DC Signal Research Articles

BENEFITS OF TRANSMISSION LINE METAL-INSULATOR-METAL CAPACITORS IN MASS PRODUCTION OF RF CIRCUITS

Coupling capacitors or DC blocks are essential tuning elements in RF/microwave applications. Their role becomes imperative in cascade amplifiers to isolate drain voltages of preceding MMIC from the gate voltage of the following chip where both RF and DC signals are carried through the same line. The purpose of this study is to explain the benefits of a newly designed thin film coupling capacitor called as transmission line metal-insulator-metal capacitor (TL MIM Cap), which serves as a DC block capacitor in microwave circuits. This novel structure provides a unique solution, which cannot be achieved with traditional single layer ceramic capacitor (SLC) structure. It combines two discrete circuit elements into one: “Microstrip transmission line of required length and width” with a “serially attached coupling capacitor”. Thin film capacitive layers ranged from 0.5pF to 50pF, which are typically needed for microwave frequencies within 1–40 GHz, constructed and embedded into 50 Ohm impedance transmission lines in series. Substrates like quartz, glass, or alumina can be used to minimize losses and to achieve higher RF/microwave performance. We used copper traces as conductive layers for optimal conductivity. After manufacturing TL MIM Caps, we tested several capacitance values for 1pF, 5pF, 15pF and 30pF corresponding to a wide frequency range. The RF tests we performed showed that TL MIM Caps exhibited a minimum of 20dB return loss and a maximum of 0.3 dB insertion loss at 1–40GHz range. We also found our technique comes with some workmanship advantages in high frequency circuit assembly as follows: Traditional coupling capacitor attachment with silver epoxy on top of a microstrip transmission line is a manual operation, which requires well trained and experienced technicians. In contrast, using the TL MIM Caps in our high frequency hybrid modules, we found that the process caused errors were eliminated such as the micro short circuit effect caused by conductive epoxy. Therefore we improved yield in assembly stage of the circuits. In addition, improvements are observed in production processes such as less consumption of adhesives (epoxy), no technician failure caused wastes, elimination of extra curing process to attach capacitors, no short circuit inspection, rework, or re-cure operations to fix assembly errors. Last but not least, blocking capacitors are embedded into the microstrip transmission lines in TL MIM Caps. This ensures that having the lowest possible impedance since very short wire bond exists from the bond pad of the TL MIM Cap to the adjacent circuit element.

A Stochastic Filtering Algorithm Using Schrödinger Equation

This paper provides a new adaptive algorithm for single-step prediction by modeling the potential field of a one dimension Schrödinger wave equation using neural network. This new architecture is referred to as the recurrent quantum neural network (RQNN). The RQNN can filter the signal embedded with non-stationary noise without any priori knowledge of the shape of the signal and statistical properties of the noise. We compared the simulation results of the RQNN with a classical adaptive stochastic filter-RLS. It is shown that the RQNN is much more efficient in denoising signals embedded with Gaussian stationary, non-Gaussian stationary and Gaussian non-stationary noise such as DC, sinusoid, staircase and speech signals. The RQNN can enhance the signal to noise rate (SNR) by 20 dB, which is more than 10 dB given by the traditional technology when it denoising sinusoid signal.

Large-Signal RF Performance of Nanocrystalline Diamond Coated AlGaN/GaN High Electron Mobility Transistors

In this split-wafer study, we have compared the dc, pulsed, small and large signal RF electrical performance of nanocrystalline diamond (NCD) coated AlGaN/GaN high electron mobility transistors (HEMTs) to reference devices with silicon nitride passivation only. The NCD-coated HEMTs were observed to outperform reference devices in transconductance, large-signal gain, output power density, and power-added efficiency at 4 GHz. The measured improvements were suspected to be related to reduced dispersion and lower source access resistance afforded by the NCD film.

Experimental investigation of a capacitive blind hollow cathode discharge with central gas injection

The operating parameters and resulting plasma properties of a blind hollow cathode (BHC) discharge have been investigated. The hollow cathode was driven capacitively with a pulsed dc signal of 200 kHz in a power range between 50 and 100 W at an ambient pressure of about 10 Pa. The working gas was argon, which was introduced with a ceramic capillary at different positions of the longitudinal axis of the hollow cathode with flow rates of between 30 and 1000 sccm. The current–voltage characteristics were recorded.The pressure at the end of the BHC was measured with a miniaturized pressure transducer with varying volumetric flow rate and axial position of the capillary in the hollow cathode. To characterize the ignition behaviour of the system, the measured breakdown voltages were compared with phenomenological Paschen curves calculated from the pressure data.Optical emission spectroscopy was used to examine the origins of the light emission, comparing the glow mode and hollow cathode mode in particular.A high-speed camera recorded some plasma processes. A mounting with an indium tin oxide coated glass was used to observe the inner volume of the BHC along the longitudinal axis, while the plasma was operated with different parameters. The optical observations revealed an inhomogeneous plasma condition along the axis.

Seebeck nanoantennas for the detection and characterization of infrared radiation.

Arrays of metallic thermocouples in the shape of spiral nanoantennas are proposed as infrared detectors, which use the thermoelectric properties of the metallic interfaces to generate electrical DC signals. The responsivity of these types of antennas is evaluated from both theoretical and numerical perspectives pointing out its potential as infrared sensors. Moreover, the same structures can be used to characterize the state of polarization of the optical near fields with a spatial resolution comparable to the wavelength.

Molecular adhesion controlled microelectromechanical memory device for harsh environment data storage

This work demonstrates a cantilever based electrostatic microelectromechanical system device operating as a memory element. Volatile and non-volatile functions are engineered by manipulating molecular adhesion force through contact dimples and restoring force using the cantilever design. For non-volatile RESET operation, a method of detaching the cantilever with 3 V pulsating DC signal at 1 MHz is proposed. SET/RESET cycles are performed up to 103 times at 300 °C without any performance degradation. A writing speed of up to 0.94 μs is achieved, which is faster than conventional high temperature flash memories. With demonstrated attributes, the fabricated device offers excellent potential for harsh environment data storage applications.

Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5–6 nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700 cm2/V s and sheet resistance of 130 Ω/□ for a 3 nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

Seebeck nanoantennas for solar energy harvesting

We propose a mid-infrared device based on thermocouple optical antennas for light sensing and energy harvesting applications. We numerically demonstrate that antennas are able to generate low-power dc signals by beneficing of the thermoelectric properties of the metals that constitute them. We theoretically evaluate the optical-to-electrical conversion efficiency for harvesting applications and finally discuss strategies to increase its performance. Thermocouple optical antennas therefore open the route toward the design of photovoltaic devices.

Design of Digital Type Axis-Angle Sensor Based on Singlechip

The synchronizer is often used for the measurement of axis-angle because of its simple structure, reliability and high precision. But the output signal from the synchronizer is an analog signal, so it is difficult to realize digital measurement. This paper introduces a measuring circuit based on a singlechip. This circuit can produce exciting signal independently and no extra exciting power supply is needed, making the application easy. The AC signals output from the synchronizer are converted into DC signals and then measured directly by the singlechip. The measuring data, after being processed, are turned into serial data to output through a RS232 serial interface. The synchronizer equipped with the circuit will be a digital axis-angle sensor. The sensor is of high precision and reliability, low price, easy application and high practical value.

On the dispersion relation of the transit time instability in inverted fireballs

Recently discovered inverted fireballs are non-linear plasma phenomena, which are formed in hollow grid anodes with high transparency in an existing background plasma. If a sufficiently large potential is applied, accelerated electrons from the bulk start to oscillate through the grid. Experimental investigations have shown that they produce different types of plasma instabilities. One of those oscillations is a transit time instability which originates from strong electron beams that travel through the inverted fireball. This type of instability is similar to vircator reflex oscillations and produces radio frequency waves. Hence, it is suitable to convert DC signals into signals oscillating in the MHz range. This paper analyses the dispersion relation of the transit time instability for three different plasma regimes. The regimes can be divided into a collision less regime, a regime with high collisionality and one in between those former two. It is demonstrated that the plasma properties of the surrounding background plasma have a strong influence on the behavior of the instability itself.

A Remote and Sensorless Stator Winding Temperature Estimation Method for Thermal Protection for Induction Motor

Three-phase induction motors are the “workhorses” of industry; they are the most widely used electrical machine; because of its simple structure and high reliability. This paper proposes a new technique to model the stator winding of the induction motor in Matlab Simulink® software. This simulation of the induction motor would have the thermal behavior of its stator winding; to study the induction motor temperature estimation using motor parameter-based method. The modified model is used to validate a remote and Sensorless stator winding temperature estimation technique; therefore a thermal protection is obtained for soft-starter-connected to induction motors. The soft-starter is used to inject a DC signal in the induction motor terminal voltage and current. The stator winding resistance/temperature is estimated from DC signal injection by changing the gate drive signals of the Thyristor in the soft starter. The level of the injected DC signal is adjusted by the value of the delay angle. The accuracy of stator winding temperature estimation increased with the increase of DC signal level; however the pulsation of the output torque increased also. The thermal behavior is simulated utilizing a thermal resistor block from the Matlab Simscape™ software. It is used to replace the fixed resistor value of the induction motor model in the Matlab Simulink. The thermal monitoring scheme has been validated from the simulation results of a 7.5 kW induction motor under various loading conditions.

Analog Circuit Parameters Measurement System Based on Multiplier

For the more complicated principles and the lower accuracy for the existing methods of the measurement of the analog circuit parameters, the paper constructs a measurement system for the analog circuits parameters based on the multiplier. The signal source generates two orthogonal sinusoidal analog signals with same frequency, and then one of the signals goes through the analog circuits. Then the multiplication and filtering are completed with the two DC signals. At last the phase and amplitude of the analog circuit are obtained through the DAQ and LabVIEW software. The amplitude and phase errors are less than 3%. The results show that the system has simple circuit, fast speed and high accuracy. So it is a feasible plan for the measurement system of the analog circuit parameters at present.

Interferometric measurement of far infrared plasmons via resonant homodyne mixing.

We present an electrically tunable terahertz two dimensional plasmonic interferometer with an integrated detection element that down converts the terahertz fields to a DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field functioning as the local oscillator. Plasmonic interferometers with two independently tuned paths are studied. These devices demonstrate a means for developing a spectrometer-on-a-chip where the tuning of electrical length plays a role analogous to that of physical path length in macroscopic spectroscopic tools such as Fourier transform interferometers.

Use and comparative assessment of the CVFEM method for Poisson–Boltzmann and Poisson–Nernst–Planck three dimensional simulations of impedimetric nano-biosensors operated in the DC and AC small signal regimes

We specialize the Control Volume Finite Element Method (CVFEM) for the solution of the Poisson–Boltzmann and Poisson–Nernst–Planck (also known as Poisson–drift–diffusion) system of equations on unstructured 3D meshes describing nanoelectronic biosensors operated in the DC and AC small signal regimes. We provide the exact analytical expressions for volume and surface integrals derived by means of a linear coordinate transformation and show that they are both accurate and efficient, especially on coarse grids. Being of great importance for the chosen application, the conservation property is investigated and we show that, for the CVFEM to be conservative, the calculations on the boundary have to be performed with special care. CVFEM is carefully compared to the Galerkin Finite Element Method (GFEM) from the point of view of the underlying theory, implementation and solution calculation. The simulation tool is used to evaluate the response of a real nanoelectrode-based biosensor array to the introduction of small nanoparticles.

Photoplethysmographic signals to predict the success of lumbar sympathetic blockade for lower extremity pain.

A prospective, observational study to investigate how photoplethysmography (PPG) signals change during lumbar sympathetic blockade (LSB), and whether these changes can predict sympathetically mediated pain (SMP). Patients with unilateral lower extremity pain and self-reported cold hyperalgesia underwent LSB. Bilateral temperature and PPG signals (AC and DC) were recorded. Power spectrum analysis (PSA) was performed. Of the total patient cohort (n = 38), eight patients (22.1%) had excellent pain-relief after LSB and were determined to have SMP. In all patients, the PPG AC signal changed immediately after drug administration, before any temperature change. DC signals decreased slowly in a linear fashion. PSA of DC signals showed significantly lower low-frequency/high-frequency (LF/HF) ratios in the SMP group than the sympathetically independent pain group, both before and after LSB. A cut-off value of 2.92 for LF/HF resulted in sensitivity, specificity and positive predictive values for SMP of 75.0%, 76.7% and 3.21 [1.5, 6.9], respectively. PPG may be used as an early indicator of a successful LSB and could also be helpful in diagnosing SMP.

A 2.1-Channel Class-D Amplifier Exploited Coupling Virtual-Audio-Image to Enhance Stereo

This brief presents a novel 2.1-channel stereo-enhanced class-D audio amplifier to improve the quality of stereophonic sound in portable devices. By a way of cross coupling, the input audio signal from one channel can be amplified at the same time, with different gains in the two channels. The ratio of gains in the two channels can be adjusted by changing the resistance and then making the position of the virtual-audio-image change, which improves the stereo effect. The bass signals from different channels, which frequency range between 30 and 300 Hz, are superimposed and then amplified in the independent bass channel by using the Sallen–Key bandpass filter. A practical implementation in the SMIC 0.18- $\mu\hbox{m}$ CMOS process has been done to validate the theoretical results. When a 200- $\hbox{mV}_{\rm PP}$ sinusoidal signal at 1 kHz is applied in one channel and a dc signal applied in the other channel, the amplifier demonstrates a gain difference of $-$ 9.4 dB. The simulation and experiment results show that the amplifier can deliver 2.5 W $\times$ 2 into 4- $\Omega$ loads at 3.6-V supply in the left or right channel, with the total harmonic distortion plus noise (THD $+$ N) of less than 0.1%. The gain in the bass channel is up to 30 dB at 3.6-V power supply, with the THD $+$ N of about 0.05%.

RHCP pattern‐reconfigurable spiral antenna biased with two DC signals

ABSTRACTA right‐hand circularly polarized beam steering spiral antenna is presented in this article. It is designed using the standard p‐i‐n technology, enhanced with arm switches and biasing lines. The ensuing design is easily manufactured and is functionally competitive with the more complex ones, based on RF‐MEMS. Three beams, tilted 40° with respect to the spiral central axis, are generated at 3.3 GHz, suitable for WiMax systems at this frequency. These beams are directed at approximately 90°, 180°, and 270° in the azimuth space. Beam directions depend on various configurations of the seven p‐i‐n diodes added to the spiral structure. The states of the diodes are subjected to the two DC bias voltages connected to the spiral arm. The radiation performance over the 200‐MHz bandwidth (3.2–3.4 GHz) is relatively stable. Measurements in this band show the reflection coefficient below −10 dB and the axial ratio below or close to 3 dB at the peak beam directions. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1636–1640, 2014

Study of cyanoethyl pullulan as insulator for electrowetting

In this paper, the dielectric and electrowetting properties of cyanoethyl pullulan (CEP) are studied as the insulator in electrowetting on dielectric (EWOD) device. The CEP film is formed by spin-coating and low-temperature annealing in atmosphere. The characterization results show that CEP can serve as the dielectric of EWOD with a high dielectric constant of 18 and a great electrowetting performance when annealed at 100°C in atmosphere. The reversibility, stability, polarity-dependence, and frequency-dependence of electrowetting on CEP are fully investigated. The spin-coated CEP exhibits little polarity-related electrowetting while having better driving performance under negative-potential. Frequency-related electrowetting is more sensitive at low-frequency alternating current (AC) potentials than at high-frequency ones. It also shows reversible and stable electrowetting with a small irreversibility of 2° after a 700-cycle test. Based on the above results, an EWOD device with 1μm thick CEP dielectric layer is fabricated. The EWOD device successfully manipulates water droplet at a low driving voltage of 20V and a large velocity under low voltage of DC or AC signals with different frequencies. The easy fabrication and excellent performance of CEP qualifies it as a superior dielectric material in the future EWOD devices and lab-on-a-chip system.

An Ultra Low Noise Optoelectronic Module Enables an in Situ Range-Finder Probe to Locate a Neurovascular Bundle in Dental Implant Surgery

Dental implantology procedures necessitate surgical drilling of a hole in the jawbone to insert an artificial root over which a dental prosthesis is placed. The success factor of a dental implant is attaining successful osseointegration. This implies a deeper placed implant closest to the Inferior Alveolar Nerve (IAN) but not too close that it carries the risk of damaging this nerve-artery bundle located along the mandible line. Implications for perforating the IAN in patients can vary from temporary numbness to permanent loss of sensation in the lower facial area. Surgeons routinely use computer-assisted navigation techniques relying on static preoperative cone-beam X-ray computed tomography or other imaging methods such as Magnetic Resonance Imaging (MRI) to assess optimal anatomical distances in the patient’s jaw. However, variability of the measured IAN bundle position with these techniques is at the moment accurate to 30% at best. These techniques are known to introduce localization errors and do not benefit from in situ guidance. Therefore there is an important need for an online, in vivo probe to assess drill distances to a critical nerve-artery bundle in situ to not only avoid jaw paralysis but to improve overall outcome of the implantation.To this aim, we investigate a combined multimodal approach using Optical Coherence Tomography (OCT) for high resolution structural imaging, and functional NIR absorption detection in an optical fiber probe eventually small enough to fit into a surgical drill bit, for real-time evaluation of the distance from the probe to the IAN. We designed a reflectance fiber-optic probe to sense the pulsation of the artery (Heartbeat ~1-2Hz) in the IAN bundle, and a detection circuit board with a high gain (2 . 106 V/A), and very low noise (10mVRMS at output) and bandwidth (10Hz) shown on Figure 1.The success of this NIR channel for accurate real-time proximity sensing by capturing low frequency pulsing signals relies on an ultra low noise photon detection module. Measurements with this fiber probe were conducted at probe-target distances varying from 0mm (probe in contact) to 3mm. The results obtained are promising: the oscillating RMS amplitude varies as a function of distance in a similar fashion to previously published work in pulse oximetry literature [1]. The DC level also has a specific trend as a function of distance. Both AC and DC signal components can be used to extract useful distance information.Original designs using a lock-in amplifier to measure the very low RMS amplitude of the of the back-reflected light intensity, modulated by the spatially oscillating absorption changes due to flowing blood surrogate in an artery simulating tube were promising, but limited.Lock-in signal detection with a reference signal modulated at only 1-2 Hz needs filtering with long time constants. Moreover, clinical implementation with the heartbeat as the reference signal would make real-time measurement impractical. As such, we have developed a flexible optoelectronic detection platform with tunable bandwidth, gain and bias enabling the system to not be limited by electronics noise.Using custom phantoms of the jawbone and including a surrogate arterial dynamic pumping circuit, we demonstrated proof of concept for potential detection range of 0.5-4 mm at l-850nm with a source-detector separation of 1.8mm using the pulsating signal from an artery simulating tube. In compliment, a swept-source OCT at 1.3mm provided finer resolution sensitivity to the proximity of the IAN bundle in the 0-0.9mm range and offered the possibility of imaging the inhomogeneous IAN interface.Methods for calibrating and processing the data to provide robust long range NIR finding capabilities in combination with short-range high precision OCT imaging towards a complete clinical solution will be discussed.

ACONDICIONAMIENTO Y DIGITALIZACIÓN DE LA SEÑAL DE UN LVDT PARA LA MEDICIÓN DEL PERFIL DE UNA SUPERFICIE SÓLIDA Acondicionamiento y Digitalización de un LVDT

El LVDT es el elemento más importante para la medición de los perfiles utilizando un perfilómetro de contacto y su función es convertir las variaciones de desplazamiento de una aguja en variaciones de voltaje, a través del desplazamiento del núcleo de una bobina acoplado a la aguja. El desplazamiento del núcleo a escala completa se determinó midiendo el recorrido total que hace la aguja, obteniendo el mismo voltaje en el secundario para los desplazamientos extremos. Con este valor y con el de los voltajes del primario y secundario se encontró una alta sensibilidad para el LVDT del perfilómetro, siendo 7,19mV/V/mil el valor obtenido, lo que significa un reto para su lectura. Para el acondicionamiento del LVDT se utilizó un circuito AD698 que genera una señal oscilante, con amplitud y frecuencia ajustable para el primario, y un demodulador síncrono que convierte la señal del secundario en una señal DC, que incrementa linealmente con respecto a la posición del núcleo. Se diseñó e implementó un sistema de conversión A/D, teniendo en cuenta la resolución, la señal de entrada, la frecuencia de muestreo, las prestaciones estáticas y las dinámicas, la interfaz de comunicación, y el tamaño y el precio. La transmisión de los datos de la medida del perfil se realizó por medio del protocolo USB, a través de un microcontroladorATxmega. Se realizaron medidas del perfil utilizando unas muestras patrón de 50, 5 y 1 KÅ, para evaluar el desempeño del sistema de acondicionamiento, obteniéndose resultados satisfactorios.