Tunable ferroelectric capacitor-based voltage-controlled oscillator

Ferroelectric capacitors made from Ba(1-0.5)Sr0.5TiO3 (BST) are applied as varactors in tunable, high-frequency circuit applications. In this context, a voltage-controlled oscillator (VCO) has been designed and implemented using discrete RF bipolar junction transistor (BJTs) and tunable ferroelectric capacitor. The designed VCO has a tuning range from 205 MHz to 216.3 MHz with a power dissipation of 5.1 mW. The measured phase noise is -90 dBc/Hz at 100 kHz and -140 dBc/Hz at 1 MHz offset.     

Manual / automated capacitance box using micro-controller technique

A capacitance box contains more than one decade capacitance. These decades have different capacitance ranges to get a much wider range of the capacitance steps obtained by the whole box. In general, a decade capacitance is constructed by ten capacitors to give ten manual capacitance steps. In this paper, a new design of a capacitance box is presented using two-decade capacitances. Each one of them is constructed by four capacitors only. This capacitance box is automatically controlled by especially designed programs using the Lab VIEW to provide a combination of 100 sequential capacitance steps from the common output of the two decades. These capacitance values can be used for the automatic calibrations of the capacitance measurement devices. Also, its capacitance steps can be obtained by manual way according to the user requirements, through an assembly language program using push-button switches. Control of each decade in this box depends on a micro-controller technique and four electronic relays as clearly investigated in this paper. Practical design, fabrication, and calibration for one decade of the capacitance box have been demonstrated in details through this research. The second decade in this box is the same as the first one, but it has different value of the capacitance per step.     

Frequency Dependence of Electrode Surface Effects in Parallel-Plate Capacitors

Electrode surface effects in parallel-plate capacitors lead to a variation in capacitance and conductance with frequency. A method is presented for the determination of absolute changes in capacitance and absolute values of conductance, as functions of frequency. The method involves the use of two variable parallel-plate capacitors, and requires the measurement of relative capacitance and conductance values over a range of frequencies and at a minimum of two different electrode spacings. A capacitor cell, incorporating two variable capacitor sections is described. The cell is designed for use in the investigation of the frequency characteristics of a range of electrode surfaces. Two current transformer ratio-arm bridges are used to perform the relative admittance measurements. The bridges are compensated for capacitance loading, and together cover the frequency range 11 Hz-52 kHz. Measurement precision is a few parts in 108 for each admittance component. Details of the bridges and measurement techniques are discussed and corrections for mechanical resonance effects and lead impedances are considered. Results are given for rhodium plated and plain brass electrodes under vacuum. Over the full frequency range the fractional capacitance change for rhodium, when referred to a 1-mm electrode spacing, is <4 × 10-7. Tan ? is < 1.5 × 10-7. Oil films and organic contaminants on electrode surfaces are thought to be the most likely sources of frequency dependence.     

PLL jitter reduction by utilizing a ferroelectric capacitor as a VCO timing element

Ferroelectric capacitors have steadily been integrated into semiconductor processes due to their potential as storage elements within memory devices. Polarization reversal within ferroelectric capacitors creates a high nonlinear dielectric constant along with a hysteresis profile. Due to these attributes, a phase-locked loop (PLL), when based on a ferroelectric capacitor, has the advantage of reduced cycle-to-cycle jitter. PLLs based on ferroelectric capacitors represent a new research area for reduction of oscillator jitter.     

Reference trimmer disc capacitor for frequencies up to 200 Mc

Conclusions The above disc capacitor can be used for various purposes as a reference single-valued effective capacitance, or as a many-valued capacitance set at will to any value within its range, for testing or research purposes.The KVCh-8M capacitors are particularly convenient for determining the frequency characteristic of effective capacitances of other capacitors by the substitution method. In this method the measured capacitor is replaced at the high frequency by the KVCh-8M capacitor, which is set to the appropriate value by adjusting the distance between its plates.The preliminary adjustment is made with the capacitor screen removed, and the final adjustment through the opening in the screen.The actual capacitance of the disc trimmer is then calculated from (4) having measured its capacitance on a low-frequency bridge. Such a method of checking capacitors is very simple, since it does not require any accurate high-frequency capacity measuring devices. It is quite sufficient to have any type of Q-meter.     

Multifiber ceramic capacitor

A new type of capacitor, multifiber capacitor (MFC) is proposed. It is made up of fiber capacitors (elements) connected in parallel and bonded together with a binder. Each element consists of fiber core (inner electrode), dielectric coating and outer electrode. Analysis indicates that MFC has the optimum capacitance in comparison with multilayer capacitor (MLC) when the diameter of fiber core is carefully matched by the thickness of dielectric coating. Since dielectric layer of a wide range of thickness can be produced more easily as fiber coating than as flat tape, MFC can cover a wider range of capacitance than MLC. Apart from as a possible substitute or supplement to MLC, MFC is potentially useful to bridge the gap between ceramic MLC and thin film capacitor used in integrated circuits. MFC also has better resistance to dielectric breakdown. The possible techniques for the preparation of MFC are also described.     

A QHE-based system for calibrating impedance standards

Coaxial transformer bridges applied to a newly formed system for calibrating impedance standards are described. In this system, an R-R bridge characterizes reference quantum Hall devices as well as directly links them to 12906.4 /spl Omega/ or 10000 /spl Omega/ standard resistors. These resistors, in turn, serve as reference standards in capacitance calibrations made by a multifrequency quadrature R-C bridge and a C-C bridge. Finally, by means of a multifrequency double-balance L bridge, 1- and 10-nF capacitors calibrated in this manner are linked to inductance standards whose values range from 1 to 100 mH.     

Evaluation of a Capacitance Scaling System

An improved error analysis of an existing capacitance scaling system for supporting measurements of higher valued (10 nF to 100 ) ceramic-dielectric four-terminal-pair (4TP) capacitance standards over the 100-Hz to 100-kHz frequency range is described. The capacitance scaling system uses a commercial impedance (inductance-capacitance-resistance) meter and a single-decade inductive voltage divider as an impedance comparator. Four-terminal-pair capacitors in decade (10 : 1) steps from 10 nF to 100 F are measured. The system's 10 : 1 scaling error is determined using 100-pF and 1-nF air-dielectric 4TP capacitance standards with known capacitance and loss characteristics over frequency. This paper discusses the significant reductions in measurement uncertainty that were attained through the use of improved calibration standards and measurement method refinements. Details of the uncertainty analysis for a 10-nF capacitor (in the 100-Hz to 10-kHz frequency range) and verification data are presented.     

Calibration of the Irradiance Responsivity of a Filter Radiometer for T Measurement at NIM

At the National Institute of Metrology of China (NIM), silicon photodiode-based narrow-band interference filter radiometers (FRs) have been designed for the radiometric determination of the thermodynamic temperature. The FR calibrations were performed on a new spectral comparator with a trap detector which was calibrated against the cryogenic radiometer at several discrete laser lines. The new spectral comparator is constructed from two grating monochromators assembled to give lower stray light and higher transmitted flux. Applying a transmittance measurement of the filter in the out-of-band region and careful control of the temperature, the irradiance responsivity of a 633 nm centered FR has been obtained over a dynamic range of nearly eight decades in the wavelength range from 450 nm to 1200 nm. The relative standard uncertainty of the responsivity is also analyzed and estimated to be less than 7 × 10^?4 at the 1 ?? level.     

Properties of Indium Antimonide Detectors for use as Transfer Standards for Detector Calibrations

The properties of 4-mm-diameter and 7-mm-diameter liquid-nitrogen-cooled indium antimonide detectors were investigated to determine their suitability as transfer standards (i.e., reference detectors) for the detector calibration facility at the National Research Council of Canada. The spectral responsivity of the InSb detectors in the spectral range 1000-3000 nm was determined by atwo-step procedure involving the use of germanium transfer standardsand suitably characterized thermopiles. It is shown that thelong-term reproducibility of the InSb detector calibrations is approximately ?1%. The uniformity and linearity as a function of wavelength, as well as the background current noise and drift of thetwo detectors, are compared. It is shown that the 7-mm-diameter detector is clearly superior to the 4-mm one for use as a transfer standard. It is estimated that the overall accuracy of the calibrations of the two InSb detectors is ?2% in the range 1200-2800 nm.     

Dosimetry with a recombination chamber in outdoor conditions and at low dose rates

A system with a recombination chamber for outdoor dosimetry in mixed radiation fields is proposed. The chamber works as a passive detector, with polarising electrodes supplied from capacitors permanently connected to the electrodes. Ions, collected on the measuring electrode, charge a measuring capacitor, also permanently connected to the electrode. A special procedure, including recharging of the supplying capacitors, was introduced in order to compensate the side charge caused by changes of ambient temperature and leakage of the electrical charge from the supplying capacitors. Experimental tests indicated that the chamber of REM-2 type or a specially designed KR-20 chamber could also be used at low dose rates. It was possible to measure the ambient dose of a fraction of μGy with accuracy of about 10%, and the H*(10) of about 1 μSv, with accuracy better than 25%, in any field of penetrating radiation, provided the time of charge collection is less than 24 h.     

New multifrequency method for the determination of the dissipation factor of capacitors and of the time constant of resistors

A new method for the simultaneous determination of the dissipation factor of capacitors and of the time constant of resistors by a multifrequency method is presented. This method is based on the measurement of impedance ratios at two or more frequencies. A bridge is set up with a programmable two-channel ac voltage source and the impedances to be compared. The impedance ratios are determined by synchronous sampling procedures and application of discrete Fourier transform. In a first experiment, a high-grade gas-filled 1 nF standard capacitor was compared with a stable 1 M/spl Omega/ ac resistor at frequencies between 31 Hz and 666 Hz. The estimated standard uncertainties (k=1) are 0.6/spl middot/10/sup -6/ for the dissipation factor of the capacitor and 0.4 ns for the time constant of the ac resistor.     

Junction fabrication by shadow evaporation without a suspended bridge

We present a novel shadow evaporation technique for the realization of junctions and capacitors. The design by e-beam lithography of strongly asymmetric undercuts on a bilayer resist enables in situ fabrication of junctions and capacitors without the use of the well-known suspended bridge (Dolan 1977 Appl. Phys. Lett. 31 337-9). The absence of bridges increases the mechanical robustness of the resist mask as well as the accessible range of the junction size, from 10(-2) μm(2) to more than 10(4) μm(2). We have fabricated Al/AlO(x)/Al Josephson junctions, phase qubit and capacitors using a 100 kV e-beam writer. Although this high voltage enables a precise control of the undercut, implementation using a conventional 20 kV e-beam is also discussed. The phase qubit coherence times, extracted from spectroscopy resonance width, Rabi and Ramsey oscillation decays and energy relaxation measurements, are longer than the ones obtained in our previous samples realized by standard techniques. These results demonstrate the high quality of the junction obtained by this bridge-free technique.     

Dual-Ramp A/D Converter Error Due to Nonideal Integrator Capacitor

It is shown that very high accuracy hybrid packaged dual-ramp analog-to-digital converters can be built using ceramic NPO-type chip capacitors that exhibit a dielectric absorption specification of 0.75 percent. Capacitor recovery voltage is shown versus time for several 0.01-/g-m/F NPO-type ceramic capacitors. An absorptive capacitor model for the NPO capacitor is shown. Typical component values for an absorptive model of an 0.01-/g=m/F NPO capacitor are determined. The worst case integrator error due to dielectric absorption in a particular synchro-to-digital converter utilizing two dual-ramp converters with 0.01-/g=m/F integrator capacitors is shown to be in the order of microvolts.     

Measurement of capacitances and their loss factors

A method is described for measuring the capacitance values and the loss factors of a pair of capacitors simultaneously. The method uses the principle of oscillators. No standard capacitor is required. The possible errors introduced in the measurements are discussed. Both theoretical and experimental results are provided. The method can be used with any other oscillator circuit that contains only two capacitors     

Measurement of dielectric absorption of capacitors and analysis ofits effects on VCOs

In the integrators applied in A-to-D converters, smart sensors and other processing circuits, the accuracy is directly limited by the performance of the integrating element: the capacitor. An important nonideality of the capacitors concerns the short-term effects of dielectric absorption. This paper presents an accurate method to measure these short-term effects and discusses the measurement results for standard industrial capacitors, MOS and junction capacitors, parasitic capacitors of assembling materials and coaxial-cable capacitors. The special precautions to be taken to obtain the required accuracy for very short measurement times are also discussed. It is shown that the dielectric absorption of a commonly used polycarbonate capacitor causes a nonlinearity of 0.6% for a VCO in the frequency range from 1 kHz to 100 kHz. A very large dielectric-absorption effect has been found for commonly used epoxy printed-circuit boards, which means that special care has to be taken when this material is applied in accurate VCOs     

Dynamics analysis of LFR model for a single‐stage high power factor correction diagonal half‐bridge flyback ac/dc converter

Abstract

By means of a graft scheme, a buck‐boost cell and a wide range diagonal half‐bridge flyback cell are combined to create a novel single‐stage high power factor correction (HPFC) diagonal half‐bridge flyback ac/dc converter in this paper. When both of the two cells operate in discontinuous conduction mode, the proposed converter exhibits high power factor and low bulk capacitor voltage stress independent of the load variations. Based on the Loss‐Free Resistor (LFR) model, a new technique, referred to as ac‐dc balancing method, is also proposed. It is useful to determine the dc values, voltage ripples, and phase angle shifts of the bulk capacitor and output voltage of the converter. Moreover, the component values are well designed according to the operation conditions and design specifications of the converter. Finally, a prototype of the proposed converter with output voltage 48 V and power 100 W is built to test the theoretical analysis. It is successfully validated by IsSpice simulations and experimental results.     

Nonaqueous Hybrid Lithium‐Ion and Sodium‐Ion Capacitors

Hybrid metal‐ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery‐type anode and the capacitor‐type cathode. Recently, some transition‐metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high‐rate candidates for hybrid MIC anodes. Here, the material design strategies in Li‐ion and Na‐ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb₂O₅, MoO₃, etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.     

10kV电力电容器跳闸故障的原因解析

介绍了某无人值班变电所10kV电力电容器开关跳闸的经过，阐述了跳闸的原因，通过电力电容器保护整定分析和电容器容量与升压值的计算，合理利用并联电容器在系统中的调压作用。