Equivalent Circuit Simulation Research Articles

A Compact Diplexer Using Coupled π-CRLH Zeroth Resonators

ABSTRACT This paper presents a new diplexer design of a new-coupled composite right/left-handed (CRLH) resonator to serve the LTE applications. The realization of the diplexer is designed as coupled two zeroth order π-CRLH resonators to represent with zero electrical length and hence attaining a significant size reduction. The filters are designed to achieve a desired frequency bandwidth of 4% ∼16.7 Q-factor and ∼0.066 coupling coefficient at a centre frequency of 2.1 and 2.6 GHz with transmission zeros. The diplexer exhibits a rejection level of 15–20 dB while maintaining insertion loss of 1 dB for the Tx and Rx bands. The circuit design concepts are verified using equivalent circuit simulations, full electromagnetic simulations and experimental measurements. In conclusion, a good agreement is perceived between the measured and simulated data with size compactness of 30 × 60 mm2.

An Improved Equivalent Circuit Simulation of High Frequency Ultrasound Transducer

The equivalent circuit simulation plays an important role in the design of ultrasound transducer. However, the existing methods are difficult to achieve the effect of matching and backing layer, and not able to accurately simulate the transducer with cable. Especially in the application of high frequency ultrasound, the long cable has a great influence on the performance of the transducer. To overcome these limitations, this paper proposed an improved equivalent circuit method, which combined Leach model and transmission line model. It can realize the complete simulation of ultrasound transducer with a long cable, matching layer, and backing layer in PSPICE circuit simulation software when the parameters were measured. Its principles were briefly introduced, and ultrasound transducers with different frequencies (12 and 20 MHz), different matching layers, and different cable lengths (0.5–2.5 m) were designed and fabricated to verify the effectiveness of the method, which is also compared with the traditional KLM method using PiezoCAD. The experiment results showed that the long cable, matching layer, and backing layer have a significant impact on the performance of high frequency ultrasound transducers, and this proposed method has good agreement with these results. Moreover, for the simulation of the complete transducer, the effect of this method is better than KLM model. Besides, this method does not need to know the specific equivalent circuit of matching, backing layer, or cable wire, it can accurately predict the impedance and phase of the transducer through the material parameters, which is very helpful for the material selection and optimization of subsequent transducer design and fabrication. The study indicates that this improved equivalent circuit method is suitable to be applied in the general circuit simulation software and provides strong support for the high frequency transducer and system design.

Direct Oil Cooling of End-Windings in Torus-Type Axial-Flux Permanent-Magnet Machines

In high power density applications, such as electric or hybrid electric vehicles, heat extraction is a crucial aspect of electrical machine design due to stringent volume specifications. In these cases, it is extremely difficult, if at all possible, to satisfy the maximum temperature requirement when using conventional cooling systems, such as housing fins, shaft-mounted fans or even water jackets. To this end, a novel direct oil cooling system conceived for Torus-type axial-flux permanent-magnet machines is proposed here. In order to demonstrate its effectiveness, lumped thermal equivalent circuit simulations, finite element analyses and experimental tests are presented. The expected performances of the machine using the proposed direct oil cooling are compared to those obtained using state of the art water cooling.

Characterization of Parasitic Impedance in PCB Using a Flexible Test Probe Based on a Curve-Fitting Method

Switching in power semiconductors with emerging materials such as silicon carbide (SiC) leads to undesired overvoltages and oscillations that limit switching frequency, largely due to impedance in the current commutation loop. Minimizing this parasitic impedance in printed circuit boards (PCB) requires precise characterization. To this end, this work presents a new measurement method based on obtaining S-parameters with a vector network analyzer (VNA) and on using a shielded flexible probe with mobile test terminals. The flexible probe uses a metal shielding plane perpendicular to the PCB to prevent the main measurement errors resulting from the variation in the magnetic flux responsible for loop inductance during the VNA frequency sweep. The proposed curve-fitting procedure consists of measuring the characteristic impedance and propagation time of the traces, considering they form ideal transmission lines. These values are used for a nonlinear least squares adjustment for the actual line (with losses). Finally, an experimental assembly with microstrip transmission lines was developed to validate the proposed method experimentally. The experimental results were compared with those obtained by using a rigid test fixture as a reference, those calculated analytically and those obtained from partial element equivalent circuit (PEEC) simulation. The curve-fitting method yields better results than the analytical and the simulation methods and they exhibit (up to 350 MHz) precisions of 1.37% in the characteristic impedance measurement and of 0.81% in the propagation time.

Experimental Studies and Optimization of a Compact Multichannel Nanosecond-Pulse Generator

The results of experimental studies of a high-voltage multichannel generator for a voltage of up to 100 kV with a pulse duration of 100 ns and a front of 8 ns are presented. Options for optimizing the output parameters using a numerical simulation of the generator equivalent circuit are considered.

Poles and Stability of Full-Wave PEEC

Time-domain simulation of full-wave partial element equivalent circuit (PEEC) often encounters stability problems. In the past, various approaches have been proposed to determine the stability of a given model. Most of these methods, however, have low efficiency and scalability. In this article, we propose a highly efficient method to obtain a particular group of the poles of the model; such information then serves as a necessary-condition test for stability. Furthermore, the method is extended to include the effects of damping resistors. From the root locus plots of the poles, we clearly see the unstable poles moving left as damping is added in, and by the time they move into the left-half-plane, we can quantitatively determine the minimum damping level required to achieve a stable model. Simulation results are provided to verify the proposed method.

Physically defined silicon triple quantum dots charged with few electrons in metal-oxide-semiconductor structures

Physically defined silicon triple quantum dots (TQDs) are fabricated on a silicon-on-insulator substrate by dry-etching. The fabrication method enables us to realize a simple structure that does not require gates to create quantum dot confinement potentials and is highly advantageous for integration. We observe the few-electron regime and resonant tunneling points in the TQDs by applying voltages to two plunger gates at a temperature of 4.2 K. Moreover, we reproduce the measured charge stability diagram by simulation with an equivalent-circuit model composed of capacitors and resistors. The equivalent-circuit simulation makes it clear that we realize three QDs in series within the nanowire, as planned. This circuit model also elucidates the mechanism of resonant tunneling and identifies a quadruple point of TQDs.

Experiments on the Pulse Repetition Frequency Optimization of 1.3-GHz, 100-kW Microwave Pulse Compressor

A microwave pulse compressor (MPC) system formed by an inductive iris, a straight rectangular waveguide, and an H-plane T-junction is experimentally studied. The MPC design, which is based on an equivalent circuit simulation model, ensures the optimum cavity-storage gain at 1.3 GHz. A low-pressure gas discharge tube (GDT) that is placed at the side arm of the T-junction implements the switching trigger for the cavity energy extraction. The experimental results show that high pulse repetition frequency (PRF) operation together with optimal cavity-extraction gain is feasible by carefully selecting the GDT gas type, pressure level, and flow rate. Under optimal conditions, the MPC system approaches the theoretically predicted cavity-extraction gain of 19 dB and a PRF up to 300 Hz.

A New Ultracompact Narrow Bandpass Microstrip Filter Using Double-Negative Quasiplanar Cells

This paper presents a novel ultracompact narrow bandpass filter with high selectivity. The proposed filter is composed of cascading two basic cells. Each cell is basically a microstrip line loaded with a quasiplanar resonator and series gaps which can be fabricated using a standard multilayer printed circuit board technology. The structure is analyzed through an equivalent circuit and full-wave simulations. The simulation results are compared with experimental measurements demonstrating a good agreement between them. The measurement indicates that the realized bandpass filter at the center frequency of 1 GHz has a fractional bandwidth of 2.2%. Most importantly, in comparison with other similar recent works, it is shown that the proposed filter has the smallest size.

A Highly Sensitive Planar Microwave Sensor for Detecting Direction and Angle of Rotation

This article presents a technique based on a modified complementary split-ring resonator (CSRR) to detect angular displacement and direction of rotation with high resolution and sensitivity over a wide dynamic range. The proposed microwave planar sensor takes advantage of the asymmetry of the sensor geometry and measures the angle of rotation in terms of the change in the relative phase of the reflection coefficients. The sensor consists of a movable modified CSRR (the rotor) and a microstrip line with a circular defect in the ground plane (the stator). By selecting the substrate material and the rotor thickness, the sensor can be designed to work at different operating frequencies. A theoretical model of the sensor is proposed and is followed by a detailed numerical analysis involving equivalent circuit simulations, full-wave computations, and measurement results. Using positioning error estimation and air-gap analysis, a technique based on phase-change measurements is found to be better than those based on magnitude measurements alone. The maximum sensitivity for measuring the angular rotation is found to be a 4.3° change in the relative phase of the reflection coefficient per 1° of rotation. The sensor has an angular measurement range from -90° to +90°. The sensor-a stator fabricated on a 0.5-mm-thick Rogers RT5880 substrate and three rotors fabricated on a 1.5-mm-thick Rogers RT5880, a 1-mm-thick FR4, and a 0.5-mm-thick Rogers RT5880-can effectively detect the direction of rotation, measure the angle of rotation and angular velocity with reasonable accuracy.

Dielectric relaxation and magnetodielectric effect in the spinel NiCr2O4

Single phase NiCr2O4 has been successfully prepared by sol–gel technique. Characterization of crystal and morphology exhibits the tetragonal structure and homogeneous growth with regular crystalline shape. Large dielectric constant of ~2447 is observed at room temperature. The relaxation behavior below room temperature is confirmed through measurements of dielectric constant, dielectric loss, electric modulus and impedance depended on frequency or temperature. The analysis through equivalent circuit simulation demonstrates the influence of grains at low temperature and the common contribution of grains and grain boundaries at high temperature. Moreover, the change in dielectric response indicates the presence of magnetodielectric coupling effect. Two different mechanisms are considered to control the magnetodielectric coupling, yielding the positive and negative coupling coefficient at different temperature ranges. The intrinsic magnetoelectric coupling gives rise to the frequency independent magnetodielectric behavior at low temperature. As temperature increases above 150 K, the large magnetodielectric coupling coefficient depended on frequency is contributed by the Maxwell-Wagner effect. The negative value of magnetodielectric coupling coefficient is attributed to the leakage current. Therefore, both mechanisms of Maxwell-Wagner and leakage are competing as a function of frequency, which results in the coefficient crossover at room temperature. Such features bring NiCr2O4 a step closer to potential applications in areas such as magnetic field sensors, actuators and others.

Directional DC Charge-Transfer Resistance on an Electrode–Electrolyte Interface in an AC Nyquist Curve on Lead-Acid Battery

Both the frequency domain Nyquist curve of electrochemical impedance spectroscopy (EIS) and time domain simulation of DC equivalent first principle linear circuit (FPLCDCequ) are some of the fundamentals of lead-acid batteries management system design. The Nyquist curve is used to evaluate batteries’ state of health (SoH), but the curve does not distinguish charging/discharging impedances on electrode–electrolyte interfaces in the frequency domain. FPLCDCequ is used to simulate batteries’ terminal electrical variables, and the circuit distinguishes charging/discharging impedances on electrode–electrolyte interfaces in the time domain. Therefore, there is no direct physical relationship between Nyquist and FPLCDCequ This paper proposes an AC equivalent first principle linear circuit (FPLCACequ) by average switch modeling, and the novel circuit distinguishes charging/discharging impedances on electrode–electrolyte interfaces in Nyquist. The novel circuit establishes a physical bridge between Nyquist and FPLCDCequ for lead-acid batteries management system design.

Biosensor Using a One-Port Interdigital Capacitor: A Resonance-Based Investigation of the Permittivity Sensitivity for Microfluidic Broadband Bioelectronics Applications

Electronics is a field of study ubiquitous in our daily lives, since this discipline is undoubtedly the driving force behind developments in many other disciplines, such as telecommunications, automation, and computer science. Nowadays, electronics is becoming more and more widely applied in life science, thus leading to an increasing interest in bioelectronics that is a major segment of bioengineering. A bioelectronics application that has gained much attention in recent years is the use of sensors for biological samples, with emphasis given to biosensors performing broadband sensing of small-volume liquid samples. Within this context, this work aims at investigating a microfluidic sensor based on a broadband one-port coplanar interdigital capacitor (IDC). The microwave performance of the sensor loaded with lossless materials under test (MUTs) is achieved by using finite-element method (FEM) simulations carried out with Ansoft’s high frequency structure simulator (HFSS). The microfluidic channel for the MUT has a volume capacity of 0.054 μL. The FEM simulations show a resonance in the admittance that is reproduced with a five-lumped-element equivalent-circuit model. By changing the real part of the relative permittivity of the MUT up to 70, the corresponding variations in both the resonant frequency of the FEM simulations and the capacitance of the equivalent-circuit model are analyzed, thereby enabling assessment of the permittivity sensitivity of the studied IDC. Furthermore, it is shown that, although the proposed local equivalent-circuit model is able to mimic faithfully the FEM simulations locally around the resonance in the admittance, a higher number of circuit elements can achieve a better agreement between FEM and equivalent-circuit simulation over the entire broad frequency going range from 0.3 MHz to 35 GHz.

Broadband cavity‐backed aperture‐coupled vertically mounted strip antenna

AbstractA novel cavity‐backed aperture‐coupled antenna having a vertically mounted (VM) strip is proposed, where the signal is fed to the antenna from a microstrip feed through an aperture‐coupled microstrip‐to‐waveguide transition. Broadband characteristics are achieved by the introduction of the VM strip. An equivalent‐circuit model for this antenna that reflects the effects of various structure parameters is proposed. Based on this equivalent circuit, an X‐band antenna was designed by optimizing for broadband, low loss, and highly efficient operation. The measured S11 of the fabricated antenna showed excellent broadband characteristics (47%) and was in reasonable agreement with predictions derived from the equivalent circuit and numerical simulation.

An immunosensor detects carcinoembryonic antigen by a double reduction strategy based on polyphenylamine as a sacrifice reducing agent

In this paper, a novel Ag NPs-PANI/MnO2 tag was synthesized for the first time, and the electrochemical immunoassay for carcinoembryonic antigen (CEA) was achieved. In this experiment, gold nanoparticles (Au NPs) were used as an electrochemical sensing platform to increase conductivity and improve electrode surface capture antibody (Ab1). We use PANI as a green sacrificial agent reduces Ag NPs and MnO2, while improving the conductivity and electrochemical stability of the immunosensor. MnO2 and Ag NPs effectively raise the sensitivity of the sensor by catalytically reducing hydrogen peroxide (H2O2) into water and oxygen to achieve a double amplified sensing signal. It is found that the surface plasmon resonance of Ag NPs has an interesting SERS characteristic structure, and the equivalent circuit simulation of the electrode assembly process results in an error of less than 10%, indicating that the electrochemical immunosensor is successfully prepared. Under optimal conditions, the electrochemical immunosensor has a linear range of 0.0005–80 ng/mL and a detection limit of 0.17 pg/mL (S/N = 3). The immunosensor is expected to be used in clinical laboratories to detect CEA and other tumor markers in human plasma for precancerous screening or surveillance.

Modelling and Validation of Electret-Based Vibration Energy Harvesters in View of Charge Migration

One of the key problems of electret-based vibration energy harvester (eVEH) modelling is that the surface voltage itself cannot precisely reveal the charge storage characteristics of the electret fabricated by different processes. In this paper, we endeavor to interpret the charge migration mechanism of the eVEH with electrets fabricated by different processes. Based on the above analysis, a unified analytical model of the eVEH is derived accordingly. The dynamic response and voltage output predicted by this model are verified numerically by the equivalent circuit simulation and experimentally with an out-of-plane eVEH prototype. According to the analysis, the maximum power output is approximately 255 μW when the prototype works at its resonance frequency and the vibration amplitude is 1 mm. This paper elucidates the working principle of the eVEH and provides a framework for further theoretical study of eVEHs from the first principle.

A simulation on neutralization performance of a corona discharge air ionizer by using an equivalent circuit

Corona‐discharge air ionizers have been used to neutralize static electricity on electronic devices during manufacturing and/or inspection processes. The neutralization performance, that is, the neutralizing current density (JW) and the electric field (EW), in work area depends on the operating conditions. Methods for estimating the neutralization performance are required to check them without stopping the production lines. In this paper, we propose an estimation method using an equivalent circuit simulation called the Simulation Program with Integrated Circuit Emphasis (SPICE) for estimating the behavior of positive and negative ions in the generation, transportation, and work areas. In the simulation, the ion generation characteristics are simulated by diodes and resistors. The transportation and accumulation of the ions are simulated by resistors and capacitors, respectively. The annihilation of ions by recombination is simulated by a circuit composed of capacitors and resistors. The simulation results are in good agreement with the experimental results when the distance between the emitter of the air ionizer and the work area is varied. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Analysis on Electrical and Thermal Characteristics of a No–Insulation HTS Coil Considering Heat Generation in Steady and Transient States

This paper presents the design process of an equivalent circuit simulation (ECS) method and its analysis results to evaluate the delayed response time and thermal stability behavior of no-insulation (NI) second-generation high-temperature superconducting (2G HTS) coils. The electrical and thermal characteristics of NI HTS coil were introduced by many researchers through the simulation method base on ECS model, but the feature of heat generation by superconducting and stabilizer layer was not considered in the previous studies. In this study, we analyze the electrical and thermal characteristics considering heat generation of NI HTS coil in both steady and transient states. First, an electrical ECS model was proposed to numerically analyze the characteristics of the NI 2G HTS coil in steady and transient states. A steady-state simulation was performed under rated operating-current shooting to estimate the magnetic-field response performance of the NI HTS coil. The transient-state simulation was performed under an overcurrent shooting to analyze the thermal quench behavior. In addition, the simulation results of the NI HTS coil were discussed and compared with the experimental ones to validate the simulation approach based on the proposed equivalent electric-circuit model.

Static Voltage Sharing Design of a Sextuple-Break 363 kV Vacuum Circuit Breaker

A balanced voltage distribution for each break is required for normal operation of a multi-break vacuum circuit breaker (VCB) This paper presented a novel 363 kV/5000 A/63 kA sextuple-break VCB with a series-parallel structure. To determine the static voltage distribution of each break, a 3D finite element method (FEM) model was established to calculate the voltage distribution and the electric field of each break at the fully open state. Our results showed that the applied voltage was unevenly distributed at each break, and that the first break shared the most voltage, about 86.3%. The maximum electric field of the first break was 18.9 kV/mm, which contributed to the reduction of the breaking capacity. The distributed and stray capacitance parameters of the proposed structure were calculated based on the FEM model. According to the distributed capacitance parameters, the equivalent circuit simulation model of the static voltage distribution of this 363 kV VCB was established in PSCAD. Subsequently, the influence of the grading capacitor on the voltage distribution of each break was investigated, and the best value of the grading capacitors for the 363 kV sextuple-break VCB was confirmed to be 10 nF. Finally, the breaking tests of a single-phase unit was conducted both in a minor loop and a major loop. The 363 kV VCB prototype broke both the 63 kA and the 80 kA short circuit currents successfully, which confirmed the validity of the voltage sharing design.

Dual direction SCR with deep well structure for high voltage ESD in communication bus

In order to improve the robustness of the ESD of the dual-direction silicon-controlled rectifier, a low doping deep well PB structure is proposed instead of the traditional high doping P+ structure. The ESD stress of the dual-direction SCR devices with deep well structure is discharged from inside and the lattice temperature of the device is low to avoid premature burnout of the device. The deep well PB structure on the surface of the device increases the parasitic resistance of the device and improve the conduction uniformity of the device. As the main conduction path of the device is located in NBL, the PB structure does not have a large influence on the sustain voltage. It is verified in a 0.25 μm BCD process. With equivalent circuit and two-dimensional device simulation, the working mechanism is analyzed. According to the transmission line pulse test results and comparing with the data from traditional dual-direction SCR structure. The device’s fault current increases from 5.486 A to 8.13 A which is suitable for communication bus high voltage electrostatic discharge (ESD) protection.