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A commercial graphene nanoplatelets-based tunable attenuator is proposed. The attenuator comprises of a couple of microstrip lines connected through a gap where the commercial graphene nanoplatelets are drop casted. The transmitted signal through the microstrip line can be varied by an applied DC bias voltage that alters the graphene resistance. The DC resistance of commercially acquired graphene is higher than lab-grown graphene and so is the resulting minimum attenuation of the transmitted signal. The proposed structure is designed to reduce both the minimum graphene resistance and the transmission. The resultant dynamic range of attenuation is more than twice as compared to other series attenuators designed with lab grown graphene nanoplatelets. The operating frequency of the attenuator is from 1 to 5 GHz with maximum dynamic range of attenuation almost 10 dB.

Zinc oxide (ZnO) varistor ceramics present excellent nonlinear current-voltage characteristics so that they are widely used as core materials in overvoltage protection. Generally, the nonlinear characteristics of traditional ZnO varistor ceramics would deteriorate under constant DC bias voltage, manifested as the continuous increase of power loss. However, it has been reported that some commercial samples experience a decrease in power loss during DC degradation, which makes them more stable in operation. The physical mechanism behind this unusual phenomenon is still unclear yet. In this paper, commercial ZnO varistor ceramics with this unique characteristic were employed for DC degradation and accelerated recovery. Current-voltage curves were measured in the ageing and recovery process. The results show that the forward barrier height declines and the nonlinearity becomes better, in contrast, the reverse nonlinearity falls off. But after enough recovery, the electrical properties of the ageing samples almost restored to the initial levels. To sum up, the opposite changes occurred between the forward and reverse characteristics in the ZnO varistors ceramics, but both are invertible.

A polarization-reconfigurable and frequency-tunable active metasurface (MS) is presented. The proposed MS can realize the dynamic switch of linear to linear, and linear to circular polarization. The MS is composed of active unit cells incorporated with voltage controlling. By controlling the DC bias voltage of the varactor diodes, the electromagnetic responses of the proposed MS can be tailored, leading to reconfigurable polarization conversions. The simulation results show that the proposed MS structure can switch between left-handed circular polarization (LHCP), right-handed circular polarization (RHCP), and linear polarization (LP) in the frequency band of 3-4GHz.

Cross-linked polyethylene (XLPE) DC cables may be affected by the impulse voltage during operation, resulting in the generation of electrical trees. In order to investigate the influence of DC pre-stress time and amplitude on the characteristics of electrical tree initiation under DC superimposed impulse voltage, -50 kV lightning impulse voltage is superimposed under DC bias voltage. The DC voltage amplitude is 0kv, 10kV, 30KV, and the pre-stress time is 1min, 10min, 60min respectively. It is shown that the electrical tree initiation length increases with increasing DC pre-stress time and becomes saturated after a certain period of pre-stress time; When the polarity of DC voltage and impulse voltage is opposite, DC voltage may be restrain the electrical tree initiation length in a certain range of amplitude; The electrical tree initiation length is related to the depth of space charge distribution.

Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in temperature sensors, based on dual 4H-SiC junction barrier Schottky (JBS) diodes and Schottky barrier diodes (SBDs). The forward bias current&ndash, voltage characteristics were acquired by sweeping the DC bias voltage from 0 to 3 V. The dual JBS sensor exhibited a higher peak sensitivity (4.32 mV/K) than the sensitivity exhibited by the SBD sensor (2.85 mV/K), at temperatures ranging from 298 to 573 K. The JBS sensor exhibited a higher ideality factor and barrier height owing to the p&ndash, n junction in JBS devices. The developed sensor showed good repeatability, maintaining a stable output over several cycles of measurements on different days. It is worth noting that the ideality factor and barrier height influenced the forward biased voltage, leading to a higher sensitivity for the JBS device compared to the SBD device. This allows the JBS device to be suitably integrated with SiC power management and control circuitry to create a sensing module capable of working at high temperatures.

A $5\times 9$ beamsteering reflectarray operating at $K_{a}$ -band is presented in this paper. Continuous beamsteering is achieved through the use of barium strontium titanate (BST) technology. BST is monolithically integrated into each unit cell using clean room fabrication techniques. With the application of dc bias voltage, an integrated tunable capacitor is realized. The unit cell design utilized in this reflectarray is analyzed and multiple biasing schemes are assessed. The reflectarray is designed to scan in the $E$ -plane only, and is evaluated using full-wave simulations and measurements. An appropriate feeding structure is designed and fabricated using a fused filament deposition 3-D printer, with micrometer stages used to make fine adjustments for final alignment. Overall a gain of 8.3 dBi, with a 1-dB bandwidth of 2% and continuous beamscanning from 0° to 25° at 32 GHz is demonstrated.

In this paper, an electrostatically actuated MEMS micromirror with enhanced stroke is presented. Unlike traditional MEMS micromirror, the proposed micromirror achieves a large out-of-plane stroke through employing a larger air gap for the micromirror surface to move as well as eliminating the pull-in instability. This novel micromirror has a central reflective micromirror surface of 400 μm by 400 μm, an L-shaped arm that holds the micromirror to the anchor on all side and 3 fixed bottom electrodes beneath each L-shaped arms. The lateral electrostatic forces on the upper L-shaped arm are equal in magnitude but opposite in direction and they counteract to neutralize out each other. The electrostatic force produced on the top L-shaped arm is larger than on the bottom. Therefore, the net electrostatic force points in the upward direction. As a result, the upper plate of the micromirror moves upwards. COMSOL Multiphysics is used to simulate and design the device in order to optimize the stroke of the micromirror for a lower input voltage. The mirror is fabricated using PolyMUMPs fabrication technique where an air cavity of 2.75 μm was achieved by combining the two available sacrificial layers. In this proposed design, an out-of-plane stroke of 2.43 μm is achieved at a 110 V DC bias voltage.

This Letter presents a novel, wrist-worn heart rate sensor, which is comprised of only a passive resonator and a voltage controlled oscillator (VCO). It is clearly demonstrated that valid heart rate data can be extracted off the DC bias circuit of the VCO, making this sensor one of the simplest of its kind ever reported. Experimental results are shown for successful measurements of the user's heart rate when the VCO was tuned to 2.42 GHz, with a DC bias voltage fluctuation of up to 10 mV representing the heart rate. These results are in agreement with those taken using a commercial optical sensor based heart monitor.

The erosion of the stress grading system of converter-fed rotating machines may occur by partial discharges and heat generation. There remain unclear issues in the formation of the potential and temperature distributions along the stress grading system of coils. In this paper, the potential distributions on the stress grading system of the model coil bar are measured under the application of 1 kHz square wave voltages of 10 kV in peak to peak value with/without 5 kV DC biased voltage. It turns out that DC bias voltage has little effect on potential distribution on a coil surface.

The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was studied using impedance spectroscopy. The measurements were performed at room temperature in a wide frequency range of 1 Hz to 1 MHz under applied DC bias voltages from 0 to 3 V in the periodic increment of 0. 2 V. The observed applied DC bias voltage effect on giant dielectric constant (e{open}? = 104) were analyzed with 'grain boundary double Schottky potential barrier height model'. The percentage of tunability (T %) at the frequency 100 Hz is found to be 45. 5% for the case of nanocrystalline CuO in contrast to 0% tunability in bulk CuO. � 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

A research on the emission charge of a BaTiO3 surface flashover trigger device and of pseudospark switch (PSS) and its trigger characteristics are presented in this paper. The experimental results have been found that BaTiO3 surface flashover trigger device has more excellent electron emission characteristics than that of ZnO. The electron emission charge Qe of BaTiO3 surface flashover trigger device is mainly influenced by the trigger pulse voltage Utr, the gas pressure p and the DC bias voltage Ubias. Then the trigger characteristics of PSS are investigated.

Electron tunneling through a nonstationary magnetic tunnel junction has been studied in the approximation of a small-amplitude ac electric field. The effect of a giant change in the magnetoimpedance of a magnetic tunnel junction, which occurs at some frequencies of an ac bias voltage, has been predicted. The dependence of the effect of a giant change in the magnetoimpedance on the height and thickness of the magnetic tunnel junction and on the dc bias voltage has been studied.

Two kinds of Photoconductive semiconductor switch(PCSSs) with bulk structure are studied experimentally, which are fabricated from semi-insulating GaAs. The first switch has a size of 10 mm×10 mm×0.6 mm, whose electrodes are 6 mm in diameter on the opposite side of the chip. The second one has a size of 15 mm×15 mm×3 mm, whose electrodes are 8 mm in diameter on the opposite side of the chip. The withstand voltage of the first switch is tested under pulse voltages with different full-width-at-half-maximum. A maximum withstand voltage of 7.6 kV is achieved, which means the breakdown electric field is 127 kV/cm. The volt-ampere performance at DC bias voltage and dark condition of the second switch is tested as well as its triggered performance. The maximum current of the switch is more th

In this paper an electrostatically driven MEMS resonator with resonance and hysteresis characteristics is reported. The resonator begins to exhibit spring-hardening effect at ac excitation voltage of 105mV and dc bias voltage of 5V in vacuum at 50Pa. An extended hysteresis at low pressure and high excitation voltage during upsweep and downsweep of excitation frequency was observed. This characteristic facilitates the usage of this type of resonator in a range of applications such as a cascaded filter array or as a high bandwidth resonator.

Effects of pulsed voltage superimposed on dc bias voltage and meniscus height on electrohydrodynamic (EHD) spraying were investigated. Results show that greater pulsed voltages were associated with jet formation while a dripping mode was apt to appear with a lower pulsed voltage. This is because that with increasing pulsed voltages the energy gain per unit area of the liquid and the tangential electric stress at the meniscus lateral were increased more quickly than the normal electric stress at the apex of the meniscus. Additionally, the increment of meniscus height led to an unchanged tangential electric stress at the meniscus lateral, but a more quickly increased energy gain per unit area of the liquid than the normal electric stress at the apex of the meniscus. For the same pulsed voltage, spraying in Dripping I mode was produced from menisci of smaller heights due to the intensive normal electric stress. A much greater meniscus height, on the other hand, led to spraying in Dripping II mode when the pulsed voltage was insufficiently great. These various modes were determined by contributions of the tangential electric stress, the normal electric stress and the meniscus height.

A set of microwave (1–30 GHz) measuring resonators and procedure of measurements for the investigation of microwave properties of ferroelectric film planar varactors were elaborated. The fabricated resonators enabled MW losses and tunability of ferroelectric varactors under dc bias voltage to be determined. The SrTiO3 and (Ba,Sr)TiO3 film planar varactors were tested on microwaves at room temperature. A ratio of varactor capacitance at zero bias to bias conditions, K, was found as 2 for the SrTiO3 varactors and K=2.2 for the (Ba,Sr)TiO3 varactors. The microwave losses in the ferroelectric varactors were measured at frequencies of R-, X-, K-, and Ka-bands. Temperature stability of the varactor capacitance was estimated.

A linearized optical modulation scheme using a dual parallel electroabsorption modulator (EAM) and an RF 180° hybrid junction is proposed. The IMD2 generated by each EAM is suppressed by controlling the dc bias voltage of the EAM, and the IMD3 is suppressed by having a proper input optical power split ratio and an RF 180° hybrid junction. Reductions of both the IMD2 and the IMD3 at the same operation voltage were achieved, and a subsequent SFDR enhancement of 29 dB was obtained. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 373–376, 2001.

Ordered Ga0.52In0.48P alloys (GaInP2 for simplicity) grown on miscut [001] GaAs resemble monolayer superlattices with alternating Ga- and In-rich layers along either the [111] or [111] directions. Recent calculations suggest that, in fully ordered GaInP2, an intrinsic ordering-induced electric field of order 1600 kV/cm should exist. In partially ordered samples, as can actually be grown, the expected field is reduced to 400 kV/cm. For such a strong internal electric field, clear Franz–Keldysh Oscillations (FKOs) would be expected in an electroreflectance measurement. We report electroreflectance measurements of ordered GaInP2 layers measured at T=100 K. For all samples measured, no FKOs are observed in the absence of an additional external dc bias voltage. At the lowest bias voltages for which FKOs are seen, the internal electric field in the GaInP2 layer, determined from the FKOs, is ∼60 kV/cm along the [001] direction corresponding to ∼100 kV/cm along the ordering direction. Hence, we conclude that, a...

A voltage activated barium strontium titanate solidly mounted resonator was fabricated and measured. The barium strontium titanate was deposited on a chemical mechanical polished acoustic Bragg reflector with a surface roughness of 0.504nm RMS. Data was collected on the device at a dc bias voltage range of 0V to 25V in 5V increments. The barium strontium titanate solidly mounted resonator showed an effective quality factor of 100 to 180 over the bias range.

TSV modeling method based on cylindrical modal basis functions is modified to consider the effect of depletion region formed by a DC bias voltage. Extended capacitance matrix equation is obtained to include depletion capacitances, and the new formula is inserted to the original formulation. The proposed method is tested for two TSVs with varying depletion depths, and the computed insertion losses, capacitance, and conductance show reasonable trends.

This paper presents design and application of a varactor loaded tunable coupled line for a polarization agile antenna. Based on the investigations, a method is proposed to reduce the required varactor tunability. Later on, the results are verified by prototyping an antenna, which consists of a liquid crystal based tunable coupled line. The antenna operates at 13.75 GHz with a return loss of better than 10 dB. The measurement results confirm that the polarization state of the antenna can be changed continuously between linear and circular polarizations by applying a DC bias voltage to the varactors.

The effects of through-silicon via (TSV) depletion are analyzed based on the frequency- and time-domain measurements in this paper. As TSV dc bias voltage increases, a TSV depletion region is generated; this region decreases TSV noise coupling at frequencies below 1 GHz. It also creates duty-cycle distortion of the coupled signal, which results from the nonlinearity of the TSV.

Tunable 3.5GHz and 1.5GHz chip antennas are presented in this paper. By applying tunable matching networks, the chip antennas show tunable characteristic. Especially, the capacitors in the matching networks are tunable thin-film BST capacitors, which have a 3∶1 tuning ratio. The capacitance of the BST capacitors can be tuned by an external DC bias voltage. By varying the capacitance, the tunable matching networks increased the bandwidth of the 3.5GHz antenna by 80%, and the 1.5GHz antenna by 26%.

Two-frequency combination technique can effectively decreases sidelobes in ultrasonic measurement on a sparse phased array. Tunable resonant-type ultrasonic microsensors have been fabricated for the measurement technique by switching the resonant frequency to the two frequencies. The ultrasonic sensor consists of a piezoelectric lead-zirconate-titanate (PZT) capacitor on a silicon-micromachined thin diaphragm structure. The piezoelectric capacitor has two kinds of electrode for ultrasonic sensing and for frequency tuning by applying a dc bias voltage. The resonant frequency has been tuned from a base frequency down to a sub-frequency which has −47% lower than the base frequency. The two-frequency measurement at the base and sub-frequencies achieves ghost suppression by decreasing sidelobes down to −17 dB.

The external electro-optic (EO) probing technique has been a very useful tool for the characterization of high-speed devices and circuits. In this paper, we propose a method to enable the traditional non-contact EO probing technique further direct DC bias voltage measurement via a special side-electrode-equipped electro-optic tip

Deep trenches were etched in silicon with SF 6 plasmas in a simple RIE system. Two process factors influence directly the silicon surface roughness generated by these processes: the dc bias voltage and the presence of oxygen. In general, the roughness increases when the dc bias voltage becomes more negative. Small traces of oxygen increase the roughness substantially. We show that this oxygen does not necessarily have to be introduced as a gas, but its origin could also be oxygen containing materials, such as glass, which are etched during the process. Processes with low dc bias voltage and without any oxygen result in smooth bottom and wall profiles.

z‐cut lithium niobate optical modulator devices were ac (Vp‐p=20 V) operated at 130 °C with an accumulated dc bias voltage of 4 and 8 V. A consequent dc drift phenomenon was larger for the 8 V bias application. After the operation, inversed domains were found along the Mach–Zehnder waveguides, particularly on the waveguide placed under the hot electrode. The results suggested that the device operation at higher voltage and temperature led to an accelerated dc drift and a fatiguelike deterioration of the lithium niobate material.

When the semiconductor substrate under the microstrip transmission lines is properly doped, a substantial phase shift of the propagating wave by an applied DC bias voltage is demonstrated. The device is inexpensive to fabricate and easy to implement, especially in monolithic structures. © 1995 John Wilet & Sons, Inc.

A bulk-micromachined electrostatic micromirror has been designed, fabricated and tested for applications to tunable optomechanical switching microdevices. Static deflections of the micromirror have been measured up to 26.5 /spl mu/m with a DC threshold voltage of 330 V. Resonant switching frequencies have been tuned in the ranges of 580-450 Hz by varying the DC bias voltage within 50-300 V for an AC drive voltage of 10 V.

Dielectric properties of Au/Ba0.6Sr0.4TiO3/La1.1Sr0.9NiO4 (Au/BST/LSNO) thin film capacitors were investigated versus excitation frequency and dc bias voltage. At low frequencies, Au/BST/LSNO capacitors exhibited a usual positive tunability [i.e., C(0V) > C(V)], while an unexpected negative tunable behavior appeared at higher frequencies. On the basis of the dielectric tunable theory and equivalent electrical circuits, a model describing the dielectric tunability of Au/BST/LSNO capacitors is proposed. The good agreement between fitted and experimental results shows that the resistance of LSNO bottom electrode in the Au/BST/LSNO capacitors plays an important role in the dielectric tunability transition from positive to negative with frequency.

Dielectric relaxation in sol-gel-derived anatase titanium oxide nanocrystals (6, 9, and 20 nm) has been investigated using impedance spectroscopy in a wide frequency range from 1 Hz to 1 MHz as a function of applied DC bias voltage, ranging from 0 to 4.2 V in a periodic interval of 0.3 V. Under the equilibrium condition, around three order of magnitude variations in the dielectric relaxation time (?) was observed for the grain size if reduced to 6 nm from 20 nm. An unambiguous evidence for the absence of such a crystallite size effect was experimentally observed in higher biased conditions because of grain boundary Schottky potential barrier height suppression. These experimental results obey the grain boundary double Schottky barrier model. � 2011 American Institute of Physics.

Magnetoresistance (MR) ratio in a magnetic tunneling junction cell with a structure of SiO2 (20nm)∕Ta (5nm)∕Cu (20nm)∕Ta (5nm)∕NiFe (2nm)∕Cu (5nm)∕MnIr (10nm)∕CoFe (4nm)∕Al–O (1.5nm)∕CoFe (4nm)∕NiFe (20nm)∕Ta (50nm) was measured by conducting atomic force microscopy to obtain I‐V curves. Tunnel magnetoresistance was characterized from these nonlinear I‐V curves. MR values of 33.9%, 30.5%, 30.3%, and 28% were obtained when applying magnetic fields of ±150Oe at various dc bias voltage ramping rates. Several ramping rate values were 0.498, 4.65, 9.3, and 27.9Hz, respectively.

By changing the negative dc bias voltage applied to substrates during rf sputtering, we have prepared compositionally modulated GdFe multilayers, which have an in-plane anisotropy. These films show a two-step magnetization process. The calculations using a pseudo-domain-wall model indicate spin flopping at the critical field causing the two-step magnetization.

This paper reports positive switching impulse flashover characteristics of thin wire-plane gaps. Flashover tests were made under both conditions that switching impulses were added with or without ac or dc corona occurring previously. Flashover distances were up to 4 m, and ac or dc bias voltage was 400 kV crest.

Electron emission into vacuum has been observed from a forward‐biased Cs‐ and O‐treated GaAs p‐n junction. The device was operated at room temperature with dc bias voltage. The effective efficiency of the device (emission current divided by internal diode current eligible for emission) was 0.05%, while the over‐all efficiency of the device (emission current divided by total diode current) was 10−6. The low over‐all efficiency is explained in terms of sample geometry and surface activation.

Double layer films of rf-sputtered amorphous GdCo have been made under different sputtering conditions. The first layer was sputtered with a dc bias voltage, and the second was successively deposited onto the first layer with non-bias. Double layer GdCo film holds as large area uniformity of magnetic properties as bias sputtered film and has good stability of bits as small as 1 µm in diameter. The films with various values of coercive force were also made by changing the ratio of thickness of these two layers. The thermomagnetic recording was carried out at a speed of 1800 rpm on this double layer GdCo disk of 150 mm in diameter.