In the fabrication of a coupled-dual resonator crystal, the fine-tuning operation is used to adjust the crystal's two resonator frequencies and synchronous peak separation frequency (SPSF) to their final values. A process for precisely adjusting these frequencies to their final values is presented. The process uses a masking and shutter arrangement, called a binary shutter system, which allows the two resonator frequencies to be lowered during the resonator adjustment by selective deposition onto the resonator electrodes and which also allows the SPSF to be increased by deposition on the ground side of the crystal in the area between resonators. The process is controlled in such a way that both the resonator frequencies and SPSF can be adjusted very precisely.
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