摘要:

AbstractIn this paper, sensitivity improvement of integrated optic micropressure sensors is discussed. The sensor is composed of a diaphragm and a ring resonator that is a multiple interference optical circuit. A part of the waveguide of the ring resonator is on the diaphragm. When a pressure is applied to the sensor, the diaphragm is deformed and the refractive index changes slightly so that a phase shift is induced on the guided wave propagating on the diaphragm. From the change of the resonant frequency caused by this phase change, the magnitude of the applied pressure is detected. In this study, particular emphasis is on the relationship between the diaphragm dimensions and the sensor sensitivity. From the analysis of the sensor operation, it is concluded that the use of a square‐shaped diaphragm with a waveguide of the ring resonator at the edge in addition to employing the TM‐like mode is most suited for a highly sensitive sensor. Further, from the evaluation of the minimum detectable pressure, it is expected that an integrated optic microprocessor sensor can be realized which is sensitive to such low pressure as underwater acoust

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790401

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

年代:1996

数据来源: WILEY

摘要:

AbstractEffects of perturbations including third‐order dispersion on the operation of logic devices constructed by asymmetric nonlinear optical fiber couplers are investigated by using the beam propagation method. In contrast to the unperturbed case, the radiation is stimulated and, consequently, the operation of logic devices is degraded. In order to remove the influence of perturbations, the bandwidth limited amplification is introduced. In a distributed gain medium with a finite bandwidth, the radiation caused by third‐order dispersion may be suppressed and the operation of logic devices is impro

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790402

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

年代:1996

数据来源: WILEY

摘要:

AbstractA novel intersection waveguide‐type polarization splitter based on total reflection using the birefringence of the GaInAsP/InP superlattice waveguide is proposed and analyzed in this paper. The semivectorial finite difference beam propagation method (FD‐BPM) (which handles both TE and TM modes) is used in the analysis. The waveguide structure including the GaInAsP/InP superlattice is designed; and it is shown that, although with a superlattice core the refractive index for the TM mode is reduced by approximately 0.4 percent, there is no change for the TE mode. Based on this result, the optimal structural parameters such as superlattice layer number, rib height (h), intersecting angle (θ), and port separation length (Lsp) are investigated using a 1.55μm wavelength. It is found that the TE and TM modes can be separated with an insertion loss of less than 0.4 dB for both modes and a crosstalk of less than −35 dB using an intersecting angle of 5° and a device length of approximately 0.9 mm. It is shown that compared to conventional devices, the device length in the proposed device structure can be reduced by using total reflection. The wavelength dependence of the device is also

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790403

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

年代:1996

数据来源: WILEY

摘要:

AbstractIn a frequency range that is between 30 and 60 MHz, piezoelectric resonators have not been employed widely in consumer electronics due to their size and the difficulty in precisely tuning their frequencies. Thus, liquid crystal (LC) resonators have been extensively used instead.The authors of this paper have successfully developed and commercialized Bleustein‐Gulyaev‐Shimizu wave free‐edge reflection resonators made of piezoelectric ceramics lead zirconate‐titanate (PZT), which have both a small temperature coefficient (9 ppm/°C) and a large electromechanical coupling coefficient (k2= 0.22).These resonators have been evaluated as additional traps for nonfrequency tuning resonators that replace both LC resonators requiring tuning and resonators needing autofrequency tuning (AFT). In the former application, the present resonators exhibit trap characteristics with steeper and larger attenuation than those of conventional LC resonators. In the latter application, the present resonators exhibited AFT sensitivity characteristics which are similar to those of conventional LC resonators. When the present resonators were incorporated into voltage‐controlled oscillator circuits, they exhibited a very wide adjustable frequency range

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790404

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

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper presents a precise measurement method for obtaining the drive power dependency of frequency in highly stabilized quartz‐crystal oscillators. The method is aimed at improving the frequency stability of crystal oscillators and, in particular, oven‐controlled crystal oscillators (OCXOs). It uses a transistor Colpitts oscillation circuit which features excellent resolution and reproducibility of electrical current measurements as well as higher operating frequencies than those of conventional techniques such as transmission or reflection methods. In this paper, the authors demonstrated concepts of this method and a corresponding measurement system. The proposed method also was applied to SC‐cut crystal oscillators used in OCXOs which had shown nonsatisfactory frequency stability (discussed earlier by the authors). Here, the authors demonstrated that those problems were caused by frequency jumps in the oscillator frequency‐versus‐current characteristic. It was shown also that OCXO circuits with excellent reproducibility of temperature characteristics can be implemented by using an appropriate level of driving current to drive the quartz oscillator in the genera

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790405

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

年代:1996

数据来源: WILEY

摘要:

AbstractVertical‐cavity surface emitting lasers (VCSELs) are expected to be used as light sources in two‐dimensional array optoelectronics because of their structure and probable characteristics. The control of spontaneous emission by wavelength‐size microcavities is effective in lowering the threshold of surface emitting lasers. The control of spontaneous emission using the spontaneous‐emission factor of three‐dimensional microcavities was presented by the authors in previously done work. This paper reports on further progress in the analysis of the spontaneous‐emission factor. The standing wave distribution inside a planar or three‐dimensional microcavity is first investigated. Increase in the spontaneous‐emission factor and control of the optical mode taken out of the microcavity are estimated under the increased optical confinement factor due to varied external boundary conditions of the distributed Bragg reflector (DBR). The variations of the spontaneous emission and output characteristics associated with injection level are discussed. It is shown that the spontaneous‐emission factor varies with cavity resonant wavelength and the injection level affects the output optica

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790406

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe MgO powder used for a screen‐printed protective layer on plasma display panels was evaluated. The MgO powder was formed by either vapor‐phase oxidation or decomposition of Mg(OH)2. For the same BET value, the diameter of MgO particles formed by the latter method was larger than that by the former method. It was found that the particle diameter calculated by Scherrer's equation using the half‐value width of an X‐ray diffraction pattern was less than one‐fifth of that calculated using the BET value. When the distribution of the particle size was evaluated by the centrifuge precipitation method, it was found that both the median and modal diameters of the MgO powders formed by the latter method were larger than that by the former method. The powder formed by the latter method also contained powder with diameters of less than 20 nm; the weight ratio of the fine powder to the entire MgO powder was 5.5 ∼15.9 wt%. The transmission electron microscopy (TEM) observation revealed that the powder formed by the former method had a higher crystallinity and that the powder formed by the latter method tended to aggregate. When protective MgO layers were fabricated by sintering MgO powder formed by the above two methods, the powders oriented in the (111) orientation and the MgO formed by the former method had a higher crystallinity. It was concluded that, since the MgO powder formed by the former method (vapor phase method) had a finer particle diameter, higher crystallinity, and higher uniformity than the powder formed by the latter method (decomposition of Mg(OH)2), the MgO powder formed by the former method is more suitable for the alternating current plasma display panel (AC‐PDP) printed pro

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790407

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

年代:1996

数据来源: WILEY

摘要:

AbstractAs the recording method for the track address in the magnetic disk drive, the Gray code with redundancy (Gray‐like code) has been used so that nearly the correct value can be obtained even if the head is located close to the track boundary. This paper proposes a recording/reproducing method for the track address in the magnetic recording where the Viterbi decoding is applied to the Gray code record. The detection performance is evaluated by the theoretical analysis and the simulation. As a result, it is seen that the same or better performance compared to the conventional method can be obtained. By the proposed method, the area for the track address recording can be reduced to one‐half to two‐thirds the conventional method. This helps to increase the recording capacity and improve the maximum seek

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790408

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

年代:1996

数据来源: WILEY

摘要:

AbstractIn the development of practical multimedia systems, greater capacity is desired in a long‐distance large‐capacity transmission system. A number of studies have been undertaken to develop a long‐distance large‐capacity system. Several long‐distance transmission experiments for high‐density transmission by wavelength demultiplexing method (WDM) have been reported recently. However, more of the experimental examples have reported on soliton transmission than on WDM systems. Hence, the former is considered more advanced. It is necessary to prepare a fiber of a length of approximately 10, 000 km for ultralong‐distance transmission experiment. Since this is difficult to obtain, repetitive experiments are often the case. However, such an experiment does not disclose the effects of dispersion and loss fluctuation in the fiber. In this paper, the effect of fluctuation in dispersion and loss in the fiber is studied by simulation so that the resilience of the soliton to the variations of the fiber characteristics

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790409

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

年代:1996

数据来源: WILEY

摘要:

AbstractA two‐input winding transformer technique for high‐power factor converters has been developed. This technique results in reduced size and enhanced conversion efficiency. Input‐current wave‐shaping and fast output‐voltage regulation are achieved by controlling charge and discharge of an energy‐storage capacitor on the primary side of the transformer to compensate for the difference between the ac input and the dc output power. Thus, most of the input power is supplied to the output through only a single conversion stage and the low‐frequency ripple in the output voltage can be reduced with a small output capacitor. In addition, operation in the continuous conduction mode makes it possible to reduce the size of the input filter, concomitantly decreasing conduction loss.This paper discusses a push‐pull current‐fed converter that uses this technique. In this circuit, it is necessary to restrict the pulsewidth for the input current control because the pulsewidth for the output voltage control should be expanded to decrease the rms value of the current flowing in the switches. The characteristics of input current distortion caused by this restriction are analyzed and optimization, which takes into account harmonic current characteristics and reduction of conduction loss, is clarified. High‐power factor and an efficiency of 88 percent were achi

ISSN:8756-663X    

DOI:10.1002/ecjb.4420790410

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

年代:1996

数据来源: WILEY