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The ability to detect abnormalities in infrastructure automatically and remotely with a small number of sensors would greatly contribute to efficient and timely infrastructure inspection. Here, we propose a passive sensor that can be installed by painting. The painted waveguide-based sensor detects abnormalities in infrastructure from abnormality-induced changes in the resonance frequency of electromagnetic waves resonating inside the sensor. In this paper, the principle of detecting loose bolts with the painted waveguide-based sensor is demonstrated by simulation and experiment. The sensor is designed and fabricated as a resonator with resonance frequencies from 100 kHz to 2.5 GHz, which includes the UHF radio-frequency identification band, and the measurement frequency was set within this range. The fabricated sensor is capable of detecting not only a single loose bolt but also two or more loose bolts on the waveguide of the sensor to monitor.

A paintable wireless passive sensor fabricated by painting it directly on a structure, and without batteries and active electronics, is proposed for efficient remote infrastructure inspection. The waveguide-based sensor was designed and fabricated as a resonator with resonance frequencies of 100 kHz‒2.0 GHz, which includes the UHF RFID band. Changes in the electrical resonance frequency of the sensor impedance caused by differences in the sensor’s resonant length clearly demonstrate a bolt is loose. Wireless resonance frequency changes were measured by using the sensor with a painted antenna, confirming successful sensor fabrication with only passive devices.

A Wide Frequency PLL-less Clock Generator with Fast Intermittent Operation is presented in this paper to replace both the external frequency reference and PLL combination used in current wearable medical devices. The system uses one loop to stabilize the amplitude and the other to stabilize the slope of a saw-tooth signal to generate stable frequency over a wide range. Measurement results from a chip fabricated in 180nm CMOS process gives a linear frequency range of 0.1MHz–10MHz and 7us settling time without using a PLL. The total power consumption is 360uW that includes output buffers and external current sources with ±0.84% variation in frequency from 0–70 degrees. Using the proposed system as a clock generator for microcontrollers used in current wearable medical devices, would result in a one or more order of magnitude reduction in power consumption.

The Internet of Things (IoT) is opening the doors to many new devices and applications. Such an increase in the variety of applications requires reconfigurable, flexible and expandable hardware for fabrication and development cost reduction. This has been achieved for the digital part with devices like Arduino. However, the sensor readout Analog-Front-End (AFE) circuits are mainly designed for a specific sensor type or application. Such an approach would be feasible for the current small number of applications and sensors used. However, it will increase cost drastically as the variety and number of applications and sensors are increased. Moreover, flexibility and expandability of the system will be limited. Therefore, a universal sensor platform that can be reconfigured to adapt to various sensors and applications is needed. Moreover, an array of such circuit can be made with the same sensor to increase measurement accuracy and reliability. It can also be used to integrate heterogeneous sensors for increasing the flexibility of the system, which will make the system adaptable to many applications through only activating the desired sensors. In this paper, an 8-mode reconfigurable sensor readout AFE with offset-cancellation-resolution enhancing scheme is proposed to serve as a step towards a universal sensor interface. The proposed AFE can be reconfigured to interface resistive, capacitive, current producing, and voltage producing sensors through direct or capacitive connection to its terminals. The proposed system is fabricated in 180nm CMOS process and has successfully measured the four types of sensor outputs. It has also been interfaced to Arduino board to allow easy interfacing of various sensors. Therefore, the proposed work can be used as general purpose AFE resulting in manufacturing and development cost reduction and increased flexibility and expandability.

A 120-GHz microstrip antenna monolithically integrated with a photodiode that has been developed for a photonic millimeter-wave emitter is described. A photodiode and a ground plane are placed on a Si substrate, and an antenna is placed on a thick polyimide layer that is formed on the Si substrate. This structure simplifies the fabrication process and enables the use of a back-illuminated photodiode. The use of the thick polyimide layer increases the bandwidth of the antenna and improves the radiation efficiency. By integrating a uni-traveling carrier photodiode with the antenna, we are able to experimentally demonstrate the emission of millimeter-wave signals with a power of 0.1 mW at a frequency of 120 GHz.

A high T/sub c/ SQUID system is developed for the application to biological immunoassay. In this application, magnetic nanoparticles are used as magnetic markers to perform immunoassay, i.e., to detect binding reaction between an antigen and its antibody. Design and set up of the system is described. Minimum detectable amplitude of the magnetic flux is 0.6 m/spl Phi//sub 0/ for the measurement bandwidth from 0.2 Hz to 5 Hz when we use a magnetometer. The system noise does not increase when the magnetic field of 0.8 mT is applied in parallel to the SQUID. An experiment to measure the antigen-antibody reaction shows that the sensitivity of the present system is 10 times better than that of the conventional method using an optical marker. When a gradiometer is used, the system noise decreased by a factor of 5, compared to the case of the magnetometer. This improvement indicates the usefulness of the gradiometer to suppress the residual environmental noise in the present system. Magnetic markers that have remanent magnetic moment are also studied in order to increase the signal.

Performances of high T/sub c/ dc SQUID utilizing bicrystal junctions with 30/spl deg/ misorientation angle have been studied. Junction resistance R/sub s/=10 /spl Omega/ and critical current I/sub 0/=10-20 /spl mu/A can be obtained rather easily at T=77 K with this technology. As a result, voltage modulation depth as high as 50 /spl mu/V, and flux noise as low as 5 /spl mu//spl Phi//sub 0//Hz/sup 1/2/ obtained for the 100 pH-SQUID. The measured values of the voltage modulation depth agree reasonably well with the numerical simulation, while the measured values of the flux noise are about 2 or 3 times larger than the simulation. The reason for the high noise level is discussed by taking into account imperfection of junctions.

Distortion of voltage versus flux (V–Φ) relation of a dc superconducting quantum interference device (SQUID) coupled to a multiturn input coil is studied. First, resonant behavior of the coupled SQUID due to the so-called input coil resonance is clarified. It is shown that large rf noise flux is produced by the input coil resonance. This rf flux is added to the SQUID, and results in large rf voltage across the SQUID. In the case where parasitic capacitance exists between the input coil and the ground of the SQUID, this rf voltage produces the rf flux again, i.e., a feedback loop for the rf flux is formed. Taking into account this capacitive feedback, we study the V–Φ relation of the coupled SQUID. Numerical simulation shows that the V–Φ relation is distorted considerably by the feedback mechanism. The simulation result explains well the experimental V–Φ relation of the coupled SQUID. The combination of the input coil resonance with the capacitive feedback is the most likely mechanism for the distorted V–Φ...

Transport properties of YBa2Cu3O7-x bicrystal junctions are studied from the relationship between the critical current Ic and the resistance R of the junction. The relation is obtained when misorientation angle of the junction is changed from 24 to 36.8 degrees. The experimental result can be well explained when two effects are taken into account in the tunnelling of electrons, i.e. resonant tunnelling of quasiparticles via localized states in an insulating barrier and d-wave symmetry of the superconducting order parameter. Low frequency 1/f noise of the junction is also measured, and the fluctuations of Ic and R are obtained as a function of junction parameters. A simple model of the barrier height fluctuation due to the capture and emission of electrons in the localized states can quantitatively explain the experimental results. The present model can consistently explain both the transport and noise characteristics of the bicrystal junction.

This paper presents a uniquely distributed identification number generation circuit based on process variation. The developed circuit utilizes current mismatch in an NMOS pair for unique ID output. To evaluate the output 1/0 probability-uniformity and process dependence, we fabricated a prototype in two different 0.18-µm standard CMOS technologies. We tested 382 chips and calculated the hamming distances between each chip. The results show the hamming distance distribution agrees with theoretical binominal distribution in mean and skewness. However, the distribution is a little wider than the theoretical one. We investigated the reason for the difference and found that circuit layout irregularity causes degradation in standard deviation and kurtosis. When the bits at both ends are excluded, the ID outputs agree with theoretical statistics. The results show the circuit architecture generates a unique and process-independent ID.

We have fabricated and characterized a low-noise direct-coupled magnetometer based on a 100 pH YBa2Cu3O7−x dc superconducting quantum interference device (SQUID) on a 10 mm×10 mm SrTiO3 bicrystal substrate with 30° misorientation angle. The thin films were deposited by hollow cathode discharge sputtering and patterned using conventional photolithography and Ar ion beam etching. The SQUID magnetometer was operated using direct-coupled flux-locked-loop electronics with bias reversal. The sensor had a usable voltage swing of 39 μV and a white magnetic field noise of 32 fTHz−1/2 with a 1/f corner at 2 Hz, including electronics and environmental noise. The voltage versus flux (V−Φ) characteristic showed a pronounced distortion on the negative slope. Numerical simulations were performed to explain the distorted V−Φ characteristic. Measurements of magnetocardiograms demonstrate the suitability of this sensor for biomagnetic applications.

Thick-gold-multilevel damascene-interconnect technology makes it possible to fabricate >10-µm-feature ultrahighspeed devices on Si. Adding H2O2 to a conventional KIO3-based slurry triples the removal rate of gold in chemical mechanical polishing (CMP). A ratio of H2O2 to slurry of ~1:1 is found to be the optimum for obtaining the highest gold removal rate. X-ray photoelectron spectroscopy (XPS) analyses show that gold is oxidized in spite of its chemical stability when the removal rate is high. The gold is oxidized due to the reduction of iodine at the optimum H 2O2 mixture ratio. This CMP of gold enabled us to make a thick (>10 µm) gold-multilevel damascene-interconnection structure for the first time. Integration of full-wafer wafer-bonded uni-traveling carrier photodiodes (UTC-PDs) with the gold multilevel interconnections as coplanar waveguides (CPWs) on a Si wafer has been achieved using this gold-CMP process.

A system is developed to magnetically measure biological antigen-antibody reactions with high T c SQUID magnetometer. In this system, antibodies are labeled with magnetic nanoparticles of γ-Fe2O3 whose diameter is a=50 nm. The antigen-antibody reactions are measured by detecting the magnetic field from the magnetic nanoparticles. Magnetic particles as small as N=1.8 x106 (or 600 pg) can be detected at present. An order of magnitude improvement of the sensitivity will not be difficult with the sophistication of the present system.

High Tc dc SQUIDs are fabricated using bicrystal junctions with 30° misorientation angle, and noise property of the SQUIDs is measured at T = 77 K. The critical-current fluctuation S Io 1/2 is estimated from the flux noise in the low frequency region. And the relationship between S Io 1/2 and junction parameters such as the critical current I 0 and the resistance R s is discussed. It is also shown that the flux noise in the white noise region depends strongly on the transfer function V and that V should be lager than 100 μV/Φ0 in order to realize low noise SQUID with L = 100 pH. The experimental values of the white noise, however, are 2 or 3 times higher than the simulation.

A high performance high T c dc SQUID was fabricated using a bicrystal junction with a misorientation angle of θ=30°. The bicrystal junctions showed junction resistance R s=10 Ω and critical current I o=25 µA (I o R s =250 µV) at T=77K when junction width is w=2 µm. The SQUID exhibited voltage modulation depths as high as ΔV=85 µV, 50 µV and 20 µV at T=77 K for the inductance values of L s=60 pH, 100 pH and 160 pH, respectively. Preliminary noise measurement showed that the flux noise of the SQUID is less than 10µΦo /Hz1/2 in the white noise region for the case of L s=100 pH. These results indicate that the bicrystal junction with a misorientation angle of θ=30° has great potential for the development of high performance SQUIDs.

Characteristics of high Tc dc SQUID, such as transfer function, voltage noise and flux noise, are studied as functions of SQUID parameters. From the comprehensive comparison between theory and experiment parameter dependencies of these characteristics have been clarified. Using these results, we discuss the performance of the SQUID magnetometer, and show optimum values of inductance for making high performance magnetometer. Finally, effect of resonance, which is caused by high dielectric constant of SrTi03, on the SQUID characteristics is shown. It is important to take into account this effect in the design of the SQUID magnetometer.

A 100 GHz high-output power uni-travelling-carrier photodiode with a monolithically integrated matching circuit is proposed and characterised by an electro-optic sampling technique. The device exhibits resonant operation with a record output power of 13 mW at 100 GHz.

We propose the use of a high-T c Josephson junction array for the measurement of high-frequency magnetic fields with high spatial resolution. The voltage vs magnetic field (V–B) relationship of the bicrystal junction was studied for this purpose. The junction array fabricated with an area of 120 µm by 50 µm showed the conversion efficiency dV/dB=63 V/T at T=77 K. This value indicates that the junction array is more sensitive, up to 1.7 GHz, than the conventional induction coil having the same area. Measurement of the magnetic field with a frequency of 130 MHz was successfully demonstrated using the junction array. Performance of the junction array will be much improved by decreasing the operational temperature.

The excess low-frequency noise of a high T c superconducting quantum interference device (SQUID) magnetometer fabricated on bicrystal substrate is studied. Direct-coupled magnetometers are fabricated using different geometries of the pickup coil, and the relationship between the geometry of the pickup coil and the low-frequency noise of the magnetometer is studied. It is shown that the weak superconducting region in the pickup coil, which is automatically formed on top of the grain boundary of the bicrystal substrate, is one of the main sources of the excess noise. By selecting an appropriate geometry of the pickup coil, we can significantly decrease the excess noise of the magnetometer without decreasing its effective area.

A system is developed to magnetically measure biological antigen-antibody reactions with a superconducting quantum interference device (SQUID) magnetometer. In this system, antibodies are labeled with magnetic nanoparticles of γ-Fe2O3, and the antigen-antibody reactions are measured by detecting the magnetic field from the magnetic nanoparticles. A setup of the system is described, and the sensitivity of the system is studied in terms of detectable weight of nanoparticles. Magnetic particles as small as 600 pg can be detected at present. An experiment is also conducted to measure antigen-antibody reaction with the present system. It is shown that the sensitivity of the present system is better than that of the conventional optical method. A one order of magnitude improvement of sensitivity will be realized by the sophistication of the present system.

Critical current fluctuation of bicrystal junctions is estimated from the 1/f flux noise of the superconducting quantum interference device (SQUID) at T=77 K. The relationships between the current fluctuation and junction parameters, such as critical current I o and resistance R, are obtained. The obtained parameter dependence can be well explained by using the parameter dependence of the resistance fluctuation reported by Marx and Gross [Appl. Phys. Lett. 70, 120 (1997)] and the relationship between I o and R obtained for the present junctions. The agreement indicates that the critical current fluctuation is correlated with the resistance fluctuation through the relationship between I o and R.

A comprehensive quantitative comparison between the measured performance of direct-coupled high T c superconducting quantum interference device (SQUID) magnetometers with 30° bicrystal junctions and a numerical simulation is presented. It is shown that the characteristics of the SQUID magnetometer are considerably affected by resonances due to the large dielectric constant of the SrTiO3 substrate. In the realized magnetometer layout, the strip line resonance occurring in the SQUID inductance increases the voltage modulation depth and the output voltage noise of the SQUID, while the flux noise of the SQUID is nearly unchanged. It is also shown that the distortion of the voltage versus flux characteristic is caused by the LC resonance in the pickup loop of the magnetometer in combination with a capacitive feedback. Good agreement between experiment and simulation has been obtained.

In order to develop YBa2Cu3O7-δ bicrystal junctions suitable for high-performance superconducting quantum interference device (SQUID), the relationship between the junction properties and the misorientation angle of the bicrystal substrate is studied experimentally. Misorientation angles of 24°, 27°, 30°, 33° and 36.8° are used, and the angular dependencies of junction resistance R s and critical current I o are investigated. It is shown that values of R s and I o approximately follow the relation I o R s 1.5=const. in these junctions. The obtained results are analyzed in terms of the direct and resonant tunneling mechanisms. It is also shown that values of R s≈10 Ω and I o≈20 µA can be obtained rather reproducibly when we use the 30° junctions. The properties of this junction are very promising for the development of high-performance SQUID.

A high T c dc superconducting quantum interference device (SQUID) was fabricated using a bicrystal junction with a misorientation angle of θ=30°. The junction with a width of 2 µ m exhibited high resistance R s=10 Ω and critical current I 0=25 µ A at T=77 K. This gives a I 0 R s as high as 250 µ V. These values indicate that the bicrystal junction has great potential for the development of high performance SQUIDs. The SQUID fabricated with a 30° junction exhibited voltage modulation depths as high as ΔV=85 µ V, 40 µ V and 20 µ V at T=77 K for the inductance values of L s=60 pH, 100 pH and 160 pH, respectively. These are the highest values reported so far. Preliminary noise measurement showed that the flux noise of the SQUID is less than 8 µΦ0/ Hz1/2 for the white noise region, and less than 70 µΦ0/ Hz1/2 at f=1 Hz when the 60 pH-SQUID is dc biased and operated with a conventional Flux Locked Loop (FLL) circuit.