Hiroshi Shiba

PSA-a new approach for bipolar LSI

Describes a new fabrication method to realize bipolar LSI. The new process, called the PSA (polysilicon self-aligned) method, is based on a new fabrication concept for dimensional reduction. The process provides smaller PSA transistors with smaller parasitic capacitance by being combined with local oxidation technology. As a production example of this modified PSA method, a static bipolar 4K TTL RAM has been manufactured. In this production, the nonepitaxial technology (triple diffusion) has also been adopted to shorten production turnaround time and to increase fabrication yield. Furthermore, PSA transistors have been combined with polysilicon diodes (PSD) and Schottky barrier diodes (SBD) to obtain low power Schottky diode-transistor logic (DTL) gates.

A new polysilicon process for a bipolar device-PSA technology

A new polysilicon process has been developed to obtain high packing density, high speed, and low-power LSIs. The new process, called the polysilicon self-aligned (PSA) method is based on a new fabrication concept for dimensional reduction and does not require fine patterning and accurate mask alignment. For an application example of this new method, an ECL gate with 0.6 ns delay time, 0.5 pJ power-delay product, and 6400 /spl mu/m/SUP 2/ gate area has been achieved. Furthermore, by introducing a polysilicon diode (PSD) and Schottky barrier diode (SBD) to the PSA method, a low-power Schottky-diode-transistor-logic (SDTL) gate with 1.6 ns delay time, 0.8 pJ power-delay product, and 2000 /spl mu/m/SUP 2/ gate area has been successfully developed.

Tonpilz Piezoelectric Transducer with a Bending Piezoelectric Disk on The Radiation Surface

In recent years, it has become necessary to use wide-band signals in various kinds of signal processing and communication technology fields. One of these is the field of underwater acoustic technology, and therefore wide-band transducers are needed in this field. To address this need, we developed a Tonpilz piezoelectric transducer with a bending piezoelectric disk on the radiation surface of the front mass. This transducer was designed by providing a bending piezoelectric disk on the radiation surface of the front mass of a conventional Tonpilz piezoelectric transducer to enable it to generate in two resonance modes: the longitudinal vibration resonance mode and the bending vibration resonance mode of the bending disk. Coupling these two resonance modes makes it possible to achieve low-frequency transmission, and wide-band signals can be attained by adjusting the phase in the two modes. We obtained the optimum design dimensions of the transducer through analysis using the finite element method (FEM), and constructed a prototype based on the analysis. Experiments verified that the measured results for the prototype correspond well to the simulation results and that the bandwidth can be widened without changing the external size of the conventional transducer.

Low-Frequency Synthetic Aperture Sonar System

An experimental synthetic aperture sonar system is developed, and a set of cruises is also conducted. The primary purpose of the system is to confirm the validity of the motion compensation technique, which combines the use of both the DPC algorithm and the motion sensor. The experiment clearly shows the effectiveness of this combination, resulting in the successful estimation of underwater motion errors and the formation of synthetic aperture images.

Transducer with coupled vibrators

A transducer includes a Langevin type vibrator, a bending vibrator, and a ring-like member. The Langevin type vibrator has a construction in which a front mass, a cylindrical vibrator, and a rear mass are provided in tandem, and those elements are tightened by a bolt. The bending vibrator is provided apart from the front mass. The ring-like member is provided in outer peripheral portions of the front mass and the bending vibrator to couple the front mass and the bending vibrator to each other. The transducer generates a large sound pressure over a wide frequency band since a sound wave radiation surface is wide and its amplitude amount is large.

Finite-Element Method Analysis of Low-Frequency Wideband Array Composed of Disk Bender Transducers with Differential Connections

In recent ocean investigations using underwater sonar transducers, low-frequency and wideband long-range sonar systems have been demanded for strong acoustic radiation and improved detective resolution capability in shallow-sea regions. We developed a disk bender transducer with a dual radiation surface as a miniaturized, light weight, low-frequency, and high-power transducer. However, there were problems in that the fractional bandwidth was small because the radiation surface was far smaller than the radiated wavelength, and the acoustic load per unit radiation area was small. Therefore, we suggest a technique to enable a wideband sonar array using differential connections of multiple disk bender transducers with different resonance frequencies to solve these problems. In this paper, we report results that endorse the above-mentioned technique obtained by finite-element method (FEM) analysis. The results confirm that this technique produces a wideband transducer array with low-frequency and high-power characteristics. We found that a wideband characteristic of more than 100% could be achieved with as a 6 dB fractional bandwidth by differential connection of disk bender transducers with three different resonance frequencies. In addition, we found that a superior horizontally oriented directivity was provided by locating the transducers in a plane symmetrical to the horizontal plane.

Investigation of Disk Bender Low-Frequency Projector with Dual Radiation Surfaces

A low-frequency disk bender projector with dual radiation surfaces was designed on the basis of finite element method (FEM) analysis and equivalent circuit analysis, in order to devise a miniature light weight projector with a high sound pressure level. These analyses suggest that a low-frequency, high-power, miniature and light weight projector can be realized. A trial projector was produced and evaluated. The resonant frequencies for the projector in air and water were 1315 Hz and 970 Hz, respectively. Experimental maximum transmitting voltage sensitivity was 132.2 dB re 1 µPa/V at 1 m.

Convergence of the phase conjugate wave to a pseudo sound source

This paper describes that in shallow water the scattered wave from the target is detected by converging the sound wave to the target using the phase conjugate wave. The phase conjugate wave radiated from the vertical linear transducer array (VLA) is converged to the sound source position. It was confirmed that the phase conjugate wave converged at the sound source position by the experiment. The sound source is replaced with a pseudo sound source. It is assumed that the sound wave is transmitted from a pseudo sound source, and obtains the wave form in the element of VLA by the calculation. The calculated waveform is excuted time reversal processing and it reradiated from VLA. And it was confirmed that the phase conjugate wave converged at the position of the pseudo sound source by the experiment. Consequently, it was confirmed to move the focus of the phase conjugate wave without a real sound source, and to be able to detect the target.