrodes. All the electrodes were divided into two groups depending on the strain polarity of the region where they were positioned (i.e., group A and group B). So the polarities of these two groups were opposite. The electrodes on the same strain polarity regions were grouped together and then divided into input electrode and output electrode (e.g., 1A and 2A). Due to the specific distribution of these electrodes, when differential signals were applied to the input side, the proposed resonator operating in the DIDO configuration should output two anti-phase signals.