An H-type resonator vibrating transversely can be used as a low frequency resonator similarly to a tuning-fork or a uniform bar which has been used for electro-acoustical devices. Because, the H-type resonator has following merits. (1) In a limited mode, the resonant frequency can be lowered as compared with that of the tuning-fork or uniform bar, (2) the resonant frequency is decided by adjusting not only dimensions of arm but also those of connecting coupler. And, it is possible to obtain lower frequency by forming stepped-arm (or adding concentrated mass to the tip of the arm). Such resonator is called the stepped H-type resonator (Fig. 1). In this paper, analyses of the resonant frequency (Chapter 3), vibration mode (Chapter 4) and equivalent circuit constants (Chapter 5) of the stepped H-type resonator are carried out by using an equivalent mechanical network (Fig. 3) corresponding to a quarter part of the resonator (Fig. 2) and taking symmetry of the vibration mode in consideration. The connecting coupler is assumed as pure bending stiffness, because it is a slender bar as compared with the arm of the resonator. First, relation between the resonant frequency and dimensions of the stepped H-type resonator is discussed (Fig. 4, 5, 6), and a convenient chart for design is presented (Fig. 6). And, theoretical values of the resonant frequency are compared with experimental values (Fig. 4, 6). Secondly, the vibration mode of the arm is calculated for some values of stiffness determined by the dimensions of coupler (Fig. 8). Furthermore, the equivalent circuit constants of the resonator, i. e. equivalent inductance, capacitance and capacitance ratio, are calculated by taking impedance of bonded piezoelectric ceramics in consideration (Fig. 9), on the basis of the vibration mode. As the results, it is found that the theoretical values are in approximate agreement with experimental values (Fig. 10, 11). Finally, the optimum dimensions of piezoelectric ceramics giving the minimum value of the capacitance ratio are shown (Fig. 12, 13).
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