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TWO-PORT IDT EXCITATION TYPE RESONATOR AND RESONANCE FILTER
TWO-PORT IDT EXCITATION TYPE RESONATOR AND RESONANCE FILTER
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机译：两端口IDT激励型谐振器和谐振滤波器
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摘要
PURPOSE:To reduce remarkably the spurious radiation due to the standing wave of the 2nd order mode by making the center of any one of input/output interdigital transducers (IDTs) coincident with nearly the center of the reflector interval. CONSTITUTION:The interval between an input IDT2 provided on a crystal piezoelectric substrate 1 and the reflector adjacent thereto and that of input and output IDT2, IDT3 are selected as 3/8lambda-1lambda the same as a conventional two-port SAW resonator, where is the excited SAW wavelength, and the output IDT3 is arranged while its center line is made nearly coincident with the center of the inner interval (l) of the reflectors 4, 4'. The output IDT3 collects the 1st order mode electric charge from the charge at the hatched parts and outputs it as an electric signal, but as to the 2nd order mode electric charge, it is cancelled because the polarity of the generated charge is inverted in left and right sides and no electric signal output is obtained. That is, no electric signal with respect to the 2nd order mode is outputted, no spurious/response is caused.
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