bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple model for evaluating offset error characteristics in CMOS autozeroed chopper‐type comparators
Authors: Tsukada Toshiro , Matsuura Tatsuji , Imaizumi Eiki
Published: July 2007

A circuit technique is proposed for reducing the offset voltage due to feedthrough charges from the MOS switches in the CMOS autozeroed chopper‐type comparators. However, unavoidable offset voltages are generated if many comparators of this kind are grouped in an array for parallel operation, as is the case for flash analog‐to‐digital (A/D) converters. Using a simple model to analyze the offset generation mechanism and characteristics, simple equations are derived that give the offset errors in terms of the array current and parasitic resistances in the power supply lines. These equations are useful for comparator array design.

CMOS autozeroed chopper‐type comparators are used as high‐speed comparators for such applications as flash A/D converters. These comparators have a relatively small offset error voltage due to their autozeroed operation. They occupy a small area and operate from a low power supply voltage because most of their logic circuitry is digital. However, the comparator offset voltages generated by the feedthrough charges from the MOS switches, which are used for the autozeroing (AZ), must often be reduced for implementation. The authors have developed a technique to reduce the offset voltages caused by the feedthrough charges from the AZ switches.
Substrate temperature and post‐annealing effects on perpendicular anisotropy of Ba‐ferrite films with excess iron ions
Authors: Hiratsuka Nobuyuki , Tojo Satoshi , Koshikawa Eiichi , Fujita Minoru
Published: July 2007

In forming barium‐ferrite films by RF magnetron sputtering, a film structure is dependent on the substrate temperature (TS) when the Fe/Ba atomic ratio in the film is between 15 and 16, i.e., the c‐axis is oriented perpendicularly to the film surface, parallel to the film surface, or it is isotropic.

The deposition temperature dependence of the crystalline orientation was investigated by evaluating the crystalline phase and structure during heat treatment. The film deposited at room temperature (TS = RT) contained a large amount of Fe2+ prior to heat treatment, where Fe2+ was randomly distributed. When this film was annealed, oxygen diffused into the film and ferrite was formed at low temperatures with a c‐axis parallel to the film surface. As TS increased, the amount of Fe2+ in the film decreased and crystalline {110} FexO was formed. When this film was annealed, the temperature at which barium ferrite formation began increased and the c‐axis was isotropic. When a film was sputtered at TS = 750°C, {111} FexO was already formed in the as‐deposited film. When this film was annealed, FexO was transitionally transformed to Fe3O4, which dissolved into barium‐ferrite; the c‐axis was oriented in a direction perpendicular to the film surface.
Millimeter‐wave AlGaAs/InGaAs heterojunction finite‐element monolithic microwave integrated circuit oscillators
Authors: Funabashi Masahiro , Ohata Keiichi , Onda Kazuhiko , Inoue Takashi , Hosoya Ken'Ichi , Maruhashi Ken'Ichi , Kuzuhara Masaaki
Published: July 2007

V‐band and Ka‐band oscillators have been developed using monolithic microwave integrated circuits (MMICs). The active elements employed are AlGaAs/InGaAs heterojunction finite element transmitters (FETs) with a 0.15‐μm T‐shaped gate. The oscillators were designed with a series feedback circuit with capacitive stubs at the FET source side for generating negative resistance and a resonance circuit at the gate side.

MMIC prototypes have power outputs of 4.5 dBm for a V‐band oscillator (fosc= 50.5 GHz) and 6.7 dBm for a Ka‐band oscillator (fosc= 30.6 GHz). The phase noise for the V‐band oscillator is ‐97 dBc/Hz (1 MHz off‐carrier), which is relatively small for a free‐running oscillator.
A tunable oscillator using magnetostatic forward‐volume wave resonator with wide strip transducer
Authors: Asao Hideki , Oh‐Hashi Hideyuki , Ohwada Tetsu , Members Osami Ishida
Published: July 2007

It is shown theoretically and experimentally that a tunable oscillator without spurious oscillations can be obtained by using a magnetostatic forward‐volume wave resonator with wide strip transducers. First, the equivalent circuit of a rectangular resonator is presented and the unloaded Q and the external Q are expressed in terms of the dimensions and the material constants of the resonator. By means of this expression, the condition is derived for selective excitation of the dominant mode and for suppression of the higher‐order modes. A 5‐GHz tunable oscillator using this resonator was fabricated. It was demonstrated that stable oscillation characteristics without spurious oscillations can be obtained.
Analysis of frequency characteristics of dielectric waveguide discontinuities using finite difference‐time difference method
Authors: Taira Midori , Morita Nagayoshi
Published: July 2007

The frequency characteristics of several discontinuous shapes in a dielectric slab waveguide have been studied numerically by means of the finite difference‐time difference (FD‐TD) method. First, an excitation method of the incident mode field suitable for the FD‐TD calculations is presented in detail and the numerical accuracy of the method is discussed. For the step and bent discontinuities, the transmission and reflection coefficients derived by the FD‐TD method are compared with rigorous values. It is confirmed that sufficient accuracy is guaranteed. Next, for the discontinuities such as step, gap, slope, crank, axial offset, and sharp bend, the frequency dependence of the transmission coefficient is studied; both amplitude and phase are investigated. Finally, with a simple model of the quadriphase‐shift keying (QPSK) modulated wave, the discontinuity transmission characteristics are examined.
A loaded‐line phase shifter with series transformers
Authors: Matsunaga Makoto , Katagi Takashi
Published: July 2007

A series transformer‐type loaded‐line phase shifter is proposed in which an impedance transformer is connected in series with a main line. The circuit configuration, a design method, and the test results are described. First, the matching condition and the relationship between the circuit parameters and the required phase shift are shown in the case where the switching semiconductor devices have dissipated. In addition, a design method is presented which determines the loss balance between the two‐phase states and the frequency dependence of the phase shift at the center frequency. The semiconductor loss characteristic to this phase shifter is expressed in terms of the figure of merit (switching cutoff frequency) of the semiconductor device for switching. The peak power handling capability of the phase shifter determined by the breakdown voltage is studied.

Based on these investigations, a 90‐degree PIN phase shifter was designed by the present method in the L band. The loss balance at the center frequency was 0.22 dB, and the phase‐shift error was less than 4 degrees at the relative bandwidth of 8 percent. These values are close to those in the design. Hence, the effectiveness of the present phase‐shifter format and the design method was confirmed.
A fin line diode switch with coupled strip conductors
Authors: Matsunaga Makoto
Published: July 2007

A design method and experimental results of a new‐type fin line diode switch using coupled strip conductors as matching elements are described. A diode and the strip conductor electromagnetically coupled with fin line are connected in shunt. By introducing coupled conductors, the forward biased diode impedance can be made low but the reverse biased diode impedance is high; so the broad band characteristic of the fin line switch with only one diode can be realized. In this switch, in order to get the greatest bandwidth, the parameters of the microstrip line switch consist of the strip conductor, the dielectric substrate, and fin conductors are uniquely determined. The validity of the design method is verified by measuring the experimental single and two‐stage SPST switches at W‐band.
Finite‐difference beam propagation method using the oblique coordinate system
Authors: Yamauchi Junji , Shibayama Jun , Nakano Hisamatsu
Published: July 2007

Until now, the rectangular coordinate system has been used mainly for the analysis of optical beam propagation. Hence, when a tilted waveguide is analyzed, the core shape is expressed by a stepped approximation which causes the quantization error so that the error accumulates as the field propagates.

In this paper, with a view to overcome this problem, the finite‐difference beam‐propagation method is proposed in which the oblique coordinate system is employed. To confirm the effectiveness of the method, the propagation error of the fundamental mode is evaluated by the model mismatch loss in a tilted step index slab waveguide. It is found that the mode mismatch loss is kept low as the quantization error in the rectangular coordinate system is now eliminated. Further, as an example of application of this method, an optical waveguide bend is analyzed and the effects of coherent coupling are investigated. It is pointed out that the computational region can be made narrower in this method compared with that required in the rectangular coordinate system.
Estimation of higher‐order modes using prony's method in the finite difference‐time difference method
Authors: Hyodo Ken‐Ichi , Sasaki Masahiro , Kashiwa Tatsuya , Tagashira Hiroaki
Published: July 2007

One of the characteristics of the finite difference‐time difference (FD‐TD) method, which is a three‐dimensional time domain analysis technique for the electromagnetic field, is its ability to obtain broadband frequency characteristics by one calculation if the pulse response waveform is Fourier transformed. However, in the system where higher‐order modes may be generated, it is not possible to obtain the frequency characteristics with this procedure. A new method to cope with this problem is proposed here. This method consists of the conventional Fourier transform and Prony's method used in signal processing. The proposed method can be applied to a system containing an arbitrary number of modes. In this paper, as an example, the method is applied to a waveguide discontinuity problem so that the validity and effectiveness of the method are confirmed.
Vector finite‐element method based on use of hybrid edge elements and its application to three‐dimensional electromagnetic waveguide‐discontinuity problems
Authors: Nomura Yoshinori , Tsuji Mikio , Shigesawa Hiroshi
Published: July 2007

As a method for eliminating the spurious solution in the finite element analysis of three‐dimensional waveguide discontinuity problems, the use of linear edge elements is most effective. However, the shape of the element has been limited to rectangular blocks and tetrahedral bodies.

In this paper, a vector finite element method using triangular‐prism elements is proposed and a formulation for three‐dimensional waveguide discontinuity problems is carried out based on this method. The present triangular‐prism elements can be used with a mixture of different edge elements so that the element division can be made highly efficient. The numerical examples demonstrate that the spurious solutions can be eliminated by using the triangular‐prism elements as other edge element methods and also the hybrid use of edge elements provides a substantial reduction in the number of unknowns compared to the conventional analysis of using only one type of edge element.
TE‐TM mode switching in tensile‐strained quantum‐well lasers induced by an electric field
Authors: Ogawa Matsuto
Published: July 2007

By inserting a strain into the active layer of quantum‐well lasers, the functionality of the laser can be improved. Regarding the valence band structure of the strained quantum‐well laser with an external electric field applied, a multiband‐effective‐mass theory is developed in which the band‐mixing effect of the valence band including the spin‐split off interaction is taken into account herein. Further, the present method is applied to the gain calculation of the TE and TM modes in a strained quantum well laser. As a result, it is found that the switching operation from the TE mode to the TM mode of the induced emission is possible with an external electric field.
A new pipelined decoder of error‐correction codes for a sync‐out data sequence of digital VTRs
Authors: Nakase Junko , Doi Nobukazu , Nakatomi Toshiji
Published: July 2007

The error‐correcting decoder is designed assuming that the input data have a constant data length. In the case of digital video technology recorders (VTR), however, there is a possibility that the length of the playback data sequence changes by desynchronization.

This paper proposes an independent reset‐type error‐correcting decoder that can cope with the playback data sequence with varying data length. In the independent reset method, the signal indicating the end of processing in the operational block composing the pipeline is used as the reset signal for the operational block in the next stage. By this mechanism, a sufficient time for the operation is secured for each operational block, even if the data length of the input data varies.

By applying the proposed method to the D2 digital VTR system, the miscorrection probability is examined. It is then shown that the miscorrection probability can be decreased compared to the conventional method, both in the normal and the special playback.

Using the proposed independent reset method, the error‐correcting LSI decoder based on the Reed‐Solomon code is constructed. LSI is shared by the decoding processes of the inner and the outer codes of D2 system. LSI is designed so that up to 4 Bytes can be corrected for both random error and erasure corrections. The additional circuit complexity due to the independent reset mechanism is several percent of the whole LSI.
Analysis of a very low‐level DC current amplifier with allowance for the distributed ground capacitance of a high‐ohmage feedback resistor
Authors: Nakamura Ikuo , Shimoji Toshihiko , Nakada Tsuyoshi , Higa Hiroki
Published: July 2007

When the response speed of a very low level dc current amplifier is increased with a shield, especially with a shielding pipe of small diameter, distortion of its output waveform increases. To elucidate the phenomenon, the new concept of distributed ground capacitances, in addition to the stray capacitances across the terminals of the high‐ohmage resistor, is taken into consideration for the circuit analysis. This paper shows that the output waveforms of the very low level dc current amplifier are distorted when Cin < KCa (where Cin, K, and Ca are the effective input capacitance, the amplification of the high‐input‐resistance amplifier and the distributed capacitance to ground, respectively) and that the distortion on its output waveforms is mainly caused by Ca.
Optical soliton switching and coupled‐soliton propagation in three‐core fiber nonlinear directional couplers
Authors: Sotobayashi Hideyuki , Fujii Yoichi
Published: July 2007

Optical switching by nonlinear directional coupler has the problem of waveform collapse. It is known that using optical soliton pulse can avoid large waveform collapse.

In this article, numerical analysis was performed for optical switching characteristics of optical soliton coupling and propagation by three‐core fiber nonlinear directional couplers. As a result, in case where multiple optical soliton pulse signals were input, it is possible to change the switching characteristics (phase‐controlled switching) by controlling relative phase difference between signals. The concept of coupled soliton in coupled nonlinear waveguide was proposed and the formation condition was discussed.
Analysis of electromagnetic fields using the finite‐difference time‐domain method in a microwave oven loaded with high‐loss dielectric
Authors: Iwabuchi Koji , Kubota Tetsuo , Kashiwa Tatsuya , Members Hiroaki Tagashira
Published: July 2007

There are few examples for three‐dimensional electromagnetic analysis for a high‐loss dielectric water load which has one of the highest relative permittivities of 80.4 among food items placed in a microwave oven. In this paper, the three‐dimensional finite‐difference time‐domain (FD‐TD) method is used for the analysis of the electromagnetic field inside the water load. In the fundamental investigation using the high‐loss dielectric loaded rectangular waveguide, it is confirmed that the FD‐TD numerical results with Yee's cell pitch which is set at about one‐tenth the wavelength reduced within the dielectric, agree almost with the exact solution based on the transmission theory. After the confirmation of the validity, the electromagnetic field within a water load placed on a metal turntable is analyzed. The water load has a cylindrical shape with a diameter of 64 mm and a height of 80 mm. As a result, the reduction of heating unevenness by the turntable can be predicted visually and quantitatively. In this analysis, the steady‐state solution can be obtained after 300 iterations while the heating pattern is stabilized after 100 to 200 iterations.
The influence of interdiffusion of metals in an evaporated multilayer metallization on the adhesion of an Sn‐Sb solder
Authors: Kurihara Yasutoshi , Hosokawa Takashi , Saitoh Ryuichi
Published: July 2007

The influence of heat treatment of Al‐Cr‐Ni‐Ag multilayer metallization on the nonuniform wetting of an Sn‐Sb solder was investigated. The goal was to obtain highly reliable semiconductor power devices by improving solder adhesion. Increase in thermal resistance after thermal fatigue testing is attributed to the nonuniform wetting of the solder to the semiconductor chips, which caused thermal stress to concentrate on the wetted regions and promoted the selective cracking of these regions. The heat treatment of the multilayer metallization at 500°C caused Al (the bottom layer) diffusion to the surface of the Ag layer. Al exposed to the surface prevented uniform wetting of the solder and caused poor wetting.
Optical time‐division multiplexing scheme for fiber‐optic millimeter‐wave radio system
Authors: Harada Hiroshi , Komaka Shozo , Tsukamoto Katsutoshi , Morinaga Norihiko
Published: July 2007

In fiber‐optic millimeter‐wave radio systems using conventional subcarrier multiplexing (SCM) scheme intermodulation distortion caused by the nonlinearity of electrooptic conversion is a serious problem in signal transmission. Laser diodes used as light sources have difficulties handling very high millimeter‐wave frequency due to their limited modulation bandwidth. A new fiberoptic millimeter‐wave radio system proposed here can provide higher received carrier‐to‐noise ratio (CNR) than the SCM scheme and also eliminate the effect of intermodulation distortion. In the proposed system, radio signals are sampled and transmitted through a fiber‐optic link using a time‐division multiplexing (TDM) scheme but maintaining the analog information of the radio signal. Since a radio frequency pulse train with TDM format is transmitted on the fiber‐optic link, it is easy to modulate directly the laser diode and no intermodulation distortion will be produced. The theoretical analysis results on transmission performance show that the received CNR of the proposed scheme is about 7 to 10 dB better than that of the SCM scheme.
Short‐time reproduction characteristics of the parametric magnetic tape recorder
Authors: Karasawa Koichi , Member Yorimoto Tanno , Mikoshiba Takashi
Published: July 2007

A parametric magnetic reproducing head consists of a reproducing head and a time‐variable capacitor connected in parallel. It is a flux response‐type head. The amplitude of the output voltage is independent of the signal frequency and proportional to the signal field. In this paper, magnetic tape recorder configuration and characteristics for low‐frequency signals with this head are described. It is also reported that this recorder is suitable for long‐time recording and short‐time reproduction. It is clear that it has excellent characteristics at a low‐frequency range and is very useful for the application of long‐time recording and short‐time reproduction of an ultralow‐frequency signal.
Electron wave propagation in potential structures with δ‐type potentials
Authors: Sanada Hirofumi , Ren Jie , Nagai Nobuo
Published: July 2007

With the recent advances in fine‐structure fabrication technology for semiconductors, it is now possible to fabricate a potential structure in which the wave nature of the electrons can be utilized. The wave phenomena caused in such structures are important as they become the operating principle of the device making use of the quantum effect. Therefore, much research has been carried out for the behaviors of the electron waves in potential structures with various shapes.

In this paper, the behavior of the electron waves in a one‐dimensional potential including a δ‐type potential is analyzed by means of the equivalent circuits. In addition, the synthesis of the transmission characteristics by making use of this method is investigated. By carrying out synthesis of the resonant levels in a single barrier structure and a structure containing δ‐type potentials in a double barrier, the resonant characteristics are compared with those obtained from the conventional double barrier and quadruple barrier. Further, a synthesis of an electron wave filter is studied by means of a structure made of δ‐type potentials placed regularly in a flat potential. It is shown that a similar transmission characteristic can be synthesized with a simpler synthesis procedure than the method in which a multilayer combination of quarter‐wavelength layers is used.
Calculation of electrostatic field in an electrophotographic development zone
Authors: Imada Hiroshi , Kiwakim Hisatomo
Published: July 2007

It is important to measure the electrostatic field in the electrophotographic development zone in designing copying machines. Since this zone is of a complex structure, no measurement method has been established and, hence, it is difficult to analyze this zone.

In this paper, new equations to obtain the electrostatic potential and field in the development zone are obtained. In formulating the equations, it is assumed that the electrophotographic development zone was composed of four layers, that is, an electrically conductive substrate, a photosensitive layer, a development space, and a development electrode. For analysis, a charge distribution having a figure similar to a resolution test chart was assumed to be present on the photosensitive surface. In addition, an image charge which satisfies the boundary condition was taken into account.

Using this method, the electrostatic potential and electric field distributions in the development zone could be evaluated when a square wave‐shaped charge with an arbitrary spread and charge density distribution was applied. Of course, this method could be applied to the case where the charge had an arbitrary shape. Moreover, this method is more precise than the finite element method. In addition, the software for this method can easily be developed and the calculation time is extremely short.
Development of single‐layer positive resist process for electron beam direct writing technology
Authors: Yamaguchi Hidenori , Sakamizu Toshio , Murai Fumio , Shiraishi Hiroshi , Hayakawa Hajime , Hasegawa Keiko , Okazaki Shinji
Published: July 2007

A single‐layer resist process using a high resistivity positive resist by solubility reversal (PSR) for electron beam direct writing is described. Conventional PSR designed for mask creation is found to have inhomogeneous dissolution characteristics due to a side effect during the stage of deprotection reaction. To overcome this problem, the efficiency of dissolution inhibition is improved by controlling the composition of base resin materials. Using an optimized base resin structure, 0.4‐μm contact window patterns were successfully delineated in a 1.6‐μm thick single‐layer with a sensitivity of 3.5 μC/cm2. The dry etching durability of a single‐layer PSR was also examined and a high level of dry etching durability for SiO2 etching was observed.
Theoretical determination of equivalent circuit parameters for natural single‐phase unidirectional surface acoustic wave transducers
Authors: Inagawa Kiyoshi , Hasegawa Koji , Koshiba Masanori
Published: July 2007

This paper proposes a method for theoretical determination of the circuit parameters in the equivalent circuit for the natural single‐phase unidirectional transducer (NSPUDT), which is one type of unidirectional surface acoustic wave interdigital transducers. The finite element method was used to find the upper and lower edge frequencies of the shorted and open‐ended gratings corresponding to the shorted and open electrical terminal of the NSPUDT, the potential standing wave distribution and the static capacitance per pair of NSPUDT, needed for determination of the circuit parameters. Due to the analysis method, the anisotropy of the substrate, the electrical perturbation effect, the acoustic perturbation effect, and the energy storage effect can be taken into account. Actually, the equivalent circuit parameters of the NSPUDT on an ST‐cut 25°X‐propagation quartz substrate were computed and the reflection and excitation characteristics of the surface wave were derived. From a comparison with the experimental values, the validity and usefulness of the present method is confirmed.
Wide dynamic range digital signal processing system for a laser radar
Authors: Abo Makoto , Nagasawa Chikao
Published: July 2007

The strength of laser radar return signals from the atmosphere is inversely proportional to the square of the range so that the long‐range return signals are very weak in comparison with the short‐range signals. Thus, the dynamic range of the return signals is extremely wide. Output signals from the photomultiplier tube (PMT), the main detector in the laser radar receivers, become analog signals when the incident light is strong. However, as the incident light becomes weaker, these signals gradually change to discrete pulses. Usually, to cover their wide dynamic range, multiple signal processing systems designed for different strengths of the incidence light are used. In this paper, a new method of covering the wide dynamic range of signals, from extremely weak light to comparatively strong light, with only one signal processing system is proposed and verified experimentally. The output signals of the photomultiplier are converted to digital signals by an A‐D converter whose sampling time is equivalent to the time constant of the photomultiplier circuit irrespective of the output signal strength. Next, the mean, variance, and pulse count value are calculated from the digital signals. It is confirmed that when this method is used for actual atmospheric observations, laser radar signals with a wide dynamic range can be processed with only one signal processing system.
Electrochromic and electromotive force characteristics of electrochemical polymerization of aniline
Authors: Iida Yosinao
Published: July 2007

A polyaniline film was deposited on a mesa glass by the constant rising voltage method using electropolymerization of electrolytic solutions containing five different kinds of compositions. There were three types of relationships between the electropolymerization total charge and voltage rise speed. When the charge decreased rapidly with an increase of voltage rise speed, the deposited film had an electrochromic (EC) characteristic. When the total charge decrease was slow, the deposited film had a different EC characteristic. When the total charge did not change with an increase of voltage rise speed, the deposited film did not have an EC characteristic but potentially it had an electromotive force (emf). The EC and emf were investigated using platinum and mesa glass opposing electrodes. As a result, it was found as reported that the EC characteristic was caused not by dopant bleaching in the supporting electrolytic solution but by the formation of a quinoidimine structure generated by oxidation of a polyaniline film. When a film was composed of a polyaniline structure which was doped easily with ions during oxidation, the film had an emf.
Optical control of the printed dipole antenna
Authors: Nishimura Kazuo , Tsutsumi Makoto
Published: July 2007

This paper describes the various properties of the printed dipole antenna on optically plasma‐induced semiconductor substrates. These properties are analyzed by using the spectral domain moment method. The input impedance and radiation pattern were calculated within the plasma densities from 0 to 2.0 × 1017m−2for semiconductor silicon substrate.

Considering the equivalent circuit performance of the antenna, it is shown that the optical illumination is equivalent to loss loading to the antenna. Therefore, it reduces the input impedance and the radiation pattern also has significantly smaller amplitude compared to that without optical illumination. A half‐wavelength antenna is fabricated on a high‐resistivity silicon wafer by aluminum vapor deposition. The input impedance and radiation pattern were measured at the S band. The measured results agree considerably well with the theory.
Simple calculation method of the intermodulation distortion of multiple‐carrier amplifiers operating in weakly nonlinear region
Authors: Suematsu Noriharu , Iida Akio , Takagi Tadashi , Urasaki Shuji
Published: July 2007

Simple calculation method of the intermodulation distortion of multiple‐carrier amplifiers operating in weakly nonlinear region is presented. This method is based on the approximation that is effective when (1) the transfer characteristics of carriers are regarded as linear, and (2) the third‐order intermodulation distortion ratio versus the output power has 2 dB/dB slope. As the number of the carriersn→∞, the intermodulation distortion ratio approaches the value of 10 log10(3/2) + 6 = 7.76 dB higher than the third‐order intermodulation distortion ratio in the case of two‐carrier amplification at the same output power.
An approach to realize deep submicron multilevel interconnection using low‐resistance and low‐ϵ materials
Authors: Homma Yoshio , Kusukawa Kikuo , Furusawa Takeshi , Miyazaki Hiroshi , Kobayashi Nobuyoshi
Published: July 2007

This paper discusses techniques for improving the performance of the multilevel interconnection of deep submicron level feature sizes, through the reduction of diffusion layer resistance, contact resistance, metallization resistance, and decrease in permittivity of interlevel dielectrics, and its global planarization. Silicidation of contact hole becomes insufficient for reducing resistance when the contact hole is extremely miniaturized. Contact between metal layers, i.e., the metallized diffusion area and the metal plug, is preferable. In order to reduce signal propagation ideally in interconnection, both low permittivity dielectrics and low resistance metallization are necessary. For reducing metallization resistance, adoption of Cu metallization is suitable.

A high‐temperature Cu dry etching and a passivation technique have been developed to reduce contamination by Cu. To provide globally planarized low‐permittivity interlevel dielectrics, an organic spin‐on‐glass (SOG) material with excellent gap filling and relative dielectric constant lower than 3 was developed. Two‐level, globally planarized interconnection test devices were fabricated by applying CMP using silica slurry and a foamed fluorocarbon polishing pad.
Efficiency enhancement in a Čerenkov laser by varying permittivity—taking into consideration mode scattering
Authors: Sata Masahiro , Kamata Hisashi , Shiozawa Toshiyuki
Published: July 2007

This paper considers a model of a Čerenkov laser consisting of a relativistic electron beam and a parallel plate waveguide loaded with a dielectric thin film. By means of numerical analysis, the improvement of the growth characteristics for the electromagnetic wave and the efficiency in energy conversion is discussed. In the Čerenkov laser, the growth of the electromagnetic wave is caused by the transfer of the kinetic energy of the electron beam to the electromagnetic energy. As a result, the drift velocity of the electron beam is decreased gradually so that the synchronism with the phase velocity of the electromagnetic wave cannot be maintained and an efficient transfer of energy is prevented. Thus, the permittivity of the dielectric material composing the waveguide is increased gradually along the direction of the propagation for the electromagnetic wave to reduce the phase velocity of the electromagnetic wave. In this manner, the synchronism with the drift velocity of the electron beam is maintained, leading to an efficient transfer of energy. The variation of the permittivity causes power loss due to the mode scattering of the electromagnetic wave or the reflection or conversion to higher‐order modes.

In this paper, the effect of the mode scattering is taken into account for detailed numerical analysis of the amplification characteristics for the electromagnetic wave. It is shown that the efficiency in energy conversion from the electron beam to the electromagnetic wave and the amplification characteristics of the electromagnetic wave can be significantly improved.
Characteristics of polarization splitters constructed from a circular hollow pit outside the cores
Authors: Kameda Kazunori , Hosono Toshio
Published: July 2007

In this paper, a polarization splitter is proposed in which a single‐core fiber (Fiber 1) and a fiber with a circular hollow pit outside the core (Fiber 2) are coupled. Corresponding to the extraction of the two linear polarizations (x and y polarizations) from the HE11 mode excited in to Fiber 1, the polarization splitting method can be clasified into the x‐polarization type or the y polarization type. In the x‐polarization type, the x‐polarization is extracted from Fiber 1 and the y‐polarization from Fiber 2. In the y‐polarization type, the y‐polarization is extracted from Fiber 1 and the x polarization from Fiber 2. This paper discussed the structural parameters (core radius, relative refractive index difference, and core spacing), which reduce the device length of the x polarization and y polarization types and at the same time make the extinction ratio small. The main results are as follows: (1) When the relative refractive index difference of Fiber 2 was made constant, the minimum values of the device length and the extinction ratio of the x polarization type can be made smaller than those of the y polarization type. (2) When the relative refractive index difference of Fiber 2 is increased from 0.4 percent to 1.0 percent, 1 the device lengths of both the x‐ and y‐polarization types can be reduced by 0.26 times, and 2 the minimum value of the extinction ratio of the x polarization type increases +4.1 dB from ‐38.2 dB and that of the y polarization increases +4.3 dB from ‐34.1 dB.
A mini‐traveling wave tube amplifier with super‐low power dissipation for ku‐band user earth stations
Authors: Mita Nagahisa
Published: July 2007

A new traveling wave tube (TWT) is realized which can reduce the power consumption significantly in a pulse operation with a small RF duty as a typical operating mode in a small‐scale satellite communication ground station.

A method is proposed which estimates the power consumption of a multistage collector by approximating the distribution of the spent beam incident on the collector by a straight line. Based on this method, the collector is made three stages to reduce the power consumption in the RF pulsed operation. It is found that the third collector voltage should be reduced as much as possible. From this result, a TWT with a 40‐W output in the Ku band is realized which has a three‐stage collector with the third collector voltage as low as 80 V. By setting the collector voltage that makes the power consumption minimum under no signal condition, the average power consumption is reduced to only 12 W in a pulse operation with a 1‐percent RF duty.
An m‐times pulse number generating circuit based on switched capacitor bootstrap‐type monostable multivibrator and its application
Authors: Sasaki Hirofumi , Fujimoto Kuniaki , Yahara Mitsutoshi , Ueno Fumio
Published: July 2007

An m‐times pulse number generating circuit is proposed which is made of a monostable multivibrator and an astable multivibrator as well as a gate circuit constructed with a switched capacitor bootstrap circuit and an RS flip‐flop. Since this circuit has the configuration of driving the switched capacitor by the oscillation output from the astable multivibrator, there is no problem of synchronization between the circuits. Since the ratio of the output pulse number to the input pulse number is proportional to the gate voltage of the linearly varying staircase wave, the operation is extremely stable even if the output pulse number becomes large.

The output pulse number can be varied significantly by simply changing the value of the capacitor in the time constant circuit in the monostable multivibrator and can be expressed by a simple equation determined only by the circuit parameters. The computed and measured results agree well. By cascading several of these mono‐stable multivibrators, an extremely large pulse number can be obtained easily. If this is cascaded with a 1/n divider, an m/n pulse number can be obtained easily. Further, for a level comparator and a trigger generator in front of the m‐times pulse number generating circuit, the circuit can be used for conversion of the voltage level of the ac signal to the pulse number.
A thin‐film reactor fabricated on an Si‐substrate and its application to dc‐dc converters
Authors: Nishijima Ken‐Ichi , Hidaka Masahito , Yamasawa Kiyohito , Saito Akira
Published: July 2007

By means of integrated circuit (IC) process technology, a monolithic thin‐film reactor was fabricated on a silicon substrate with lamination of a thick‐film conductor and a magnetic thin film. In addition to the fundamental characteristics of the reactor, the dynamic characteristics are evaluated when the reactor is used in a dc‐dc converter. For the buck converter application, the output of more than 2 W with the efficiency of more than 70 percent is achieved.
Columnar structure in anodized porous silicon
Authors: Aoyagi Hidekazu , Motohashi Akira , Kinoshita Akira , Satoh Akinobu
Published: July 2007

Porous silicon (PS) anodized below a constant temperature, for example 12°C which depends on anodization parameters, is composed of an assemble of columnar shaped sponge like Si. The width of a column is several micrometers, and columns stand almost perpendicular to Si substrate, and the laterals of columns are in contact with each other directly. The average cross‐sectional area of columns is related to both the boron density in Si substrate and HF concentration in anodization solution, but is not related to both anodization current density and anodization temperature. The average area of a column is determined such like that only one boron atom exists in an atomic layer in a column. In samples anodized at the temperature around and above 12°C, needle and wall‐shaped unanodized crystal Si are observed at the interface between PS columns, respectively.
Reconstruction of magnetic fields by reflection electron tomography
Authors: Matsuda Jin‐Ichi , Otawa Yasuhiko , Nomizu Shigeaki
Published: July 2007

The trend in magnetic record development is toward ever higher areal storage density. Methods for accurate measurement of the magnetic field distribution in the very small region surrounding the gap of the recording head have been the focus of several recent studies. Using transmission electron beam tomography, a new reconstruction technique is proposed and applied to measure three‐dimensional magnetic stray field extending beyond a commercial magnetic head by a developed measurement system. Results have demonstrated the applicability of this technique for measuring a magnetic stray field of several kGauss with an error of less than 10 percent. With transmission electron beam tomography, however, it is difficult to measure directly the magnetic field just beyond the gap of a magnetic head. This is because the stronger Lorentz force of the magnetic field on the electron beam causes the electron beam to collide with the head surface. A new method, called reflection electron beam tomography, is presented herein to overcome the forementioned limitation in which the electron beams are injected perpendicularly to the surface of a magnetic head and their deflection vectors are measured at the deflection plane set above the head. Our method is tested with a known magnetic field model of a one‐turn coil by computer simulation. Results have shown that the magnetic field just beyond the gap of the magnetic head can be estimated with an error of approximately 20 percent.
Whispering gallery mode resonance on an elliptical dielectric cylinder
Authors: Matsubara Mari , Kogami Yoshinori , Matsumura Kazuhito , Tomabechi Yoshiro
Published: July 2007

With a view to application to millimeter wave integrated circuits, we analyze theoretically resonance characteristics of a whispering gallery mode (W.G. mode) propagating along a circumference of an elliptical dielectric cylinder. A wave equation is derived in an elliptic coordinate system and an eigenvalue equation includes Mathieu functions with a large order is obtained. Since this eigenvalue equation is an infinite dimensional determinant, we introduce a new technique to solve the eigenvalue equation. In this determinant, we pay our attention to diagonal elements that affect mainly resonance order. By means of this approach, it becomes possible to estimate a number of approximate terms of the eigenvalue equation to keep an accuracy of a resonance frequency constant even if an eccentricity of the ellipse is increased, namely the ellipse is flatter. It is also possible to find numerically the resonance frequency and electric field distribution of the W.G. mode for the elliptical cylinders with various eccentricity.
A reduced size branch‐line hybrid‐ring using coupled lines
Authors: Nagamine Shinji , Sakagami Iwata
Published: July 2007

To miniaturize the hybrid‐ring, a design method is presented herein for the circuit in which there is an electromagnetic coupling between the transmission lines in folded transmission lines. A 3‐dB branch‐line hybrid‐ring is treated. Analysis is carried out for the two cases of homogeneous and inhomogeneous circuit configurations in which each section has only one coupled line. It is found that in the circuit with a homogeneous configuration, perfect match and complete isolation hold at the center frequency as in the conventional type; additionally, the bandwidth becomes narrower as the coupling becomes stronger. In the inhomogeneous structure where the phase velocities of the even and odd modes are different, there is a shift in characteristics. An equal power division can still be accomplished if the degree of coupling and the phase shift in the coupled lines are appropriately chosen. The overall characteristics differ little from the conventional type. To confirm these findings, an inhomogeneous circuit is constructed and the results are found to agree with the theory.
Circularly polarized absolute value ray vectors in absorbing media—fundamental relations
Authors: Tokumaru Shinobu
Published: July 2007

In a nondispersive absorbing medium, a geometrical optics field using a complex eikonal is defined. The field is decomposed into two circular polarization components. If the circularly polarized electromagnetic energy fluxes are considered, it is shown that two rays can be defined for the right‐handed and left‐handed circularly polarized field, not in the sense of the energy flux (or the effective power flux), but of the absolute value of the energy flux (or the apparent power flux).

This paper presents the basic relationships such as the relationship between the eikonal and the ray vectors and the propagation equations of the ray intensities.
Extended kinetic ising model and its application to magnetization pattern relaxation
Authors: Hayata Kazuya , Higaki Hiroyuki , Koshiba Masanori
Published: July 2007

To analyze the magnetization‐pattern relaxation by the nonlinear dynamical approach, an Ising model in the time‐dependent spin system (kinetic Ising model) is extended to a space‐dependent spin field. By solving the nonlinear diffusion equation on the spin order parameter derived by this formulation, the space‐time evolution of the magnetization pattern can be traced. Specifically, the fifth‐order Ginzburg‐Landau‐type equation in the null applied magnetic field is derived.

Two kinds of nontrivial stationary solutions (lump and hole solutions) are presented. The spatial distributions of the stationary solutions are algebraic. Particularly, the lump solution is given as a square root of the Lorentz distribution. From the results of the numerical experiment, it is found that the lump solution is extremely unstable and decays very quickly whereas the hole solution is stable and is not subjected to relaxation. An approximate lump solution for many spatial dimensions is investigated as well.
Electrostatic voltage sensor using surface acoustic waves delay‐line oscillator
Authors: Ishido Masahiro , Xiao‐yan Zhu
Published: July 2007

A surface acoustic wave (SAW) electrostatic voltage sensor was fabricated using an SAW oscillator. In the electrostatic voltage sensor, the electrodes to apply electrostatic voltage and produce strain by piezoeffect are not located on the top and bottom surfaces of the substrate but rather on the propagation surface in parallel to the propagation path. Therefore, it is possible to reduce the gap spacing between the electrodes to apply an electrostatic voltage so that the sensitivity can be improved. When an electrostatic voltage is applied, the LiNbO3 single crystal and PZT ceramic were used as substrates in this experiment. The most sensitive crystal plane in a rotated Y‐X plate rotating about the X axis was obtained for LiNbO3 single crystal. It was found the result shows that the 90° rotation Y‐X plate is the best.

In the experiment, a 131° rotation Y‐X plate with 20 × 25 × 1.0 mm3 was used which is close to the derived angle and is obtained easily. The interdigital transducer (IDT) electrodes and the electrodes for applying electrostatic voltage were fabricated by Al evaporation. The characteristics of the oscillation frequency versus electrostatic voltage of the sensors were studied. The sensitivity was 0.133 Hz/V and 0.03 Hz/V for the 131° rotation Y‐X plate and a Y‐X plate in the case of LiNbO3. In the case of PZT ceramic, the sensitivity was 12 Hz/V. The dependence of the sensitivity on gap distance between the electrodes for applying electrostatic voltage and on temperature was also studied.
Controllability of gap‐filling for intermetal SiO2 deposition by biased helicon plasma chemical vapor deposition
Authors: Tamura Takahiro , Inoue Youichi , Satoh Makoto , Yoshitaka Hikaru , Sakai Junto
Published: July 2007

The gap between patterned aluminum was filled with SiO2 formed by the reaction of SiH4‐O2 gas using helicon plasma and a biased substrate. The relationship between the SiO2 deposition rate and plasma source power was investigated.

It was found that the SiO2 deposition rate was dependent on the rate of SiH4 supply and was independent of the plasma source power. The sputtering rate due to biasing the substrate decreased with increase of the plasma source power. It was found also that the sputtering rate at which void generation is suppressed could be controlled not only by the bias power but also by the plasma source power. Even when the plasma source power and bias power were set at a low level, a sufficient sputtering rate was obtained. The gap‐filling rate (the net deposition rate) was determined by the difference between the raw deposition rate determined by SiH4 supply and the sputtering rate and could be controlled by the plasma source power.