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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.

Second harmonic generation (H2) is not desirable for BAW filter applications. Recent BAW filter requires reduction of H2 to achieve high receiver sensitivity. In order to reduce H2, nonlinear parameters of AlN and ScAlN are important because it is widely used in BAW filters. Irieda et al. indicated that second order nonlinear piezoelectric coefficients $\chi_{11}{}^{\mathrm{T}}$ and dielectric $\chi_{02}{}^{\mathrm{E}}$ are dominant for H2 [1], [2]. They showed these nonlinear coefficients $\chi_{11}{}^{\mathrm{T}}$ and $\chi_{02}{}^{\mathrm{E}}$ can be approximately estimated from the change of parallel resonant frequency $f_{\mathrm{p}}$ and inverse dielectric constant $\beta^{\mathrm{S}}$ during a DC bias voltage application. In this study, AlN and ScAlN films were grown on Al bottom electrode/Ta2O5/SiO2 Bragg reflector (SMR) by RF magnetron sputtering. $f_{\mathrm{p}}$ and $\beta^{\mathrm{S}}$ of AlN/SMR and ScAlN/SMR as a function of the DC bias voltage were measured. Nonlinear parameter $\chi_{11}{}^{\mathrm{T}}$ and $\chi_{02}{}^{\mathrm{E}}$ of films were estimated. $\chi_{11}{}^{\mathrm{T}}$ was decreased with increasing of Sc concentration.

The Airy beam, known to present particular unique features, such as diffraction-free, self-healing, and self-bending, has attracted considerable interest in recent years. Here, an electronically controlled reflective coding metasurface is exploited to generate and dynamically manipulate the Airy beam over a wide frequency band in the microwave regime. By judiciously controlling the external dc bias voltage applied to the programmable metasurface, two distinct control states, ``0'' and ``1'', are engineered as digital codes for \ensuremath{-}\ensuremath{\pi}/2 and +\ensuremath{\pi}/2 phase responses, respectively. The programmable binary-phase-coding metasurface enables the generation and active reshaping of the Airy beam to be numerically simulated and experimentally validated. Moreover, the metasurface allows the bandwidth limitation of passive counterparts to be overcome and is able to modulate electromagnetic waves over a broad frequency range, spanning from 9 to 12 GHz, to realize diffraction-free Airy beams.

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.

A novel approach to generate the flattened optical frequency comb (OFC) with tunable frequency spacing is proposed. The proposed generator consists of two cascaded polarization modulators driven by two radio frequency signals with different frequencies. By adjusting the parameters, 9, 12, and 16 comb lines can be generated with tunable frequency spacing. The scheme requires no DC bias voltage of the modulators and no optical filter, which makes our method simple and stable. A concept proof simulation is conducted to confirm the feasibility of the generation schemes of the 9-, 12-, and 16-line OFCs.

This article describes a new electrical configuration for driving piezoelectric benders. The ‘Biased Bipolar’ configuration is compatible with parallel-polled, bimorph and multimorph benders. The new configuration is similar to the standard three-wire drive method where the top electrode is biased with a DC voltage and the bottom electrode is grounded. However, the new configuration uses an alternate DC bias voltage and adjusted range for the central electrode which allows the full range of positive and negative electric fields to be utilized. Using this technique, the predicted deflection and force can be increased by a factor of 2.2 compared to the standard two wire configuration and 1.3 times for the standard three wire configuration. These predictions were verified experimentally where the measured factor of improvement in displacement and force was of 2.4 and 1.3 compared to the standard two-wire and three-wire configurations.

A novel and noninvasive method to determine the in situ etch rate (ER) of inductively coupled plasma (ICP)-etched Hg1−x Cd x Te in real time is described. Various relevant output parameters from the ICP tool were analyzed with the goal of finding correlations with the Hg1−x Cd x Te ER. Of the parameters analyzed, the most promising is the chuck direct-current (DC) bias voltage. Correlations between the chuck DC bias voltage and two different types of Hg1−x Cd x Te detector wafers are reported with a correlation coefficient of R > 0.94. Analyses of these results are presented. Estimates of the Hg1−x Cd x Te ER for all the samples based on the new method are presented and compared with the actual ER. The results show less than 3% differential between the actual and estimated ER.

Filters operated at high power levels and comprising BAW resonators produce 2nd harmonic emissions. To model the emissions of a BAW resonator, Feld and Shim constructed a nonlinear Mason model, which implements an “extended” pair of piezoelectric constitutive equations containing arbitrary 2nd order terms: T = cES − eE + [1/2δ 3 cES2 − δ 1 eSE + 1/2δ 2 eSE2] D = eS + eSE + [1/2δ 1 eS2 − δ 2 eSSE +1/2δ 4 eSeE2/cE] (1) cE, e, eS, δ 1 -δ 4 are the 1-D stiffness, piezoelectric, and dielectric, and 2nd order constants respectively. The values of the 2nd order coefficients, δ 1 & δ4, which are found to be the dominant terms — can be found by measuring the on- and off-resonance levels of H2 respectively. We present an alternate measurement technique to determine these coefficients by measuring linear parameters of a resonator under large DC bias voltage conditions.

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.

We propose and demonstrate a novel reconfigurable instantaneous frequency measurement (IFM) system based on the dual-parallel Mach-Zehnder modulator (DPMZM). The IFM system can be reconfigurable with tunable measurement range and resolution by simply adjusting the dc bias voltage of the DPMZM. In principle, the measurement range could be tuned to any frequencies, which is only limited by the bandwidth of the optical transmitter and receiver employed. Alternatively, the IFM system can also work with a fixed wide measurement range and moderate resolution by generating two complementary power-fading functions.

A method for controlling electrostatic charge on particles with positive ions and/or electrons generated by an atmospheric pressure plasma jet was studied experimentally. The atmospheric pressure plasma jet was generated by applying AC voltage and DC bias voltage to a cylindrical electrode in a quartz glass tube with helium gas flow. By changing the value of the DC bias voltage, positive ions and/or electrons could be extracted from the plasma. Two experiments, one in which particles were allowed to fall in the plasma jet and the other in which particles were irradiated with the plasma jet, were performed, and comparison of their results showed that both methods allowed the particles to acquire positive ions and/or electrons because of the electric field caused by the space charge. In addition, particle charging could be controlled by applying an external electric field. Based on these experimental results, the particle charging mechanism involved was discussed.

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

An experimental analysis was performed to understand the effects of environmental and operational conditions on the frequency stability of a piezoelectric microcantilever sensor (PEMS). Variation of the resonant frequency was analyzed with changes in the relative humidity (RH), vacuum state, DC bias voltage, oscillating voltage, and time.

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.

In view of the practical situation, sometimes there is side error of the comb capacitor through superposition of the deep reactive ion etching (DRIE) process, and these manufacturing tolerances can lead to the movable comb fingers offset. Using the software of ANSYS to explore the electrostatic-structural coupled field. Then, the effect of sensitive direction offsets on the static displacement of micro-resonator is analyzed, in addition, the different initial finger overlap, dc bias voltage and side error are considered based on the traditional structure, at the same time, the fringe effect and the corner-effect of comb need to be taken into consideration. The ideas and the simulation results in this paper have a guiding significance for improving the performance of the micro-resonators.

This study presents two curve-fitting models of concave and convex magnetic field-effect transistor (MAGFETs) with a dc bias voltage supplied at the gate of the MAGFET. Experimental results indicate that the highest absolute sensitivity S A , supply-current-related sensitivity S RI and supply-voltage-related sensitivity S RV are 1.39 V/T, 2004.8 V/AT and 0.46 V/VT for the concave MAGFET, and S A = 0.77 V/T, S RI = 512.4 V/AT, and S RV = 0.29 V/VT for the convex MAGFET with a 3 V dc supply voltage. A magnetic device with geometric parameters, L / W = 40 μm/40 μm and d = 2 μm, is the best choice to optimize sensitivity, but a MAGFET with geometric parameters, L / W = 40 μm/40 μm and d = 4 μm, is another good choice because of its consistent geometric correction factor. The proposed arrayed and symmetrical designs can increase output voltages and eliminate unwanted errors. Broadening the drain gap not only improves the linearity of the output voltage, but also clearly makes the error correction factor consistent for both concave and convex MAGFETs. Minimizing the aspect ratio reduces the sensitivity of the concave MAGFET faster than that of the convex MAGFET. In general, both concave and convex MAGFETs are suited to fabricating magnetic devices with a wide drain gap.

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.

We report studies of the in-plane magneto-transport properties of a 2DEG in an InAs inserted InGaAs/InAlAs heterostructure with a DC bias voltage. Temperature dependent zero-bias reduction of the longitudinal resistance was observed when high magnetic field is applied along the sample growth direction. We interpret the observed resistance reduction as the result of a Coulomb gap existing at the Fermi level of the 2DEG.

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 impedance characteristics of a CuO/ZnO oxide semiconductor heterocontact were investigated to study a new method of gas identification. This was done by applying a dc bias voltage in atmospheres of air-balanced, flammable CO or H2 gas (4000 ppm). The frequency dependence of the reactance component showed a characteristic behavior that varied according to the testing atmosphere under the applied negative dc voltage at 400°C. The discrimination of CO gas from H2 gas in air was demonstrated as feasible by either varying the bias voltage in negative values at constant frequency or sweeping the frequency on a negative bias voltage. The new method of gas identification suggested by the present study uses a ceramic-semiconductor heterocontact, on which a combination of dc bias voltage and ac signal is applied.