Portable Telephones Research Articles

Micro drilled ‘via holes’ in III-V semiconductors

Etching backside via-holes in III-V semiconductors is a critical step in the process of fabricating Monolithic Microwave Integrated Circuits (MMIC), used for mixing, amplification and tuning signals in portable telephones and related communications equipment.

Development of Electrode Materials for Semiconductor Devices

Recent strong demands for optoelectronic communication and portable telephones have encouraged engineers to develop optoelectronic devices, microwave devices, and high-speed devices using heterostructural compound semiconductors. Although the compound crystal growth techniques had reached at a level to control the compositional stoichiometry and crystal defects on a nearly atomic scale by the advanced techniques such as molecular beam epitaxy and metal organic chemical vapor deposition techniques, development of ohmic contact materials (which play a key role to inject external electric current from the metals to the semiconductors) was still on a trial-and-error basis. Our research efforts have been focused to develop, low resistance, refractory ohmic contact materials using the deposition and annealing techniques for n-GaAs, p-ZnSe, InP, p-SiC p-CdTe etc. It was found the growth of homo- or hetero–epitaxial intermediate semiconductor layers (ISL) was essential for low resistance contact formation. The importance of hetero-structural ISL was given taking an example of n-type ohmic contact for GaAs.

1A1-N-033 カメラ機能付き携帯電話を用いた視覚障害者支援システムの開発(ユニバーサルデザイン,生活を支援するロボメカ技術のメガインテグレーション)

1A1-N-033 カメラ機能付き携帯電話を用いた視覚障害者支援システムの開発(ユニバーサルデザイン,生活を支援するロボメカ技術のメガインテグレーション)

Managing infinite variability in mobile terminal software

Mobile terminals have evolved from basic portable telephones to complex and diverse devices that encompass dozens of other features, ranging from tri-dimensional games to office suites with data transmission capabilities. Variability is value: mobile terminal manufacturers must succeed in fulfilling the requirements of hundreds of mobile telecom operators worldwide, and at the same time increase the value of their brand by adopting a common user interface style while offering the features that the target end-user category desires. This makes for practically infinite variability and creates a business problem. The complexity of the variability problem increases due to issues such as the ability to ‘plug and play’ and ‘feature descension’ (the down-scaling of high-end features and their introduction into lower-end models). The main lesson we have learned from our experience in this field is that the application of relatively simple architectural patterns usually eases up management of the complexity at the architectural level. However, tackling the variability problem at the technical level is ineffective unless the organization is able to ensure the application of the solutions. We analyze the main challenges that lie behind the variability problem in mobile terminals, at both technical and organizational level, and illustrate some of the solutions we have implemented together with our product developers and system architects. Our experience calls for more applied research in the area of variability management, as well as for a number of enhancements to academic curricula. Copyright © 2005 John Wiley & Sons, Ltd.

Audio signal amplifier circuit and portable telephone set and portable electronic device using the same audio signal amplifier circuit

An audio signal amplifier circuit includes an external output terminal of an IC to which an output line of a power amplifier circuit is connected, a first resistor connected between a certain terminal of the IC other than the external output terminal and a feedback input of a differential amplifier circuit, a first capacitor connected between the external output terminal and a loud speaker, a second capacitor between the certain terminal of the IC and a wiring line between the external output terminal and the loud speaker, a filter circuit provided on a signal input side of the differential amplifier circuit and including a second resistor and a third capacitor for attenuating signal components having frequencies in a middle and high frequency ranges and voltage follower means provided between an input stage and an output stage of the audio signal amplifier circuit, wherein the first capacitor is a small capacitor having a capacitance value in the order of 30 μF or smaller and an attenuation characteristics of the first capacitor and an impedance of the loud speaker in a low frequency range is compensated for by a relative amount of increase of amplification gain in the low frequency range determined by a time constant of the second capacitor and the first resistor and a time constant of the third capacitor and the second resistor.

A new artificial life body: biologically inspired dynamic bipedal humanoid robots

Recently, a biologically inspired, bipedal, dynamic, humanoid robot was developed at the Artificial Life and Robotics Laboratory of Oita University. This bipedal humanoid robot is able to walk dynamically and to go up and down stairs. The central pattern generator developed produces various types of walking pattern. This robot has a pair of small CMOS color CCD cameras, a speaker, and a microphone in the head part, and will have a GPS, a portable telephone, and other sensors in the body part, so that the integration of locomotion and behavior to achieve specific demonstrations will be realized. This project develops dynamic mobility and the ability for autonomous recognition and navigation using the biological central nervous system, the brain system, and the real-time control system. Also, the design principles that demonstrate the dynamic interaction between neural and mechanical controls will be clarified. In Phase I, the platform of a small, bipedal, humanoid robot is used to develop autonomous locomotion and autonomous sensing and navigation. In Phase II of the project, an iteration on the platform design for human-size, bipedal, humanoid robots will be performed for operational testing. The development of bipedal humanoid robots that capture biological systems with unique principles and practices could dramatically increase their performance in tasks for national security needs.

Non-Geo systems—where have all the satellites gone?

Non-GEO satellites were being hailed as the means that would bring connectivity to the masses. Anyone, it was said, would be able to buy a portable telephone that would allow them, no matter where they might be, to call or be called by anyone else in the world. In the early 1990s, there were predictions that, by now, literally many hundreds of new non-geostationary communications satellites would be in orbit. Furthermore, people all over the world would also be able to buy an inexpensive satellite terminal that would allow them to access the Internet with a broadband connection, at prices on par with or even far below what the terrestrial competition would be able to offer. Many companies were set up to compete to establish this “Nirvana of Communications.” To do so, however, the companies in question would have to attract sufficient financial backing from investors to actually begin such an undertaking. Surprisingly, at least in retrospect, a tremendous amount of investment capital was forthcoming, and a number of contracts were awarded to manufacturers to develop the requisite satellite systems. Today, almost a decade later, satellite manufacturers and their suppliers have been subjected to a massive belt-tightening exercise as contracts were cancelled and expected future orders were not forthcoming. The launch vehicle industry, which had geared up to meet the bonanza of expected launch orders, is also going hungry. Where are all the proposed systems? This paper will attempt to answer this question, as well as to provide some insight into why the systems that are no longer with us fell by the wayside. Finally, it will look into the future and try to predict what the long-term prospects might be for non-GEO communication satellites in general.

La rue, l'adolescent

The adolescent is pushed toward the outside world, both in search of himself and in search of an encounter with the other. The adolescent is fascinated by the world outside. The street is the symbol of the new space that he alone can occupy. From the time that he leaves the intimate space of the family unit until he has been able to create another space, the street personifies the intermediary state between the two. It is there, in the course of his sexual development, that he encounters the sexual and carnal aspect of the other. It is also there that he exhibits his intimacy: his public display of the personal, ‘extimacy’, is also expressed through his use of the portable telephone. Violence is continually present both at a sexual level and in the adolescent’s relations with others, in an outside environment that he has to make a continual attempt to conquer. The world outside, i.e. the street, is the place where an encounter takes place with the opposite sex, but also with violence at a symbolic level. It is a necessary passage and training ground adulthood, and which requires complete commitment on the part of the individual concerned.

Portable telephone maraca which produces musical tones in synchronization of the swings and vibration of the user

A portable telephone is designed to realize portable telephone functions and game device functions, particularly music games, which are embodied by a vibration device such as a vibration sensor and a vibration motor. When the user swings and vibrates the portable telephone like a maraca in synchronization with the rhythm of a prescribed musical tune, the vibration device produces vibration pulses, which are compared with rhythm pulses. Then, a score is marked on user's operation to swing the portable telephone on the basis of time differences detected between the vibration pulses and rhythm pulses and is displayed on the screen of a display.

Thermal Index Evaluation of Local SAR in MRI-Based Head Models of Adult and Children for Portable Telephones

Biological hazards due to radio-frequency (RF) waves result mainly from the temperature rise in tissue. It should be, therefore, clarified to what extent the RF waves of portable telephones increase the temperature-rise in human brain that includes the central part governing the body-temperature regulation function. In this paper, we calculated both the specific absorption rate (SAR) and the resultant temperature-rise for 900 MHz and 2 GHz portable telephones using the finite-difference time-domain (FDTD) method for three typical use positions, i.e., the vertical position, cheek position and tilt position. As a result, we found that there was an increase for median and 1% value of the cumulative distribution of temperature-rise in children’s brains for any use positions of the portable telephones compared to that in the adult’s brain, and also that the increasing trend in children’s brains for temperature-rise is identical to the temperature-rise trend in children’s hypothalamus. In addition, we found that the ten-gram averaged peak SAR among the adult and children heads had the same trend as that of the 0.1% value of the relatively cumulative distribution of temperature-rise, which shows that the ten-gram averaged peak SAR reflects only the localized temperature-rise in the brain surface.

環境放射能に係る異常現象（原子力事故の前兆現象含む）の携帯電話による監視システムの導入

環境放射能に係る異常現象（原子力事故の前兆現象含む）の携帯電話による監視システムの導入

The Safety Education through an Experiment on Human’s Reaction Time: Thinking about the Usage of the Portable Telephone

The Safety Education through an Experiment on Human’s Reaction Time: Thinking about the Usage of the Portable Telephone

Computation With a Parallel FDTD System of Human-Body Effect on Electromagnetic Absorption for Portable Telephones

Using our recently implemented parallel finite-difference time-domain computation system on Linux-based personal computers, we investigated the human-body effect on the peak specific absorption rate (SAR) in the human head for portable telephones. Taking into account the whole human body, we found that there was a difference within 5.3% for the 1- and 10-g averaged spatial peak SARs and a difference within 19% for the SAR in the brain and eyes compared to the isolated head model. Moreover, in most realistic-use positions, we found that the SAR was slightly decreased due to the body effect. These results further support the rationale of using an isolated human-head model in the SAR evaluation for portable telephones.

Development of high‐frequency SiC‐MESFETs

AbstractWith rapid growth of mobile communications represented by portable telephones, further increases in the output of high‐frequency power transistors for the base stations are required. Also, in the fields of satellite communications and radar, realization of high‐power transistors replacing electron tubes such as TWTs and magnetrons is desirable for size reduction, weight reduction, and extension of transmitter life. As a transistor meeting such needs, the metal semiconductor field effect transistor (MESFET) based on silicon carbide (SiC) has been attracting attention. SiC is superior in material characteristics such as the electric breakdown field and thermal conductivity and is expected theoretically to provide high power density as a high‐frequency transistor. To date, higher output power density than MESFETs based on Si and GaAs of the same size has been achieved, including an output power density of 4.2 W/mm at 1 GHz. In this paper, the high‐frequency characteristics of the tested SiC high‐frequency MESFET are presented and trends in research on improvement of the high‐frequency characteristics are described. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(11): 1–10, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10160

Compact multi‐layer diplexer for dual mode portable telephones

AbstractA new compact and effective lumped‐element diplexer structure targeted for low‐temperature co‐fired ceramic (LTCC) implementation that can exhibit high levels of isolation between low‐pass and high‐pass filters is proposed. Design equation formulations that take into account the isolation between the two filters are presented. As an example, a multilayer ceramic (MLC) chip diplexer in a dual‐mode portable telephone for 900‐MHz digital‐cellular and 1.9‐GHz personal communication systems is designed and fabricated. The simulated results are compared with the measured data and good agreement is reported. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 237–239, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11179

3101 自由曲面 NC 加工の自動プログラミングとシミュレーションソフトシステムの研究と開発

Research and development of an auto-programming and 3D-simulation system for NC (Numerical Control) machining of free-form surfaces are carried out. First, the architecture and interface of the system, theoretical basis of NURBS, format of NURBS-NC machining program, compensation of cutting path and 3D-NC simulation method are described. Then, NC machining of free-form surfaces on gas turbine blade, portable telephone and vacuum-cleaner is performed by using the developed system and the results discussed.

1A1-2F-D7 携帯電話を用いた視覚障害者支援システムの開発

現在, 携帯電話のカメラ画像を健常者に送り, その画像の状況を視覚障害者に伝えるという支援システムがボランティアにより運用されている。本研究では, 画像処理技術を応用して, このシステムの自動化を目指している。携帯電話からサーバーに画像を転送し, サーバー側で画像認識した結果をユーザーに音声で知らせる。

The visual appearance of the Iridium ® satellites

A new generation of communications satellites orbiting the Earth is presenting amateur astronomers and the general public with an exciting new experience—the ability to view objects that at times will be brighter than the brightest star or planet in the sky! Named the Iridium satellite constellation, this collection of artificial satellites circles the Earth 14 times daily. Each one is physically about the size of an automobile. Originally planned as a way for persons with portable telephones to communicate anywhere in the world using space-based technology, an unexpected feature of the design has caused the visual appearance of these spacecraft to reflect the light of the Sun like a giant mirror. While one might argue that the relative sameness of the night sky is rarely punctuated by anything dramatic, the Iridium satellites are about to change that view.

A design method of beam tilting antenna with multiple reactive loadings

For the cellular systems used in portable telephones, down beam tilting is required from base station antennas. The authors have reported a design method of wire antennas with one or two loads for deriving the loading impedances to realize the tilt angle and directive gain provided as a condition. In the present paper, a method of design of a beam tilting antenna with more than three loads for better characteristics is discussed. In such a loaded wire antenna, determination of the locations for the loads and the antenna length is important. This paper proposes a method of determining the locations of the loads and the antenna length. In addition, by including a previously reported method of determining the loading impedance, a design method that achieves the desired tilt angle and high gain with suppressed sidelobes is presented. © 2002 Scripta Technica, Electron Comm Jpn Pt 1, 85(5): 1–10, 2002

An analysis of higher‐order of a GaAs FET depending on IMD source impedance and its application to a design of low‐distortion MMIC power amplifiers

AbstractAlthough the π/4 phase shift modulation schemes used in quadrature phase shift keying (QPSK) are important approaches to ensuring efficient frequency usage in digital portable telephone systems, they also require linearity of the power amplifiers, they also require linearity of the power amplifiers, which is an undesirable constraint from the standpoint of efficiency. In this work, we describe a unified approach to this problem based on the idea that distortion can be effectively decreased by creating dips or “bumps” in the intermod characteristics, due to the dependence of the adjacent channel power (ACP) leakage on input power. For the special case of an impedance Zes connected to the gate of a FET, we use Volterra series to quantitatively demonstrate how the appearance of such dips or bumps is related both to Zes and to the fifth intermod (IM5). We then show analytically that when these dips or bumps are generated effectively, they can suppress IM5. Finally, we show that the resulting decrease in intermodulation distortion and improved efficiency make this method useful in the design of MMIC power amplifiers used in Personal Handy Phone (PHS) service. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(4): 10–21, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.1100