| 摘要 |
PROBLEM TO BE SOLVED: To excite only the desired higher harmonic with high efficiency by dividing each electrode finger into 3 steps, regardless of the order number of the desired higher harmonic to be excited. SOLUTION: Each electrode finger 4 of a sending surface acoustic wave converter 2 is divided into 3 steps 1, 2 and 3. The shift value is defined D1 =2λ0 in the propagation direction of an SAW of step 2 against step 1, and the shift value is defined as D2 =4λ0 /5 in step 3 against step 1. The electrode finger lengths of steps 1, 2 and 3 are referred to as W1 , W2 and W3 , respectively. If the center of step 1 is decided as a reference point, the signals of 5th-order higher harmonics excited in each step are added together in the same phase at the reference point to strengthen with each other. In regard to a basic wave, the amplitudes of SAWs excited in steps 1 to 3 are proportional to the lengths W1 to W3 , respectively. Therefore, the length W1 to W3 can be decided so as to set the sum of signals at zero for the basic wave.
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