The present status of variability in characteristics of the state-of-the-art MOS transistors is presented. The statistics of threshold voltage of arrayed transistors show the normal distribution. Special emphasis is placed on the analysis of random threshold voltage fluctuations. A new method to compare the amount of random variations in different fabs and different technologies is proposed. Finally, the measures to the variability of scaled CMOS are discussed.
An NRD guide pulse radar front-end was fabricated for level sensor applications at 60 GHz. Main emphasis was placed on circuit configuration. Typically, an oscillation power is divided by a junction circuit and is introduced into two parts. One is for transmitting wave, and the other is for LO wave to perform hetero-dyne detection. The frequency of the former is up-converted so as to be different from the frequency of the LO wave, and thus, a power amplifier is installed in the transmitting side due to low output power of the up-converted millimeter-wave. In this paper, we proposed a new circuit configuration, which consists of a Gunn oscillator with two output ports to eliminate a junction circuit, a direct pulse-modulator to obtain a high level transmitting power without an expensive millimeter-wave power amplifier, and a filter-based down-converter with an up-converter as a local oscillator. Range finding was performed by using the NRD guide pulse radar, however multi-reflection occurred between a target and a planar antenna due to a pencil beam radiation of our developing planar antenna, so that precise distance estimation could not be performed for short range detection. With this in mind, an FPGA-based signal processor was developed in order to eliminate such multi-reflection. The sequential sampling method was employed to reduce experimental errors, which were investigated in terms of difference of periods between a modulated pulse train and a sequential sampling clock. The error of range finding was successfully reduced to be less than 2 % for the distance range from 2 m to 10 m under multi-reflection environment.
Terahertz (THz) electromagnetic waves, which cover an unexplored portion of spectrum between infrared and microwaves at frequencies from 100 GHz to 10 THz, have been expected to offer innovations in sensing, imaging, spectroscopy, and communications. This paper reviews recent advances in the terahertz technology, focusing on recent system applications and key devices to enable practical use.
GaAs/AlGaAs hetero-junction bipolar transistors (HBTs) have attracted much attention because of their high-speed performance. However, long-term operation seriously degrades the device characteristics: Current gain decreases and low-bias-leakage current increases. This degradation has long been an issue in GaAs-based devices operated under minority-carrier injection, like laser diodes. The cause of degradation is thought to be in the carbon-doped base, but this is not yet certain. In this paper degradation of HBTs is described, especially GaAs/AlGaAs HBTs with heavily carbon-doped base layer. Here, two types of the device degradation are found, i.e., hydrogen-related degradation and carbon-related degradation. The mechanisms governing the degradation are discussed from the framework of recombination enhanced defect reaction (REDR) and charge state effect (CSE).
This paper examines λ/4 type wave absorber using priodically-arranged short carbon fibers whose length is λ/2 or λ/4 for two arbitrary frequencies. The measurement result of wave absorber shows wideband absorption characteristics of around 20dB from 4 to 7GHz, and the thickness of the absorber is 34% thinner than a traditional λ/4 type wave absorber at 4.5GHz. Next, we performed for an estimate of the surface resistance of the aspect arranged short carbon fibers to enable the theoretical design of the absorber, and an estimate of the aspect confirmed what was performed precisely by the agreement of calculated and measured absorption characteristics of wave absorber. Then, we changed the thickness and materials of the spacer, and calculated absorption characteristics with estimated surface impedance. The spacer was thinner, absorption characteristics was wider than measured one by calculation. As a result, we showed that a design of wave absorber using periodically arranged short carbon fibers was theoretically possible.
Recently, compact wideband BPFs for UWB system are studied actively. In this paper we propose a compact diplexer in LTCC substrate for UWB system and 2.4GHz wireless systems. Firstly, a wideband BPF for UWB system and an LPF with multiple attenuation poles for 2.4GHz wireless systems are described. Secondly, we design matching circuits of a common port to keep basic performance of both the BPF and the LPF. Thirdly, in accordance with the result of the study, we design a compact diplexer in LTCC substrate. Finally, we verify the effectiveness of proposed method by experiments.
The dependences of source resistance, Rs, transconductance, gm, gate capacitance, Cgs, Cgd, and cutoff frequency, fT, of InP-based HEMTs on an InAlAs barrier layer thickness, d, were investigated. We divided Rs into 4 elements and analyzed the effect of thinning a barrier layer. The resistance originated from the large band discontinuity between InAlAs and InGaAs decreased by thinning a barrier layer, while the resistance in the gate-recessed region increased. As a result, InP-based HEMT with d=10 nm showed lowest Rs. On the other hand, gm increased monotonically with d, due to the reduction of the gate to channel distance, and gmint reached to 2.6 S/mm at d=5 nm. We also estimated fT by using small-signal measurements. fT increased with the reduction of d, which results in the improvement in noise characteristics.
Direct analysis for a millimeterwave amplifier module has been demonstrated by using FDTD electromagnetic and semiconductor device co-simulation technique. The millimeterwave amplifier module consists of an HFET and planar dielectric transmission lines (PDTL) at 60-GHz region. The PDTL with a surface wave transmission mode has a low-loss transmission characteristic at millimeterwave region using a low-loss ceramic substrate. However, the transmission wave on the PDTL tends to be scattered by irregular structures and impedance mismatching. Furthermore, it is predicted that reflected scattered waves at edges of the substrate interfere with incident and transmission waves on the PDTL. Using the co-simulation technique, influence of the scattering waves was investigated in detail for the amplifier module.
The GaN material has good semiconductor and peizoelectric nature. It is used to realize various electronic, optical and surface acoustic wave (SAW) devices with high power and high frequency. In this paper, we study basic characteristics of a GaN ultraviolet (UV) sensor based on effect of acoustic wave charge transfer on GaN epitaxial film. We fabricated the test devices using GaN film with different conductance and measured basic sensing characteristics using two measuring systems. For conductive GaN film, the carriers in GaN film could be controlled by side electrode. When applied voltage of side electrode is 15V, the AC component of output signal is increasing with increasing of SAW input RF power. The DC component of output signal is proportional to UV intensity form 0.1μW/cm2 to 5μW/cm2. For semi-insulating GaN film, the DC component of output signal of SAW mode and layer mode also are proportional to UV intensity from 0.1μW/cm2 to 1.5μW/cm2, but it indicated different polarity. For insulating GaN film, the charge transfer efficiency is relatively higher than the semi-insulating film and the conductive film. We detected very small UV intensity about 0.2μW/cm2 under -25dbm SAW input RF power.
We focus on various dual-band microstrip-line bandpass filters(BPFs) based on tap-coupled resonators. In this study, three types of the BPFs such as basic type, multiple poles based type and wide-band type are proposed and designed by classical filter theory based on narrow-band approximation method. These filters are analyzed by original computation programs and commercial circuit and electromagnetic simulators. And then, the proposed BPFs are fabricated and measured in our laboratory. From the results, we have confirmed that the proposed BPFs produce dual pass-band response, multiple attenuation poles and wide-passband characteristics. We also have observed very good agreements between the simulations and experiments.
Si ion-implanted GaN/AlGaN/GaN HEMTs with extremely low gate leakage current and low source resistance without any recess etching process are demonstrated. The source/drain regions were formed using Si ion implantation into undoped GaN/AlGaN/GaN on sapphire substrate. Using ion implantation into source/drain regions with energy of 80 keV, the performances were significantly improved. On-resistance reduced from 26.2 to 4.3 Ω·mm. Saturation drain current and maximum transconductance increased from 284 to 723 mA/mm and from 48 to 147 mS/mm.
We propose a three-terminal nanometer metal switch in this paper that utilizes a solid electrolyte where the nanoscale metal filament is stretched and retracted. Its operating principle is based on the electrochemical reaction and ion-migration in the electrolyte. The fabricated device is comprised of a solid electrolyte layer (Cu2S), a gate (Cu), a source (Cu) and a drain (Pt). After the Cu-filament is formed between the source and the drain by applying the drain voltage, repeatable ON/OFF switching in the drain current is obtained by controlling the gate voltage. The ON/OFF current ratio can be as high as 105, and the programmable cycle is around 50. Each state can be kept for up to 40 days. Since the gate is separated from the current path, the current for the switching can be reduced down to 10 μA, which is two orders of magnitude smaller than that in two-terminal switches. In this paper, we show the operating principle and electrical characteristics of the three-terminal switches, and discuss how suitable they are for reconfigurable circuits.
An annealing study of the AlGaN/GaN 2DEG structure for HEMTs with or without SiN surface passivation films was conducted with the AlGaN layer thickness dependence taken into consideration. Without SiN, the sheet resistance of the samples with thin AlGaN layers increased significantly upon annealing at 900°C. In contrast, samples with SiN were thermally stable after annealing at up to 900°C even when the AlGaN layer was as thin as 14 nm. Even in the region where the sheet resistance had increased due to the annealing, depositing SiN recovered the sheet resistance to the original values.
The selective etching process for elevated self-aligned silicide (salicide) utilizing PtSi has been investigated. We have developed novel selective etching process utilizing a diluted aqua regia followed by a diluted HF light etching. It was found that the residual Pt-rich silicide layers on the sidewall have been successfully removed. We have also investigated a work function modulation of PtSi alloying with Hf. The barrier height for electron of PtSi has been reduced approximately 0.1 eV for PtxHf1-xSi formed by the silicidation of Pt(17 nm)/Hf(4 nm)/Si(100) stacked layer structures.
A simple measurement method is proposed for extracting capacitances in nanometer-scale metal-oxide-semiconductor field-effect transistors (MOSFETs). The method utilizes two serially connected MOSFETs and an optional metal layer above the intermediate node between MOSFETs. Gate-drain overlap capacitance and capacitances around the intermediate node, including one related to the metal layer, can be obtained by measuring the transfer current when two MOSFETs are alternately turned on at high frequency. High sensitivity in the order of attofarad is demonstrated using silicon-on-insulator (SOI) MOSFETs with gate length of 140∼300 nm and channel width of 320 nm. The proposed method is useful not only in optimizing the high-frequency performance of the scale-down devices, but also in estimating the instability (i.e. kT/C noise) and single-electron charging effect in nanometer-scale circuits.
The unwanted electromagnetic(EM) radiation wave generated from the wireless module in millimeter-wave band used for the car radar influences some error and performance degradation of electronic equipments. In this paper, to reduce this unwanted EM wave, a optimal design to add the function of EM wave absorption to the lid for the module is examined. Therefore the alumina containing carbon black is used as a wave absorption material of the lid. The absorption of 20dB or more is obtained as a measured result with the cover added the EM wave absorption function in 60GHz. Furthermore, we analyzed the wireless module in millimeter-wave band by using the designed material for the lid. It is clarified that the radiation and the reflection electric power are greatly suppressed by loss electric power of the lid. Therefore, the effective data for suppressing the unwanted EM radiation noise from wireless module in millimeter-wave band can be provided.
A Flex-Pass-Gate SRAM, i.e. a fin-type-field-effect-transistor- (FinFET-) based SRAM, is proposed to enhance noise margin during both read and write operations. In its cell, the flip-flop is composed of usual three-terminal- (3T-) FinFETs while pass gates are composed of four-terminal- (4T-) FinFETs. The 4T-FinFETs enable to adopt a dynamic threshold-voltage control in the pass gates. During a write operation, the threshold voltage of the pass gates is lowered to enhance the writing speed and stability. During the read operation, on the other hand, the threshold voltage is raised to enhance the static noise margin. An asymmetric-oxide 4T-FinFET is helpful to manage the leakage current through the pass gate. In this paper, a design strategy of the pass gate with an asymmetric gate oxide is considered, and a TCAD-based Monte Carlo simulation reveals that the Flex-Pass-Gate SRAM based on that design strategy is expected to be effective in half-pitch 32-nm technology for low-standby-power (LSTP) applications, even taking into account the variability in the device performance.
A compact feed circuit with a λ/4 transmission line matrix circuit for use in array antennas to control beams in three directions, including boresight, is presented. The feed circuit antenna is composed of five switches and λ/4 transmission lines, and the feeding matrix circuit yields phase differences of ±90° and 0°. The feed circuit can obtain a reliable output signal, as there is only a small degree of deviation of output signal with variations in the line width. The feed circuit is simulated, fabricated, and evaluated for ISM band, and the measured characteristics agree well with the results of the simulation. The size of feed circuit is 45 (H) × 48 (W) × 3 (T) mm.
In this paper, we propose a new modulo multiplier suitable for repeated operations using redundant representations. First, we consider a computation rule for radix-2 modulo multiplications. In radix-2 operation, we show two methods to calculate (2i-1 mod n) from (2i mod n) and decide product digits sequentially from upper side. These methods make it possible to perform (2i-1 mod n) and multiplications simultaneously. Second, we attempt to apply these methods to radix-4 operations which enables us to reduce clock cycles by only shift and sign change. We propose some structures to perform each part efficiently for radix-4 modulo multiplications. The high-speed redundant binary adder/subtractor which we have already proposed is applied to these structures. By using this adder/subtractor, the longest delay path of this modulo multiplier becomes very short. Finally, by using PARTHENON which is a design system for VLSI, this modulo multiplier is designed and evaluated. As a result, we show the speed of this proposed modulo multiplier becomes over 2.5 times as compared with the conventional structures.
An electrohydraulic total artificial heart (EHTAH) system has been developed. The EHTAH system consists of diaphragm-type blood pumps, an electrohydraulic actuator, an internal control unit, a transcutaneous energy transfer system (TETS), a transcutaneous optical telemetry system (TOTS), and an internal battery. The reciprocating rotation of the impeller generates oil pressure which drives the blood pumps at alternating intervals. The blood pumps and the actuator were successfully integrated into the pump unit without oil conduits. As a result of miniaturizing the blood pumps and the actuator, the displacement volume and weight of the EHTAH system decreased to 872 ml and 2492g, respectively. Furthermore, the maximum flow rate and efficiency increased up to 12 L/min and 15.4%. The pump units and the EHTAH systems were successfully implanted in 36 calves weighing from 55 to 87kg. In the longest case, the ca1f with the pump unit survived for 87 days and the calf with the EHTAH system survived for 70 days. The EHTAH system was powered by the TETS, and was powered everyday by the internal battery for 40 minutes. These results indicate that the EHTAH system has the potential to become a fully implantable cardiac replacement system.
Recently, high-quality 3D graphics has become available at a low cost. A number of attempts have been made to visualize information of a very large system by using 3D graphics. Development of a 3D graphical user interface system needs, however, more cost than that of a 2D graphical user interface system. To solve this problem, we propose an effective method to easily construct 3D graphical user interface for SCADA. Then we demonstrate the advantage of 3D graphical user interfaces constructed by our method through user experiment.
We developed an imaging system and image analysis software for phenotype analysis of rice seedlings growth. The developed imaging system could collect rice seedlings growth images in test tubes every 10 minutes. The image analysis software could detect leaf tip points and collect measurement of leaf height. Using this system, we could obtain detailed measurement and analysis phenotype of rice seedlings growth depends on time parameters, germination timing and leaf elongation timing.
This paper is concerned with robust filters with H∞ disturbance attenuation for a class of uncertain linear systems with time varying delays. We develop a sufficient condition that guarantees the H∞ disturbance attenuation for an error dynamics of an uncertain time-delay system and its filter. Based on such a sufficient condition, we give a design method of robust filters with H∞ disturbance attenuation for uncertain time-delay systems. Finally, numerical examples show the effectiveness of our methods.
This paper presents a new self-position estimation method of an autonomous mobile robot whose processing time can be variable. In this method, the current position of the robot is estimated with the image template matching with the normalized correlation coefficient between an input image and stored images. Based on the idea of anytime sensing, the time for self-position estimation can be varied by changing the image size. Moreover, in order to realize the efficient self-position estimation, image templates are generated with Genetic algorithm. In this paper, the usefulness of the proposed method is shown through some simulation results using test images and some experimental results using a real robot.
Since the pioneer work of Evolution Strategies, experiment-based optimization is one of the promising applications of evolutionary computation. Recent progress in automatic control and instrumentation provides us with a smart environment called Hardware In the Loop Simulation (HILS) for such application. However, since optimization through experiment has severe condition of limited evaluation time and fluctuation of observation, we have to develop methodologies that overcome these problems. This paper discusses application of Multi-Objective Evolutionary Algorithms (MOEAs) to Experiment-Based Multi-objective Optimization of parameters of dynamical systems. In such applications, we have to apply various parameter candidates spreading near the Pareto frontier to the system, and it causes fluctuation of the observed criteria due to the transient response by parameter switching. For reduction of loss time caused by such transient response in evaluation of criteria, we propose techniques called Evaluation Order Scheduling and Evaluation Time Scheduling. Numerical experiments using a formal test problem and experiment in a HILS environment for real internal-combustion engines have demonstrated the effectiveness of the proposed methods.
Frequent patterns mining is one of the important problems in data mining. Generally, the number of potential rules grows rapidly as the size of database increases. It is therefore hard for a user to extract the association rules. To avoid such a difficulty, we propose a new method for association rule induction with pseudo artificial life approach. The proposed method is to decide whether there exists an item set which contains N or more items in two transactions. If it exists, a series of item sets which are contained in the part of transactions will be recorded. The iteration of this step contributes to the extraction of association rules. It is not necessary to calculate the huge number of candidate rules. In the evaluation test, we compared the extracted association rules using our method with the rules using other algorithms like Apriori algorithm. As a result of the evaluation using huge retail market basket data, our method is approximately 10 and 20 times faster than the Apriori algorithm and many its variants.
Automatic detection of proximity Acoustic Emission (AE) doublets is described in this paper. Proximity AE doublets are microseismic data in which the second event with a similar waveform arrives before attenuation of the first event. Number of AE events is much more than thousand when a subsurface fracture reservoir is stimulated during hydraulic fracturing. It is routine and huge work to detect proximity AE doublets in the many AE events. Cepstrum of proximity AE doublets has a peak at quefrency that shows interval between P-waves. We analyze three-component AE signal, which represents three-dimensional particle motion of AE. Three-component AE measurement is often carried out in subsurface AE measurement. Quefrency of the maximum of cepstrum is compared among three components. Cepstrums of proximity AE doublets have the maximum at similar quefrency in three components. On the other hands, cepstrums of AE events except for proximity AE doublets have the maximum at different quefrency in three components. 94 % of proximity AE doublets are detected automatically and 100 % of AE events that are not proximity AE doublets are not recognized as proximity AE doublets in the automatic detection.