Bulk acoustic wave (BAW) resonators with 5-wt%-La2O3-doped PbTiO3 (PT)
piezoelectric films were fabricated. The La-doped PT films had a dense,
homogeneous morphology, as well as high crystallinity caused by the use of bottom
electrodes with pure Pt-like surface layers. These PT films had remanent polarization
of 110 mC/m2 at 200°C. Resonant frequencies of the fabricated devices were 1.4 GHz and 2.0 GHz. The electromechanical coupling coefficient (k
t
2) was estimated to
be 11% at 1.4 GHz and 9.4% at 2.0 GHz, respectively. The PT films had superior k
t
2 in
the GHz band. The capability of the RF devices with broad bandwidth was
investigated.
Acoustic field analysis results of surface acoustic wave dispersive delay lines using inclined chirp IDTs on a Y-Z LiNbO 3 substrate are described. The calculated results are compared with optical measurements. The angular spectrum of the plane wave method is applied to calculation of the acoustic fields considering the anisotropy of the SAW velocity by using the polynomial approximation. Acoustic field propagating along the Z-axis of the substrate, which is the main beam excited by the inclined chirp IDT, shows asymmetric distribution between the +Z and −Z directions. Furthermore the SAW beam propagating in a slanted direction with an angle of +18 • from the Z axis to the X-axis is observed. It is described that the SAW beam propagating in a slanted direction is the first side lobe excited by the inclined chirp IDT. The acoustic field shows asymmetric distribution along the X-axis because of the asymmetric structure of the inclined chirp IDT. Finally, acoustic field of a two-IDT connected structure which consists of the same IDTs electrically connected in series is presented. The acoustic field of the two-IDT connected structure is calculated to be superposed onto the calculated result of the acoustic field exited by one IDT on the calculated result shifted along the X-axis. Two SAW beams excited by IDTs are observed. The distributions of the SAW beams are not in parallel. The calculated results show good agreement with the optical measurement results.
An ultrasonic pulse compression system is presented, which employs complementary series phase modulated signals as transmit signals to obtain theoretically zero range sidelobes and high efficiency. In correlation based signal processing, echoes are correlated with reference signals that have the same wave forms as the echoes. The effectiveness of this signal processing over the conventional one using transmit signals as reference signals is verified by experiments.
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