The third overtone resonator using 36/spl deg/ rotated Y cut LiNbO/sub 3/ crystal

A thickness expansion mode third overtone resonator has been developed using a 36 degree rotated Y cut LiNbO/sub 3/ single crystal. The crystal has a large electromechanical constant and a high velocity factor. This paper describes the design method of a resonator using energy trapping which only occurs with third overtone operation. The optimum dimensions of the resonator element were determined experimentally. The resonator realized single mode response for the third overtone resonance, while suppressing undesirable fundamental resonance. A pilot production program yielded practical devices suitable for clock signal oscillators. The resonator has Q greater than 10000, a capacitance ratio of 100, and -70 ppm/degree C temperature coefficient.