AC Carrier Research Articles

Development and experimental investigation of a high-precision capacitive displacement transducer of the inertial sensor for TianQin

Capacitive sensing electronics are critical to space gravitational wave detection missions, providing the test mass motion information for the inertial sensor’s non-sensitive axis control and the drag-free control of the satellite. For the TianQin mission, the capacitive sensor requirement is at 6 mHz, corresponding to a displacement noise of . This paper presents the system design scheme, noise analysis, and performance testing of the capacitive sensor for the TianQin mission. Based on the previous work of our group, a capacitive sensing scheme based on a transformer bridge and modulation–demodulation is adopted. A transformer with a better high LQ product is fabricated, and the preamplifier current noise is reduced to further improve the performance above mHz. The amplitude stability of the AC carrier and the performance of the lock-in amplifier circuit are further improved to reduce the low-frequency noise at and below. Finally, a capacitive sensor prototype is developed and tested, the experimental results show that the capacitance measurement noise is better than above 1 mHz and better than at about , which meets the overall performance requirement of the TianQin mission.

Effect of EAM on Capacitive Detection of Motion in MEMS Vibratory Gyroscopes

The Electromechanical Amplitude Modulation (EAM) is frequently used to eliminate feed-through signals between forcer and pick-off electrodes of resonant microstructures. However, there are some undesirable effects of EAM that need to be considered. This work studies the contribution of EAM on dissipation of energy and appeared non-linear dynamics in MEMS Coriolis Vibratory Gyroscopes (CVGs). We presented an analytical model, capturing the effect of AC carrier signal on amplitude-frequency coupling, scale factor instability, and in-run noise performance of CVGs. The effect of EAM on a Dynamically Amplified dual-mass Gyroscope (DAG) was experimentally demonstrated and compared to the simulation results of the analytical model. We concluded that the AC carrier signal in EAM influences the amplitude-frequency couplings along both the drive and sense modes of the gyroscope through modifying the non-linear electrostatic stiffnesses, which was also proven to be one of the dominant sources of both the scale factor nonlinearity and frequency instability in the near-mode-matched DAG, operating in the open-loop rate mode.

Enhancing effects of activated carbon supported nano zero-valent iron on anaerobic digestion of phenol-containing organic wastewater

Activated carbon supported nano zero-valent iron material (NZVI/AC) was prepared and added to an anaerobic digestion tank to reduce the toxicity inhibition of phenols and increase the methane yield of phenol-containing organic wastewater (POW). The anaerobic digestion (AD) characteristics, including conversion rate of organic substances, removal rate of phenol, and methane yield of POW with different concentrations of phenol were studied, and moreover, the enhancing effects of NZVI/AC on the AD of POW were focused. When the concentration of phenol was below 500 mg/L, the methane yield from AD of POW was 387.5 mL, which was 10.71% higher than that from control organic water without phenol, however, phenol concentrations greater than 1000 mg/L severely inhibited AD, and methane yield was only 50% of the control sample. Indicating that anaerobic microorganisms had a certain degree of tolerance to phenol, and low concentration of phenol could promote AD of organic water although the phenol with high concentration showed severe inhibition. The methane yield increased due to the probable conversion of phenol to methane by microbial actions. In the AD of POW with 500 mg/L phenol, the conversion rate of organic substances increased from 37.49% (control group without any accelerant) to 66.56% after adding NZVI/AC. The removal rate of phenol also increased from 39.03% to 81.32%. Cumulative methane yield increased by 145.5%–810 mL compared with the control group. The AC carrier in NZVI/AC exerted a good adsorption effect on phenols, reducing the concentration of phenols in the solution and thus minimizing their toxic effects on microbial activity. The NZVI loaded on AC particles strengthened the electron transfer between methanogens by its good electrical conductivity, and then promoted the AD performance of organic matter. Furthermore, NZVI exerted a micro-electrolytic effect on phenolic substances, which could increase the removal rate of phenol. Therefore, NZVI/AC could be used as an efficient accelerant for the AD of POW to enhance the AD process.

AC plasma anemometer—characteristics and design

The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s−1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

Effect of the solvent used to prepare the photoactive layer on the performance of inverted bulk heterojunction polymer solar cells

The initial performance and subsequent degradation of inverted polymer solar cells [indium–tin oxide/titanium oxide (TiOx)/[6,6]-phenyl C61 butyric acid methyl ester (PCBM): regioregular poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid)/Au, TiOx cell] are studied by photocurrent–voltage measurements as well as ac impedance spectroscopy (IS) and carrier mobility measurements. The TiOx cells containing a P3HT:PCBM layer prepared from a solution of chlorobenzene (CB) showed a maximum power conversion efficiency (PCE) of 2.23%. In contrast, the TiOx cells containing a P3HT:PCBM layer prepared from a solution of 1,2,3,4-tetrahydronaphthalene (tetralin) containing 2 vol % 1,8-octanedithiol (ODT) exhibited a maximum PCE of 2.92%. However, after exposure to light irradiation for 100 h, the maximum PCE of the tetralin:ODT cell decreased to 68% of its initial value. On the other hand, over 96% of the maximum PCE was maintained in the CB cell after 100 h of irradiation. The IS measurement results suggest that the degradation of the Tetralin:ODT cell was caused by a morphological change of the P3HT:PCBM layer that made efficient photoinduced charge separation difficult.

The influence of annealing temperature and tellurium (Te) on electrical and dielectrical properties of Al/p-CIGSeTe/Mo Schottky diodes

p-CuIn0.7Ga0.3(Se(1−x)Tex)2 type thin films were synthesized by thermal evaporation method on Mo coated glass substrates. To obtain Al/CuIn0.7Ga0.3(Se(1−x)Tex)2/Mo Schottky diode structure for two compositions of x = 0.0 and 0.6, Al metal was evaporated on upper surface of CuIn0.7Ga0.3(Se(1−x)Tex)2 as a front contact. Al/p-CuIn0.7Ga0.3(Se(1−x)Tex)2/Mo structures were annealed temperature range from 150 °C to 300 °C for 10 min under vacuum. The electrical and dielectrical properties of Al/p-CuIn0.7Ga0.3(Se(1−x)Tex)2 (CIGSeTe) Schottky barrier diodes (SBD) have been investigated. Capacitance–Voltage (C–V) characteristics, Conductance–Voltage (G/w–V) characteristics and interface state density were studied in order to obtain electrical and dielectrical parameters. The effects of interface state density (Nss), series resistance (Rs), the dielectric constant (ɛ′), dielectric loss (ɛ″), dielectric loss tangent (tan δ), ac electrical conductivity (σac) and carrier doping densities were calculated from the C–V and G/w–V measurements and plotted as a function of annealing temperature. It was observed that the values of carrier doping density NA for annealing temperature at 150 °C decreased from 2.83 × 10+15 cm−3 to 2.87 × 10+14 cm−3 with increasing Te content from x = 0.0 to 0.6. The series resistance for x = 0.0 found to be between 10 and 75 Ω and between 50 and 230 Ω for x = 0.6 in the range of annealing temperature at 150–300 °C.

Preparation of the AC/TiO2 Composite Particles in Normal Temperature and Degradation of TNT

AC/TiO2 composite particles were prepared by sol-gel method in normal temperature. Three kinds of particles were obtained by adding Phytic Acid (ab. PA), Benzoyltrifluoroacetone (ab. BTA) and SnCl4 during the preparation. The photo catalytic activity and adsorptive capability of different particles were compared. Raman analysis showed TiO2 grain on the surface of the AC carrier was anatase. FE-SEM photos showed particles with PA were homogeneously coated by TiO2, but more fine TiO2 particles were formed with BTA. The results showed that the adding of PA and BTA helped to get fine grains. The degradation ratio of the TNT solution showed that the photo catalyses activity and adsorptive capability of all composite particles were higher than that of single AC, and the accumulated degradation ratio of TNT solution reached 99.3 % (repeated by 20 times). The degradation of single AC to TNT solution is thought mainly by physical adsorption, but for other composite particles the degradation is by both of the adsorption and photo catalysis. The interface between AC carrier and TiO2 crystal may be affected by PA or BTA, and helping to form synergic effect of AC and TiO2.

Frequency-Adaptive Power System Modeling for Multiscale Simulation of Transients

A multiscale power system modeling methodology for the integrative simulation of electromagnetic and electromechanical transients is introduced, implemented and validated. It makes use of frequency-adaptive simulation of transients (FAST) in which the shift frequency appears as a new parameter in addition to the time step size. For fast electromagnetic transients, tracking of instantaneous waveforms as in the Electromagnetic Transients Program (EMTP) is performed. When slower electromechanical transients involving power oscillations prevail, the Fourier spectra of the waveforms are shifted by typically either 50 or 60 Hz to eliminate the ac carrier and enable envelope following as in phasor-based simulation. An algorithm for the automatic setting of both shift frequency and time step size is proposed. Multiscale models of transformers, synchronous machinery, and transmission lines based on FAST are developed. The line model is distinguished in that it bridges both lumped and distributed parameters to efficiently emulate scale-bridging phenomena from steady state to traveling waves. The overall methodology is thoroughly validated: first against a staged field test involving transients of line energization and recovery on the network of the Bonneville power administration (BPA); then through comparison with an EMTP-type simulator in modeling diverse transients on a four-machine two-area power system.

Acquisition of Position Error and Magnet Polarity for Sensorless Control of PM Synchronous Machines

Sensorless control of a permanent-magnet synchronous machine at low and zero speed is based on the injection of an oscillating high-frequency carrier signal. A particular demodulation technique serves to eliminate the estimation error introduced by pulsewidth modulation delay and the nonlinear characteristics of the inverter. Before the drive is started, the initial rotor position and the magnet polarity are detected. The initialization is performed by injecting an AC carrier and two short current pulses in a sequence.

Frequency-Adaptive Network Modeling for Integrative Simulation of Natural and Envelope Waveforms in Power Systems and Circuits

Algorithms for the simulation of transients in power electric systems and circuits can be classified into two major categories. For the simulation of diverse transients in ac and dc networks, the algorithms process instantaneous signals in the time domain to track natural waveforms as observed in reality. For the simulation of lower frequency transients that modulate ac carriers in ac networks, algorithms that process phasor signals to track envelope waveforms are popular. The methodology proposed in this paper uses analytic signals to bridge the merits of instantaneous and phasor signals and enable the efficient simulation of both natural and envelope waveforms as well as the smooth transition between both. The key enabling method referred to as frequency-adaptive simulation of transients (FAST) is distinguished by the introduction of the shift frequency as a simulation parameter in addition to the time-step size. This distinguishes the methodology from the known methods of power system and circuit simulation, which only use the setting of the time-step size to adapt the simulation process. By setting the shift frequency to a nonzero value, the Fourier spectra of the analytic signals are shifted and adapted according to the waveform type of interest. This adds value because different types of transients with and without an ac carrier can be simulated efficiently and accurately within one and the same simulation run. To provide compatibility with existing tools, the numerical integration is formulated to model the network branches such that nodal analysis can readily be used to construct the overall network model. Calculations of the accuracy as well as test studies that cover network energization and deenergization, angle modulation, and amplitude modulation substantiate the claims made and demonstrate the application of the methodology

AC conductance of (Co0.45Fe0.45Zr0.10)X(Al2O3)1−X nanocomposites

The influence of the composition on the AC carrier transport of the composite films containing ferromagnetic CoFeZr nanoparticles in amorphous aluminium oxide matrix has been investigated. The films 3–5 μm in thicknesses and with variable composition 30 at.% < X < 60 at.% were sputtered on a single substrate from the compound target in the chamber with argon–oxygen gas mixture. TEM and SEM measurements and Mossbauer spectroscopy data have shown that all the studied films of (Co0.45Fe0.45Zr0.10)X(Al2O3)1 − X with 30 at.% < X < 65 at.% have revealed the structure with crystalline granular metallic alloy (with particles of a few nanometers in size) and amorphous alumina. AC conductance measurements were performed over the frequency range 102–106 Hz at temperatures from 80 to 330 K. DC conductance measurements have been carried out for this temperature region also. The presence of two critical regions for the metallic fraction (X1 = 33–40% and X2 = 50–55%), where diagram “electric property–composition” exhibited pronounced peculiarities, has been confirmed. A qualitative structural model of nanocomposite was offered to explain this behavior. In accordance with the model, the first critical region at X1 is associated with a shift of percolation threshold due to the formation of oxide layer on metallic nanoparticles, owing to the presence of oxygen in gas ambient during the sputtering process. The second critical region of the composition at X2 is ascribed to the formation of percolation net of magnetic metallic nanoparticles in the dielectric amorphous alumina matrix.

On the defects introduced by AC and DC hot carrier stress in SOI PD MOSFETs

The defects introduced by hot carrier stress during on-state operation (DC stress) and dynamic operation (AC stress), ofUnibond SOI MOSFETs (0.25μm gate length), are investigated. These defects are monitored by means of Deep Level Transient Spectroscopy (DLTS) technique, which is based on drain current transient signal recording. DLTS spectra of devices subjected to hot carrier stress revealed the presence of traps, some of which were previously reported in literature. Transient effects such as overshoot/undershoot, presented at DLTS spectra of partially depleted SOI devices, was overcome by using body contacted devices. The latter were studied further in order to monitor the body potential transients and to emerge information about the body excess charge recombination paths.

Frequency-domain multiplexing of TES microcalorimeter array with CABBAGE

Properties of Transition-Edge Sensor (TES) microcalorimeters operated with AC bias are studied utilizing the calorimeter Wheatstone bridge circuit called Calorimeter Bridge Biased by an AC Generator (CABBAGE). The CABBAGE eliminates the AC carrier significantly, thus enables us to study the AC responses of the TES with high sensitivity. We tested two kinds of TES devices operating at 110 and 440mK, respectively. With the 110mK device biased with 25kHz, an energy resolution of 28eV is obtained for Mn Kα line. On the other hand, we multiplexed the signals from two 440mK device biased with 50 and 20kHz, respectively, and obtained 167 and 271eV energy resolutions. Even at the balance point of the bridge, AC signal did not disappear and odd-order harmonics were observed. They are considered to arise from the current dependence of the TES resistance, which is characterized by β≡dlogR/dlogI. Numerical solution for the CABBAGE response can reproduce the experimental results well if β=0.24±0.02. Since the harmonics may cause severe problem in the SQUID operation even after attenuated by a band-pass filter, especially at high bias frequency operation such as several hundred kHz, it is important to make β small.

高周波キャリア型薄膜磁界センサの検出磁界分解能

This study reports the performance of a high-frequency carrier-type thin-film magnetic field sensor that uses impedance change at high frequencies. To obtain high resolution, we reduced environmental electromagnetic noise and used high resolution instruments. A voltage change ratio (similar to the MR ratio) of 26.7% was achieved when ac carrier frequency was 400MHz. The resolution of the sensor was dc 2 × 10-4 Oe and ac 8 × 10-5 Oe, respectively.

Voltage-dependent membrane displacements measured by atomic force microscopy.

Cells use polar molecules in the membrane to sense changes in the transmembrane potential. The opening of voltage-gated ion channels and membrane bending due to the inverse flexoelectric effect are two examples of such electromechanical coupling. We have looked for membrane motions in an electric field using atomic (or scanning) force microscopy (AFM) with the intent of studying voltage-dependent conformational changes of ion channels. Voltage-clamped HEK293 cells were either untransfected controls or transfected with Shaker K+ channels. Using a +/- 10-mV peak-peak AC carrier stimulus, untransfected cells moved 0.5-15 nm normal to the plane of the membrane. These movements tracked the voltage at frequencies >1 kHz with a phase lead of 60-120 degrees, as expected of a displacement current. The movement was outward with depolarization, but the holding potential only weakly influenced the amplitude of the movement. In contrast, cells transfected with a noninactivating mutant of Shaker K+channels showed similar movements, but these were sensitive to the holding potential; decreasing with depolarization between -80 and 0 mV. Searching for artifactual origins of these movements, we used open or sealed pipettes and AFM cantilever placements just above the cells. These results were negative, suggesting that the observed movements were produced by the cell membrane rather than by movement of the patch pipette, or by acoustic or electrical interactions of the membrane with the AFM tip. In control cells, the electrical motor may arise from the flexoelectric effect, where changes in potential induce changes in curvature. In transfected cells, it appears that channel-specific movements also occurred. These experiments demonstrate that the AFM may be able to exploit voltage-dependent movements as a source of contrast for imaging membrane components. The electrically induced motility will cause twitching during action potentials, and may have physiological consequences.

Anomalous ac dielectric response and carrier state of c-axis oriented La 2− xSr xCuO 4 films

In order to study the “fractional Hall effect model” of the carrier state of high temperature superconductors, we measured the x dependence of the capacitance C t of multilayer structure Pd/La 2− x Sr x CuO 4/(100)SrTiO 3/Pd. A strong correspondence is found between the x- C t relationship and the filling factor ν dependence of the system energy in the fractional quantum Hall effect.

A new numerical method for quasi-three-dimensional small-signal simulation of silicon bipolar transistors

A new approach to modeling the high-frequency (h.f.) small-signal characteristics of a real three-dimensional bipolar transistor (BJT) is presented. It is based on the joint use of the BIPOLE3 program[1] and a special code HFCALC. First, BIPOLE3 calculates the DC electric field and carrier distributions in the vertical direction and the DC potential distribution in the base region in a horizontal plane. Then HFCALC calculates the vertical one-dimensional (1D) AC potential and carrier distributions and identifies the parameters of the small-signal one-dimensional hybrid-π BJT model for each section of the distributed AC model of intrinsic BJT region. Finally, it performs a circuit analysis for this distributed model plus external elements. As a result, current gain, Y, S and the other AC parameters are computed versus frequency under given DC bias conditions.

磁気‐インピーダンス効果を用いた薄膜磁気センサの基礎特性

This study reports on the performance of a thin-film magnetic sensor that uses impedance change at a high frequency. A closed magnetic circuit, a strip pattern for the magnetic films, and an NiFe/SiO2 multilayer film structure were adopted for high sensitivity and large voltage change. A voltage change ratio of 50-60% was achieved by applying an external field of several Oe with an AC carrier of ∼800 MHz. The sensor was confirmed to perceive a highfrequency external field as an amplitude modulation of the AC carrier voltage, and exhibited broad frequency bandwidth, high linearity, and no hysteresis or Barkhausen noise.

Thin-film magnetic head using impedance change at high frequency

This article reports on the reproducing characteristics of a new type of thin-film magnetic head, which is based on impedance change due to field dependent permeability at a frequency of several MHz. The head is flux responsive, and a field from a medium is perceived as an amplitude modulation of an AC carrier voltage and reproduced by detection. In order to obtain a large change, the head element is composed of magnetic core/sensing lead/magnetic core sandwich structure, and a NiFe/SiO/sub 2/ multilayer film is adopted for the cores. The lead is also used for a DC bias. A single pole type head and a ring type head, both with this simple core/lead/core structure, were examined for two fundamental operations, and were confirmed to exhibit a differential waveform and an integral waveform, respectively.

Sensor for Right Ventricular Volumes Using the Trailing Edge Voltage of a Pulse Generator Output

Cardiac and thoracic volume (Vol) signals are useful for diagnosis and adaptive rate pacing. Present systems need an AC or pulsed constant current carrier to measure conductivity (proportional to Vol), causing high battery drain and requiring complex detection algorithms or special leads. The aim of this study was to propose a new and simple sensor for cardiac volumes using standard pacing leads and no AC carrier signal. "Constant voltage" pulse generators (PG) deliver a square pulse to the lead via a capacitor (Cap). The signal resulting from the interaction between the PG and the tissues and blood is trapezoidal, with a leading edge voltage determined by PG output and a trailing edge voltage (TEV) dependent on electrode surface and Cap value (device constants), and patient load. The hypothesis that right ventricular (RV) and chest Vol variations could produce load-related TEV changes was tested. Four PGs were connected to bipolar (Bip) leads within containers with 5-80 cc of saline, and TEV was measured with every 5 cc Vol change. Fifteen patients with previously implanted Bip PGs were studied during VOO pacing, scanning the intrinsic cardiac cycle. TEV was noninvasively measured as a function of time from onset of QRS.(ABSTRACT TRUNCATED AT 250 WORDS)