摘要:

AbstractIn ultrasonic flaw detection and medical diagnosis, shorter pulses tend to be used for improvement of the time resolution. It is then necessary that the transmitting and receiving systems have large bandwidth. In order to obtain information from the ultrasonic wave in the propagation direction over a long distance, a pulse with high peak power needs to be used so that theS/Nis enhanced. However, it is not simple to attain the requirements for both large bandwidth and highS/N.In this paper, a system is proposed in which, instead of using short pulses, the transmitted pulses are combined into a pulse train and pulse compression is carried out on the receiving side by a correlation process, so that short pulse transmission is realized effectively. First, we describe the generation of an ultrasonic pulse train using a stacked piezoceramic transducer made of several piezo‐ceramic resonators without complex electronic circuits. We next describe the principle of the reception correlation process, using stacked transducers with the same characteristics. We fabricated stacked transducers for transmission and reception of an ultrasonic pulse train with a Barker code of length 7. Transmission and reception experiments show that both the transmission of the pulse train and the correlation process are possible. Transmission and reception experiments were carried out under differentS/Nconditions by adding external noise to the input. When theS/Nratio of the transmitting pulse train was 0 dB, a gain of 4.6 dB was obtained. The gain margin was found to be 7.2 dB. Hence, it was demonstrated that the present method is effective under lowS/Ncondition

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractIn this paper, the scattering characteristics of an optically controlled microstrip gap fabricated on a silicon substrate are analyzed theoretically using the (FD)2TD method, and the effects of the spot diameter of the laser beam, the location of illumination, and the plasma thickness on such characteristics are studied. The theoretical results show that twin peaks can be observed in the transmission coefficient (S21) by the use of a laser beam with a spot diameter smaller than the gap, and that nondispersive characteristics can be developed by a laser beam having a large spot diameter. Finally, the theoretical results are compared with measurements.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe problem in designing an automatic gain controller (AGC) for a low‐frequency oscillator is to assure that the dc voltage is related to the amplitude of oscillation. For a switched‐capacitor (SC) oscillator composed of three SC phase‐shifters, the capacitances yielding a dc voltage proportional to the square of the oscillation amplitude are discussed. By the stated‐variable method, the SC oscillator was analyzed to determine the conditions under which the outputs of three phase‐shifters are equal in amplitude and different in phase by 120 degrees. When the condition is satisfied, the dc voltage is obtained by summing the three squared outputs. An SC oscillator was designed based on the circuit analysis, and its performance agreed well with the analytica

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractTo realize a linear voltage‐controlled oscillator (VCO), a voltage‐controlled resistor (VCR) whose reciprocal resistance is linear with respect to the control voltage Vcwas fabricated and tested. The VCR was composed of an analog multiplier (AM) and an operational amplifier (OA). The. static effective resistanceReof the VCR varied asR−1e=R−1(1 + αVc), whereRis the feedback resistance used in the VCR and α the scale factor of the AM. As for die dynamic characteristics, the reciprocal of the effective resistance of the VCR was not linear with respect toVcat high frequencies or for low control voltages, which resulted from an equivalent reactance of the VCR caused by the time lag at both the AM and the OA. Experimental testing of the Wien bridge oscillator with the VCRs showed that the oscillation was stable and that the frequency of oscillation varied linear

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractNonlinear coupling characteristics taking account of evanescent field overlap were evaluated numerically by assuming a Gaussian field distribution for the mode field in nonlinear directional couplers (NLDC). The nonlinear coefficientsQ3toQ5were found to beQ3= 3.7 × 10−12cm−1,Q4=Q5= 0 for the plane wave approximation used in Jensen's paper [1], with a core radius of 4 μm, a core spacing of 5 μm, a core refractive index of 1.455, and a nonlinear refractive index of 1.1 × 10−12esu; and the wavelength of the incident light was 1.06 μm. On the other hand, in the case of the Gaussian field approximation,Q3= 2.5 × 10−12cm−1,Q4= 2.2 × 10−14cm−1, andQ5= 7.3 × 10−14cm−1were obtained, indicating that these values cannot be ignored. The full coupling period is increased by increasing the core spacing, and the full coupling period is decreased by using a longer wavelength. Further, from the dependence of nonlinear coupling characteristics on optical wavelength, it is confirmed that wavelength selective characteristics with a sharp bandpass filterin

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAn ultra‐high vacuum silicon selective epitaxial method has been used in the LSI process for the first time. Using this epitaxial growth method, the gap between the oxide film pattern and epitaxial layer (facet width) is as small as 0.03 μm and selective epitaxial growth can be produced in the microscopic active regions. Therefore, this method is suitable for reducing device size. The leak currents between source and drain and between devices are comparable with those in Si‐bulk MOS devices, indicating that crystalline defect density is small in this epitaxial film. The channel in the MOS transistor formed using this epitaxial layer is extremely small. Transconductance of an nMOS transistor with an extremely short and narrow channel (gate length 0.1 μm and gate width 0.3 μm) was 530

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe bipolar enhanced transistor action (BETA)‐MOSFET, operating in a mixture of FET mode and bipolar mode, has been fabricated. Unlike the lateral bipolar transistor, its base current can be automatically controlled by the gate voltage. Hence, the device operating voltage can be in a wide range and is a maximum of −4 V. It is confirmed that the device can be treated as a high‐performance MOS‐FET in circuit analysis. Three types of device structures, with a gate‐substrate contact that includes an ultrathin‐film tunnel junction, are fabricated and evaluated. In the p‐channel BETA‐MOSFET, the drain current and the maximum transconductance are about four times those of the conventional MOSFET while maintaining the same threshold voltage. This result implies that the BETA‐MOSFET with a gate length of 1.3 μm exhibits a superior performance equivalent to

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWe investigated the impact of high‐temperature rapid thermal annealing (HT‐RTA) for CMOSFET design in the deep‐submicrometer regime. HT‐RTA (>1000 °C) carried out immediately after ion implantation can reduce the transient enhanced diffusion of implanted impurities and suppress interactions between these impurities, both of which are usually observed in low‐temperature furnace annealing processes. HT‐RTA is definitely effective in CMOSFET design optimization, since it can control impurity profiles more precisely than conventional thermal processes, leading to improvements in the short‐channel effects, current drivability, and reliability of MOSFETs. We also show that HT‐RTA serves as a methodology for analyzing the RSCE (reverse short‐channel effects) and ESCE (enhanced short‐channel effects) taking place simultaneously in deep

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractIn recent years, high‐efficiency oscillation of Yb:YAG lasers has been demonstrated, although it used to be considered unsuitable as laser material. Yb:YAG has received attention as a next‐generation high‐power, high‐stability laser because Yb3+has a low quantum defect rate and a long upper‐state lifetime of 1 ms, and has no state higher than the laser upper state. However, single axial mode oscillation is difficult as Yb has a very wide fluorescence width of 2.66 THz, and no information on high coherency has yet been reported.In this paper, the single axial mode oscillation of a Yb:YAG microchip laser is investigated experimentally and theoretically. In microchip lasers, when a single axial mode oscillation is attempted by matching the axial mode separation of the cavity to the fluorescence width and a laser material with very wide fluorescence width is used, the pump absorption efficiency degrades significantly. To compensate the absorption efficiency, a pump scheme using the resonant effect in an etalon is investigated. Single axial mode oscillation with an output power of 30 mW, a threshold of 13 mW, and a slope efficiency of 14.8 percent is achieved in an 80‐μm‐thick Yb:YAG (10 atom percent doped) microchip laser pumped by a

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWe investigated a method of solid‐phase epitaxy (SPE) using low‐vacuum, low‐pressure chemical vapor deposition (LPCVD) equipment without the load lock chamber that is usually used for the Si LSI process. This is a new method of clean surface formation in which the Si substrate is heated after seed formation in an atmosphere of SiH4gas. Using this method, an L‐SPE length of 4 μm was obtained. The reason for the success of this method appears to be that the seed surface cleaned by HF dipping is preserved by the SiH4gas.To evaluate the quality of the silicon‐on‐insulator (SOI) layer formed by this method, a MOSFET and a PN diode were experimentally produced. The MOSFET exhibited normal transistor action, which confirmed that the SOI layer had satisfactory quality without any problem in manufacturing the MOSFET. However, it was found that thenvalue of the forward direction current characteristic of the PN diode was 1.156 and that the SOI layer had more recombination centers than the Si substrat

ISSN:8756-663X    

DOI:10.1002/ecjb.4420791210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY