Resistance Capacitance Research Articles

Macro Model for Discrete-Time Sigma‒Delta Modulators

This work presents a macro model for discrete-time sigma‒delta modulators, which can significantly reduce the simulation time compared to transistor level circuits. The proposed macro model is realized by effectively combining active and passive ideal circuit components with Verilog-A modules. As such, since the macro model is a true representation of the actual transistor level circuit, a moderately good accuracy can be obtained. In addition, the proposed macro model includes the major amplifier, comparator, and switch‒capacitor non-idealities of the sigma‒delta modulator such as amplifier DC gain, GBW, slewrate, comparator bandwidth, hysteresis, parasitic capacitance, and switch-on resistance. The results show the simulation time of the proposed macro model sigma‒delta modulator is only 6.43% of the transistor level circuit with comparable accuracy. As a result, the proposed macro model can facilitate the circuit design and leverage non-ideality analysis of discrete-time sigma‒delta modulators. As a practical design example, a second order discrete-time sigma‒delta modulator with a five-level quantizer is realized using the propose macro model for GSM and WCDMA applications.

An Improved EKF Algorithm for SOC Estimation of Lithium Battery Considering Temperature Effects

In order to improve the estimation accuracy of the state of charge (SOC) of lithium-ion power batteries during use, an estimation method that considers different temperature effects is proposed in this paper. First, the second-order resistor-capacitor (RC) circuit model is selected as the research model based on a comparative analysis of different models. Then, the parameters in the circuit model are identified online in real time under different temperatures to analyze the temperature effects on internal parameters. Lastly, the noise variance can be automatically adjusted according to the environment by using the improved extended Kalman filter (EKF) algorithm with the differential evolution algorithm, which optimizes the fixed process noise variance in the original EKF algorithm. The changing noise variance is substituted in the original EKF algorithm to estimate SOC under cycle working conditions online. The results show that the improved EKF algorithm increases the estimation accuracy of the SOC of lithium batteries. Using the improved EKF algorithm, the estimated value can quickly converge to the actual value at different temperatures, and the SOC error remains within 2% in the whole estimation process.

Design of Inductive Power Taking System for Smart Grid Monitoring Equipment

Due to the continuous growth of urban electricity load and the increasing development of high-voltage transmission technology, the effective operation of the online monitoring equipment of the transmission line is particularly important, which is also a necessary condition for the development of the smart grid. However, the power supply conditions for the usage scenarios of smart grid monitoring equipment are limited. Conventional power supply methods such as battery power supply and new energy power generation have disadvantages such as cumbersome battery replacement, and the power supply stability is greatly affected by the environment, so they are difficult to meet the development trend of a rapid capacity increase of power grid and stable power supply of power equipment. Aiming at the technical bottleneck of smart grid monitoring equipment in power supply, this paper proposes a current transformer inductive power taking method based on capacitive reactance matching shunt, using the open air gap current transformer secondary winding set on the bus to connect the capacitor and its excitation inductance in series carry out capacitive impedance matching, and then shunt through another branch with load and connect it at both ends of the open air-gap current transformer to obtain electric energy. Through the circuit model experiment of the inductive power-taking system, it is verified that the current transformer inductive power-taking method based on capacitive reactance matching shunt can obtain more power.

Enhancement of microstructure characteristic and dielectric constant of BaMn0.05Ti0.95O3 ceramics

Barium Titanate or BaTiO3, a ferroelectric material with good dielectric properties, is widely studied. The performance of BT is influenced by synthesis and doping. Here, Barium Titanate has been doped with Manganese via the co-precipitation procedure sintered at 900°C and 1000°C. The purposes of this study were to examine the microstructure and dielectric constant of BaMn0.05Ti0.95O3 with variation sintering temperatures at 900°C and 1000°C. The testing employed X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Resistance Capacitance Inductance (LCR Meter). The XRD data exposed that the crystal size of the BaMn0.05Ti0.9503 sample enlarged from 48.27 nm to 72.41 nm with increasing sintering temperature. The analysis results using FTIR exhibited the existence of Ba-O and Ti-O bonds which confirmed the perovskite structure of BaTiO3. FTIR data also indicated the presence of C-H atomic bonds, which is the peak of impurities in the carbonate phase. The C-H bond vibration decreased at the higher sintering temperature. The dielectric constant value was obtained from the measurements using an LCR meter. In conclusion, increasing the sintering temperature improved the dielectric constant of BaMn0.05Ti0.95O3 from 119 to 386.

Parameter extraction of three-diode solar photovoltaic model using a new metaheuristic resistance–capacitance optimization algorithm and improved Newton–Raphson method

Parameter extraction of three-diode solar photovoltaic model using a new metaheuristic resistance–capacitance optimization algorithm and improved Newton–Raphson method

C-Band GaN Dual-Feedback Low-Noise Amplifier MMIC with High-Input Power Robustness

In this paper, using the 0.2 μm ETRI GaN HEMT process, we developed a C-band GaN dual-feedback low-noise amplifier MMIC for an RF receiver module that requires high-input power robustness. By applying a feedback microstrip line at the source of the transistor and series resistor-capacitor (RC) feedback between the gate and the drain of the transistor, we obtained stable amplifier operation and a compromised impedance trace for both input impedance matching and noise matching while suppressing performance degradation of the maximum available gain and minimum noise figure. The developed low-noise amplifier MMIC, which implements simple matching circuits by using biasing elements as matching elements, had a linear gain of more than 21.4 dB and a noise figure of less than 1.91 dB in the wide bandwidth of 4.3–7.4 GHz. Under the single-tone power test, the low-noise amplifier MMIC had an output P1dB of 14.3–20.1 dBm, and the two-tone intermodulation distortion measurement exhibited an input third-order intercept point (IIP3) of 2.2–5.6 dBm in the same frequency range as the above.

Design and Fabrication of Interdigital Supercapacitors as Force/Acceleration Sensors

The integrated device for energy supply and sensing (IDESS) is a potential candidate for relieving the energy and space burdens caused by the rising integration degrees of microsystems. In this article, we propose a force sensor based on an interdigital supercapacitor (IDTSC). The capacitance and internal resistance of the IDTSC change under external loads, resulting in a transient current fluctuation at a constant bias voltage, which can be used to sense external force/acceleration. The IDTSC showed a specific energy and specific power of 4.16 Wh/kg and 22.26 W/kg (at 0.1 A/g), respectively, which could maintain an essential energy supply. According to the simulation analysis, the designed IDTSC's current response exhibited good linearity with the external force. In addition, benefiting from its light weight and the applied gel electrolytes, the IDTSC showed good high-g impact sensing performance (from 9.9 × 103× g to 3.2 × 104× g). This work demonstrated the feasibility of realizing an integrated energy supply and force-sensing device by empowering energy storage devices with sensing capabilities.

Piezoelectric Micromachined Ultrasonic Transducers (PMUTs): Performance Metrics, Advancements, and Applications

With the development of technology, systems gravitate towards increasing in their complexity, miniaturization, and level of automation. Amongst these systems, ultrasonic devices have adhered to this trend of advancement. Ultrasonic systems require transducers to generate and sense ultrasonic signals. These transducers heavily impact the system's performance. Advancements in microelectromechanical systems have led to the development of micromachined ultrasonic transducers (MUTs), which are utilized in miniaturized ultrasound systems. Piezoelectric micromachined ultrasonic transducers (PMUTs) exhibit higher capacitance and lower electrical impedance, which enhances the transducer's sensitivity by minimizing the effect of parasitic capacitance and facilitating their integration with low-voltage electronics. PMUTs utilize high-yield batch microfabrication with the use of thin piezoelectric films. The deposition of thin piezoelectric material compatible with complementary metal-oxide semiconductors (CMOS) has opened novel avenues for the development of miniaturized compact systems with the same substrate for application and control electronics. PMUTs offer a wide variety of applications, including medical imaging, fingerprint sensing, range-finding, energy harvesting, and intrabody and underwater communication links. This paper reviews the current research and recent advancements on PMUTs and their applications. This paper investigates in detail the important transduction metrics and critical design parameters for high-performance PMUTs. Piezoelectric materials and microfabrication processes utilized to manufacture PMUTs are discussed. Promising PMUT applications and outlook on future advancements are presented.

A facile supercritical fluid synthesis of cobalt sulfide integrated with MXene and PANI/PEDOT nanocomposites as electrode material for supercapacitor applications

We report the synthesis of ternary CoS/MXene/PANI and CoS/MXene/ PEDOT composites using supercritical fluid (SCF) method for the first time. These fabricated materials along with CoS/MXene was gone through electrochemical investigations using three electrode system. Enhancement in specific capacitance was observed with inclusion of PANI (407 F/g) and further enhanced with PEDOT (630 F/g) at 2 A/g. Therefore, symmetric device using coin cell technique was fabricated by taking CoS/MXene/PEDOT and CoS/MXene/PANI as electrode material. These coin cells were further be examined on the basis of CV, GCD and EIS and it was observed that the specific capacitance was enhance in CoS/MXene/PEDOT (331.1 F/g) over CoS/MXene/PANI (246 F/g) at 2 A/g. For the material, the capacitance retention was calculated to evaluate the charge storage stability and it was observed that the CoS/MXene/PEDOT (97%) is slightly higher stable than CoS/MXene/PANI (96%). Overall electrochemical performance was observed to be enhanced by inclusion of PANI and PEDOT because it has lower resistance and higher specific capacitance along with these polymers, MXene nanosheets also play a vital role in enhancing the specific capacitance of the heterostrucutre by providing the larger surface area.

Transient lateral photovoltaic effect observed in Ti–SiO2–Si structure

The transient response of the lateral photovoltaic effect (LPE) was observed when Ti–SiO2–Si structure was irradiated by a 650 nm laser which is attributed to the remarkable absorptivity. LPE is linearly dependent on the laser irradiation position. The LPE has high sensitivity of 68.4 mV/mm and linearity of 0.9853, respectively. This paper focuses on the transient response process of LPE at different laser irradiation positions. The mechanism of the response time of the MOS structure is caused by the diffusion of electrons to the positive and negative electrodes. We experimentally verified this mechanism by laser irradiation on different positions. The principle of transient LPE is revealed by carrier diffusion and recombination theory. LPE has faster response time and larger amplitude when the laser irradiation points are close to electrodes. A resistor–capacitor (RC) circuit model combines with LPE which is established to simulate and analyze the transient process. The research provides a new direction for LPE-based sensors with regard to the amplitude and response time which change with laser irradiation position in Ti–SiO2–Si structure for researchers to develop position-sensitive sensors.

Space heating demand profiles of districts considering temporal dispersion of thermostat settings in individual buildings

Future energy infrastructures are expected to be smart, with the application of energy storage and demand-side management strategies. To size the energy storage and assess the flexibility of the heat demand in a district, insight into its heat demand profile is a prerequisite.A tool was developed to generate the hourly space heating demand of a district. A crucial element in the calculation is the behaviour of occupants, particularly the temporal dispersion of thermostat settings in individual buildings. This dispersion smooths out the morning (and evening) peaks in the space heating demand of a district when occupants turn up their thermostats.Hourly gas consumption data were obtained of 8077 buildings with gas fired boilers in 2020. A dynamic resistance capacitance (RC) building model of a single aggregated building representing the 8077 dwellings was used to calculate their space heating demand profile in 2020. A comparison with the actual gas consumption data (corrected for domestic hot water use and cooking) allowed the estimation of the temporal thermostat settings, the dispersion thereof and the thermostat temperature levels of buildings in the district. The combined space heating demand profile of the individual buildings calculated using the same RC building model (each with its own thermostat settings) reproduced the actual space heating demand profile relatively well.

Mass and Charge Transport in Li1-δCoO2 Thin Films-A Complete Set of Properties and Its Defect Chemical Interpretation.

Lithium insertion materials are an essential class of mixed ionic and electronic conductors, and their electrochemical properties depend on the resistive and capacitive interplay of ions and electrons. However, complete sets of the corresponding elementary material parameters, that is, composition-dependent ionic and electronic conductivity, chemical capacitance, and charge-transfer resistance, are rarely reported for lithium-ion battery electrode materials. Moreover, the interpretation of these properties from a defect chemical point of view is not very common. In this work, the impedance of sputtered Li1-δCoO2 thin films is analyzed to extract the fundamental electrochemical properties as a function of state-of-charge (SOC). Within the accessible SOC range, the charge transfer resistance and ionic conductivity vary by more than 1 order of magnitude. The chemical capacitance determined from impedance spectra agrees excellently with the differential capacitance from charge/discharge curves, and, in the dilute regime, even matches the absolute values predicted by defect thermodynamics. The evolution of lithium diffusivity along the charge curve is deconvoluted into the separate contributions of ionic conductivity and chemical capacitance. Finally, we apply the principles of defect chemistry to evaluate the observed trends in terms of lithium activity and point defect concentrations and provide a tentative defect model that is consistent with our results. The consistency of impedance measurements, cycling data, and thermodynamic theory highlights the key role of the chemical capacitance as a powerful material descriptor and emphasizes the relevance of defect chemical concepts for all lithium insertion electrode materials.

A virtual adaptive RC damper control method to suppress voltage oscillation in DC microgrid

In DC Microgrid tightly regulated load converters operate as a constant power load (CPL). CPLs have negative incremental resistance characteristics, which leads to voltage oscillations and instability in DC microgrid systems. As a result, a virtual adaptive resistance–capacitance (VARC) damper control mechanism has been developed in this study to overcome the instability impact generated by the CPL. To satisfy the need for system stability, a technique to insert a virtual R-C connected in parallel with the capacitor (located on the feeder-side converter) is proposed. The proposed active damping control is self-adaptive for variations in load current. The proposed method allows for a straightforward setting of the control parameters, in which the dynamic performance of the load converter was unaltered. Stability is provided by an inherent and accurate adaptive control technique, as well as by strong resilience during sudden changes in input voltage and CPL plug-and-play. Both of these factors contribute to high levels of robustness. Therefore, practical restrictions such as weight reduction and low power dissipation, which are essential for onboard DC MGs, are maintained. The simulation results are carried out and the effectiveness of the proposed technique is tested by considering various operating conditions. Furthermore, the proposed technique is compared with the existing methods and it is found to be superior under various operating conditions.

Optimize the dielectric properties of CaCu3Ti4O12 ceramics by adjusting the conductivities of grains and grain boundaries

Reduction of dielectric loss for CCTO ceramics is a prerequisite for their applications. Considering internal barrier layer capacitance effect, improving the capacitance and grain boundary resistance is an effective way to reduce dielectric loss. Therefore, more conductive Ti3+ and Cu+ ions were introduced to grains by adding carbon to ceramic bodies, improving the permittivity of CCTO ceramics. Annealing was performed to increase the grain boundary resistance. The dielectric loss of the CCTO ceramics thus prepared, which maintain a giant permittivity, is significantly reduced. Specifically, the CCTO ceramic with carbon addition, which was sintered at 1080 °C for 8 h and air annealed at 950 °C for 2 h, exhibits a giant permittivity of about 2.50(5)×104 and a low dielectric loss of less than 0.050(2) from below 20 Hz to 50 kHz at room temperature. Meanwhile, its dielectric loss at 1–10 kHz is less than 0.050(2) from below room temperature to about 100 °C.

An 11-Bit 10 MS/s SAR ADC with C–R DAC Calibration and Comparator Offset Calibration

An 11-bit 10 MS/s successive approximation register (SAR) analog-to-digital converter (ADC) is proposed for low-power and small-area applications. A 10-bit differential capacitor–resistor (C–R) digital-to-analog converter (DAC) is used to minimize the area of a DAC. The use of a C–R DAC reduces the capacitor area of a SAR ADC used CDAC by 75%. A capacitor calibration for the upper 5-bit capacitors of the C–R DAC is proposed to increase the linearity of the C–R DAC. To evaluate the proposed SAR ADC, an 11-bit 10 MS/s SAR ADC is implemented using a 180 nm 1-poly six-metal CMOS process with a supply of 1.8 V. The proposed SAR ADC has an effective number of bits (ENOBs) of 10.3 bits at a sampling rate of 10 MS/s for a 3.6-VPP differential sinusoidal analog input with a frequency of 4.789 MHz. The measured ENOBs is 10.45 bits when the frequency of the analog input signal is 42.39 kHz. The proposed C–R DAC calibration including comparator offset calibration improves the performances of differential nonlinearity (DNL) and integral nonlinearity (INL) from −1/+1.26 LSBs and −1.98/+1.96 LSBs to −0.97/+0.85 LSBs and −0.79/+0.83 LSBs, respectively.

Dielectric properties of graphene/nano-Fe2O3 filled poly (vinyl alcohol)/Chitosan blends

Novel nanocomposites based on Poly (vinyl alcohol) (PVA), Chitosan (CS), Graphene quantum dots (GQDs) and iron oxide (Fe2O3) nanoparticles (NPs) have been synthesized by solution casting method. The structural modifications and morphological studies were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy/Energy-dispersive X-ray (SEM/EDX) techniques. The results confirm the microscopic interactions and sphere-like morphology of the nanocomposites due to the presence of GQDs and Fe2O3 within the polymer blend. The thermal stability with almost 25% leftover residue for higher nanofillers loading in the nanocomposite was estimated by thermo-gravimetric analysis (TGA). Moreover, the frequency and temperature-dependent dielectric properties were investigated. The dielectric constant and loss tangent values are greatly influenced by reinforcement of GQDs/Fe2O3 and the obtained values were in the range of ∼104 and ∼101, respectively at 150 °C and 50 Hz. The rise in ac conductivity i.e., 9.8 x 10−4 (S/m) with increasing nanofiller loadings suggests the reduction in capacitive reactance and impedance. However, the semi-circular arcs are observed in the cole-cole plot where the fitted impedance data along with the equivalent circuit is also presented. The reduction of bulk resistance and impedance on increasing the nanofiller loadings with enhanced dielectric properties signifies the use of PVA/CS/GQDs/Fe2O3 nanocomposites as a potential material for energy storage applications.

The Optimization Design for Suppression of CRAFT TF Magnet Power Converter Switching Overvoltage

The switching overvoltage due to the operation of the switching device is considered to be one of the important research contents during the design phase of a high-power supply system based on thyristor rectifier topology in the comprehensive research facility for fusion technology (CRAFT). Switching peak overvoltage is suppressed by resistors–capacitors (RC) snubber circuit generally; however, the traditional RC design often relies on some simple empirical formulas and blind amplification margins, which is unable to meet the precision requirements of engineering design. All the work that has been done is based on the cophase counter parallel connection structure of the converter module, and a new strategy is proposed to optimize the RC snubber circuit in order to suppress the operating peak overvoltage better. First, the no-load transformer breaking overvoltage is analyzed, then RC parameters are designed based on a new strategy. Compared with traditional methods, the RC parameters selected by this strategy are more accurate, which meets the accuracy requirements of engineering design and suppresses switching better than before.

Surface film characterizations and electrochemical behavior of type I collagen-immobilized interconnected porous Ti–Nb–Zr–Sn alloy scaffolds in simulated inflammatory environment

Inflammation in the tissue surrounding titanium (Ti)-based alloy implants can lead to increased acidity and the release of reactive oxygen species (e.g., H2O2), which can undermine the corrosion resistance of surface protective films. This study created 3D-printed interconnected porous Ti–24Nb–4Zr–8Sn (Ti2448) alloy scaffolds, over which was applied alkali treatment followed by type I collagen immobilization via natural cross-linker procyanidin. The samples were characterized in terms of polarization curves, surface film characterizations, and electrochemical impedance spectroscopy analysis under simulated inflammatory (SI) environment (150 mM H2O2-containing simulated body fluid with pH 5.2). The SI environment was shown to compromise the corrosion resistance of untreated Ti2448 scaffolds. The surface-treated samples presented a dense, homogeneous surface film of mainly TiO2 and Nb2O5, which moderated the adverse effects of SI environment. Electrochemical equivalent circuits of the surface-treated Ti2448 scaffolds under SI environment included two resistor-capacitor (RC) circuits, corresponding to a protective inner film and a less protective outer film. This might be the first study which proposed a unique surface treatment to provide a protective surface film over 3D-printed interconnected porous biomedical Ti2448 alloy scaffolds under SI environment.

Improving the building energy flexibility using PCM-enhanced envelopes

Pre-formed internal insulative panels with impregnated phase change materials (PCM) can significantly increase both the thermal resistance and thermal capacitance of existing or new building envelopes, thereby improving the overall energy performance of buildings. A further advantage is that such measures have the potential to enhance the energy flexibility of the building, thereby offering the possibility of participation in demand side management measures such as demand response programmes. The current literature on building envelope physics lacks research on energy flexibility and demand response, especially in the context of the building envelope integrated design with high latent heat materials such as PCM for demand response applications. The objective of the current study is to examine how the addition of PCM impregnated building envelopes affects both the thermal performance of the building envelope, as well as the wider building energy characteristics when subject to different demand response events. A reference building is utilised, which is a residential detached house with a floor area of 160 m 2 and a south-easterly facing aspect. Another contribution of this study is proposing new energy flexibility indicators taking into consideration envelope pre-cooling and pre-heating periods prior to the demand response event. Simulation results show that shorter envelope pre-cooling periods (0.5 hr) together with longer demand response periods (4 h) are preferable for all envelopes to achieve the maximum power curtailment for cooling. PCM-enhanced envelopes are shown to give best cooling demand shifting and energy flexibility efficiency. The MW PCM-1 and MW PCM-2 envelopes have the highest flexibility efficiency with a value of 244%. For heating, gypsum board enhanced with PCM retrofitted on the envelopes are shown to give an overall good performance in energy flexibility efficiency and in power curtailment compared to the other building envelopes in all durations of an energy flexibility event. For heating, the maximum energy flexibility efficiencies range from 250% for the LW Gypsum Board envelope to 356% for the LW PCM-2 envelope. • Energy flexibility is mapped for building envelopes with sensible and latent TES. • Building envelopes are optimised for different demand response events. • An energy flexibility sensitivity analysis algorithm is developed in EnergyPlus. • In buildings with only sensible TES short demand response events should be used. • Envelopes with PCM have better energy flexibility in long demand response events.

Stability analysis of photovoltaic interface converter using the dynamic model of photovoltaic cell

In a photovoltaic (PV) power generation system, a power interface converter is required to manage the power flow between the PV cells, battery, or load. Conventionally, while designing loop controller parameters, an ideal current or voltage source with a fixed resistor is adopted to simulate the panel characteristics However, significant differences exist between the actual performance of real panels and that of the above two alternatives; additionally, controllers designed with a definite equivalent model may lack a response. In this study, the small-signal model of a power interface converter, comprising the dynamic characteristics of PV cells, was developed for different operating modes to solve the aforementioned problems. On this basis, frequency response comparisons of the power stage transfer function were used to analyze the stability margin with parameter variations. Consequently, it was concluded that the dynamic capacitance and equivalent output resistance of the PV cells could not be ignored. Therefore, a controller design approach for the worst case was developed. The mathematical analysis was verified based on a prototype simulation and a thorough investigation of the waveforms.