bluuebunny/crossref_metadata_2025 huggingface dataset:
Fiber‐optic millimeter‐wave subcarrier transmission links using HBTs as photodetectors
Authors: Suematsu Eiji , Imai Nobuaki
Published: July 2007

The authors utilized monolithic microwave integrated circuits (MMIC) compatible devices, GaAs HBT and InP/InGaAs HBT, as photodetectors for a fiber‐optic/millimeter‐wave subcarrier link, and investigated the link loss characteristics, subcarrier‐to‐noise ratio (SNR) characteristics, and IM3 characteristics of the fiber‐optic millimeter‐wave subcarrier link, comparing them with those of the link using a pin photodiode. The link gain characteristics are compared with those of the links which use other MMIC compatible photodetectors (MSM and HEMT) and pin photodetectors (pin‐PD). It is found that for both the common emitter HBT link and the common‐base HBT link, good response and flat frequency characteristics can be seen over several gigahertz in the millimeter‐wave band.

The SNR characteristics of the common emitter HBT link governs the noise characteristics of the optical/RF transducer in the low‐frequency region where there is internal gain. However, in the millimeter‐wave region (where there is no gain), it is dependent on the noise characteristics of the LNA connected after the HBT or in the common base HBT link. The input/output characteristics and IM3 characteristics of the HBT link are dependent on the power characteristics of the external optical modulator (EOM) when the optical power is less than ‐ 3 dBm.

An optical/RF transducer combining an HBT photodetector, LNA, and horn antenna is designed. Using this optical/RF transducer, an optical fiber/millimeter‐wave radio link is designed and the FM video transmission characteristics are investigated experimentally. It is shown that this link was effective at wavelengths of 0.83 μm and 1.3 μm.
Finite‐element analysis of electron waveguide discontinuities with arbitrary potential and effective mass distributions
Authors: Gotoh Hitoshi , Koshiba Masanori
Published: July 2007

For the two‐dimensional discontinuity problems in an electron waveguide with arbitrary potential distributions and arbitrary effective mass distributions, an analysis method based on the finite‐element method is proposed and formulated. Specifically, the method is applied to a rectangular bend in an electron waveguide so that its validity and effectiveness are presented. Also, a formulation is carried out for a more practical electron wave circuit in which the potential outside the waveguide is finite. The formulation is applied to a rib‐type discontinuity in an electron waveguide and the transmission characteristics are analyzed. The results are compared with those for the case in which the potential outside the waveguide is infinite.
Method of evaluating facet and bulk degradation in semiconductor lasers
Authors: Fukushima Takehiro , Furuya Akira , Kito Yasuhiro , Sudo Hisao , Sugano Mami , Tanahashi Toshiyuki
Published: July 2007

A new method has been proposed to evaluate bulk (crystal) and facet degradation in semiconductor lasers separately by cleaving the degraded laser diodes into three regions along a resonator direction. By applying the method to AlGalnP visible light laser diodes, it has been demonstrated that it is possible to evaluate the changes in facet reflectivity and the effects of bulk and facet degradation on performance characteristics of as‐cleaved laser diodes as well as laser diodes with antirefiection and high‐reflection (AR‐HR) facet coating.
A scalar finite element analysis of nonlinear optical channel waveguides using isoparametric elements
Authors: Niiyama Akira , Koshiba Masanori , Tsuji Yasuhide
Published: July 2007

With a view to increasing the efficiency of the scalar finite element for nonlinear optical channel waveguides, triangular isoparametric elements are introduced. In addition, the numerical integration formula by Hammer et al. is used for the integration needed for deriving the element matrix. The numerical analysis is carried out for the nonlinear optical fibers. It is confirmed that accurate solutions can be obtained by the present method with a small‐size calculation. Also, the analysis of a nonlinear graded channel optical waveguide is carried out for the first time. The effect of the refractive index profile of the substrate on the optical power dependence of the effective index of the guided mode is investigated.
Laminated polarizer with ultrathin germanium for the shorter wavelength with emphasis on modeling the transition layer at the boundaries
Authors: Matsuda Jun‐Ichi , Uchidam Toshiyuki , Kawakami Shojiro
Published: July 2007

The authors have been carrying out research and development of a laminated polarizer (LAMIPOL) as a polarizer suitable of integration. In this paper, with a view to obtain a high‐performance LAMIPOL over a broad, shorter wavelength region (0.6 μm < λ < 1 μm), a LAMIPOL with an ultrathin germanium thin film (20 to 80 Å) was designed and fabricated. As a result, high performance as designed was realized in the wavelength region of 0.6 μm < λ < 1 μm. However, as the Ge laminated layer is made even thinner (such as 20 Å or 30 Å), the computed and measured values for the attenuation constant αTM for the TM wave do not agree and the cause was studied.

First, from the experimental results for various Ge thin films, it was found that the nature of the boundary layer does not depend on the lamination thickness of the Ge layer. Further, the model with a boundary layer having a uniform relative permittivity (step approximation) and the model with continuously varying permittivity (linear approximation) were considered. With the latter, it was possible to compute accurately the characteristics of the LAMIPOL for the TM wave if the Ge laminated layer thickness is more than 30 Å.
Observation of internal states of chaos generator with CMOS inverter
Authors: Takakubo Kawori , Takakubo Hajime , Shono Katsufusa
Published: July 2007

The one‐dimensional mapping circuit for chaos generation is constructed using a CMOS source‐follower and a parallel connection of two CMOS inverters. Two one‐dimensional mapping circuits and CMOS switches are used to form a loop to generate the chaos. The initial value is set iteratively by the 12‐bit D‐A converter. The time‐course of the internal state is observed through an A‐D converter with 10‐bit precision. The internal state is determined successively according to the transfer curve of the one‐dimensional mapping circuit. The Lyapunov exponent is determined based on the transition of the internal state near the cycle point.
Optimum design for polarization crosstalk reduction in a polarization maintaining optical fiber of PANDA profile
Authors: Kitamura Fujikazu , Sasaki Yutaka
Published: July 2007

This paper investigates theoretically the polarization‐maintaining optical fiber with a circular stress‐applying part (PANDA fiber) with a high design accuracy and ease of fabrication, with a view to realizing a low crosstalk polarization‐maintaining optical fiber for coherent optical sensing. In general, two orthogonal polarization modes exist in a polarization‐maintaining fiber. Due to the coupling between these two modes, the transmission of a polarized wave is difficult. The infinitesimal polarization component caused by this coupling is called the minor component. The cause of generation of the minor component is confirmed theoretically as the generation of the off‐diagonal term in the relative permittivity tensor. In the past, the off‐diagonal terms have been neglected in the optical fiber in which symmetry is maintained.

In this paper, the off‐diagonal terms of the relative permittivity tensor appearing in a PANDA fiber with symmetry are investigated. The effect of the structural characteristics of the PANDA fiber on the crosstalk degradation is analyzed. It is found that the improvement of the polarization crosstalk by 20 to 35 dB is expected with a modal birefringence of less than one‐half the previous case, by making the normalized stress‐applying part half‐spacing 2.83 and the normalized stress‐applying part diameter 0.44.
New reflowable organic spin‐on glass for advanced interlevel dielectric planarization
Authors: Furusawa Takeshi , Homma Yoshio , Shimamura Yasuo , Morishima Hiroyuki , Yamamoto Yasuhiro , Satoh Hidetada
Published: July 2007

New reflowable organic spin‐on glass (SOG) was developed to form planarized multilevel interconnections for ULSIs. This SOG had superior gap‐filling and plan‐arizing characteristics compared to those of conventional organic SOGs. For example, using this SOG, a 0.025‐μm wide trench with an aspect ratio of over 10 could be perfectly filled without void. The surface of a three‐layered interlevel dielectric structure with this SOG was four times smoother than that with a conventional organic SOG.

It was found that the excellent gap‐filling planar‐izing property of this SOG was due to the low temperature reflow (100 to 200°C). The film quality was almost the same as that of an organic SOG which has been widely used and has exhibited sufficient reliability. That is, this organic SOG gives a sufficient reliability with far improved gap‐filling and planarization. Since the relative dielectric constant of this SOG is as low as 3.0, this SOG is promising to improve the operation speed of ULSI.
Molecular dynamics simulation of void electromigration under a high‐density electric current stress in an aluminum interconnection
Authors: Shingubara Shoso , Utsunomiya Isao , Fujii Taizo
Published: July 2007

Three‐dimensional molecular dynamics simulation of behaviors of a void in an Al interconnection under high current stress has been accomplished employing empirical two‐body potential and the Huntington‐Grone ballistic model for an electron wind force. Stability of a void under a uniform strain field was first investigated; it was shown that a void was stable under a tensile strain, while it was unstable under a compressive strain. Then, a void movement into cathode direction was clearly demonstrated in the single‐crystalline Al interconnection at the high current density of 1 × 1010 A/cm2. The activation energy of the drift velocity of the void was 0.76 eV. Next, behaviors of a void in [111] bicrystal grains with a periodic boundary condition which resembled a bamboo structure interconnection was investigated. A void was stabilized at the grain boundary at low current density conditions; however, it could go across the grain boundary and move further to the cathode direction when the current density was high enough. It was shown that when a void comes close to the grain boundary, it suddenly annihilates into vacancies and rapid movement of vacancies into the grain boundary occur. A void was formed again at the grain boundary. This model will explain the void annihilation phenomena, reported by the in situ scanning electron microscope (SEM) observations. After stopping the current, a backflow of a void was observed as a consequence of the strain energy relaxation when the current density was high. These obtained results explained well the experimental observations qualitatively; furthermore, new predictions were obtained with quantitative analysis based on total potential energy analysis.
A new very fast pull‐in phase‐locked loop with antipseudo‐lock function
Authors: Shirahama Hiroyuki , Taniguchi Kenji , Nakashi Kenichi
Published: July 2007

With the development of high‐speed digital communications, e.g., optical fiber communications, smaller, faster, retiming devices are being required. The phase‐locked loops (PLLs) are suited to an integration compared to surface acoustic wave (SAW) or liquid crystal (LC) passive filters. Therefore, PLLs have been put to use gradually as clock extraction devices in any frequency range over 100 MHz. The authors have developed the previously reported PLL with frequency difference detector (FDD) to provide a new function, which is useful to overcome the pseudo‐lock problem in conventional retiming PLLs and also improved performance of the FDD. The proposed PLL has been constructed with ECL‐IC, PLA and other discrete parts. It has been evaluated experimentally and the PLL designed with a 0.8‐μ design‐rule bipolar transistor has been evaluated by simulation to confirm the following characteristics.

1. The PLL can detect an initial unlock state and pseudo‐lock state within almost the same time as FDD sampling time and can recover rapidly.

2. The jitter transfer function is almost equal to the usual first‐order PLL and is independent of input data patterns.

3. The FDD frequency detecting range, corresponding to the PLL lock‐in range, is more than four times that of the previously proposed FDD‐PLL.
Detection of the complex amplitude distribution of a kinoform using an iterative fourier‐transform algorithm
Authors: Akahori Hiroshi
Published: July 2007

This paper presents a method for recovering, by using the iterative Fourier‐transform algorithm, the complex amplitude transmittance of a recorded one‐dimensional Fourier transform‐type kinoform. A method for estimating the phase‐recording characteristic of the kinoform fabrication system by comparing the retrieved phase with the theoretical phase is also presented. The spatial variations of both the magnitude and phase inside each of the kinoform cells were evaluated to improve estimation of the phase‐recording characteristic. The initial estimate of the kinoform phase given to the algorithm was derived using the knowledge that the recorded phase is an approximation of the phase to be recorded.

The relationship between the shift of the central sampling point of the Fourier image from the optical axis and the retrieved phase of the kinoform is investigated; a kinoform phase pattern with a structure suitable for indirectly detecting the shift is then proposed. In an experiment using a kinoform fabrication system including a photographic process, the recorded phase distribution is retrieved at five sampling points of each cell. The phase‐recording characteristic is estimated using the retrieved phase values.

Next, a computer simulation is executed to reveal the influence of errors in the measurement of magnitude. The simulation result shows that the recorded phase distribution can approximately be retrieved when the rms error added to the magnitude is approximately 10 percent of its average. Furthermore, the validity of the phase distribution retrieved in the experiment is discussed.
Optimum design technique for optoelectronic devices using simulated annealing
Authors: Hara Kunihiko , Iwamoto Takashi , Kyuma Kazuo
Published: July 2007

A new procedure for the optimum design of optoelectronic devices is explained in this paper and an automatic search is made simultaneously for the structure satisfying various demands. The feature of this procedure is in the introduction of cost by which the quantitative evaluation of the structure becomes possible and the global search for the required structure by simulated annealing can be carried out.

First, the definition of cost and details of the optimization procedure are clarified. In optimization, in addition to convergence to the minimum point of the cost function (the optimum configuration from theoretical viewpoint), the convergence also is possible in structures with great tolerance to fabrication errors (neighborhood cost (NC) and finite temperature annealing (FTA) methods).

Next, these three proposed methods are used in the design of a pnpn differential optical switch and the effectiveness of the methods is verified. The method of cost expression, the relation between annealing parameters, and convergence are investigated. It is shown that cost expression with large degree of freedom improves the search for high‐performance structures and the initial temperature of annealing or the fixed temperature of FTA method is the important parameter which sets up the probability of acceptance. Further, it is shown that the convergence cost is inversely proportional to the time spent in annealing. These results are useful guidelines in the optimum design of arbitrary optoelectronic devices.
Multilevel interconnection technology without via‐hole mask (maskless pillar process)
Authors: Ueda Tetsuya , Yano Kousaku
Published: July 2007

Recently, with the miniaturization of ULSI patterns, the percentage of the LSI production cost occupied by the multilevel interconnection process is increasing due to the increase in the process steps and the introduction of new materials. In order to realize miniaturization process and achieve cost reduction at the same time, via‐hole maskless multilevel interconnect technology (mask‐less pillar process) has been developed. By merging the via‐hole mask information on the underlying interconnection mask and by a selective etching of the multilevel metal films which depends on the mask width, underlying interconnection and metal pillars are formed simultaneously. The reduction of process steps has become possible by eliminating the via‐hole lithography, etching, and filling process. As a result of electrical measurement of samples formed by the maskless pillar process, the feasibility for two‐level metal interconnection has been verified, which confirmed it to be a multilevel interconnection process suitable for sub‐half micron devices with guaranteed reliability.
Tuning and wideband intensity modulation of noncollinear quasi‐phase‐matched second‐harmonic generation using pockels effect
Authors: Koyanagi Kojiro , Mishima Teruhito , Sakuraba Ichiro
Published: July 2007

The difficulty in highly efficient quasi‐phase‐matched second‐harmonic generation (QPM‐SHG) using periodic nonlinear structures is the strictness of the allowance of the period length or the fundamental wavelength in the quasi‐phase matched condition. As a result of these difficulties, the increase of the allowance and the easy fine‐tuning of quasi‐phase matching are very important. In this paper, the fine‐tuning of the quasi‐phase‐matched condition in bulk noncollinear (two‐dimensional) QPM‐SHG by adjusting the angle of incidence of the fundamental wave and by using the Pockels effects by the applied electric field is proposed and its properties are investigated theoretically. For wavelength variations of the fundamental wave, relaxed allowance by automatic readjustment of the angle of incidence using angular dispersions of a diffraction grating is also proposed. The relaxation is adopted in light‐intensity modulation of bulk‐type noncollinear QPM‐SHG, which is achieved by variations in phase‐matched condition by electro‐optic effect. Because nonlinear material, periodic domain inverted LiNbO3 is assumed and tuning, relaxation, and modulation characteristics are investigated through numerical simulations. As a result, it is shown that rapid tuning can easily be achieved and the proposed wide wavelength‐band light intensity modulator is expected to realize applications in optical disks, etc.
Complex permittivity measurement of dielectric materials using nonradiative dielectric guide at millimeter wavelength
Authors: Ishikawa Youhei , Tanizaki Tohru , Saitoh Atsushi , Yoneyama Tsukasa
Published: July 2007

In this paper, as a method for measurement of complex permittivity of millimeter‐wave dielectric materials, a transmission resonator method is proposed which is made of a dielectric resonator with both sides open placed in a nonradiative dielectric (NRD) guide. For the evaluation of the surface resistance of the conductor indispensable for measurement of the complex permittivity, a pair of TEoml mode resonators are placed coaxially and are mutually coupled. The difference of the conductor losses for the even and odd mode resonances of this resonator system is detected as the difference of the unloaded Q's so that the surface resistance is derived.

The special features of the present measurement method are to evaluate the conductor surface resistance at a high sensitivity in a condition close to the resonator with both ends short‐circuited and to use a resonator with both ends open‐circuited for sample measurement because the effect of the surface resistance is small so that high accuracy is obtained as a whole. By using an NRD guide excitation method, a measurement system is realized which affects very little the unloaded Q of the resonator system and the electromagnetic field distribution.

For the calculations of the complex permittivity, the eigenvalue calculation by the finite element method and the perturbation method by Kajfez are combined. For the samples with its relative permittivity of 24 and the loss tangent of 2 × 10−4, the measurement fluctuations are less than 0.005 percent for the resonant frequency and less than 1 percent for the unloaded Q. The measurement accuracy for the relative permittivity is less than 0.4 percent and that for the loss tangent is less than 3 percent.
A high‐speed high‐density array‐multiplier‐accumulator for digital signal processing
Authors: Minami Toshihiro , Kasai Ryota , Matsuda Hiroaki , Kusaba Ritsu
Published: July 2007

This paper discusses the downsizing and speed improvement of short‐word multiplier‐accumulators, which are frequently used in digital signal processors. As a first step, the optimal configuration for an array‐type carry‐save adder is considered where the shortest path in the full‐adder is used to propagate the sum signal and the carry signal is sent to the full‐adder of the two lower stages by skipping a stage. A configuration of the full‐adder suitable for the structure is proposed. The case of eight partial product additions shows that the delay can be reduced by 22 percent compared to a simple array‐type carry‐save adder. Then the short‐word carry look‐ahead adder using the pass‐transistor logic is considered. It is shown that a single‐stage carry look‐ahead circuit with a four‐bitwise iterative structure exhibits nearly the same delay as a two‐stage carry look‐ahead circuit. In other words, the former is better suited to downsizing. This paper intends to examine the effectiveness of the foregoing new array‐type carry‐save adder and the single‐stage carry look‐ahead circuit using the 0.5‐μm CMOS technology. A 16‐bit X 14‐bit + 31‐bit multiplier‐accumulator has been designed and is evaluated for cases where the array‐type carry‐save adder is used to handle accumulation as well as partial products. The resulting area and delay are 0.77 × 0.78 mm2 and 6.8 ns, respectively. The effectiveness of the approach used in this paper is evaluated by constructing a multiplier‐accumulator, but the method is also useful in constructing a multiplier.
A time A‐D converter LSI for accurate measurement of multitime‐interval by digital processing
Authors: Watanabe Takamoto , Ohtsuka Yoshinori , Akita Shigeyuki , Hattori Tadashi , Agatsuma Syuuji , Isomura Hirofumi
Published: July 2007

The authors previously have reported on the “ring gate delay” system which digitizes the infinitesimal time interval with the delay time of the inverter as the resolution, without using the high‐speed reference clock [1]. A problem then is the improvement of the accuracy since the delay time of the inverter depends on various conditions such as the ambient temperature, the supply voltage, and the fabrication condition. To remedy this point, an LSI is constructed and the delay time of the original circuit is monitored continuously using the quartz oscillation clock of a relatively low frequency as the reference, and the time to be measured is digitized with a high accuracy based on the delay time. In this system, it is not necessary to control the delay time, which makes it possible to utilize the shortest delay time.

By a single measurement process using a single input port, up to four pulses can be measured consecutively. If the pulse interval to be measured in less than the specified time, the pulses are combined into a single pulse and an incorrect operation is prevented.

In this study, a sample device is constructed by a 1.5‐μm CMOS process. The measurement range of 2200 ns (12 bit) with the time resolution 0.5 ns is achieved using the supply voltage of 5 V. The minimum pulse interval that can be measured is 55 ns (at 25°C). The reference clock used is 2 MHz. The number of transistors is 15, 000 and the chip size is 3.5 mm × 3.8 mm. The constructed LSI is composed totally of digital circuits. The operation is robust against the environmental condition, and a stable operation is realized for the ambient temperature of −35 to 140°C.
Low‐profile filter using open disk dual‐mode dielectric resonators
Authors: Ishikawa Youhei , Hidaka Seiji , Ise Tomoyuki , Matsui Norifumi
Published: July 2007

In this paper, a low‐profile filter using an open circular dual‐mode dielectric resonator is proposed as a filter for a mobile communication base station. The basic configuration of the dielectric resonator consists of two dielectric disks with electrodes on both sides stacked in the axial direction; they are installed in a shielded cavity. The doubly degenerate fundamental mode has an electric field parallel to the axial direction of the dielectric disks, and the resonator can be made low profile without significantly changing the resonant frequency. The equivalent circuit of the dual‐mode resonator is given in terms of a ring‐shaped transmission line with its electric length of 2°. The equivalent circuit of the multistage filter using this resonant circuit can be designed by the Chebyshev filter design method. A six‐stage filter with the center frequency of 985 MHz and the passband width of 10 MHz was fabricated. The results agreed well with those of the simulation. The insertion loss at the center frequency is 1.3 dB, and the external dimensions are 158 × 54 × 23.5 mm.
Bleustein‐Gulyaev‐Shimizu wave resonators formed on ceramic substrates and their applications
Authors: Morozumi Kazuhiko , Kadota Michio
Published: July 2007

In 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 of 3.7 MHz.
Spontaneous emission behavior and its injection level dependence in three‐dimensional microcavity surface emitting lasers
Authors: Hamano Tetsuko , Iga Kenichi , Baba Toshihiko
Published: July 2007

Vertical‐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 optical characteristics.
A coding and decoding method of track address with viterbi decoding
Authors: Hayashi Nobuhiro
Published: July 2007

As 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 time.
An ultrabroadband monolithic lossy match power amplifier using prematching circuits
Authors: Itoh Yasushi , Mochizuki Mitsuru , Nii Masatoshi , Kohno Yasutaka , Takagi Tadashi
Published: July 2007

This paper describes the design, fabrication, and performance of wideband monolithic lossy match power amplifiers employing prematching circuits, which make the frequency‐dependence of input and output impedance of FETs small. First, it is shown theoretically that a wide bandwidth can be achieved by using prematching circuits in the design of lossy match power amplifiers. Second, a novel constant‐resistance network and a parallel resonant circuit are proposed as prematching circuits. Impedance matching methods using prematching circuits are also described. Finally, by employing these prematching circuits in the design and fabrication of a C∼K band‐power amplifier, it is experimentally shown that the impedance matching methods using prematching circuits are useful in the design of wideband lossy match power amplifiers. The amplifier exhibits a linear gain of 10 ± 2.3 dB, a saturated power of 28.3 ± 1 dBm, and a drain efficiency of 12.6 ± 2.2 percent over 5∼21 GHz. These measured performances are in good agreement with the calculated results. The prematching circuits, which make the frequency‐dependence of input and output impedance of FETs small, are useful for achieving a wide bandwidth of lossy match power amplifiers. In addition, the parallel resonant circuit, which comprises only reactive elements, is also useful in the design of output matching circuits for achieving high gain and high power.
Design of dielectric multilayer bandpass filters using fundamental thickness of layers
Authors: Wakabayashi Isamu , Miyauchi Kazuhiro
Published: July 2007

The general design principle of the dielectric multilayer bandpass filters proposed by the authors is applied to the case where only the fundamental thickness of dielectric layers are used. The actual design procedure, layer structure, necessary formulation in the design, conditions, and design examples are presented. Further, with respect to various combinations of the parameters, 900 filters are designed and their characteristics are verified to show the distribution of their design errors.

In actual designs, the objectives are third‐, fifth‐, and seventh‐order Butterworth and Chebyshev filters (0.5‐dB and 1‐dB ripples) using SiO2 and TiO2 and the center wavelength of 1.3 μm. The percentage bandwidths are taken to be up to 10 percent with angles of incidence up to 30 deg with P or S polarizations.

It is understood that, when the bandwidth is set to be less than 5 percent or when it is set in the range of 5 to 10 percent, it is possible to achieve designed filters with percentage bandwidth errors below 1 percent and 3 percent, respectively. In all Butterworth filters, the insertion loss at the center wavelength was below 0.04 dB. For the objective ripple in Chebyshev filters set at 0.5 dB, the maximum ripples of all filters distribute within 0.15 to 2 dB while, in the case of 1‐dB objective ripple, they are in the range from 0.4 to 2.3 dB.
The analysis of polarization‐insensitive characteristics for semiconductor optical amplifiers with tensile strained multiple quantum wells
Authors: Takaya Hironobu , Kambayashi Toshio
Published: July 2007

In this paper, the aims of our study are to analyze the gain of semiconductor optical amplifiers with tensile strained multiple quantum wells and to examine the structure for polarization‐insensitive characteristics for the purpose of showing the design guidelines. Since lasers with conventional lattice‐matched multiple quantum wells have large optical confinement coefficient and large gain coefficient for TE mode, they are not polarization insensitive. Since the modal gain is the product of the optical confinement coefficient and the gain coefficient, the elimination of polarization sensitivity requires increasing the gain coefficient for the TM mode by applying the tensile strain to the well layer in order to compensate for the difference in the optical confinement factor. Assuming a multiple quantum well structure, the analysis obtains the strain distribution over the structure and an envelope function of the wave function and calculates the gain using a density matrix method by electron relaxation effect. It includes the band mixing effect of valence bands. As a result, a structure with little modal gain difference over a wide range at 1.55‐μm wavelength has been designed. Also, as a result of examining the effect of deviation from the designed values, it has been found that the variation in the material composition (amount of strain) has a larger effect on the modal gain difference than the variation in the quantum well thickness.
High‐frequency analysis of radiation field excited by incident whispering‐gallery mode over concave‐to‐convex boundary
Authors: Goto Keiji , Ishihara Toyohiko
Published: July 2007

An asymptotic method of analysis is studied for the radiation field when the lowest‐order whispering gallery (WG) modes propagating from the concave side of the concave‐to‐convex boundary with a variable radius of curvature are radiated into the free‐space on the convex side. The modal ray congruences of the WG mode are radiated into the free space after being converted to geometrical rays. Both the caustics and the shadow boundaries are created in the space. As the expression of the radiated field near the caustic, the modal rays incident into the concave part are used for deriving the physical optics integral.

By applying the high‐frequency asymptotic analysis in the case of two saddle points closely spaced to the evaluation of the integral, the uniform asymptotic solution was derived. Also, as the radiating field on the sufficiently shadow side of the caustic, the complex ray solution was derived. On the other hand, as the radiating field in the transition region near the shadow boundary caused by the convex region, an asymptotic solution was derived in the form of an extension of the conventional UTD (Uniform GTD) to the case where the geometrical ray converted from the modal ray is incident to the boundary. The numerical results obtained by various asymptotic expressions are compared with the reference solution and the geometrical optics figure drawn by the modal ray tracing. The effectiveness of the asymptotic solution and the propagation and radiation phenomena of the WG mode were derived.
Vibration mode analysis of piezoelectric‐ceramic cylinder vibratory gyroscopes with interdigital electrodes
Authors: Abe Hiroshi , Yoshida Tetsuo , Nakamura Kiyoshi
Published: July 2007

Using the deviation of vibration mode axes from their ideal positions, an equivalent circuit is introduced for bending mode‐based cylindrical piezoelectric ceramic vibratory gyroscopes which have interdigital electrodes for both driving and detection. By comparing experimentally determined impedance characteristics with numerically simulated impedance characteristics, it is possible to estimate shifts in a vibration mode axis of a resonator. Furthermore, it is possible to design a high‐performance vibratory gyroscope that produces no output voltage even when it is not subjected to an angular velocity by degenerating two vibratory modes. This degeneracy can be induced by laser machining a groove at the high‐frequency vibration mode axis.
Effects of deposition rate control process on the adhesion of evaporated aluminum films
Authors: Kobayashi Fumitoshi , Nomura Akio , Kano Tetsuo
Published: July 2007

Effects of the deposition rate control process were investigated by measuring adhesion strengths of Al films using the scratch test method. The Al films tested were deposited on glass substrates. The results indicate that the adhesion strength depends strongly on the deposition rate and increased by a factor of three when the deposition rate was increased from 1 nm/s to 10 nm/s. When the deposition rate was accelerated at a constant acceleration rate of 0.01 to 0.05 nm/s2, the adhesion strength was constant regardless of the acceleration rate and the final deposition rate used. Effects of the two‐stage evaporation process also were investigated. In the two‐stage evaporation process, the initial deposition rate was set at a constant value of 1 nm/s. Subsequent deposition rates used were 3 nm/s, 6 nm/s, and 9 nm/s. The thickness ratio of the initially evaporated films to subsequently evaporated films was varied. The results indicate that the adhesion strength decreased with increasing thickness of the initial film. However, when the thickness of the initial film reached 50 nm, the adhesion strength was no longer affected by the subsequent films. Microstructural analyses of the evaporation film indicate that the films with higher adhesion strength had larger particle size.
orientation measurement of Al(111) planes in Al‐Si‐Cu interconnection layers by the image‐plating glancing‐angle x‐ray diffraction method
Authors: Kitamura Taira , Hara Tohru , Okuda Tomohisa , Shinada Kiyotaka , Kino Yosihiro
Published: July 2007

The orientation of Al(111) planes in Al‐Si‐Cu interconnection layers is determined precisely by the image‐plating glancing‐angle X‐ray diffraction measurement technique. Contrary to the results obtained by the conventional X‐ray diffraction method, the Al(111) planes are tilted randomly at axial angles between 0° and 16°. A 50‐nm thick layer has a large number of nuclei which were rich in Cu and has an average grain size of 0.12 μm. Furthermore, the Al(111) planes are oriented parallel to the substrate surface. However, the grain size increased with increasing film thickness and reaches a grain size of 1.10 μm. In addition, the Al(111) planes are determined to be tilted at random.
Blue‐light emitting vacuum fluorescent display using Te‐doped ZnS phosphors
Authors: Araki Hiroyuki , Kanie Hisashi , Nagano Mashiro , Sano Masatoshi , Yonezawa Yoshihisa
Published: July 2007

Zinc sulfide (ZnS), which is one of the wide‐gap II‐VI compound semiconductors, has been used as the blue phosphor for vacuum fluorescent displays (VFD). Because the ZnS phosphor has a high resistivity, it is usually mixed with a conductive powder such as In2O3. ZnS crystals grown from Sb2Te3 solutions showed a blue emission at room temperature due to the Te impurities (the isoelectronic centers of the Te‐Te pair) and had relatively low resistivities (about 105 Qcm), due to the presence of Sb impurities. The VFDs prepared directly from these crystals as phosphors without use of conductive powder were investigated. The VFDs emitted light at an anode voltage higher than 15 V. The luminance increased linearly with the anode voltage. For VFDs employing crystals with 0.2 at.% Te, the luminance was 530 cd/m2 and the luminous efficiency was 0.30 lm/W at an anode voltage of 60 V. The emission had a peak at 460 nm and a chromaticity coordinate of (0.15, 0.15) that was independent of the anode voltage. The luminance decreased with increasing temperature and at 80°C was 3 percent of that at 25°C. The luminance and the luminous efficiency improved with increasing Te concentration in the phosphor crystal.
Analysis of electrical characteristics of anodic foils with tunnel pits for electrolytic capacitors
Authors: Nakamura Jin , Maeda Takao
Published: July 2007

In the electrolytic capacitor, the tunnel pits of the anodic foil provide most of the overall capacitance and it is important from the viewpoint of analyzing the essential characteristics of the capacitor to investigate the mechanism inside the tunnel pits. The purpose of this paper is to promote such an understanding and to present a new analysis of the principle and the actual situation of the tunnel pits. First, the internal state of the pit in the normal operation is assumed. Then, a new parallel distributed C‐R equivalent circuit is presented based on the path resistance concept related to the existence probability of the movable charge. By analyzing the characteristics of the equivalent circuit, the characteristics inside the pit can be estimated.

It is shown that the path branch (1) of the charge moving between the infinitesimal oxide layer adjacent to the deepest part of the pit and the pit entrance has tan δ, which is approximately 1.5 times the reference * tan δ of the pit. It is proposed that the relation between tan δ, and the tan δ specification anticipated in the pit should be used in the decision of the limit f (frequency). The equation for the forementioned decision is simple in that it is composed of basic factors but meets most of the requirements, and it is expected to be useful in estimating the internal state.

Next, the basic equation for the internal impedance Z of the pit is derived in a reasonable way, in comparison to the known typical expression for Z. It is shown that the existing expression has a complicated error. The relation between the decision expression for the limit f and the new expression for Z is clarified, and they are shown to complement each other. In other words, the framework for the analysis of the inside of the pit is now completed. The result also provides a new knowledge as to the analysis of the general distributed circuit.
Control of magnetostrictive vibration of amorphous ribbons by magnetic patterns
Authors: Asuke Naoshi , Namikawa Tatsuru , Yamazaki Yohtaro
Published: July 2007

A contactless readable medium using a combination of amorphous magnetostrictive ribbon and semihard magnetic material has been investigated. The data are recorded onto the semihard magnetic material, whereas the readout utilizes the fact that the appearance of higher‐order resonant peaks of the magnetostrictive vibration of the ribbon by the application of an ac magnetic field can be controlled by the leakage magnetic flux from the semihard material.

The effect of the leakage magnetic flux generated during longitudinal magnetic recording on the semihard magnetic material by MIG head as a localized bias magnetic field has been examined.

The results of using a direct magnetic field from a pair of single‐pole heads as a localized bias magnetic field has been further examined; determination of wavelength recorded on the semihard magnetic material also has been done. As a result of observing the power spectrum in the ac magnetic field of the medium combining amorphous magnetostrictive ribbon (Metglas 2826 MB) of 80 × 5 × 0.04 mm3 and semihard magnetic material (CuNiFe alloy) of 100 × 10 × 0.2 mm3, the resonant peak of the amorphous magnetostrictive ribbon has been almost individually detected from the second to fifth orders corresponding to the recorded magnetization patterns.
Device characteristics of MOSFETs with self‐aligned punch‐through stopper structure
Authors: Umeda Kazunori , Hisamoto Digh , Nagai Ryoo , Kimura Shinichiro
Published: July 2007

Self‐aligned punch‐through stopper (SPS) MOSFETs are made using high energy ion implantation; punch‐through stopper (PTS) layers are formed after gate electrode delineation. The SPS structure features: 1) a retrograded PTS layer with a gradually increasing impurity profile; and 2) a relatively lower impurity concentration around the source and drain region. These characteristics of the PTS structure permit both junction capacitance reduction and adjustment of threshold voltage (Vth) (specifically, a reducedVthand suppressed reverse short‐channel effect) and improved current drivability, short‐channel characteristics, and hot‐carrier immunity. The proposed structure is also effective in reducing process steps because only one implantation is needed to adjust the profile.
0.15‐μm n‐n gate CMOS technology with channel selective epitaxy and transient enhanced diffusion suppression
Authors: Abiko Hitoshi , Ono Atsuki , Ueno Ryuuichi , Masuoka Sadaaki , Shishiguchi Seiichi , Nakajima Ken , Sakai Isami
Published: July 2007

An n‐n gate CMOS process with a minimum gate length of 0.15 μm was developed. By means of the epitaxial channel and the transient enhanced diffusion suppression, a shallow buried‐channel layer was realized. It is shown that there is an optimal thickness of the buried‐channel layer that maximizes the drain current, and that theVtstability is higher in the pMOS in which the channel is fabricated by epitaxy than the conventional pMOS fabricated by channel ion implantation. When the gate poly‐Si and the silicon layer selectively grown on the SD were silicide‐reacted with titanium, a low‐resistance gate electrode with an 0.15‐μm width and the low‐leak SD diffusion layer was realized. From the transistor characteristics obtained in the experiment, the circuit characteristics were simulated. It was found that the delay time of the inverter was 21.5 ps.
A device simulation of the BBT effect in flash memory cells and implications for the development of high‐reliability memory cells
Authors: Hayashi Takahisa , Fukuda Koichi , Ohno Morifumi , Nishi Kenji , Kita Akio
Published: July 2007

In order to analyze the BBT (band‐to‐band tunneling) phenomenon in flash memory cells by simulation, a new model is proposed, which improves on the BBT model by introducing the concept of “average electric field.” This model agrees well with the measured results in a wide drain N‐concentration range. Using this model, the reliability of memory cells is analyzed. It is found that the difference of the amount of BBT generation does not directly affect the endurance characteristics but does affect the disturb characteristics. The same model can be used to analyze problem points of the present cells and to estimate the BBT current of next‐generation devices accurately.
Design of switched‐capacitor oscillators composed of three phase‐shifters
Authors: Miyazaki Tomoyuki , Nomiyama Teruaki , Horie Yuuji , Yoshida Hiroshi
Published: July 2007

The 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 analytical results.