IEICE Transactions on Electronics - recent issues

Special Section on The Forefront of 21st Century Organic Molecular Electronics

Onoda, M. — 2008-12-19

Characterization of Zinc Oxide and Pentacene Thin Film Transistors for CMOS Inverters

IECHI, H., WATANABE, Y., YAMAUCHI, H., KUDO, K. — 2008-12-19

We fabricated both thin film transistors (TFTs) and diodes using zinc oxide (ZnO) and pentacene, and investigated their basic characteristics. We found that field-effect mobility is influenced by the interface state between the semiconductor and dielectric layers. Furthermore, the complementary metal oxide semiconductor (CMOS) inverter using a p-channel pentacene field-effect transistor (FET) and an n-channel ZnO FET showed a relatively high voltage gain (8–12) by optimizing the device structure. The hybrid complementary inverters described here are expected for application in flexible displays, radio frequency identification cards (RFID) tags, and others.

Control of P3HT-FET Characteristics by Post-Treatments

IIZUKA, M., YAMAUCHI, H., KUDO, K. — 2008-12-19

The control of the organic field-effect transistor characteristics is necessary to produce the integrated circuits using organic semiconductors. Variations in the poly (3-hexylthiophene) field-effect transistor characteristics upon post-treatment such as thermal treatment and voltage treatment in N₂ atmosphere have been investigated. The controllability and reproducibility of the threshold voltage and mobility were achieved as a result of the post-treatments.

Characterization of Organic Static Induction Transistors with Nano-Gap Gate Fabricated by Electron Beam Lithography

YAMAUCHI, H., WATANABE, Y., IIZUKA, M., NAKAMURA, M., KUDO, K. — 2008-12-19

Organic static induction transistor (OSIT) is a promising driving device for the displays, since it shows high-speed, high-power and low-voltage operation. In this study, the OSIT with fine gate electrode patterned by electron beam exposure were fabricated. We investigated the basic electrical characteristics of copper phthalocyanine OSIT and compared with the calculation results obtained by two-dimensional (2D) device simulator. The experimental results show that the gate modulation improved by reducing the electrode gap and on/off current ratio depends on the gate gap.

Potential Drop at Electrode Contact of Organic Field-Effect Transistors Evaluated by Optical Second Harmonic Generation

MANAKA, T., NAKAO, M., LIM, E., IWAMOTO, M. — 2008-12-19

Time-resolved microscopic optical second harmonic generation (TRM-SHG) imaging measurement revealed quantitatively the potential drop at the electrode contact of pentacene field effect transistors (FET). An activation of the SH signal at the edge of Ag-source electrode indicates the presence of large potential drop at pentacene-Ag contact during device operation, whereas negligible potential drop was observed at pentacene-Au contact. These findings agree with the injection characteristics of electrodes owing to the relationship between the work function of the metal and the HOMO level of pentacene.

Organic Photodetectors Using Triplet Materials Doped in Polyalkylfluorene

HAMASAKI, T., MORIMUNE, T., KAJII, H., OHMORI, Y. — 2008-12-19

The characteristics of violet-sensitive organic photodetectors (OPDs) utilizing polyalkylfluorene and triplet materials have been studied as a host and a dopant material, respectively. For the photo absorption layer, poly(9,9-dioctylfluorene) [PFO] and a phosphorescent iridium complex (Iridium (III) bis(2-(4,6-difluorophenyl)pyridinato-N,C²) [FIrpic] or Iridium (III) bis(2-(2'-benzothienyl)pyridinato-N,C³')(acetyl-acetonate) [(btp)₂Ir(acac)]) were used as a host and a dopant material, respectively. PFO: (btp)₂Ir(acac) device showed less photocurrent than PFO device because (btp)₂Ir(acac) enhances recombination of the photo generated carriers in the photo absorption layer. On the other hand, PFO : FIrpic device showed larger photocurrent than PFO device due to triplet energy transfer from FIrpic to PFO. A cutoff frequency of 20 MHz was observed using a sinusoidal modulated violet laser light illumination under the reverse bias of 8 V.

An Amperometric Sensor for Chemical Imaging Using Photoconductive Organic Film

HAGIWARA, T., TAKAZAWA, M., UCHIDA, H., HASEGAWA, Y., YAJI, T. — 2008-12-19

We have developed an amperometric sensor employing a photoconductive organic thin film that enables the measurement of the two-dimensional distribution of redox current on a sensor surface. The sensor simply consists of photoconductive film and transparent electrode. A focused light beam through the transparent electrode excites the photoconductive film that leads to detect local redox current at the beam position. Intensity of the redox current depends on local concentration of redox species of solution on the sensor. We investigated several materials for the photoconductive film and found a suitable structure is Cu-phthalocyanine doped polyvinylcarbazole film/indium tin oxide/glass substrate. Compared with a conventional two-dimensional chemical sensor, our newly developed sensor can be prepared by lower cost fabrication methods without complex semiconductor processes. The sensor showed a good signal dependence on the concentration of K₃Fe(CN)₆/K₄Fe(CN)₆ in an aqueous solution at 15.4 nA/dec at a constant bias voltage of 0.8 V. We measured the two-dimensional distribution of ions in an agarose gel of 2 mm thickness. The result showed a photograph of the diffusion process of redox species. We also discuss the discrimination of redox species like voltammetry.

Evanescent-Field Modulation of Amplified Spontaneous Emissions from {pi}-Conjugate Polymer Film by a One-Dimensional Photonic Crystal

KAMIYAMA, Y., TOMIOKA, A., MIZUTANI, T., YAMAZAKI, M., MORIMOTO, K. — 2008-12-19

One-dimensional photonic crystal (PC) with alternating layers of TiO₂ and SiO₂ was fabricated with spin coating and low temperature baking, resulting in a successful tuning of the PC stop band so as to block the amplified spontaneous emission (ASE) of a -conjugate polymer film. Single PC as a substrate, not a cavity with two PC's, of the polymer film was sufficient to shift the tangential ASE to the energy at PC stop band edge, indicating that the tangential ASE propagating along the interface was modulated by its evanescent-field tail in the PC, which opens the new pathway for low-threshold coherent luminescence from an ultrathin -conjugate polymer film with ultimate mode volume.

Novel Humidity and Gas Detector Using Langmuir-Blodgett Cellulose-Thin-Film Coated Quartz Crystal Oscillator

KUSANO, H., KITAGAWA, M. — 2008-12-19

We have developed novel humidity and gas detector system using quartz crystal oscillators (QCO) deposited with cellulose Langmuir-Blodgett (LB) films. We have realized stable humidity detection by the LB-based QCO sensor for extremely high humidity subsequent to the water dipping condition. Also, specific gaseous molecules such as alcohol could have been sensitively detected.

Electrocatalytic Oxidation Properties of Ascorbic Acid at Poly(3,4-ethylenedioxythiophene) Films Studied by Electrochemical-Surface Plasmon Resonance Spectroscopy

BABA, A., SANO, Y., OHDAIRA, Y., SHINBO, K., KATO, K., KANEKO, F. — 2008-12-19

In this report, we demonstrate electrocatalytic oxidation properties of ascorbic acid at poly(3,4-ethylenedioxythiophene) (PEDOT) thin films in view of their potential application for bio-sensing devices. PEDOT thin films were deposited on gold thin films by electropolymerization of EDOT monomer in acetonitrile solvent. In-situ electrochemical-surface plasmon resonance spectroscopy (EC-SPR) was used to detect both electrochemical and optical signals upon an injection of ascorbic acid.

Surface Plasmon Excitation and Emission Light Property for Otto/Kretschmann Configuration with MEH-PPV Film

2008-12-19

Attenuated total reflection (ATR) property utilizing surface plasmon (SP) excitation was investigated for BK-7 prism/Mg₂/Ag film/fluorescent organic dye film structure. In the structure, it is expected that SPs are excited at MgF₂/Ag and Ag/dye film interfaces by Otto and Kretschmann configurations, respectively. In the experimental ATR curve, reflection dips for the SP excitations at the interfaces could be detected. Furthermore, SP emission lights were observed by irradiation of Ar ion laser beam from the dye film side. The SP emission light curve with two peaks was observed and it was also considered that the peaks corresponded to the SP excitation of Otto and Kretschmann configurations. The SP emission light spectra indicated the excited fluorescent dyes induced the SP emission lights. Intense emission light of Otto configuration was observed in this sample.

In-situ Measurement of Photoelectron Spectroscopy in Air of Polypyrrole during Electrochemical Undoping

TADA, K., MIYOSHI, Y., ONODA, M. — 2008-12-19

In-situ measurement of photoelectron spectra of polypyrrole during electrochemical undoping/doping cycles has been carried out by using an open-type electrochemical cell. It has been observed that the ionization potential decreases with decreased electrochemical potential. This result seems to be reasonable because the decreased electrochemical potential corresponds to the undoping or recovery of electrons into vacant state of valence band.

Electrochromic Thin Film of Water-Dispersible Prussian-Blue Nanoparticles

2008-12-19

The insoluble Prussian-blue (PB) pigment becomes possible to disperse in aqueous solution by covering their surfaces with ferrocyanide anions. The thin film fabricated with these water-dispersible PB nanoparticles shows evident electrochromic color changes between +0.8 V to –0.4 V on an ITO substrate. The mass change of the thin film during an electrochemical reaction is measured by means of electrochemical quartz crystal microbalance (EQCM). According to the EQCM analysis, the filling rate of water-dispersible PB nanoparticles in the film is 37.7% as compared with an assumed perfect crystal PB film.

Conducting Polymer Based Nucleic Acid Sensor for Environment Monitoring

MALHOTRA, B. D., PRABHAKAR, N., SOLANKI, P. R. — 2008-12-19

Nucleic acid sensor based on polyaniline has been fabricated by covalently immobilizing double stranded calf thymus (dsCT) DNA onto perchlorate (ClO₄^– doped polyaniline (PANI) film deposited onto indium-tin-oxide (ITO) glass plate using 1-(3-(dimethylamino) propyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS) chemistry. These dsCT-DNA-PANI/ITO and PANI/ITO electrodes have been characterized using square wave voltammetry, electrochemical impedance, and Fourier-transform-infra-red (FTIR) measurements. This disposable dsCT-DNA-PANI/ITO bioelectrode is stable for about four months, can be used to detect arsenic trioxide (0.1 ppm) in 30 s.

High-k Dielectric Layers for Bioelectronic Applications

BORSTLAP, D., SCHUBERT, J., ZANDER, W., OFFENHAUSSER, A., INGEBRANDT, S. — 2008-12-19

In many different bioelectronic applications silicon field-effect devices such as transistors or nanowires are used. Usually native or thermally grown silicon oxides serve as interfacing layer to the liquid. For an effective voltage to current conversion of the devices, the main demands for interface layers are low leakage current, low defect density, and high input capacitance. In this article we describe the fabrication and characterization of ultra-thin silicon oxide/high-k material stacks for bioelectronics. A combination of ultra-thin silicon oxide and DyScO₃ revealed the best results. This material stack is particularly interesting for future fabrication of field-effect devices for bioelectronic applications.

In Situ Observation of Time Dependent Electrochemical Activity of Cytochrome c at Bare Indium-Tin-Oxide Electrodes by Cyclic Voltammetry and Slab Optical Waveguide Spectroscopy

AYATO, Y., TAKATSU, A., KATO, K., MATSUDA, N. — 2008-12-19

In situ observation of electrochemical activity and time dependent characteristics of cytochrome c (cyt c) was carried out in 0.01 M phosphate buffered saline (PBS, pH 7.4) containing 20 µM cyt c solutions at bare indium-tin-oxide (ITO) electrodes by using a cyclic voltammetry (CV) and a slab optical waveguide (SOWG) spectroscopy. The bare ITO electrodes could retain the electrochemical activity of cyt c in the PBS solutions, indicating the great advantage of using ITO electrodes against other electrode materials, such as gold (Au). The CV curves and simultaneously observed the time-resolved SOWG absorption spectra in the consecutive cycles implied that the cyt c molecules could retain its own electrochemical function for a long time.

Analyzing Bioelectric Potential Response of Plants Related to Photosynthesis under Blinking Irradiation

ANDO, K., HASEGAWA, Y., MAEKAWA, H., KATSUBE, T. — 2008-12-19

The bioelectric potential of plants is generated by ion concentration difference between inside and outside of plant cells. It has been reported that the bioelectric potential of leaves changes at the beginning of steady irradiation and intensity of the potential response increases with the photosynthetic rate. Although it has been reported that photosynthesis is accelerated by blinking irradiation, the potential response under the blinking irradiation have not been fully clarified. In this study, we measured the bioelectric potential and CO₂ consumption of plants under various types of the blinking irradiation. This result showed that the potential response under the blinking irradiation has various behaviors and intensity of the response related to photosynthetic rate. We conclude that our method is suitable for monitoring the biological activity of plants such as photosynthesis.

Step Width Tolerable for Offset of the Aperture in a Millimeter-Wave Transducer between Post-Wall and Hollow Standard Waveguides

LEE, J., HIROKAWA, J., ANDO, M. — 2008-12-19

A transducer with a wide step from a post-wall waveguide to a hollow waveguide width is proposed which is tolerant against the aperture offset. The modes in the step width of about 1.50 wavelengths are stable for the aperture offset and the fields are not so perturbed while in the conventional stepped structure with step width of about 1.00 wavelength, the higher evanescent mode of TE₃₀ is excessively enhanced by the aperture offset. The operation of the transducer with the wider step is robust for the fabrication errors in the millimeter wave band. It is also suggested that the anti-symmetrical TE₂₀ mode which is excited only by non-zero offset or the misalignment of the aperture exists in both structures and can not be the dominant factor for the improvement. The transducers are designed and fabricated at 61.25 GHz using PTFE substrate with glass fiber of _r = 2.17. The bandwidth for the reflection lower than –15 dB is almost unchanged (6.30–6.60 GHz) for the offset from –0.2 mm to 0.2 mm, while it is degraded in the conventional stepped structure, from 7.65 GHz for no offset to 3.30–5.70 GHz for the same range of the offset.

Active Frequency Selective Surfaces Using Incorporated PIN Diodes

CHANG, K., KWAK, S. i., YOON, Y. J. — 2008-12-19

In this paper, active frequency selective surfaces (FSS) having a squared aperture with a metal plate loading are described. Active FSS elements using switched PIN diodes are discussed with an equivalent circuit model. A unit cell consists of a square aperture element with metal island loading and one PIN diode placed at the upper gap, considering the vertical polarization. The electromagnetic properties of the active FSS structure are changed by applying dc bias to the substrate, and they can be estimated by the equivalent circuit model of the FSS structure and PIN diode. This active FSS design enables transmission to be switched on or off at 2.3 GHz, providing high transmission when the diodes are in an off state and high isolation when the diodes are on. The equivalent circuit model in the structure is investigated by analyzing transmission and reflection spectra. Measurements on active FSS are compared with numerical calculations. The experimentally observed frequency responses are also scrutinized.

Driving Voltage Analysis for Fast Response of Waveguide Optical Switch Based on Movement of Liquid Droplet Driven by Electrostatic Force

IKEMOTO, T., KOKUBUN, Y. — 2008-12-19

The electrostatic force required for the driving of liquid droplet injected in a microchannel was studied to obtain the guiding principle to reduce the driving voltage of waveguide optical switch based on the movement of droplet. We analytically calculated the relation between the threshold voltage and velocity of droplet and the surface roughness of microchannel, and clarified some unconfirmed parameters by comparing experimental results and aeromechanical analysis. The driving of droplet in a microchannel was best analyzed using the Hagen-Poiseuille flow theory, taking into account the movement of both ends of the droplet. When the droplet is driven by some external force, a threshold of the external force occurs in the starting of movement, and hysteresis occurs in the contact angle of the droplet to the side wall of the microchannel. The hysteresis of contact angle is caused by the roughness of side wall. In our experiment, the threshold voltage ranged from 200 to 350 V and the switching time from 34 to 36 ms. The velocity of droplet was evaluated to be 0.3–0.4 mm/s from these experimental results. On the other hand, the measured angle distribution of side wall roughness ranged from 30 to 110 degrees, and the threshold voltage was evaluated to be 100–320 V, showing a good agreement with experimental results. The reduction of threshold voltage can be realized by smoothing the side wall roughness of microchannel. The switching time of 10 ms, which is required for the optical stream switch, can be obtained by shortening the horizontal spot size down to 1.5 µm.

Thermal Gain Variation Compensation Technique Using Thermistor on HPA Module for W-CDMA System

2008-12-19

The thermal gain variation of a high-power amplifier (HPA) module for a wide-band code division multiple access (W-CDMA) system application was reduced to within ±1 dB by applying a thermistor to compensate the gain variation. Two techniques for gain variation compensation with respect to temperature were investigated: base bias control according to temperature, and use of a thermistor in a matching network. Experimental comparison of two techniques indicated that the thermistor-based technique was more effective in reducing the gain variation without affecting linearity. A fabricated two-stage HPA module with a thermistor in its input matching network achieved a small gain variation within ±1 dB and ±5 MHz offset adjacent channel leakage power ratio (first ACLR) below –36 dBc over the temperature range from –10 to +85°C, where the first ACLR was measured under a load-mismatched condition with a voltage standing wave ratio (VSWR) of 1.4:1.

Highly Accurate and Efficient Current-Mode PWM CMOS DC-DC Buck Converter with On-Chip Current-Sensing

CHENG, K.-H., SU, C.-W., KO, H.-H. — 2008-12-19

In this paper, a high accuracy, high efficiency, and wide current-sensing range current-mode PWM buck converter with on-chip current-sensing technique is presented. The proposed current-sensing circuit uses simple switch technique to achieve high accuracy, high power efficiency, and high line regulation. The test chip is fabricated using TSMC 0.18 µm 1P6M 3.3 V CMOS process. The measurement results show that the buck converter with on-chip current-sensing circuit can operate from 700 kHz to 3 MHz with a supply voltage of 1.5–5 V and the output voltage of 0.5–4.5 V for lithium ion battery applications. The accuracy of the proposed current-sensing circuit is exceeds 89.8% for load current from 50 mA to 500 mA and for temperature from 0°C to 100°C. The peak power efficiency of the buck converter is up to 95.5%.

Eliminating the Reverse Charge Sharing Effect in the Charge-Transfer-Switch (CTS) Converter

SHIAU, M.-S., LIU, D.-G., LIAO, S.-S. — 2008-12-19

A novel voltage level controller for low-power charge pump converters will be presented in this paper. The proposed voltage level controller would react according to the pumped voltage in the charge-transfer-switch (CTS) converter. For the CTS circuit, the pumping operation would be degraded by the charge sharing effect in the auxiliary switch path. In this study, a voltage shifter was used as the voltage level controller to overcome this serious problem without consuming too much chip area. The simulation results showed that the converter can accept a rated input of 1.5 V and generated an output up to 8 V based on the TSMC 0.35-µm CMOS technology. The layout consumed an area of 125*160 µm². The highest output obtained in measuring the real chip was 5.5 V which is primarily due to the limitation that the transistor could tolerated. The largest load was estimated as high as 6 mW which is large enough for on-chip application.

An Experimental Study of Head Instabilities in TMR Sensors for Magnetic Recording Heads with Adaptive Flying Height

TONGSOMPORN, D., AFZULPURKAR, N., BARGMANN, B., LEKAWAT, L., SIRITARATIWAT, A. — 2008-12-19

We did an experimental study to investigate the effect of the thermal stress due to the heater for adjusting adaptive flying height (AFH) on the readability and instability of tunneling magnetoresistance (TMR) sensors. The slider head consists of a small heater nearby the read/write elements for controlling the clearance between the read/write elements and the recording medium of the magnetic recording system. It is firstly reported that the thermal stress from the AFH heater induces instabilities and caused head degradation. The thermal stress degrades the reader performance by inducing voltage fluctuations and large noise spikes that causes the magnetic recording system having poor bit error rate (BER). The open loop of the transfer curve indicates that the flipping of a synthetic antiferromagnet (SAF) edge magnetization causes these instabilities. The thermal stress reduces the exchange bias field and the energy barrier to flop the SAF edge magnetization. The dispersion and thermal stability of the antiferromagnetic (AFM) layer are the potential root causes of these SAF instabilities because the larger AFM dispersion in these heads gives less net stabilizing field to SAF layers that lowers the energy barrier to flop the SAF edge magnetization. Scanning electron microscope (SEM) images of these weak heads show rough surface and scratches close to the sensor element. The mechanical stress due to these scratches may additionally impact to the stabilizing field of the SAF.

Wide Band Metallic Waveguide with Asymmetric In-Line Dielectric Rods

KOKUBO, Y., KAWAI, T. — 2008-12-19

A system that has an array of dielectric rods at the center of a waveguide was previously suggested for single mode propagation with a wide frequency range. However, it is difficult to introduce the wave source from a coaxial cable, due to use of the TE₁₀-like and TE₂₀-like modes. In this investigation, an asymmetric setup of the dielectric rods is proposed for better coupling efficiency of the TE₁₀ mode.

A CMOS RF Power Detector Using an Improved Unbalanced Source Coupled Pair

PARK, H., LEE, J., LEE, J., NAM, S. — 2008-12-19

This paper presents the design of a CMOS RF Power Detector (PD) using 0.18 µm standard CMOS technology. The PD is an improved unbalanced source coupled pair incorporating an output differential amplifier and sink current steering. It realizes an input detectable power range of –30 to –20 dBm over 0.1–1 GHz. Also it shows a maximum data rate of 30 Mbps with 2 pF output loading under OOK modulation. The overall current consumption is 1.9 mA under a 1.5 V supply.

A Novel Fast-Lock-in Digitally Controlled Phase-Locked Loop

CHEN, X., YANG, J., SHI, L.-x. — 2008-12-19

A novel fast lock-in digitally controlled phase-locked loop (DCPLL) is proposed in this letter. This DCPLL adopts a novel frequency search algorithm to reduce the lock-in time. Furthermore, to reduce the power consumption, the frequency divider is reused as a frequency detector during the frequency acquisition, and reused as a time-to-digital converter module during the phase acquisition. To verify the proposed algorithm and architecture, a DCPLL design is implemented by SMIC 0.18 µm 1P6M CMOS technology. The Spice simulation results show that the DCPLL can achieve frequency acquisition in 3 reference cycles and complete phase acquisition in 11 reference cycles when locking to 200 MHz. The corresponding power consumption of DCPLL is 3.71 mW.

Special Section on Microwave and Millimeter-wave Technologies

Joshin, K. — 2008-11-10

Digital-Centric RF CMOS Technologies

MATSUZAWA, A. — 2008-11-10

Analog-centric RFCMOS technology has played an important role in motivating the change of technology from conventional discrete device technology or bipolar IC technology to CMOS technology. However it introduces many problems such as poor performance, susceptibility to PVT fluctuation, and cost increase with technology scaling. The most important advantage of CMOS technology compared with legacy RF technology is that CMOS can use more high performance digital circuits for very low cost. In fact, analog-centric RF-CMOS technology has failed the FM/AM tuner business and the digital-centric CMOS technology is becoming attractive for many users. It has many advantages; such as high performance, no external calibration points, high yield, and low cost. From the above facts, digital-centric CMOS technology which utilizes the advantages of digital technology must be the right path for future RF technology. Further investment in this technology is necessary for the advancement of RF technology.

Pseudolinear Circuit Theory for Sinusoidal Oscillator Performance Maximization

OHIRA, T., WUREN, T. — 2008-11-10

This paper introduces a theory for fast optimization of the circuit topology and parameters in sinusoidal oscillators. The theory starts from a system model composed of standard active and passive elements. We then include even the output load in the circuit, so that there is no longer any interaction with the outside of the system through the port. This model is thus called no-input-no-output (NINO) oscillator. The circuit is cut at an arbitrary branch, and is characterized in terms of the scalar impedance from the cut point. This is called active impedance because it is a function of not only the stimulating frequency but also the active device gain. The oscillation frequency and necessary device gain are estimated by solving impedance-domain Barkhausen equilibrium equations. This estimation works for the adjustment of circuit elements to meet the specified oscillation frequency. The estimation of necessary device gain enables us to maximize the oscillation amplitude, thanks to the inherent negative-slope nonlinearity of active devices. The active impedance is also used to derive the oscillation Q (quality) factor, which serves as a key criterion for sideband noise minimization i.e. frequency spectrum purification. As an alternative measure to active impedance, we also introduce branch admittance matrix determinant. This has the same numerical effect as the scalar impedance but can be used to formulate oscillator characteristics in a more elegant fashion, and provides a lucent picture of the physical behavior of each element in the circuit. Based on the proposed theory, we provide the tabled formulas of oscillation frequency, necessary device gain, active Q factor for a variety of typical Colpitts, Hartley, and cross-coupled twin-FET (field-effect transistor) oscillators.

4.8 GHz CMOS Frequency Multiplier Using Subharmonic Pulse-Injection Locking for Spurious Suppression

TAKANO, K., MOTOYOSHI, M., FUJISHIMA, M. — 2008-11-10

To realize low-power wireless transceivers, it is necessary to improve the performance of frequency synthesizers, which are typically frequency multipliers composed of a phase-locked loop (PLL). However, PLLs generally consume a large amount of power and occupy a large area. To improve the frequency multiplier, we propose a pulse-injection-locked frequency multiplier (PILFM), where a spurious signal is suppressed using a pulse input signal. An injection-locked oscillator (ILO) in a PILFM was fabricated by a 0.18 µm 1P5M CMOS process. The core size is 10.8 µm x 10.5 µm. The power consumption of the ILO is 9.6 µW at 250 MHz, 255 µW at 2.4 GHz and 1.47 mW at 4.8 GHz. The phase noise is –105 dBc/Hz at a 1 MHz offset.

A Very Low Spurious X-Band Frequency Quadrupler with Very High Integration Using 3D-MMIC Technology

YAMAGUCHI, Y., KAHO, T., UEHARA, K. — 2008-11-10

A highly integrated frequency quadrupler MMIC that uses three-dimensional MMIC (3D-MMIC) technology is presented. It consists of four driver amplifiers, two doublers, and a 2-band elimination filter. These seven circuits are integrated in only a 2.36 mm² area. The filter sufficiently suppresses spurious output components. The third and fifth harmonic components, which are the spurious components nearest to the desired component, are well suppressed. The desired/undesired ratio is about 40 dB. The driver amplifiers make the quadrupler output a constant power of the desired multiplied signal under low input power. The MMIC supplies +5 dBm of the fourth harmonic component in the input power range from –10 dBm to +5 dBm. The power dissipation of the MMIC is only 160 mW.

K-Band Second Harmonic Oscillator Using Mutually Synchronized Gunn Diodes Embedded on Slot Line Resonators

KAWASAKI, K., TANAKA, T., AIKAWA, M. — 2008-11-10

This paper represents a novel second harmonic power combining oscillator using mutually synchronized Gunn diodes embedded on slot line resonators. A both-sided MIC technology is adopted in the oscillator. The oscillator consists of Gunn diodes, slot line resonators and microstrip lines. By embedding Gunn diodes on the slot line resonators, the harmonic RF signal can be generated very easily. The microstrip lines are used for the power combining output circuit. This oscillator has advantages such as easy circuit design, simple circuit configuration and miniaturization of the circuit size. The second harmonic oscillator is designed and fabricated in K-Band. The output power is +5.75 dBm at the design frequency of 19.0 GHz (2f₀) with the phase noise of –111.7 dBc/Hz at the offset frequency of 1 MHz. Excellent suppression of the undesired fundamental frequency signal (f₀) of –39 dBc is achieved.

Compact and High-Power Spatial Power Combiner by Active Integrated Antenna Technique at 5.8 GHz

SEITA, H., KAWASAKI, S. — 2008-11-10

Compact and planar active integrated antenna arrays with a high power multi-stage amplifier were developed with effective heat sink mechanism. By attaching an aluminum plate to the backside of the creased amplifier circuit board, effective cooling can be achieved. The nonlinear behavior of the amplifier agrees well with the simulation based on the Angelov model. The high power amplifier circuit consisted of the three-stage amplifier and operated with an output power of 4 W per each element at 5.8 GHz. The 32-element active integrated antenna array stably operated with the output power of 120 W under the effective heat sink design. With a weight of 4 kg, the weight-to-output power ratio and the volume-to-output power ratio of the antenna array are 33.3 g/W and 54.5 cm³/W, respectively. Wireless power transmission was also successfully demonstrated.

A Left-Handed Transmission Line Composed of Two Waveguides with Stubs

KUBO, H., KUWAHARA, H., SANADA, A. — 2008-11-10

A new structure of a waveguide-type left-handed transmission line is proposed. It is composed of two rectangular waveguides with many stubs. One waveguide is put on another waveguide symmetrically. When one mode with odd electric field distribution is excited, the stubs work as open stubs and the mode propagates with very small loss. Guided regions of the left-handed mode and a right-handed mode are discussed using an approximate equivalent circuit. Tuning the structure parameters, the band gap between the two regions can be removed, and the wave propagates continuously from the left-handed frequency regions to the right-handed frequency region. The transmission line is applied to a leaky waveguide. It is confirmed experimentally that the beam angle of the radiation wave changes from the backward to the forward directions.

An Elliptic-Function Bandpass Filter Utilizing Left-Handed Operations of an Inter-Digital Coupled Line

UCHIDA, H., YONEDA, N., KONISHI, Y. — 2008-11-10

A new elliptic-function bandpass filter (BPF) is proposed, which utilizes an inter-digital coupled line (IDCPL) as a left-handed transmission line. The IDCPL is employed in order to realize a negative coupling between non-adjacent resonators in a wideband BPF. As the authors' knowledge, the left-handed operations of the IDCPL has rarely utilized before, although the IDCPL itself has been widely used in many microwave circuits without being paid attention to the left-handed operations. Measured characteristics of two BPFs are presented in this paper, one is targeted for 3–4 GHz WiMAX systems, and the other is for 3–5 GHz ultra wideband communication systems (UWB).

Broadband Planar Antenna Combining Monopole Element with Electromagnetic Bandgap

MATSUGATANI, K., SAKAKIBARA, K., KIKUMA, N., HIRAYAMA, H. — 2008-11-10

New structure of broadband planar antenna, combining monopole elements with electromagnetic bandgap (EBG) structures, is proposed. The antenna has a simple single layer structure and unique beam pattern. Antenna is fabricated on a surface of a single layer dielectric substrate and back side of the substrate is covered with metal layer. At the center of the substrate, an inverted L monopole strip is fabricated and on both sides of this monopole, EBG unit cells are placed. By tuning monopole length and EBG bandgap frequency, the monopole resonates even if metal layer exists close to the monopole radiator. Three types of EBG, one dimensional (1D), square two dimensional (2D) and hexagonal 2D, are tested. By combining monopole strip with hexagonal 2D-EBG, the bandwidth of prototype antenna, whose return loss is less than 10 dB, is 840 MHz in 5 GHz band. To control beam patterns of antenna, parasitic elements are placed close to the monopole radiator and EBGs. These parasitic elements work as directors of quasi Yagi-Uda antenna and radiation gain at lower tilt angles is improved.

Novel Compact Ultra-Wideband Bandpass Filter by Application of Short-Circuited Stubs and Stepped-Impedance-Resonator

CHEN, C.-P., MA, Z., ANADA, T. — 2008-11-10

To realize the compact ultra-wideband (UWB) bandpass filters, a novel filter prototype with two short-circuited stubs loaded at both sides of a stepped-impedance resonator (SIR) via the parallel coupled lines is proposed based on a distributed filter synthesis theory. The equivalent circuit of this filter is established, while the corresponding 7-pole Chebyshev-type transfer function is derived for filter synthesis. Then, a distributed-circuit-based technique was presented to synthesize the elements' values of this filter. As an example, a FCC UWB filter with the fractional bandwidth (FWB) @ –10 dB up to 110% was designed using the proposed prototype and then re-modeled by commercial microwave circuit simulator to verify the correctness and accuracy of the synthesis theory. Furthermore, in terms of EM simulator, the filter was further-optimized and experimentally-realized by using microstrip line. Good agreements between the measurement results and theoretical ones validate the effectiveness of our technique. In addition, compared with the conventional SIR-type UWB filter without short-circuited stubs, the new one significantly improves the selectivity and out-of-band characteristics (especially in lower one –45 dB@1–2 GHz) to satisfy the FCC's spectrum mask. The designed filter also exhibits very compact size, quite low insertion loss, steep skirts, flat group delay and the easily-fabricatable structure (the coupling gap dimension in this filter is 0.15 mm) as well. Moreover, it should be noted that, in terms of the presented design technique, the proposed filter prototype can be also used to easily realize the UWB filters with other FBW even greater than 110%.

Dual-Band Wilkinson Power Dividers Using a Series RLC Circuit

KAWAI, T., NAKASHIMA, Y., KOKUBO, Y., OHTA, I. — 2008-11-10

This paper describes a novel Wilkinson power divider operating at two arbitrary different frequencies. The proposed divider consists of two-section transmission lines and a series RLC circuit connected between two output ports. The circuit parameters for a dual-band operation are derived by the even/odd mode analysis. Equal power split, complete matching, and good isolation between two output ports are numerically demonstrated. Dual-band and broadband Wilkinson power dividers can be successfully designed. Finally, verification of this design method is also shown by electromagnetic simulations and experiments.

Miniaturized Lumped-Element Power Dividers with a Filtering Function

HAYASHI, H., KAWASHIMA, M. — 2008-11-10

Three miniaturized lumped-element power dividers with a filtering function for use in quadrature mixers are described. Simulation results showed that they can be miniaturized, as compared to conventional ones with open/short stubs, while maintaining the filter characteristics. A fabricated 0.95-GHz 0° power divider with a filtering function had a chip size about half that of a conventional lumped-element one. Its insertion loss at 0.95 ± 0.05 GHz was 4.0 ± 0.1 dB.

A Complementary-Coupled CMOS LC Quadrature Oscillator

YUN, S.-J., YOON, D.-Y., LEE, S.-G. — 2008-11-10

A novel CMOS LC quadrature oscillator (QO) which adopts complementary-coupling circuitry has been proposed. The performance improvement in I/Q phase error and phase noise of the proposed QO, is explained in comparison with conventional QOs. The proposed QO is implemented in 0.18 µm CMOS technology along with conventional QOs. The measurement result of the proposed QO shows –133.5 dBc/Hz of phase noise at 1 MHz offset and 0.6° I/Q phase difference, while oscillating at 1.77 GHz. The proposed QO shows more than 6.5 dB phase noise improvement compared to that of the conventional QOs over the offset frequency range of 10 K–1 MHz, while dissipating 4 mA from 1.4 V supply.

Biofuel Cell Based on a Complex between Glucose Oxidase and a Plasma-Polymerized Film Containing a Redox Site

MUGURUMA, H. — 2008-11-10

This article presents a new design concept of a glucose oxidase (GOD) electrode as an anode for a biofuel cell based on plasma-polymerized thin film (PPF) of dimethylaminomethylferrocene (DMAMF), which plays a role as an electron transfer mediator between the active site of the enzyme and anodic electrode. The configuration of the anode is a multilayer mixture of DMAMF-PPF and GOD, in which a nano-thin DMAMF-PPF containing a redox mediator was plasma-deposited directly onto a GOD-physisorbed electrode. The optimized biofuel cell with bioanode, in a 20 mM phosphate buffer solution of pH 7.4 containing 10 mM glucose, exhibited a maximum power density of 2.7 µW/cm² at 20°C. The film deposition was performed using microfabrication-compatible organic plasma, which therefore suggests this fabrication process has significant potential for enabling high throughput production of micro biofuel cells.

Traveling Wave Amplification within a Waveguide

MIZUSHIMA, Y. — 2008-11-10

A novel amplification mechanism of traveling TM wave on an electron beam within a waveguide structure is proposed. Under boundary constraint of the waveguide, a hybrid coupling of longitudinal plasma wave and transverse guided one occurs to result in traveling instability. The instability refers to a backward traveling amplification. The new amplification in the waveguide due to the interactive coupling between the space charge mode and the waveguide one is firstly pointed out. The analysis is extended to the relativistic energy range to get a large gain. The features and properties are discussed for a wide frequency range as well as a high gain-bandwidth product.

Avalanche Amplification in Silicon Lateral Photodiode Fabricated by Standard 0.18 {micro}m CMOS Process

IIYAMA, K., SANNOU, N., TAKAMATSU, H. — 2008-11-10

A silicon lateral photodiode is fabricated by standard 0.18 µm CMOS process, and the optical detection property is characterized. The photodiode has interdigital electrode structure with the electrode width of 0.22 µm and the electrode spacing of 0.6 µm. At 830 nm wavelength, the responsivity is 0.12 A/W at low bias voltage, and is increased to 0.6 A/W due to avalanche amplification. The bandwidth is also enhanced from 12 MHz at low bias voltage to 100 MHz at the bias voltage close to the breakdown voltage.

Design of 5 GHz-Band Power Amplifier with On-Chip Matching Circuits Using CPW Impedance (K) Inverters

POKHAREL, R. K., KANAYA, H., YOSHIDA, K. — 2008-11-10

This Letter employs transmission-line theory for the impedance-matching circuits for a single-chip power amplifier (PA) and verifies for 5 GHz-band wireless LAN (IEEE 802.11a) applications. The presented matching circuits are composed of conductor-backed coplanar waveguide (CPW) meander-line resonators and impedance (K) inverters. One of the advantages of the presented circuits is that it can save on-chip space occupied by the matching circuits compared to that using the spiral inductors, thus reducing the cost. The prototype chip, which consists of PA and matching circuits, is designed employing the presented theory and fabricated. A few of the measured results to verify the design theory are presented.

InGaP/GaAs HBT MMIC Amplifier with Low Power Consumption and Low Noise Characteristics for Full-Band UWB Receiver Systems

ISHIKAWA, R., ABE, T., HONJO, K., SHIMADA, M. — 2008-11-10

A wideband InGaP/GaAs HBT MMIC amplifier with a low noise characteristic has been developed as a full-band UWB receiver. The amplifier was designed by applying a scaling law to a driver amplifier in order to decrease power consumption, including a modification for decreasing a noise figure. A triple base structure for a double-emitter HBT was employed to decrease a base resistance and to decrease a noise figure of the amplifier. A fabricated amplifier provided a 3-dB gain roll-off bandwidth from 1.1 GHz to 10.6 GHz with a 14.1 dB peak power gain. The amplifier exhibited a low power consumption of 15.9 mW and a low noise figure of less than 3.7 dB in the full-band of the UWB.

Power and Skew Aware Point Diffusion Clock Network

JUNG, G., KIM, C., CHAE, K., PARK, G., PARK, S. B. — 2008-11-10

This letter presents point diffusion clock network (PDCN) with local clock tree synthesis (CTS) scheme. The clock network is implemented with ten times wider metal line space than typical mesh networks for low power and utilized to nine times smaller area CTS execution for minimized clock skew amount. The measurement results show that skew amount of PDCN with local CTS is reduced to 36% and latency is shrunk to 45% of the amount in a 4.81 mm² CortexA-8 core with 65 nm Samsung process.

Special Section on Electronic Displays

Iimura, Y. — 2008-10-10

High-Efficiency Phosphorescent and Fluorescent Pure-White Organic Light-Emitting Diodes by Incorporating Small Nano-Dot in Non-emissive Layer

2008-10-10

High-efficiency pure-white organic light-emitting diodes (OLEDs) were fabricated using small polysilicic acid nanodot embedded polymeric hole-transporting layer. By incorporating the nanodot, the efficiency of a solution-processed phosphorescent white OLED was increased from 6.8 to 23.7 lm/W, an improvement of 250%. 17.1 lm/W was obtained while the same concept was applied on a mixed-host composed fluorescent white OLED.

Integration of Multiple Organic Light Emitting Diodes and a Lens for Emission Angle Control

RAHADIAN, F., MASADA, T., FUJIEDA, I. — 2008-10-10

We propose to integrate a single lens on top of multiple OLEDs. Angular distribution of the light emitted from the lens surface is altered by turning on the OLEDs selectively. We can use such a light source as a backlight for a liquid crystal display to switch its viewing angle range and/or to display multiple images in different directions. Pixel-level integration would allow one to construct an OLED display with a similar emission angle control.

Improvement of Luminescent Characteristics of BaGd4Si3O13:Tb Green VUV Phosphor by F-Incorporation

KOBAYASHI, A., KUNIMOTO, T., YAMANE, A., OHMI, K. — 2008-10-10

Luminescent characteristics of BaGd₄Si₃O₁₃:Tb phosphor powder including fluorine, which is synthesized at about 1000°C, have been investigated. This phosphor shows the green emission due to Tb³⁺ under VUV excitation. By incorporation of F ion based on low-temperature synthesis, the photoluminescence excitation band lying in the wavelength region from 130 to 170 nm increases drastically in comparison to BaGd₄Si₃O₁₃:Tb phosphor synthesized at 1550°C. This phosphor is a candidate for a green PDP phosphor for both 147 nm resonance line and 172 nm excimer band of Xe plasma.

Properties of Transparent Conductive Ga-Doped ZnO Films on Glass, PMMA and COP Substrates

2008-10-10

The dependences of the structural, optical and electrical properties of highly transparent conductive Ga-doped ZnO (GZO) films on thickness have been studied. GZO films were prepared on unheated glass, polymethyl methacrylate (PMMA) and cyclo olefin polymer (COP) substrates by ion plating deposition with direct-current arc discharge. Polycrystalline GZO films with good adherence to a substrate having a (0002) preferred orientation have been obtained. Very little difference was found between the resistivity values of the GZO films on the glass substrate and those of the GZO films on the different polymer substrates, at any given film thickness. On both plastic substrates, the resistivity of the GZO films decreased from 2 x 10^{– 3} to 5 x 10^–4 cm with increasing film thickness.

Surface Conduction Electron Emission from ZnO Film

WU, S., WANG, C., ZHANG, J., HU, W., LIU, C. — 2008-10-10

The properties of the surface-conduction electron-emitter display (SED) are mainly decided by the surface-conduction electron emitters (SCE), which are normally made from the expensive metal Pd. In this study, we propose to use metal Zn instead of Pd as the emitter material. Both the device electrode and ZnO thin film are deposited by a sputter, and the electron emitters (SCE) are formed by the electro-forming process. The electron emission characteristic is obtained and the luminescence is observed.

Device Characterization of Thin-Film Phototransistors for Photosensor Applications

KIMURA, M., NISHIZAKI, Y., YAMASHITA, T., SHIMA, T., HACHIDA, T. — 2008-10-10

Two types of thin-film phototransistors (TFPTs), p/i/n TFPT and n/i/n TFPT, are characterized from the viewpoint of operation condition and device behavior. It is found that the detected current can be both independent of the applied voltage (Vapply) and linearly dependent on the photo-illuminance in the saturation region of the p/i/n TFPT. This characteristic is because even if Vapply increases, the depletion layer remains in the whole intrinsic region, and the electric field changes only near the p-type/intrinsic interface and intrinsic/n-type interface but remains in the most intrinsic region. This characteristic is preferable for some kinds of photosensor applications. Finally, an application example of the p/i/n TFPT, artificial retina, is introduced.

Back- and Front-Interface Trap Densities Evaluation and Stress Effect of Poly-Si TFT

TAKATORI, K., ASADA, H., KANEKO, S. — 2008-10-10

The polycrystalline silicon (poly-Si) TFT has two insulator interfaces between the polycrystalline silicon and front and back insulators. These interfaces have trap states, which affect the characteristics of poly-Si TFT. In the silicon-on-insulator (SOI) technology area, using the dual-gated, fully-depleted SOI MOSFET under the depleted back-channel condition, the back-interface trap density can be calculated through the front-channel threshold voltage and film thicknesses. The front-interface trap density is also evaluated changing the roles of both gates. This evaluation method for front- and back- interface trap densities is called the threshold-voltage method. To apply this threshold-voltage method to the "medium-thickness" poly-Si TFT, of which the channel is not fully depleted in normal single gate bias operation, the biases for both front and back gates are controlled to realize full depletion. Under the fully-depleted condition, the front- or back- threshold voltage of poly-Si TFT is carefully extracted by the second-derivative method changing back- and front- gate biases. We evaluated the front- and back- interface trap densities not only for normal operation but also under stress. To evaluate the bias and temperature stress effect, we used two types of samples, which are made by different processes. The evaluated front- and back- interface trap densities for both samples in initial state are around 5 x 10¹¹ to 1.3 x 10¹²cm^–2eV^–1 which are almost the same as the reported values. Applying bias and temperature stress shows the variation of these interface-trap densities. Samples with large shifts of the front-channel threshold voltage show large trap density variation. On the other hand, samples with small threshold voltage shifts show small trap density variation. The variation of the back-interface trap density during the stress application showed a correlation to the front-channel threshold voltage shift.

Electrical Characteristics of Driver LSI with 35{micro}m Thickness for Flexible Display

2008-10-10

Electrical characteristics of the mechanically flexible driver LSI as thin as 35 µm mounted directly on a flexible display panel were precisely analyzed. The high-voltage transistors on this LSI show the current decrease by 10–30% in high voltage region, comparing with that of an ordinary thickness LSI. These phenomena can be associated with a self-heating effect. We considered the thermal diffusion on the thin chip by changing material of the measurement stage. Moreover, we analyzed the transistor characteristics on the thin chip under convex and concave bending conditions. The drain current change by piezoresistive effect was observed.

Optical Rewritable Electronic Paper

MURAVSKY, A., MURAUSKI, A., CHIGRINOV, V., KWOK, H.-S. — 2008-10-10

We developed new principle of electronic paper that is one side (for 2D image) or double side (for stereoscopic 3D image) light printable rewritable matter with polarization dependent gray scale. It consists of one or two liquid crystal displays based on Optical Rewritable (ORW) technology, which is the development of rotation azo-dye photoalignment. Each ORW display uses bare plastic or polarizers as substrates. The conductor is not required, as the image is formed by rewritable states of azimuthal direction, which results in 2D pattern of the liquid crystal twist angle. Continuous grey image maintains proper performance even when the device is bent. Simple construction provides durability and low cost, thin substrates minimize parallax for 3D image. Fluorescent dye dopant of liquid crystal partly absorbs light in blue and re-emit in green specter range improving photopic reflection and enhancing color of the ORW e-paper.

Fabrication of Micro-Grating Structures by Direct Laser Writing Based on Two Photon Process and Their Liquid Crystal Alignment Abilities

LEE, C. H., YOSHIDA, H., MIURA, Y., FUJII, A., OZAKI, M. — 2008-10-10

The authors have demonstrated the local alignment of nematic liquid crystal with local micro-grating structure fabricated by the curing of an ultraviolet curable material via a three dimensional micro-fabrication technique known as two photon excitation direct laser writing [1]. The molecular alignment of the nematic liquid crystals on the fabricated micro-grating structures was firstly investigated by the observations of a local twisted nematic region in a liquid crystal cell made of a substrate with locally fabricated micro-grating structure and a counter substrate with rubbed polyimide. The optical polarizing microscope observation of the micro-grating structures indicated that liquid crystals molecules have aligned parallel to the grooves of the micro-grating structure and that local alignment was successfully achieved. The alignment characteristics of the liquid crystals on these micro-gratings was also investigated and discussed quantitatively in details through the measurement of anchoring energy by the conventional torque balance method and the Berreman method. The azimuthal anchoring energy for the micro-grating was found to be in the order of 10^–6 J/m² and inversely proportional to the grating period.

Dependence of Kind of Solvents for Washing on Surface of Rubbed Polyimide Film

KOGANEZAWA, T., HIROSAWA, I., SAKAI, T. — 2008-10-10

We report effects of washing rubbed polyimide film on the near surface. Especially we focused dependence of solvent. Rubbed polyimide films have been used as liquid crystal alignment films in Liquid crystal displays (LCDs), and in actual LCD panel fabrication washing on film surfaces after rubbing is essential process to remove dust and pollution. We investigated the effects of washing by grazing incidence X-ray diffraction (GIXD) measurements. In GIXD, the X-ray penetration into the polymer was changed from 8 nm (suface sensitive) to 4 nm (bulk sensitive) by variation of the X-ray incidence angle. It was found that crystallization near the surface induced by soaking was considerably dependent on solvent. However, in-plane distribution of the surface polymer chains of polyimide film was not found to be dependent on the solvents.

Effects of Rubbing Condition and Soaking Time on Surface Crystallization of Rubbed Polyimide Film by Soaking into Acetone

HIROSAWA, I., KOGANEZAWA, T., SAKAI, T. — 2008-10-10

Rubbed polyimide films have been widely used as liquid crystal alignment films for liquid crystal displays. Washing after rubbing is essential to fabricate liquid crystal displays, and should affect alignment of liquid crystal as well as rubbing. We investigated the effects of rubbing condition and soaking in acetone on polyimide films by grazing incidence X-ray diffraction. It was found that soaking in acetone promoted crystallization of surface aligned polymers, and that the crystallization by acetone was dependent on the initial polymer alignment. The larger initial crystalline phase was, the more newly crystallization occurred by soaking. It was also revealed that the crystallization by soaking in acetone was completed within 1 min.

Variable-Focus Liquid Crystal Lenses Used in Imaging Systems as Focusing Elements

YE, M., WANG, B., YANASE, S., SATO, S. — 2008-10-10

Liquid crystal (LC) lenses that have hole-patterned electrodes and are driven by two voltages used as imaging devices are reported. Two different LC lenses are applied in image formation systems. One LC lens is used with a polarizer in a relay lens scope, and another LC lens that is polarization independent is used in a TV lens. Both LC lenses play roles of focusing elements in lens systems; objects are separately brought into focus by the LC lenses. Very sharp black-and-white and color images are formed by the systems.

Automated Fast and Accurate Display Calibration Using ADT Compensated LCD for Mobile Phone

HAN, C.-H., PARK, K.-H. — 2008-10-10

Gamma correction is an essential function and is time consuming task in every display device such as CRT and LCD. And gray scale CCT reproduction in most LCD are quite different from those of standard CRT. An automated fast and accurate display adjusment method and system for gamma correction and for constant gray scale CCT calibration of mobile phone LCD is presented in this paper. We develop the test pattern disply and register control program in mobile phone and devleop automatic measure program in computer using spectroradimeter. The proposed system is maintain given gamma values and CCT values accuratly. In addition, This system is possible to fast mobile phone LCD adjusment within one hour.

An Illumination-Adaptive Colorimetric Measurement Using Color Image Sensor

LEE, S.-H., LEE, J.-H., SOHNG, K.-I. — 2008-10-10

An image sensor for a use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between RGB output signals and CIE XYZ tristimulus values. This paper proposes an adaptive measuring method to obtain the chromaticity of colored scenes and illumination through a 3 x 3 camera transfer matrix under a certain illuminant. Camera RGB outputs, sensor status values, and photoelectric characteristic are used to obtain the chromaticity. Experimental results show that the proposed method is valid in the measuring performance.

Electrostatically Actuated Two-Dimensional Optical Scanner Having a High Resonant Frequency Ratio of Fast/Slow Axes

NOGE, H., HAGIHARA, Y., KAWANO, K., UEDA, H., YOSHIHARA, T. — 2008-10-10

Two-dimensional resonant optical scanners actuated by vertical electrostatic combs with a unique electrical isolation structure have been developed. The isolation on the movable frame surrounding 1 mm-diameter gimbal mirror is made by trenching the top silicon layer of an SOI wafer with leaving the thick bottom layers. Thanks to the large mass of the frame, the resonant frequencies range in 65.0–89.2 Hz for the frame and in 11.9–36.8 kHz for the mirror in a 4 mm x 4 mm chip. The resultant frequency ratio of the fast/slow axes reaches over 500 and such a high frequency ratio is utilized to display QVGA image by raster scanning of a laser beam.

Laser Breakdown 3D Display

CHEKHOVSKIY, A., OHIRA, Y., TOSHIYOSHI, H. — 2008-10-10

Liquid medium was investigated for creation of real 3D dynamic color images on a basis of laser breakdown effect experimentally. It was shown, that breakdown plasma flash in liquid can be used as a shining voxel of white color. Plasma flashing voxels were produced by means of YAG laser with repetition rate up to 2000 Hz of nanosecond mJ pulses. Breakdown bubbles were found to be not hampering the displaying by flashes. Tens of liquids were tested concerning the lowest breakdown threshold. Up to now, tap water was found to be an optimal medium for displaying due to its low breakdown threshold, low attenuation of laser beam and safety. Seeing through electronic driven color filter made a burst of voxels to be perceived like colored one. TFT matrix from LCD was successfully used for the test coloring. A kind of hysteresis was also found out for dependence of laser breakdown probability on laser repetition rate for fixed laser beam in tap water.

Special Section on Functional Thin Films for Optical Applications

Ishii, K. — 2008-10-10

Achievements and Challenges in the Design and Production of High Quality Optical Coatings

TIKHONRAVOV, A., TRUBETSKOV, M., KASAHARA, I. — 2008-10-10

A new paradigm in the design of optical coatings connected with an outstanding computational efficiency of modern design techniques is discussed. Several other topics including pre-production error analysis, monitoring of coating production, and computational manufacturing of optical coatings are considered.

Magnetophotonic Materials and Their Applications

2008-10-10

Experimental and theoretical studies of light coupling to various magnetic nanostructured media and nanocomposites are briefly reported. Enhancement of the magneto-optical response is shown to occur when the constitutive materials of photonic crystals are magnetic. Transmission and reflection types of 1D magnetophotonic crystals (MPCs) have been studied. New possibility to enhance the magneto-optical response has been found when utilizing localized surface plasmon resonances in bismuth-substituted yttrium iron garnet (Bi:YIG) films impregnated with Au nanoparticles. Examples of integrated optic devices are discussed in which functional elements are 1D and 2D magnetophotonic crystals.

Fabrication of Rugate Optical Filters Using a-SiOx:H Thin Films

YODA, H., MURO, K., SHIRAISHI, K. — 2008-10-10

Rugate thin film optical filters are useful for designing arbitrary-shaped spectra, such as multistep or triangular spectra. A technique for synthesizing the refractive index distribution of rugate filters was used to suppress unwanted ripples on the spectrum. The refractive index of an amorphous hydrogenated silicon oxide (a-SiO_x:H) rugate thin film was minutely controlled with a resolution of 0.001 using radio-frequency (RF) magnetron sputtering. The fabricated rugate filters had multistep bands over a wavelength range of 1260–1670 nm or good linearity over 1290–1650 nm.

High-Rate Oblique Deposition of SiO2 Films Using Two Sputtering Sources

HOSHI, Y., YAGI, K., SUZUKI, E., LEI, H., SAKAI, A. — 2008-10-10

In this paper, we proposed a new high-rate oblique deposition method using two sputtering sources to obtain SiO₂ films for a liquid crystal alignment layer. One sputtering source that operates in a metal mode supplies Si atoms to a substrate, and the other source that operates in an oxide mode supplies oxygen radicals to a substrate. To reduce the gas pressure of a deposition chamber and make the two sputtering sources operate in different modes, the sputtering sources were separated from the deposition chamber with stainless meshes, and Ar and oxygen gases were introduced separately through the two sputtering sources, i.e., Ar gas was introduced through the Si supply source and oxygen gas was introduced through the oxygen radical source. When Ar gas of 30 sccm and oxygen gas of 4 sccm were introduced into the system, the gas pressure of the deposition chamber was maintained below 1.7 mTorr and the films deposited at an incidence angle of more than 70° showed an elongated inclined columnar structure. Under this condition, a deposition rate of 30 nm/min was realized even at an incidence angle above 70°, where most of the Si atoms incident to the substrate were supplied by the Si supply source and the oxygen radical source supplied oxygen radicals and promoted the oxidation of the film.

Characteristcs of Ga-Doped ZnO Films Prepared by RF Magnetron Sputtering in Ar + H2 Ambience

MUTO, K., ODASHIMA, S., NASU, N., MICHIKAMI, O. — 2008-10-10

Ga-doped ZnO thin films were prepared by RF magnetron sputtering. The effects of adding H₂ to pure Ar sputtering gas were investigated. In the case of pure Ar at 2 Pa, the resistivity is 7.45 x 10^–3 cm, whereas for Ar + 1%H₂ at 0.3 Pa, it markedly decreases to 2.52 x 10^–4 cm. In this case, the carrier density and Hall mobility are 1.12 x 10²¹ cm^–3 and 23.4 cm²/Vs, respectively. This conductive film also exhibits a transmittance of 90% within the visible-wavelength range. The addition of H² and the decrease in the pressure results in the fabrication of a significantly more transparent and conductive film.

Estimation of Optimum Ion Energy for the Reduction of Resistivity in Bias Sputtering of ITO Thin Films

ISHII, K., SAITOU, Y., FURUTANI, K., SAKUMA, H., IKEDA, Y. — 2008-10-10

Tin-doped indium oxide (ITO) thin films were prepared on a polyethylene terephthalate (PET) foil by bias sputtering. In the absence of a substrate bias, films having a high resistivity of 2 x 10^–2 ·cm were formed. On the other hand, by the application of an rf substrate bias, films having a low resistivity of 2.6 x 10^–4 ·cm were formed. The energy of ions that bombarded the substrate during bias sputtering was estimated by a simulation of the ion acceleration. The optimum ion-energy required for the reduction of resistivity was found to be approximately 50 eV.

Investigation of Low-Damage Sputter-Deposition of ITO Films on Organic Emission Layer

LEI, H., ICHIKAWA, K., WANG, M., HOSHI, Y., UCHIDA, T., SAWADA, Y. — 2008-10-10

The damage to the organic layer of aluminum (III) bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq) film was investigated on the basis of the change in photoluminescence (PL) intensity. To suppress the bombardment of the substrate with high-energy particles such as -electrons and negative oxygen ions, we used a facing-target sputtering (FTS) system. A marked reduction, however, of the PL intensity of the organic layer was still observed upon the deposition of an indium tin oxide (ITO) film on the organic film. To reduce this reduction, we proposed the insertion of a sector-shaped metal shield near the target electrode, and we showed its effectiveness in reducing the damage. This reduction of the damage is thought to be caused by the elimination of -electrons incident to the organic film surface escaping from the target area near the substrate side. We confirmed that high-energy electron bombardment leads to a significant reduction of PL intensity of the organic layer. This indicates that high-energy electrons incident to the organic film surface play a key role in the damage of the organic layer during the sputtering process.

Adsorption and Surface Plasmon Emission Light of Polystyrene Spheres with Fluorescent Dye on Ag Thin Film

SHINBO, K., MIURA, H., OHDAIRA, Y., BABA, A., KATO, K., KANEKO, F. — 2008-10-10

In this study, attenuated total reflection (ATR) utilizing surface plasmon (SP) excitation and SP emission lights were observed for the adsorption of polystyrene (PS) spheres and a water-soluble polymer. The PS spheres contained fluorescent dyes and exhibited red fluorescence. The ATR properties indicated film deposition with increasing number of adsorption cycles. The SP emission light induced by the fluorescent dye in the spheres was also measured, and an increase in the peak intensity, as well as an angle shift, was observed. Furthermore, the SP emission light spectra were investigated at various emission angles. The dispersion relation obtained from the SP emission light almost corresponded to that obtained from the ATR curves.

Observation of Blue-Light Emission from Tantalum Oxide Films Deposited by Radio-Frequency Magnetron Sputtering

MIURA, K., MIYAZAKI, H., HANAIZUMI, O. — 2008-10-10

We obtained blue photoluminescence from tantalum oxide films deposited by radio-frequency magnetron sputtering after annealing. The maximum peak intensity of the photoluminescence was observed from a sample annealed at 600°C for 20 min, and the peak wavelength was approximately 430 nm. Tantalum oxide films that emit blue light may be useful materials for novel active optical devices utilizing Ta₂O₅/SiO₂ multilayered photonic crystals.

Indirectly Reactive Sputtering Coater for High Quality Optical Coatings

NAMIKI, K.-i. C., CHENG, X., TAKAHASHI, H. — 2008-10-10

An indirectly reactive sputtering coater has been developed to deposit various high quality metallic and metal oxide films at high deposition rate. In this letter, several kinds of filters such as antireflection (AR) coating, IR-cut filter, and Rugate filter were deposited for the benchmark test of implemental capabilities. Our coater was established to be a powerful tool for both discrete multilayer and Rugate filters due to high stability and reproducibility of the refractive index and the deposition rate.

Eigenpolarization States of Photoinduced Anisotropy in Azobenzene Film

BARADA, D., TAMURA, K., FUKUDA, T., EMOTO, A., YATAGAI, T. — 2008-10-10

Optical anisotropy was induced in azobenzene copolymer film using linearly or elliptically polarized laser beams. The Jones matrix of the anisotropic film was calculated from the change in polarization of the probe light. Two eigenpolarization states were obtained from the matrix. These two eigenstates are useful as a polarization basis for a polarization-tunable component.

A Nearly Perfect Total-Field/Scattered-Field Boundary for the One-Dimensional CIP Method

ANDO, Y., SAITO, H., HAYAKAWA, M. — 2008-10-10

A total-field/scattered-field (TF/SF) boundary which is commonly used in the finite-difference time-domain (FDTD) method to illuminate scatterers by plane waves, is developed for use in the constrained interpolation profile (CIP) method. By taking the numerical dispersion into account, the nearly perfect TF/SF boundary can be achieved, which allows us to calculate incident fields containing high frequency components without fictitious scattered fields. First of all, we formulate the TF/SF boundary in the CIP scheme. The numerical dispersion relation is then reviewed. Finally the numerical dispersion is implemented in the TF/SF boundary to estimate deformed incident fields. The performance of the nearly perfect TF/SF boundary is examined by measuring leaked fields in the SF region, and the proposed method drastically diminish the leakage compared with the simple TF/SF boundary.

A Strip Line Broadside Hybrid Coupler Tolerant to Displacement Error and Thickness Variation in Multi-Layered LTCC Substrate

YUASA, T., TAHARA, Y., OH-HASHI, H. — 2008-10-10

A strip line broadside hybrid coupler which is tolerant to manufacturing errors in a multi-layered LTCC substrate has been developed. The tolerance to a displacement error and a thickness variation in the multi-layered LTCC substrate can be achieved by using the tandem arrangement of diagonally shifted coupled lines with adjacent ground walls. It has been demonstrated that the coupling deviation from designed characteristics in our proposed hybrid coupler is very small.

BAT: Performance-Driven Crosstalk Mitigation Based on Bus-Grouping Asynchronous Transmission

YAN, G., HAN, Y., LI, X., LIU, H. — 2008-10-10

Crosstalk delay within an on-chip bus can induce severe transmission performance penalties. The Bus-grouping Asynchronous Transmission (BAT) scheme is proposed to mitigate the performance degradation. Furthermore, considering the distinct spatial locality of transition distribution on some types of buses, we use the locality to optimize the BAT. In terms of the implementation, we propose the Differential Counter Cluster (DCC) synchronous mechanism to synchronize the data transmission, and the Delay Active Shielding (DAS) to protect some critical signals from crosstalk and optimize the routing area overhead. The BAT is scalable with the variation of bus width with little extra implementation complexity. The effectiveness of the BAT is evaluated by focusing on the on-chip buses of a superscalar microprocessor simulator using the SPEC CPU2000 benchmarks. When applied to a 64-bit on-chip instruction bus, the BAT scheme, compared with the conservative approach, Codec and Variable Cycle Transmission (DYN) approaches, improves performance by 55⁺%, 10⁺%, 30⁺%, respectively, at the expense of 13% routing area overhead.

A Nonlinear Piecewise Scheme for Non-uniformity Correction in IRFPA

DAI, S.-s., ZHANG, T.-q. — 2008-10-10

A nonlinear piecewise scheme for non-uniformity correction in infrared focal plane arrays (IRFPA) is presented. In this method, utilizing the nonlinear piecewise scheme of detector response has extended the larger dynamic range of IRFPA response and the higher correcting accuracy than the non-uniformity correction algorithms based on linear response model of IRFPA detector. Based on the principle of this method, the mathematical model is established. At last experimental results are given out. The results show that it has higher correction precision, fewer calculations, and is easier to implement real-time non-uniformity correction of IRFPA by hardware circuit.

Multi-Stage Wavelength Conversion by Cascaded SSB Modulators

FUJIWARA, T., KIKUSHIMA, K. — 2008-10-10

We present the first demonstration of multiple-stage wavelength conversion using cascaded LiNbO₃ Mach-Zehnder SSB modulators. Wavelength is accurately shifted by 18 GHz at each stage. 72 GHz frequency shift with the relative intensity noise (RIN) value of –144.5 dB/Hz is achieved by four stages. The achieved equivalent noise figure is 7.5 dB.

Dual-Band Wilkinson Power Divider with Extended Outputs

PARK, M.-J., LEE, B. — 2008-10-10

A new dual-band operation scheme is proposed for the Wilkinson power divider. The proposed structure has an open stub at the input and its two output ports are extended through a transmission line section. It offers improved bandwidth performance in the dual-band operation along with some structural advantages.

A Compact Circuit Model of Five-Port Transformer Balun for CMOS RF Integrated Circuits

CHANG, S., SHIN, H. — 2008-10-10

A compact circuit model for five-port on-chip transformer balun is presented. Compared to the conventional model, the proposed model is simpler without any accuracy degradation and ensures faster convergence time, which in turn enables flexible RF circuit design optimization. The validity of the proposed model is confirmed through extensive EM simulations and measurements.

A New Built-in Self Test Scheme for Phase-Locked Loops Using Internal Digital Signals

KIM, Y., KIM, K., KIM, I., KANG, S. — 2008-10-10

Testing PLLs (phase-locked loops) is becoming an important issue that affects both time-to-market and production cost of electronic systems. Though a PLL is the most common mixed-signal building block, it is very difficult to test due to internal analog blocks and signals. In this paper, we propose a new PLL BIST (built-in self test) using the distorted frequency detector that uses only internal digital signals. The proposed BIST does not need to load any analog nodes of the PLL. Therefore, it provides an efficient defect-oriented structural test scheme, reduced area overhead, and improved test quality compared with previous approaches.