Equivalent Circuit Calculation Research Articles

Research and Design of the RF Cavity for an 11 MeV Superconducting Cyclotron

In contrast to the room temperature cyclotron, the superconducting cyclotron’s high operational magnetic field and small extraction radius lead to a magnet design with a reduced radius. This limits the space available for the RF cavity in the 11 MeV superconducting cyclotron, necessitating a more compact RF cavity design. By using the transmission line theory, the complex structure of the quarter-wavelength coaxial cavity can be represented as a microwave circuit. Through relevant theoretical analytical formulas, equivalent circuit parameters can be derived. The resonant frequency of the RF cavity is then determined using the equivalent circuit method. The optimization of the RF cavity structure was achieved by creating a numerical model and conducting finite element numerical calculations on the high-frequency resonant system. The comparative results between the equivalent circuit and numerical calculations indicate that the frequency error remains within 0.1%, validating the compact RF cavity design. A multiple linear regression analysis facilitates the prediction of resonance frequency across various parameter variables. By analyzing the fitting formula, RF cavity machining error requirements are established, ensuring a prediction error within 1%, thus meeting engineering design criteria.

Corrosion Behavior of X80 Steel in a Simulated Soil Solution Under Square-Wave Current Interference

The buried pipeline is disturbed by the dynamic direct current (DC) stray current with the subway as the main leakage source, which has the safety risk of accelerating corrosion, resulting in pipeline failure, which not only causes economic losses but also threatens personal safety. Therefore, it is necessary to study the corrosion behavior of pipeline steel under dynamic DC interference. The corrosion behavior of X80 steel under dynamic DC interference were studied by a mass loss test, alternating current impedance, circuit simulation, x-ray diffraction, and a Pourbaix diagram. Combined with the corrosion efficiency and Pourbaix diagram of the Fe-H2O system, the reversible process and reduction process mechanism in the Faraday process are proposed. The reason why the corrosion efficiency slows down in the process of non-Faraday is analyzed by the electric double-layer model of equivalent circuit calculation. In addition, based on the above corrosion process, the corresponding conceptual model of the corrosion mechanism is proposed. The experimental results show that with the asymmetry of positive and negative half-cycle interference duration and the increase of current density, the corrosion efficiency, and current corrosion efficiency of X80 steel decrease, and local corrosion intensifies. The length of the negative half-cycle interference affects the capacitive charge-discharge effect at the metal/solution interface and the reduction reaction process of corrosion products, resulting in corrosion slowing down and corrosion efficiency reduction. This is also an important reason for the reduction of corrosion mass loss observed in the experiment compared with steady-state DC.

Wideband and Wide-Angle Switchable Spatial Filter/Shielding With Polarization-Independent Response

In this Letter, an active second-order frequency-selective surface (AFSS) that features a switchable wide pass-band is proposed. Compared to other multi-layer feeding structures, only one layer of FSS is elaborately reconfigured in this design, whose full planar symmetry structure is not destroyed, to achieve the desired all-polarized controlled behavior. The presented design provides good responses under different incident angles and polarizations. The fulfilled structure is composed of three FSS layers and is controlled by semiconductor switches. When the switches are in OFF-state, the proposed design acts as a high-transmittance second-order filter with a low ripple level, whose -0.5 dB passband width is over 24.4% and minimum insertion loss is only 0.1 dB. By switching the semiconductors to ON-state, the unit cells of the top FSS layer are short-connected, which leads to an ultra-wideband shielding behavior from 0 to 10 GHz. Moreover, the proposed structure presents consistent responses under 0°-90° rotation polarizations. Both filter and shielding responses can be obtained up to the 60° incidence. Finally, a prototype is fabricated and measured, and the desired wideband, high-efficiency, wide-angle, and polarization-insensitive switchable performances are obtained through equivalent-circuit calculations, numerical simulations, and experimental measurements.

A new method with integration of matching and decoupling for MIMO antenna applications

A novel design concept of multiple-input and multiple-output (MIMO) antenna with aiming to improve matching and port isolation at the same time is proposed. As the only additional component, a cross resonator is connected between the two patch antennas. The equivalent circuit model and calculation formula of resonant frequency of cross resonator in differential mode (DM) and common mode (CM) state are given, respectively. The same resonant frequency in the two states is the goal to want, and which is proved to be achievable by the relevant expression. Then, the two port antenna system can obtain good matching and high isolation. The coincidence between simulation and measured results brings the possibility of practical implementation.

Wide-Angle Ultra-Broadband Metamaterial Absorber with Polarization-Insensitive CharacteristicsSupported by the Six Talent Peaks Project in Jiangsu Province (Grant No. XYDXX-072), the National Natural Science Foundation of China (Grant Nos. 61372048 and 61771226), and the Natural Science Foundation of Jiangsu Province (Grant No. BK20161186).

An ultra-wideband metamaterial absorber is developed, which is polarized-insensitive and angular-stable. Three layers of square resistive films comprise the proposed metamaterial. The optimal values of geometric parameters are obtained, such that the designed absorber can achieve an ultra-broadband absorption response from 4.73 to 39.04 GHz (relative bandwidth of 156.7%) for both transverse electricity and transverse magnetic waves. Moreover, impedance matching theory and an equivalent circuit model are utilized for the absorption mechanism analysis. The compatibility of equivalent circuit calculation results, together with both full-wave simulation and experimental results, demonstrates the excellent performance and applicability of the proposed metamaterial absorber.

Coupling Analysis of Adjacent Substrate-Integrated Waveguides Based on the Equivalent Transmission Line Model

This article presents a method for analyzing the coupling between two adjacent substrate-integrated waveguides (SIWs) sharing a common row of metallic cylinders, which is based on the concept of equivalent circuit and wavenumber calculation. When the specific sizes of two adjacent SIWs are known, the scattering parameters of the shared common row of metallic cylinders can be derived, and the equivalent transmission line model of the SIW coupling structure is extracted. The even-and odd-mode wavenumbers in both transverse and propagating directions are calculated for this equivalent circuit. For an ideal forward-wave directional coupler, the transmission and coupling coefficient are then derived directly from the wavenumber and the length of the structure. Based on the proposed method, three SIW directional couplers with different coupling levels are designed and fabricated for verification. Good agreements between the calculated and simulated coupling parameters are observed. The proposed method provides a simple and accurate approach to estimate the coupling between two closely spaced SIWs sharing one common row of metallic cylinders and is expected to use for the design of millimeter-wave SIW-based circuits and systems.

Split ring resonator inspired THz antenna for breast cancer detection

A circular split ring resonator inspired (THz) antenna for breast cancer detection is proposed in this paper. The proposed metamaterial antenna is made from a simple rectangular patch antenna loaded with a Circular Split Ring Resonator (CSRR) structure in the ground plane. The design equations for the CSRR along with its equivalent circuit and permittivity calculations are also discussed in this paper. The experimental technique for detection of tumor in human breast model are also offered in this paper. The proposed circular split ring resonator inspired antenna operates at 1.5 THz resonant frequency with the VSWR ≤ 1.5 along with 24.2 dBi of gain and 90% of efficiency. The proposed circular split ring resonator inspired (THz) antenna could be a suitable candidate for a breast cancer detection application.

Metamaterial inspired THz antenna for breast cancer detection

Metamaterial inspired Terahertz (THz) antenna for breast cancer detection proposed in this paper. The proposed antenna consists of a simple rectangular patch configuration integrated with Complementary Split Ring Resonator (CSRR). The design equations along with the equivalent circuit and permittivity calculations also presented in this paper. The experimental technique for detection of tumor in human breast model by the simulation technique also presented. The proposed metamaterial inspired antenna operates at 1 THz frequency with 20 dBi of gain. Its design evolution process, parametric study, and results such as farfield radiations also presented in this paper.

Low-Profile Filtering End-Fire Antenna Integrated With Compact Bandstop Filtering Element for High Selectivity

A high-selectivity low-profile filtering end-fire antenna is proposed using a bandstop filtering (BSF) element integrated into the feedline of the conventional quasi-Yagi antenna. Three transmission zeros (TZs) and six transmission poles (TPs) of the BSF element can be obtained through the odd–even mode equivalent circuit analysis and calculation. With the help of TP and TZ of the BSF element, an additional resonant mode within the operating band and additional radiation null at the upper band edge of the antenna can be obtained, respectively. Consequently, the impedance bandwidth and frequency selectivity of the proposed antenna can be improved compared with the conventional quasi-Yagi antenna. For demonstration, an antenna is fabricated whose measured results exhibit a stable end-fire gain response with two radiation nulls close to two sides of the operation band.

Annular Apertures in Metallic Screens as Extraordinary Transmission and Frequency Selective Surface Structures

A 2-D periodic array of annular apertures (or ring slots) is studied using an accurate circuit model. The model accounts for distributed and dynamic effects associated with the excitation of high-order modes operating above or below cutoff but not far from their cutoff frequencies. This paper allows to ascertain the substantial differences of the underlying physics when this structure operates as a classical frequency selective surface or in the extraordinary-transmission (ET) regime. A discussion of two different designs working at each regime is provided by means of the equivalent circuit approach (ECA), full wave simulation results, and experimental characterization. The agreement between the equivalent circuit calculation applied here and the simulation and experimental results is very good in all the considered cases. This validates the ECA as an efficient minimal-order model and a low computational-cost design tool for frequency selective surfaces and ET-based devices. Additional scenarios such as oblique incidence and parametric studies of the structural geometry are also considered.

Influence of tertiary stabilizing windings on zero-sequence performance of three-phase three-legged YNynd transformers. Part II: Tank overheating hazard and short-circuit duty

This paper analyzes the influence of stabilizing windings in three-phase three-legged YNynd transformers on tank overheating hazard and on the short-circuit performance of such transformers in the event of unbalanced conditions involving zero-sequence currents as asymmetrical faults. It complements a previous companion paper that presented experimental zero-sequence measurements and equivalent circuit calculations for three power transformers. Those previously calculated zero-sequence equivalent circuit parameters are used here to evaluate the comparative performance of YNynd power transformers when the delta stabilizing winding is closed and when it is open. Additionally, it analyzes the effects of other variables, such as relative position of the stabilizing winding, presence of magnetic shunts in the tank walls, and system grounding.

Multi-directionally non-linear magnetic equivalence circuit calculation (MACC) of rotational magnetization intensity in transformer cores

This paper puts a novel methodology of multi-directionally non-linear magnetic equivalent-circuit calculation (MACC) for discussion. It models transformer cores of Goss texture through local elements that are represented by non-linear magnetic resistances. From its concept, it allows for 2D or 3D distributions of induction components, considering arbitrary degrees of non-linearity and anisotropy. The present work describes modelling of rotational magnetization by means of a network of elements for flux in three different directions, the rolling direction (RD), the transverse direction (TD) and the diagonal direction (DD) in overlaps. Other directions are assumed to be hard, thus being neglected. A 3-phase core package is modelled by 41 elements, assuming two main flux paths. Three sets of nonlinear permeability functions are attributed to the individual elements, starting withroughly estimated induction distributions. The corresponding system of Kirchhoff equations is solved in well known ways. Step-wise approximations of the set of induction components are performed until they correspond with the set of permeability values in acceptable grades. The resulting local distribution of induction components indicates maximum values of TD-components in the T-joint region and the adjoining yoke regions corresponding to maximum rotational magnetization. In comparison with experimental findings, the results of modelling show similar tendencies. However, as a specific advantage of MACC-modelling, it allows flexible and rapid checks of consequences of changes of material parameters and geometric parameters, respectively.

Simulation of a through cell via contacts architecture for HCPV multi-junction solar cells

In this study we quantify the possible gains in cell performance obtained with an architecture based on through-cell via contacts (TCVC). We review how the front metallization of solar cells introduces a compromise between shadowing and resistive losses. The work models the trade-offs that directly impacts the device efficiency. Gains at the cell level are important because they are highly leveraged in HCPV systems. For a very high illumination flux, a standard cell optimization leads to a large metallized area for finger grid designs. Our modeling shows that the back-contact architectures can offer an interesting alternative. The TCVCs were evaluated using a multijunction InGaP/InGaAs/Ge solar cell (MJSC). The proposed architecture is modeled and compared with a conventional grid design. The absolute efficiencies of the different solar cells were calculated to quantify their shadowing and resistive losses. A combination of finite-element modeling and equivalent-circuit calculations were used. Our study finds that an absolute efficiency improvement of 1.8% could be obtained over a conventional MJSC design by using a basic via contact design for a light concentration of 2000 suns. This gain attains 3.0% when cross-fingers are added to the design. Furthermore, we show that the TCVCs are expected to be a cost-effective solution because the removal of bus bars area improves significantly the wafer utilization. The latter improvement is estimated to result in an increase in power generation of about 20% per wafer.

Impact of Sandblasting on Fresnel Lens for Concentrator Photovoltaic

When installing concentrator photovoltaic (CPV) systems in desert areas, we must consider the impact of sandstorms on the Fresnel lens in CPV modules. CPV systems are much more sensitive to sandstorms than flat-panel PV systems because they can only use the direct beam component of sunlight. In this study, the transmittance of a PMMA substrate after sandblasting was evaluated and the influence of sandblasting on the output of a CPV system was assessed. The transmittance of PMMA decreased with an increase in the momentum of blown sand. The conversion efficiency of a CPV module was determined by equivalent circuit calculation. The conversion efficiency decreased with increasing momentum. The coefficient of degradation was 0.17 point per unit momentum.

Triple-Band Marchand Balun Filter Using Coupled-Line Admmittance Inverter Technique

This study presents the first reported design and implementation of triple-band Marchand balun filter. The novel balun filter is constructed from the short-circuited coupled line with a triple-band resonator to demonstrate the triple-band admittance inverter characteristic. To improve the amplitude and phase responses within three passbands, the compensation techniques for phase-angle, impedance-matching, and susceptance-slope discrepancies are employed in the balun filter design. Four types of triple-band balun filters with significantly different bandwidths and passband separations are designed and the results are consistent with the specifications. The design procedure for the triple-band Marchand balun filter is established to obtain the amplitude and phase balances in three operating bands with arbitrarily controlled center frequencies and fractional bandwidths. The proposed Marchand balun filter realized by the microstrip coupled-line sections and the defected ground structure stubs is measured and a good agreement among equivalent-circuit calculation, full-wave simulation, and measurement is observed, demonstrating the validity and versatility of the proposed design methodology and balun filter configuration.

Optimized Design of a Novel Modular Tubular Transverse Flux Reluctance Machine

This paper presents a new type of tubular electrical machine with a modular construction. The structure of the machine, concerning its construction, is discussed in the first part of the paper. A semi-analytical method based on the magnetic equivalent circuit calculation is used in order to obtain the flux densities in different parts of the iron core of the machine. A Gauss elimination procedure is applied to the system of linear equations resulted from the magnetic equivalent circuit, in order to express the flux in the air gap. The problem of optimization of the traction force is analyzed. The maximization of the function is handled with the Nonlinear Conjugate Gradient method and verified with a Gauss Newton algorithm. An application of the presented theory shows the usefulness of this approach. The results provided by the optimization method applied on a designed tubular machine illustrate its advantages. A numerical analysis performed on both a designed and then optimized structure confirmed the results obtained in the optimization process.

Sandblasting durability of acrylic and glass Fresnel lenses for concentrator photovoltaic modules

The impact of sandblasting on Fresnel lenses for concentrator photovoltaic (CPV) modules must be carefully considered when CPV systems are installed in desert areas. In this study, the transmittance after sandblasting of acrylic polymethylmethacrylate (PMMA) and glass substrates was evaluated, and their durability was assessed. The transmittance decreased as the momentum of the blown sand increased. The conversion efficiency of the CPV modules was estimated using equivalent circuit calculations, and the influence of sandblasting on the output of the CPV modules was quantitatively predicted. The coefficients of degradation for the PMMA and glass CPV modules were 0.17 and 0.08 points per unit of momentum, respectively. The durability of the CPV module with the glass Fresnel lens is approximately twice that with the PMMA lens.

Broadband metamaterial absorber based on coupling resistive frequency selective surface

We report the design, fabrication, and measurement of a broadband metamaterial absorber, which consists of lossy frequency selective surface (FSS) and a metallic ground plane separated by a dielectric layer. The compact single unit cell of the FSS contains crisscross and fractal square patch which couple with each other. Both qualitative analysis by equivalent circuit and accurate numeric calculation show that the coupling between the crisscross and the fractal square patch can enhance the bandwidth with the reflectivity below -10dB in the frequency range of 2-18GHz by producing a third absorption null. In the end, the designed absorber was realized by experiment.

Development of a novel single sensor multiplexed marker assay

There is an increasing desire to measure multiple analytes simultaneously for disease management and detection. However, in the case of invasive devices, it would be better to obtain one small sample and immediately be able to detect the analytes rapidly, as in the case of self-monitoring blood glucose, without the need for additional steps, arrays, or reagents. Electrochemical impedance spectroscopy is used to measure the interaction between ultralow levels of analyte and molecular recognition element in a label-free and rapid manner. Gold nanoparticles were attached to antibodies against interleukin-12 and tumor necrosis factor-α, typical inflammatory markers found with near overlapping responses, on an impedance spectroscopy based biosensor. Cross-reactivity and specificity of tuned antibodies were verified using ELISA. Impedance frequency was quantified by concentration gradients of marker against the device. The natural impedance frequency for interleukin-12 (5.00 Hz) was tuned to a lower frequency four Hertz away from one another for better signal processing. This was accomplished without significantly altering the lower limits of detection (<4 pg ml(-1) and ∼60 pg ml(-1) for interleukin-12 and tumor necrosis factor-α, respectively), no cross-reactivity and specificity as determined by ELISAs. With modeling the nanoscale effects and further development, a larger tuning will be possible for making a better multiplexed sensor. Although interleukin-12 and TNF-α equivalent circuit calculations were modeled here, a sensor with the potential to measure multiple markers at once might offer a solution on the sensor front for simplified management of conditions such as diabetes, where both glucose and hemoglobin A1c values could be obtained.

A Short Open-End Slot Antenna With Equivalent Circuit Analysis

A novel configuration is described for a compact microstrip-line fed slot antenna which is shorter than one-eighth wavelength at the operating frequency. Antenna size is reduced by placing two matching capacitors at both sides of an electrically small open-end slot, through the use of a wideband antenna equivalent circuit model established by considering the physical geometry. With the proposed antenna configuration, a 2.45 GHz slot antenna is first designed using an open-end slot of size 9 mm by 1.5 mm that is originally resonant at 4.8 GHz in a conventional design. Experimental results correlate well with those of the full-wave simulation and the equivalent circuit calculation, which shows a bandwidth of 109 MHz and peak gain of 1.89 dBi. By using the same slot size, several slot antennas operating at even lower frequencies (1.9, 1.64, 1.57 GHz) are then designed and demonstrated. Nearly omni-directional radiation patterns with peak gains 0 dBi and radiation efficiencies larger than 45% are obtained. Given its simplicity and compactness, the proposed electrically small antenna is feasible for circuit integration and highly promising for wireless mobile devices.