Size‐reduced two‐dimensional integrated magnetic sensor fabricated in 0.18‐μm CMOS process

Two‐dimensional integrated magnetic sensors have been investigated in order to reduce their size for use in a magnetic self‐levitation motor. The two‐dimensional integrated magnetic sensor investigated in this paper is composed of a 16 × 16 array of Hall sensors and fabricated by a 0.18‐μm complementary metal–oxide–semiconductor (CMOS) standard process. The sizes of the Hall elements are 1 × 1, 2 × 2, 3 × 3, and 6 × 6 μm². Hall element of dimension 1 × 1 μm²was the minimum size in the fabrication process rule. The dimension of one pixel in which the Hall element was embedded was 20 × 20 μm². The average sensitivity of the arrayed Hall sensors at four sizes was about 0.140 mV/mT with a DC magnetic field. The product sensitivity at four sizes of Hall sensors was about 0.089 mV/(mA·mT), which is better than that of our previous work. Degradation of the product sensitivity was not seen in reduced‐size Hall elements. These results reveal that a Hall element of size 1 × 1 μm² has enough sensitivity for sensing the impeller position of a magnetically suspended motor. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fabrication and characterization of co-planar type MEMS structures on SiO2 /Si 3 N 4 membrane for gas sensors with dispensing method guided by micromachined wells

MEMS structures for micro gas sensors had advantage for lower power consumption, reducing size, and easily making cavity structures. Also, co-planar type MEMS structures (CPMS) for gas sensors with low power consumption heater and dispensed sensing materials were newly proposed and investigated. CPMS, which were formed with micro heater and sensing electrodes at the same layer, to reduce process steps, diffusions between upper layer and lower layer, and thermal differences between the center and the periphery of the sensing layer compared with stacked structure. Dispensing method guided by back-side etched well was good for forming sensing material on sensing electrode and had advantage that various sensing materials could be applied for array type sensors. CPMS were fabricated on four-inch diameter and double side polished (100) silicon wafers and using anisotropic bulk silicon micromachining for membrane formation and etched well. A size of chips with 1.15 mm × 1.15 mm membrane was 4.8 mm × 4.8 mm. And co-planar type sensing electrodes were located in the middle of low stress SiO₂/Si₃N₄ (400 nm /1 μm) membranes. Membranes are thermally isolated from the chip frame because they have low thermal conductivity, generally. Temperatures were measured using IR thermometer with linearly increasing applied power. Power consumption at 400^∘C was 150 mW. Membranes of CPMS were withstood up to 730^∘C at the power of 350 mW. Characteristics of micro heaters for various heater widths of 50 μm, 75 μm, 100 μm and ratios of membrane dimension to heater dimension were measured. Sensing materials guided by micromachined well were dispensed on sensing electrodes. CPMS were mounted on a TO-8 package. From these results, fabricated and characterized CPMS could be used for applications in portable gas sensors for detection of CO, NO_x, CH_x, H₂S, and so on.     

Development of Corrosion‐Resistant Pressure Sensor with Semiconductor Strain Sensor

In automotive and industrial fields, pressure sensors are a key component for precisely controlling the mechanical systems. Conventional micro electro mechanical system (MEMS)‐based pressure sensors have an advantage in noise resistance, because both strain gauges and control circuits are integrated in one chip. However, the MEMS‐based pressure sensors are generally fabricated on an Si substrate, and have a low stability against various active gases. Thus, we have newly proposed a pressure sensor which consists of an Si‐based strain sensor set on a stainless steel diaphragm with a high stability against the active gases. The key technology is that a Koval plate is inserted between the strain sensor and the stainless steel diaphragm, for preventing the breakage or the delamination of the strain sensor at the bonding interface due to a difference in thermal expansion. Structure of the sensor including the shape and the size of Koval plate and the assembly position of the strain sensor were designed using structural simulation and experiments. Eventually, the 2.8 mm wide and 0.17 mm thick Koval beam was bridged on the stainless steel diaphragm for efficiently transmitting the diaphragm deformation to the strain sensor. The strain sensor was assembled at the edge of Koval beam with a glass bonding technique. Consequently, the developed pressure sensor has achieved a small dispersion of less than 1% F. S. in a temperature range from 0 °C to 85 °C.     

RF transmitter using the dual‐pulse position modulation method for low‐power smart micro‐sensing chip

This paper presents a low‐power radio frequency (RF) transmitter using dual‐pulse position modulation (DPPM) for a smart micro‐sensing chip (SMSC) with sensors and large scale integrated circuit (LSI) on the same chip. The DPPM method is presented by a fixed pulse and a variable pulse within the same time frame. The distance between the fixed pulse and the variable pulse describes the amplitude of the input signal. A modulator and a ring oscillator were designed for the RF transmitter using the DPPM method. In the modulator, the pulse width modulation (PWM) signal is generated by the intersective method, and narrow pulses are extracted at the rising and falling positions of the generated PWM signal. The designed oscillator has the function of an oscillation controller. The RF transmitter was fabricated with sensors for an SMSC by complementary metal–oxide–semiconductor (CMOS) technology. The power consumption of the fabricated modulator was 4.5 mW. The power consumption of the proposed RF transmitter was measured as 7.0–7.3 mW at an input signal of 0.8–2.5 V. The RF transmitter using the DPPM method was able to reduce the power consumption by a maximum of 50.3% compared to a transmitter using the PWM method, because in the latter the dissipated power was 8.4–14.5 mW at the same input signal. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Three‐dimensional vibration characteristics of the permanent magnet–HTSC magnetic bearing

The three‐dimensional vibration of the rotor in a permanent magnet– HTSC magnetic bearing system is studied. We have developed a magnetic bearing system which can revolve at up to 12,000 rpm, and three‐dimensional vibration of the rotor is measured with laser displacement sensors. To consider the rotor vibration in a mechanical resonance state, the static lateral and vertical pinning forces of the magnetic bearing are measured. The results are used to obtain the resonant frequency. There are two factors in the mechanical resonance caused by the magnetic bearing. One is the lateral equivalent spring coefficient and the other is the vertical equivalent spring coefficient. The influence of mechanical resonance caused by the lateral spring coefficient is large, and that of the vertical one is small. The three‐dimensional vibration of the rotor position around the mechanical resonant frequency is measured. Because the revolution of the rotor increases the lateral force to the center, the resonant frequency obtained in a free revolution experiment is larger than that obtained from pinning force measurement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 58–64, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20586     

Development of multi‐analyte DNA microchip using 3D nanoprototyping fabrication method

The importance of microfluidics systems for high‐throughput postgenome analysis has been steadily increasing. We conceived and fabricated an integrated six‐microchip capillary electrophoresis unit on a small area of 30 × 30 mm for high‐throughput DNA analysis. The design of the structure was performed using a fluid dynamics simulation of electrophoresis to improve the DNA separation resolution. A narrow width of the micro channel at the corners was adopted. For simple fabrication of the microchip, we developed the PMMA structure of the micro fluid channel using lithography, molding, and fusion bonding techniques. It was demonstrated that the proposed integrated structure of micro channels results in good performance of on‐chip DNA separation in a small one‐unit area of 9 × 9 mm. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(1): 32–36, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21156     

High-accuracy magnetic position encoder concept

Position sensors based on the detection of magnetic flux densities by Hall sensors or magnetoresistors are used in automotive applications for crankshaft and camshaft position sensing, which are needed for engine control. This paper identifies the limitations of traditional designs, which introduce an angular error between the position signal pulse and the actual location of the corresponding triggering feature on the sensor target wheel. It proposes a solution ensuring that the position signal pulse coincides with a point of symmetry in the triggering target wheel feature, thus eliminating the angular error. Two interesting implementations are described in this paper. One of them is analyzed in full detail, and a methodology for its design is provided. In particular, specific design rules are derived which link some of the design parameters to relevant dimensional specifications. These rules are established on the basis of a geometrical method developed for this particular type of problem which necessitates the calculation of flux densities in a few specific locations, namely, where the sensing elements are located. The overall approach, including these design rules, is validated by finite-element analysis, as well as by experimental data     

MEMS-based microheaters integrated gas sensors

Abstract

In the present work efforts have been made to develop microheater integrated gas sensors with low power consumption. The design and simulation of a single-cell microheater is carried out using ANSYS. Low power consumption (<35?mW) platinum micro-heater has been fabricated using bulk micromachining technique on silicon dioxide membrane (1.5?μm thin), which provided improved thermal isolation of the active area of 250?×?250?μm². The micro-heater has achieved a maximum temperature of ～950?°C at an applied dc voltage of 2.5 V. Fabricated mircro-heater has been integrated with SnO₂ based gas sensors for the efficient detection of H₂ and NO₂ gases. The developed sensors were found to yield the maximum sensing response of ～184 and ～2.1 with low power consumption of 29.18 and 34.53?mW towards the detection of 1?ppm of NO₂ gas and 500?ppm of H₂ gas, respectively.     

Circuit and system design for an 860–960 MHz RFID reader front‐ends with Tx leakage suppression in 0.18 − µm CMOS technology

This paper presents an RF Front‐END for an 860–960thinspaceMHz passive RFID Reader. The direct conversion receiver architecture with the feedback structure in the RF front‐end circuit is used to give good immunity against the large transmitter leakage and to suppress leakage. The system design considerations for receiver on NF and IIP3 have been discussed in detail. The RF Front‐END contains a power amplifier (PA) in transmit chain and receive front‐end with low‐noise amplifier, up/down mixer, LP filter and variable‐gain amplifier. In the transmitter, a differential PA with a new power combiner is designed and fabricated in a 0.18‐µm technology. The chip area is 2.65 mm × 1.35 mm including the bonding pads. The PA delivers an output power of 29 dBm and a power‐added efficiency of 24% with a power gain of 20 dB, including the losses of the bond‐wires. Copyright © 2011 John Wiley & Sons, Ltd.     

Improvement of sensing characteristics of self‐sensing active magnetic bearings

A winding‐current interference model of self‐sensing magnetic bearings (AMBs) and an improvement technique of position‐sensing characteristics are proposed. In the self‐sensing AMB systems, the electromagnets work not only as actuators suspending the rotor but also as position sensors. The self‐sensing position signal, however, includes errors because of nonlinearity of the magnetic circuits. In the proposed model, the current is directly transmitted to the self‐sensing position signal. This transmission means degradation of the self‐sensing characteristics. This winding‐current interference to the self‐sensing signal is reduced by the proposed compensation method. The characteristics of the proposed self‐sensing method agree well with a reference sensor signal up to over 1 kHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 70– 77, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20732 Copyright © 2004 Wiley Periodicals, Inc.     

Asynchronous cellular logic network as a co‐processor for a general‐purpose massively parallel array

This paper demonstrates an implementation of an asynchronous cellular processor array that facilitates binary trigger‐wave propagations, extensively used in various image‐processing algorithms. The circuit operates in a continuous‐time mode, achieving high operational performance and low‐power consumption. An integrated circuit with proof‐of‐concept array of 24×60 cells has been fabricated in a 0.35µm three‐metal CMOS process and tested. Occupying only 16×8µm² the binary wave‐propagation cell is designed to be used as a co‐processor in general‐purpose processor‐per‐pixel arrays intended for focal‐plane image processing. The results of global operations such as object reconstruction and hole filling are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

一种新型智能金属管浮子流量计的实验研究

基于霍尔元件的新型智能金属管浮子流量计，其技术的关键在于对浮子位置的准确检测。本设计方案通过浮子内嵌永久磁铁，利用霍尔敏感元件对磁场变化的检测，确定浮子准确位置，本文介绍该仪表的实验研究，算法，温度补偿及误差分析。     

新型磁流体水平传感器的研究与设计

磁流体作为一种新型的功能材料,兼具流动性和磁性,并具有许多独特的性质。利用永磁体在磁流体中受到二阶浮力可悬浮的特性,设计了一种新型的一维磁流体水平传感器。该磁流体水平传感器由外壳、芯体、磁流体和永磁体构成,芯体采用永磁体和铁芯组合而成。将芯体置入外壳中,在芯体两端部永磁体与外壳内壁间注入磁流体,磁流体产生二阶浮力使芯体径向稳定悬浮于外壳中,外壳端部永磁体与芯体端部永磁体间的磁斥力提供芯体轴向的回复力使芯体处于轴向平衡位置。当传感器偏离水平位置时,芯体将产生轴向位移并反映出倾角的大小。芯体中的铁芯和外部的电感线圈,可实现芯体位移的亚微米级检测。理论分析了其原理,设计并制作了实验样机。实验结果表明,-10~10°倾角范围内,检测分辨率可达0.03°。     

“六步换向”法控制无刷直流电机设计

介绍了无刷直流电机的一种控制方法,即以dsPIC30F系列微控制器为控制核心,用霍尔效应传感器感知转子磁体位置,按照“六步换向”法给定子线圈有序通电,产生一个旋转磁场,带动转子运转,实现无刷直流电机的运行.电机的转速可通过调整微控制器的MCPWM模块的PWM信号占空比值大小来调节.这种BLDC电机控制系统结构简单,容易实现.     

A proposal for high‐performance CCII‐based analogue CMOS design

A novel fully differential CMOS second‐generation current conveyor (CCII) topology is presented. It can be considered as a universal fully differential programmable active element. The circuit operates in moderate inversion region, and features high linearity over a wide input range. Current gain between terminals X and Z can be continuously tuned in a wide range. These features are essential to extend the utilization of CCII‐based circuits to high‐performance VLSI applications. Analogue design based on this new cell is illustrated by various examples. The proposed CCII has been fabricated in a 0.5‐µm CMOS technology and its main performance characteristics have been measured. They are in good agreement with theory and demonstrate that operation in moderate inversion can lead to distortion levels much lower than those achieved in strong inversion. Experimental results for a Tow–Thomas biquadratic filter fabricated on the same chip are also presented, showing continuous frequency tuning in more than a decade. Copyright © 2005 John Wiley & Sons, Ltd.     

A subthreshold current‐sensing ΣΔ modulator for low‐voltage and low‐power sensor interfaces

A continuous‐time (CT) ΣΔ modulator for sensing and direct analog‐to‐digital conversion of nA‐range (subthreshold) currents is presented in this work. The presented modulator uses a subthreshold technique based on subthreshold source‐coupled logic cells to efficiently convert subthreshold current to digital code without performing current‐to‐voltage conversion. As a benefit of this technique, the current‐sensing CT ΣΔ modulator operates at low voltage and consumes very low power, which makes it convenient for low‐power and low‐voltage current‐mode sensor interfaces. The prototype design is implemented in a 0.18 µm standard complementary metal‐oxide semiconductor technology. The modulator operates with a supply voltage of 0.8 V and consumes 5.43 μW of power at the maximum bandwidth of 20 kHz. The obtainable current‐sensing resolution ranges from effective number of bits (ENOB) = 7.1 bits at a 5 kHz bandwidth to ENOB = 6.5 bits at a 20 kHz bandwidth (ENOB). The obtained power efficiency (peak FoM = 1.5 pJ/conv) outperforms existing current‐mode analog‐to‐digital converter designs and is comparable with the voltage‐mode CT ΣΔ modulators. The modulator generates very low levels of switching noise thanks to CT operation and subthreshold current‐mode circuits that draw a constant subthreshold current from the voltage supply. The presented modulator is used as a readout interface for sensors with current‐mode output in ultra low‐power conditions and is also suitable to perform on‐chip current measurements in power management circuits. Copyright © 2014 John Wiley & Sons, Ltd.     

Representation,methods, and circuits for time‐based conversion and computation

In this paper, we present an efficient representation of the analog signal using the inter‐pulse interval (IPI) time. Based on this representation, methods and circuits for conversion and computation have been developed. To validate these methods and circuits, a test chip has been fabricated using a 0.35µm mixed‐signal CMOS process. Together, the circuits occupy 59.52 × 10^?3mm² of chip area and consume 8.8 mW of power from a 3.2 V supply. Test results at 10 MHz and simulations results at 100 MHz show good accuracy over ±600mV range. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a 3‐dimensional LIGA process and application to fabricate a spiral microcoil

LIGA process has been developed in the 2.5‐dimensional world. We introduced new technologies of a 3D X‐ray lithography and a worm injection molding with an unscrewing de‐molding mechanism, and succeeded in the deployment of a 3D LIGA process. Furthermore, we fabricated a spiral microcoil using the 3D‐LIGA process and a metallization technique combining flat and smooth electroplating and isotropic chemical etching. The microcoil diameter was 0.5 mm and the length was 1 mm. The width of coil lines was 10µm and the pitch was 20µm. Characteristics of this microcoil as an inductor combine the inductance of 91 nH and the quality factor of 5.8 at the frequency of 1 GHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 43–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20679     

A wirelessly powered low-power digital temperature sensor

A wirelessly powered temperature sensor is presented in complementary metal-oxide-semiconductor (CMOS) 180-nm process. The wireless power transfer (WPT) is performed using resonant magnetic coupling, and a diode-less AC to DC conversion is achieved through a quadrature-oscillator with native-MOS. The quadrature-signals are subsequently used to control the diode-less rectifier switches. The on-chip temperature sensor exploits the subthreshold region temperature, and the sensed temperature is converted to frequency using a ring-oscillator, which is implemented using differential cross coupled oscillator-based delay cells. The temperature sensor architecture also employs a temperature-insensitive replica circuit to minimize process dependence and enhance power-supply rejection ratio (PSRR) of the sensing process. The application-specific integrated circuit has been designed and fabricated in 180-nm CMOS process and has dimensions of 2 mm × 2 mm. The measurement results demonstrate that the WPT circuit generates a DC voltage of 1V with a power transfer efficiency of 85% for distances 2 to 8 mm with settling time of microseconds to milliseconds. The temperature sensor demonstrates a resolution of < ±0.6C with a sensitivity of 0.52 mV/C and 126.9 Hz/C along with PSRR of −63dB and Integral Non-Linraity (INL) of 5% measured across six different dies. The back-scattering communication demonstrates a −53-dB signal at a distance of 4 mm without affecting the WPT efficiency. The total power consumption of the temperature sensor along with the integrated biases is 120 nW.     

Construction and levitation guidance experiment of magnetic levitation system without gap sensors using inductance model of thin steel plates

Recently, the noncontact conveyance methods that are applied magnetic levitation techniques have been studied in many institutes. In this paper, from the view point of practical use, the authors construct a magnetic levitation system without using gap sensors which have been essential for the conventional magnetic levitation of thin steel plates. This system adopts both current sensors and Hall‐effect sensors in place of the gap sensors. In addition, we consider the peculiar inductance characteristics of magnetic levitation for a thin steel plate. Moreover, we conduct the levitation, guidance, conveyance and disturbance experiments.