抵抗一体型デカップリングコンデンサの開発と放射ノイズ抑制効果

ABSTRACTMost vibration-based energy harvesters, including piezoelectric harvester system, perform efficiently at only its resonant frequency as linear resonators, usually at very high frequency which are out of the range of frequency of interest. In real life applications, these linear resonators are impractical since real ambient vibrations are simply having varying lower frequencies. Hence, design a tuneable vibration energy harvester at a lower and useful frequency range of interest are essential in allowing promising energy output to meet intended power input at a more practical approach. In this paper, the piezoelectric voltage energy harvester (PVEH) was designed with a flexible fixture with the aim to reduce its first fundamental natural frequency. Two thickness of elastic fixtures were applied to generate power on PVEH. Three experimental techniques were used to measure the vibration characteristics of PVEH. First, the full-field optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) measured simultaneously the resonant frequencies and mode shapes. This is followed by the pointwise measurement system, laser Doppler vibrometer (LDV) in which the resonant frequencies were measured by dynamic signal swept-sine analysis. The resonant frequencies and anti-resonant frequencies were also obtained by impedance analysis. The results obtained from experimental measurements were compared with finite element numerical calculation. It is found that the boundary conditions under the elastic fixtures can effectively reduce the resonant frequency of the PVEH with a reasonable voltage output. The fundamental natural frequency of PVEH with the thickness of 0.58-mm elastic fixture is reduced to 37 Hz maintaining at 7.1 volts (1.2 mW), in comparison with the natural frequency on cantilevered PVEH at 78 Hz that produces 7.7 volts (6.5 mW).

The static and dynamic characteristics of the annular piezoceramic actuating disk transducers are theoretically modeled and analyzed. The transducer consists of an annular piezoceramic disk laminated on an unequal radius isotropic elastic disk to form the asymmetric configuration. Piezoceramic actuator excites the transducer in extension and flexure coupled vibrations. An electroelastic theory is developed to analyze the mechanical, electrical and electromechanical behaviors. Resonant and antiresonant frequencies and the electromechanical coupling coefficients are computed and shown sensitive to geometric parameters of the elastic and piezoceramic materials. Numerical results are presented by the easy-to-use figures. Comparisons between experimental measurements of the transducer's resonant and antiresonant frequencies and modeling results exhibit a good agreement.

High-efficiency energy conversion, primarily limited by internal losses of piezoelectric materials, is an important target for piezoelectric actuators or sensors. There are three internal losses in piezoelectric materials: dielectric, elastic, and piezoelectric. In this paper, a new equivalent circuit of a piezoelectric ring in radial vibration mode is proposed considering three types of fundamental losses. First, the decoupled equivalent circuit with inherent losses is derived based on the conventional electromechanical equivalent circuit. In order to verify the feasibility of the new circuit, an ultrasonic motor operating in radial vibration mode is explored and simulated. The resonance and antiresonance frequencies and their corresponding mechanical quality factors are obtained from the new circuits and then compared with those of an actual stator sample. The simulation results match well with the experimental measurements of the stator. Finally, a prototype is fabricated due to the simulation results and a maximum torque of 270 mNm is acquired.

This paper describes a high-frequency bulk acoustic wave resonator (BAWR) with a solidly-mounted (SM) structure using single crystal LiTaO3 (LT) thin plates. A Bragg reflector solidly supports the LT thin plate, which is fragile if self-suspended. The two kinds of BAWRs use a strip-type thickness shear mode in 0.56 μm thick X37°Y LT and X127°Y LT. The Bragg reflector is made of 5 pairs of Al and Ta films, i.e. 10 layers in total. The X37°Y LT SM structure BAWRs exhibited a resonance frequency (f r) of 3.250 GHz, an anti-resonance frequency (f a) of 3.463 GHz, a bandwidth (BW) of 6.6%, and an impedance (Z) ratio of 48 dB. The X127°Y LT BAWR has a similar characteristic with f r of 3.153 GHz, f a of 3.367 GHz, a BW of 6.8%, and a Z ratio of 46 dB. The X37°Y LT BAWR showed an advantage of 2 dB compared with the X127°Y LT one. The Al film acts as a low acoustic impedance film, but an acoustic impedance layer combination of Al and Ta films is not suitable and that of SiO2 and W films suitable among the four combinations, Al/Ta. SiO2/Ta, Al/W, and SiO2/W films. Although the acoustic impedance layer combination, the acoustic film quality, the structure, electrode design, and fabrication process of the fabricated BAWRs were not optimized yet, this result suggests the high potential of this device.

In a single-phase grid-connected nanogrid system, a bidirectional ac–dc converter is usually required to transfer energy between the ac grid and a dc bus. Active ac power balancing is often implemented to prevent the ac grid ripple power from injecting into the dc bus. A four-phase-leg sinusoidal pulsewidth-modulation (SPWM) converter can readily provide power factor correction and active ac power balancing. In this paper, the use of three-phase-leg SPWM converters for achieving these functions is analyzed. A family of bidirectional single-phase ac–dc three-phase-leg SPWM converters with an ac storage capacitor for use in a nanogrid system is designed with a general control structure and a modulation scheme for minimizing the ac storage capacitance. The general control structure is designed to achieve a decoupled system of a power-factor-correction converter cascaded with an active ac power load at the dc bus. The decoupled system is developed based on decomposition to differential-mode and common-mode voltages. The modulation method involves an extra zero-sequence voltage injection derived from the three-phase-leg SPWM voltages without introducing higher order harmonic distortions. A significant reduction of the ac storage capacitance and an improvement of converter efficiency are achieved. The design and analysis are verified by simulations and experimental measurements.

In some very low noise mixed-signal circuits, designers may use intentional slots in order to create a better isolation between a noisy digital ground and a very quiet analog ground, especially in low-frequency applications ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; $</tex-math></inline-formula> 1 MHz) when the current spread in the return plane may interfere with the quiet analog ground. Traces on the signal planes, crossing over these slots, are well-known sources for electromagnetic interference (EMI) due to discontinuities on the return current path. This article presents a novel interdigital slot structure used in the reference planes. The interdigital structure increases the coupling and, hence, provides a low impedance path for the return current of the signal line. This, in return, significantly reduces the radiated emission level in the printed circuit boards (PCBs). Furthermore, due to the periodic nature of transmission lines and the slow-wave effect provided by the interdigital structure, the periodically repeating resonance frequencies of the interdigital defect can be tuned by simply changing the geometric parameters such as digit length and the number of digits. It is shown that the electromagnetic radiation from these slots exhibits peak levels at these antiresonance frequencies, which are also the transmission zeros of the circuit. Conversely, radiation levels are minimized at passbands, where a good signal transmission is achieved. Therefore, this relationship would allow designers to tune the slot length to minimize radiation at the frequency of the signal passing through the trace. Four PCBs with three different-size interdigital structures and a traditional slot structure are first simulated and then fabricated. Well-agreed simulation and measurement results show that the EMI is suppressed by as much as 30 dB within the frequency range of 250 MHz–1 GHz. The radiation peaks and dips match with the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$S_{21}$</tex-math></inline-formula> minima (transmission zeros) and maxima, respectively, in measurement results as well.

In order to use I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> L in the low power range the base current must be minimized. Two previous models have been presented to explain the observed base current values. The first model assumes that the observed base current mainly consists of electrons injected into the inactive metal and oxide covered base, whereas the second model claims that hole injection into the epi and buried layer is the main component of base current. These models have been checked experimentally only at moderate or large current levels and at fixed V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BE</inf> values. The purpose of this paper is to investigate experimentally the importance of the different base current components over the entire low current range (0.1 nA - 1µA). Conclusions relevant to the magnitude and the temperature dependence of these different components will be given. It will be demonstrated experimentally that surface recombination in the emitter-base sidewall of the I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> L gates is one of the most important contributions to the base current. This component also causes the degradation of the current gain at lower temperatures. Different methods to eliminate this component will be given. New findings about the influence of the deep n+ isolation in the low current range will be presented. The experimental measurements will be illustrated by computer results of one- and two-dimensional computer-aided device analysis programs.

Summary Traditionally, the Poisson-Boltzmann equation is solved to describe the electrical potential in the diffuse layer of an electrolyte adjacent to a charged interface and the electrostatic contribution to the total interaction potential between the interface and the ionic species. A major assumption of the Poisson-Boltzmann equation is that ions act as point charges, which allows for an infinite ion and charge density near to the charged interface, and thus predicts that the zeta potential falls to zero at high ionic strength (typically >0.1M). However, experimental measurements have reported small but measurable zeta potential values at high ionic strength, showing the zeta potential does not tend to zero as predicted. Electrostatic forces acting between electrically charged mineral-brine and oil-brine interfaces in the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory have been used to explain observed increases in oil recovery during low salinity waterflooding. Injection of a low salinity brine is expected to create a more negative zeta potential at the mineral-brine interface. If the oil-brine interface is negatively charged, this increases the electrostatic repulsive force per unit area which, if larger than the disjoining pressure, should lead to improved oil recovery. However, the calculation of the electrostatic forces are normally based on the traditional Poisson-Boltzmann model which underestimates the electrostatic contribution at high salinity. Here, a modified Poisson-Boltzmann equation ( Borukhov et al., (1997) , Physical Review Letters, 79(3), 435), which accounts for steric effects in the diffuse layer at high salinity but recovers the original Poisson-Boltzmann equation at low salinity, has been combined with a triple layer model which accounts for charge in the Stern layer ( Revil et al., (1999) , Journal of Geophysical Research, 104). This combined model has been used to match experimental zeta potential measurements made on natural, intact sandstones across the ionic strength range 10–5 – 5M, including small and constant zeta potentials observed at ionic strength >0.4M. The effect of this modified Poisson-Boltzmann model on the total interaction potential and DLVO theory has further been investigated. Our relatively simple modification shows that the electrostatic forces at high salinity are larger than previously thought and should not be neglected when calculating total interaction forces. Previous models using classic DLVO theory for understanding low salinity waterflooding may be inaccurate as they incorrectly estimate the changes in the electrostatic forces that occur during injection of low salinity brines.

Linearized inverse scattering methods are applied to the shape reconstruction of defects in elastic solids. The linearized methods are based on the Born approximation in the low frequency range and the Kirchhoff approximation in the high frequency range. The experimental measurement is performed to collect the scattering data from defects. The processed data from the measurement are fed into the linearized methods and the shape of the defect is reconstructed by two linearized methods. The importance of scattering data in the low frequency range is pointed out not only for Born inversion but also for Kirchhoff inversion. In the ultrasonic measurement for the real structure, the access points of the sensor may be limited to one side of the structural surfaces and a part of the surface. From the viewpoint of application, the incomplete scattering data are used as inputs for the shape reconstruction methods and the effect of the sensing points are discussed.

Embedded decoupling is normally considered a better solution than surface mount decoupling for suppressing the switching noise of a high speed digital board/package because of its shorter leads that result in smaller parasitic inductance. This leads to lower impedance over a higher frequency band. It is presumably better in reliability and lowers the cost as well. Designers tend to use large value capacitors for efficient decoupling. Usually, to increase capacitance of an embedded capacitor, one can use a material with higher dielectric constant, design larger electrodes, and reduce the thickness of the dielectric. However, these strategies may sometimes lead to lower performance at high frequency band. This paper will discuss the pros and cons of different embedded capacitor approaches through simulation. As an application example, a typical power/ground network with an embedded capacitor will be compared with that of surface mount discrete capacitor.

A simple conductivity measurement method using a peak-frequency feature of ferrite-cored eddy current sensor

The semiconductors impedance is a primary electrical parameter that determines the performance of electronic devices and circuits. For this reason many papers [1,] [2], [3] discus the frequency-dependent impedance of semiconductor junctions. Subject of this contribution is the investigation of physical model of the diode and bipolar power semiconductor devices (silicon) in the low frequency range between 0–100kHz. The goal of this contribution is to demonstrate through experimental measurements that the impedance of the power semiconductors depends on the signal frequency, junction's geometry and properties of the electronic structure. In the paper a procedure for computing the equivalent semiconductor impedance has been described and by experiments validated.

This paper calculates lattice thermal expansion (LTE), thermal conductivity (TC) and melting temperature (MT) of ThO2 using classical molecular dynamic simulations. In this study we consider two set of interatomic potential consisting of Coulomb-Buckingham (Buck) and Coulomb-Buckingham-Morse-Many body (BMM) potential form. The MD calculated LTE of 10.29 × 10−6 and 10.61 × 10−6 K−1 using BMM and Buck potential, respectively, is slightly higher than the experimentally determined values (9.54 – 9.86 × 10−6 K−1). The MD calculated TC values in the high temperature range (600 to 1200 K) accords very well with the experimental measurements and at the low temperature range (300-500 K) our results are slightly different from experimental results as our presumption that the dominant mechanism for phonon scattering is the Umklapp process. The MD calculated MT of ThO2 using Buck and BMM potential model is 3662.5±12.5 K and 3812.5±12.5 K, respectively, and these values are in reasonable agreement with previous experimental values.

There exist absorption windows (i.e., Cooper-minima) in the photoabsorption cross sections of some atomic systems because of the relative phase shifts between the initial and final state wave functions due to the atomic screening potentials in contrast to the Coulomb potentials. Such window positions are sensitive to the accuracy of the initial and final state wave functions. Using our modified Breit-Pauli $R$-matrix code, the photoionization cross sections of ground Na are calculated. Our calculated cross sections and minimum position in the low photoelectron energy range $(l9\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ are in excellent agreement with the experimental results. In the high energy range $(g9\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, there is an abnormal bump in the experimental measurements, which is a long-standing experimental puzzle. It is interesting to note that there is also an absorption window in the photoabsorption (i.e., photodissociation) cross sections of $\mathrm{Na}_{2}{}^{+}$. Such an absorption window provides an answer to the puzzle.

Aeroelastic energy harvesting can be used to power wireless sensors embedded into bridges, ducts, high-altitude buildings, etc. One challenging issue is that the wind speed in some application environments is low, which leads to an inefficiency of aeroelastic energy harvesters. This paper presents a novel nonlinear magnetic-coupled flutter-based aeroelastic energy harvester (FAEH) to enhance energy harvesting at low wind speeds. The presented harvester mainly consists of a piezoelectric beam, a two-dimensional airfoil, two tip magnets and two external magnets. The function of magnets is to reduce the cut-in wind speed of the FAEH and enhance energy harvesting performance at low wind speeds. A theoretical model is deduced based on Hamilton’s principle, theory of aeroelasticity, Kirchhoff’s laws and experimental measurements, etc. A good agreement is found between numerical simulation and experimental results, which verifies the accuracy of the theoretical model. Stability analysis is provided to determine the characteristics of the presented harvester. More importantly, it is numerically and experimentally verified that the presented harvester has a much lower cut-in wind speed (about 1.0 m s−1) and has a better energy harvesting performance at a low wind speed range from 1.0 m s−1 to 2.9 m s−1, when compared with traditional FAEHs.