エネルギーとじこめ形圧電セラミック共振子の一構成法
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概要
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In this paper, it is investigated for a trapped-energy ceramic resonator that the value of the elastic stiffness constant c^<D'>_<44> in the plated region is lower than that of c^D_<44> in the unplated region of a piezoelectric ceramic plate in the thickness-shear mode, for the purpose of reducing unwanted responses (Fig. 1). In the construction, the elastic effect R_c similar to high plate-back ratio is expected to be obtained easily (Fig. 2). The desirable values of c^D_<44> and c^<D'>_<44> are expected to be obtained from the difference between the thoroughness of poling in the plated and unplated regions. For the proof of the expectation, it is investigated that the direction of poling in the plated region differs from that in the unplated region parallel to major surfaces of a piezoelectric ceramic plate (Fig. 3). The electromechanical coupling factor k'_<15> in the plated region decreases monotonously with increasing the angle θ (Fig. 4). The constant c^<D'>_44 decreases monotonously with decreasing k'_<15> (Fig. 5). The frequency lowering Δ of the normalized cut-off frequency Ω_e in the plated region from Ω_s in the unplated region is calculated as a function of k'_<15> for the piezoelectric ceramic resonator shown in Fig. 3 (Fig. 6). The Δ remains fairly constant for 0≦k'_<15>≦k_15. On the other hand, the proportion of elastic effect R_c to Δ can be controlled widely and high R_c may be obtained easily. The frequency spectrum of trapped-energy modes is calculated (Fig. 7). The antiresonance frequency f_a keeps away from the cut-off frequency f_s in the unplated region with increasingc^D_<44>/ c^<D'>_<44>. The design of the difference between f_a and f_s is also investigated for the piezoelectric ceramic resonator shown in Fig. 3 (Fig. 8). In the experiment, the thoroughness of poling was controlled by applying DC electric field between the top and bottom electrodes in the piezoelectric resonator polarized uniformly in the direction parallel to the electrodes. The constant c^<D'>_<44> in this process was measured at several different levels of k'_<15>, in comparison with the calculated values obtained from Eq. 16 (Fig. 9). Response of trapped-energy resonators shown in Fig. 10 was measured at several different levels of k'_<15> (Fig. 11). the antiresonance frequency keeps away from unwanted response with decreasing k'_<15>. Furthermore, response of monolithic filter shown in Fig. 12 was measured at the level of k'_<15><k_<15>, in comparison with that in case of k'_<15>=k_<15> (Fig. 13). The attenuation level is improved in the higher stop band of the filter with decreasing k'_<15>.
- 社団法人日本音響学会の論文
- 1977-07-01
著者
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