Koichiro Misu

Preparation and Piezoelectric Property of Lead Titanate Thin Films for GHz-Band Resonators

Film bulk acoustic wave resonators (FBAWRs) at the GHz band were successfully fabricated using piezoelectric lead titanate, PbTiO 3 (PT) films on GaAs substrates by a process similar to that used in microwave integrated circuit (MIC) fabrication. PT films deposited on Pt/Ti bottom electrodes by RF magnetron sputtering oriented preferentially along the (111) crystal direction. Resonances of the bulk acoustic mode were observed around 1.9 GHz. The effective electromechanical coupling coefficient (k t 2 ) and electrical Q were estimated to be ∼9.4% and ∼65, respectively. The relationship between residual stress in the PT films and Q was investigated. It was found that stress in the PT film exerted a large influence on Q.

Piezoelectric Properties of La-Doped PbTiO3 Films for RF Resonators

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 (kt2) was estimated to be 11% at 1.4 GHz and 9.4% at 2.0 GHz, respectively. The PT films had superior kt2 in the GHz band. The capability of the RF devices with broad bandwidth was investigated.

Differential mode noise on the PCB's signal traces converted from external common mode noise

This study experimentally clarifies the relationship between the common mode noise induced on the cable connected to the signal trace of PCB and the differential mode noise on signal trace, converted from the common mode noise, due to the unbalance of differential signal trace by applying the measurement method that Test baluns are used as a load of the cable and a signal source. In this study, S13 (Differential mode noise) and S23 (Common mode noise) are measured by the network analyzer for evaluation. Finally, the effectiveness of the common mode choke on signal trace and the shielding for the cable for both common mode and differential mode noise reduction are evaluated.

A simplified model of a common mode choke coil for 3D field simulators

We studied a CMC model with a one-turn toroidal core, which is easily used in 3D field simulators. The calculation model of a CMC differs from the actual shape, so we need to correct the CMCs characteristics. When we calculated the noise-suppressing effect of the CMC, we used relative permeability, which differs from the actual value, to approximate the actual characteristics of a CMC. From the comparison of calculated results with measurement results, the calculated results were comparable to the measurement results. We confirmed the validity of our model.

Electromagnetic field immunity test system applying array antenna technology

We examined about the electromagnetic field immunity test system applying the array antenna technology. This system is able to get the electric field uniformity and the high power electric field near the antenna, in a wideband, by the beam forming technology. We constructed an electromagnetic field immunity test system consisting of 64 elements array antenna as a prototype. In this paper, we calculated the electric field uniformity near electromagnetic field immunity test system. We measured electric distributions and compared with the calculated value and the measured value. From these results, the validity of the calculation method of the electric field uniformity near the test system was confirmed.

Piezoelectric properties and micro structures of lead titanate thin films for GHz-band bulk acoustic wave filters

Abstract The bulk acoustic wave filters at GHz bands were fabricated using lead titanate, PbTiO3 (PT) piezoelectric films which were deposited by RF magnetron sputtering and were oriented along crystal direction. To improve the quality of PT films, the bottom electrodes which had the Ti-diffusion suppressible layers were designed and prepared. X-ray diffraction intensity of the PT(111) became 5 times larger and degree of crystal orientation became 2 times stronger in comparison with those of the former PT films. The filters using the improved PT films had the insertion loss of -14dB. The PT film had effective electromechanical coupling coefficient (k) of 31% and electrical Q of 50. This k value was superior to those of well-known ZnO and AlN piezoelectric films.

Analysis of echoes in ultrasonic testing for round bar using angle beam immersion technique

A design is presented for a probe, used for automatic ultrasonic testing for a round bar using the angle beam immersion technique, to improve a signal to noise ratio. It is defined based on a flaw echo height and a spurious echo height, taking into consideration of a time gate and variation of the flaw echo height along with a rotation of the probe round the bar. The result of the design is in good agreement with that of experiments.

A Pulse Compression Ultrasonic Test Instrument and Its Applications

In recent years, so called “digital ultrasonic test instruments” have been commercially available. These conventional instruments employ electrical impulse excitation of ultrasonic probes. In this configuration, waveforms of ultrasonic pulses into a test object are determined only by the characteristics of probes. This means that variation of probe characteristics causes variation of evaluated results and reproducibility of evaluation is poor. Furthermore, some of the conventional instruments do not provide enough information required for quantitative nondestructive evaluation (QNDE) about a test object, since ultrasonic echo signals are A/D converted after an envelope detector in a receiver and only information of echo height and position is obtained.