Lumped Equivalent Circuit Model Research Articles

High frequency modeling of dry type detuned reactor for transient studies: Simulation and experimental analyses

Dry-type detuned reactor (DDR) is a key component for power quality management. Improper design of DDR may result in insulation failure during power system transient events. This can be avoided by developing a proper DDR high frequency model that can accurately capture the behavior of the reactor during transients and provide better insight into its performance under various operating conditions. One of the main challenges of proper DDR modeling is the shape of the leakage flux, which is strongly dependent on the shielding effect of the foil conductors and hence affecting the winding frequency response at high frequencies. This paper proposes a high-frequency lumped equivalent circuit model for DDR with frequency-dependent parameters. The frequency-dependent inductances and resistances are calculated using anisotropic equivalent complex permeability to represent the damping effects in the core and winding. A combined analytical-finite element modelling approach is employed to calculate the winding capacitances. The accuracy of the proposed model is verified by comparing its frequency response with the experimental results obtained from a laboratory prototype. Furthermore, the impulse voltage distribution within the windings is obtained through simulation and measurement analyses to attest the robustness of the proposed model. The proposed model is expected to aid in the proper design and optimization of DDR to improve its insulation withstand capability and enhance its performance during transient events within power grids.

Textile-based quad-band electromagnetic absorber design for wearable applications

In this article, a textile-based quad-band electromagnetic absorber (TQA) is presented for wearable applications in the S-band frequency region. The proposed TQA consists of two asymmetric X-shaped resonators (AXRs) with different arm lengths placed on fully grounded denim fabric. Since each arm of the two AXRs excites a different resonance mode, four distinctive absorption bands can be achieved by adjusting the arm lengths. The proposed structure with optimal design parameters, designed and optimized using CST Microwave Studio Suite v.2021, provides over 0.99 absorption peaks at 2.68, 2.80, 3.00, and 3.18 GHz frequencies in the simulation environment. Also, an efficient lumped equivalent circuit model is extracted for the absorber to demonstrate the principle of the quad-band operation in the respective frequencies. In addition, a good agreement between simulated and measured results is observed and thus the numerical design is validated. More importantly, to the best of the authors’ knowledge, this is the first textile based absorber design that provides absorbance in four different frequency bands.

An optically transparent dual-band frequency selective surface for polarization independent RF shielding

This article reports on a compact dual band, Frequency Selective Surface (FSS) based spatial filter for Wi-Fi and WLAN shielding applications on a transparent glass surface with optical transparency of 70%. The unit cell comprises an outer square loop resonator with a disconnected and concentric annular ring resonator. To introduce frequency tuning and compactness T shape stubs are strategically loaded on these resonators and it is ensured that the mutual coupling remains minimal. The outer square resonator suppresses the 2.4 GHz band, and the inner circular ring resonator stops the 5.4 GHz band. The unit element is four-fold symmetric thus it offers complete polarization independence. A detailed parametric and electromagnetic field analysis has been conducted to elucidate the significance of different sections of the unit element. An equivalent lumped circuit model is also derived for the proposed unit element to better explain the underlying working mechanism. A finite prototype of 15 × 11 elements is fabricated on a soda lime float glass by using ordinary adhesive copper foils with a standard chemical etching process. Polarization independence and angular stability up to 45° are measured and compared with the simulated responses. The FSS shield offers frequency suppression up to 45 dB and 43 dB for 2.4 GHz and 5.4 GHz bands respectively. With high optical transparency, the design allows maximum light through it and causes no extra burden on energy consumption for indoor applications. The compact dual band design and the possibility of direct application on host surfaces like glass windows and doors make this design an excellent candidate for data security and privacy applications in secure installations with an esthetically pleasing outlook.

Planar Circular Spiral Inductors With Improved Q and Self-Resonance Frequency Using Compensatory Capacitance Technique

This paper presents a planar circular spiral inductor introducing an optimum compensatory ground capacitance to improve its quality factor and self-resonance frequency. The equivalent lumped electrical circuit model of the proposed inductor is developed for both top and bottom layers. In this electrical model, the compensatory capacitance is introduced in series with the substrate capacitance. This compensatory capacitor is in the form of a modified ground conductor, which is realized using a transmission line based technique. The total parasitic capacitance is reduced in this manner, and consequently, the quality factor and self-resonance frequency are increased without any fringing field or back radiation effects. Three circular spiral inductors are fabricated on FR4 substrate to verify the proposed design. The measured results show that the resonance frequency and quality factor are improved as compared to a conventional spiral planar inductor, without any increase in the inductor area. The quality factors are improved by 21.28%, 19.60%, and 17.12% for the inductors having 1.5, 2.5, and 3.5 turns, respectively. In addition, the self-resonance frequency is improved by 27%, 18.05%, and 17.85% for the inductor having 1.5, 2.5, and 3.5 turns, respectively. The proposed inductor design is scalable for different frequencies of operation.

Electronically Tunable UWB Band Stop Filter Using Varactor Diode

An electronically tunable Ultra-Wideband (UWB) Band Stop Filter (BSF) using the varactor diode is investigated. The open stubs and Step Impedance Resonator (SIR) topology are utilized to obtain UWB bandstop response. The concept of variable capacitive loading to get tuning, which is achieved by a varactor diode (SMV2019-079LF) and a biasing network is clearly elucidated. The validation of the |S| parameter of the proposed tunable BSF filter is carried out using the filter's transmission line model (TLM), consequently, even and odd mode impedances are calculated analytically, and a lumped equivalent circuit model of the proposed BSF filter is extracted. Moreover, the filter is fabricated, and corresponding |S| parameters are measured which offers a UWB response (2.44 GHz–9.65 GHz) with five Transmission Zeros (TZ) and has tuning of 1 GHz frequency range (8.65 GHz–9.65 GHz) at the upper edge. The proposed miniaturized BSF has a size of 0.23λg × 0.32λg. The simulation results of the electromagnetic (EM)/distributed model, and the measured results of the fabricated prototype are in good agreement. Additionally, a very high skirt factor (SF) of 380 dB/GHz is achieved.

High-Sensitivity Sensor Loaded With Coupled Complementary Spiral Resonators for Simultaneous Permittivity and Thickness Measurement of Solid Dielectric Sheet

High-precision measurement of permittivity and thickness enables advanced quality control of microwave substrates. In this article, a subwavelength planar microwave sensor is proposed, which is composed of a single-microstrip transmission line with a pair of coupled circular complementary spiral resonators (CSRs). Thus, two robust band-stop notches in the transmission response are developed, which can be utilized for simultaneous thickness and permittivity measurements of a dielectric sheet. The mutual capacitance and inductance, which quantify the coupling effect between the two resonators, are added to the equivalent lumped circuit model. They enhance the frequency shifts, thus improving sensitivity. The results of full-wave simulations and measurements on five different types of samples verify the concept’s effectiveness.

Lightweight ultra-wideband antenna array equipped with thin frequency selective surface for high-gain applications

Abstract This article begins with an explanation of a frequency selective surface, also known as an FSS, which is used to increase gain across a wide frequency range. The proposed unit design is a modified combination of circular and square elements with two cross dipoles and a T-type structure at the inner side. In the second step of the process, a single wideband antenna that covers the same range as FSS is designed and then analyzed in terms of its gain and radiation patterns. After that, an antenna array was built using the same solo structure in order to take advantage of the benefits that come with using an array system. The array is made up of elements that are CPW fed. A ground-backed T-shaped power divider network with additional shorting pins is used to supply power to the entire array. In the fourth step, an array of the FSS unit cell has been positioned beneath the UWB solo antenna and its array in order to investigate the possibility of improved gain and radiation pattern. The FSS equivalent lumped circuit model is presented here for validation purposes. It has been determined that the results of the experiment and the simulation are consistent with one another. In contrast to the structures that have been reported in the past, the newly developed model possesses a greater bandwidth, a higher gain, and a lower profile.

Impedance modeling and analysis of multi-stacked on-chip power distribution network in 3D ICs

An accurate impedance modeling of a multi-stacked on-chip power distributed network (PDN) based on through-silicon-vias (TSVs) is vitally important to estimate the electrical performance in three-dimensional integrated circuits (3D ICs). This paper proposes a method for calculating the impedance matrix of the multi-stacked on-chip PDN, which mainly consists of arbitrarily distributed TSVs and grid-type on-chip PDNs. First, a real stack-up structure of a multi-stacked on-chip PDN is separated into discrete components intentionally. Then, the equivalent lumped circuit models of all discrete components are assembled into a whole to build the transmission matrix of the multi-stacked on-chip PDN through the relationship between the nodal voltage and the nodal current. Finally, the impedance matrix can be derived through the transmission matrix. In this paper, the coupling of the arbitrarily distributed TSVs and the distributional effect of the on-chip PDN are considered in the impedance matrix through the transmission matrix method (TMM). The proposed method replaces the simulation of the complex equivalent circuit model with the matrix calculation. The verification results show that the deviation of resonant frequency is about 6 $$\%$$ and the conversation of the simulation time is about 99.9 $$\%$$ compared with the HFSS model. It can accurately and quickly calculate the impedance of the multi-stacked on-chip PDN.

Analysis of integrated UWB MIMO and CR antenna system using transmission line model with functional verification

This paper discusses the equivalent circuit model and functional verification of an integrated antenna system as its main focus. The integrated antenna system consists of two independent antenna systems, namely the Cognitive Radio antenna and the Ultra Wide Band Multiple Iinput Multiple Output antenna. This article is split into two parts: The first part discusses the equivalent circuit of an integrated antenna system by optimizing the RLC values. The developed lumped equivalent circuit model produces the NB resonant frequencies, which is the same as the S-parameter obtained through EM simulation. The second part of this paper aims to discuss the experimental verification of an integrated CR antenna system with Bayesian learning-based spectrum sensing algorithms using Universal Software Radio Peripheral devices. Real-time sensing and communication functionalities are visualized in the LABVIEW monitor. The integrated antenna system is fabricated and measured after the simulation.

Graphene-Based Optically Transparent Metasurface Capable of Dual-Polarized Modulation for Electromagnetic Stealth.

Microwave stealth technology with optical transparency is of great significance for solar-powered aircrafts (e.g., satellites or unmanned aerial vehicles) in increasingly complex electromagnetic environments. By coating them with optically transparent absorbing materials or devices, these large-sized solar panels could avoid detection by radar while maintaining highly efficient collection of solar energy. However, conventional microwave-absorbing materials/devices for solar panels suffer from bulky volume and fixed stealth performance that significantly hinders their practicality or multifunctionality. Particularly, dynamic modulation of microwave absorption for dual polarization remains a challenge. In this paper, we propose the design, fabrication, and characterization of an optically transparent and dynamically tunable microwave-absorbing metasurface that enables dual modulations (amplitude and frequency) independently for two orthogonal linearly polarized excitations. The tunability of the proposed metasurface is guaranteed by an elaborately designed anisotropic meta-atom composed of a patterned graphene structure whose electromagnetic responses for different polarizations can be dynamically and independently controlled via bias voltages. The dual tunability in such a graphene-based absorbing metasurface is experimentally measured, which agrees well with those numerical results. We further build an equivalent lumped circuit model to analyze the physical relation between the tunable sheet resistance of graphene and the polarization-independent modulations of the metasurface. Taking into account the advantages of optical transparency and flexibility, the proposed microwave-absorbing metasurface significantly enhances the multitasking stealth performance in complex scenarios and has the potential for advanced solar energy devices.

Electromechanical Equivalent Circuit Model for Axisymmetric PMUTs With Elastic Boundary Conditions

Here we present an electromechanical lumped equivalent circuit model for the purpose of deriving the electrical input impedance and response of air-coupled axisymmetric polymer-based piezoelectric micromachined ultrasonic transducers (pMUT). In particular, this study presents the derivation and validation of polyvinylidene fluoride-co-trifluoroethylene P(VDF-TrFE) unimorph pMUT equivalent circuit models operating in the fundamental axisymmetric mode. Derivation of the equivalent circuit model is performed via the application of the Rayleigh-Ritz energy method towards determining effective pMUT radii due to an elastic boundary condition. The results of the model are shown to be in good agreement with finite element (FEM) simulations and experimental measurements of discrete pMUTs in air. In particular, the model is able to accurately predict the effective expansion in the pMUT radius due to the elastic boundary. The electromechanical model may also be used as a tool to characterize and/or evaluate the behavior of pMUT designs for ultrasound transducer applications.[2021–0156]

A circular monopole antenna with uniquely packed quad T-shaped strips for WLAN/WiMAX application

Abstract This paper presents a circular monopole antenna with uniquely packed quad T-shaped strips etched on FR4 epoxy substrate having material permittivity 4.4, loss tangent 0.02, and thickness 1.6 mm. The 3.5 GHz band is achieved through this arrangement, which has return loss less than −10 dB while maintaining VSWR <2. It provides a peak gain of 2.65 dBi at 3.5 GHz and average gain of 2.52 dBi in the entire operating frequency band. The radiation pattern is almost omnidirectional in E plane and bidirectional in H plane. The proposed antenna has a compact size of 41.25 mm × 30.55 mm. The simulated results of S11 parameters, gain, VSWR, radiation pattern, and efficiency are studied and verified with the measured results of fabricated antenna as well as its equivalent lumped circuit model. Investigation shows that the proposed antenna can be employed for WLAN/WiMAX applications efficiently.

A compact high-gain key-shaped monopole antenna for RF sensitive environment, and X-Ku-band applications

Abstract This paper describes a new design for a coplanar waveguide (CPW) fed high gain key-shaped resonator based microstrip monopole antenna for ultra-wideband (UWB), X-band to Ku-band applications. An ellipse and circular combinational patch with three stepped transitions of appropriate dimensions at the lower edge and a circular parasitic patch at the back end is used in this proposed antenna. The antenna was simulated, constructed, and tested in order to show how the analysis worked. A modest profile of 0.30λ 0 × 0.16λ 0 is recommended for the proposed prototype. The designed antenna has a gain of 7.3 (dBi). It attained a fractional bandwidth (FBW) of 146% with an impedance bandwidth of 2.95–19.15 GHz. The bandwidth of the Full Width Half Maxima (FWHM) is more than 17.38 GHz and ranges from 2.62 GHz to greater than 20 GHz. For validation, the proposed antenna’s equivalent lumped circuit model and the time domain to evaluate the transient behaviour of the antenna are presented. The findings of the experiment and simulation are found to be in concurrence. In comparison to previously reported structures, the developed antenna has a wider bandwidth, a higher gain, and a lower profile.

An Electronically Reconfigurable Single to Dual-Band Bandstop Filter for RFID and Modern Wireless Communication Application

The excessive demand of electronically reconfigurable Band Stop Filter (BSF) for radio frequency identification (RFID) and for reducing the Electromagnetic Interference (EMI) for modern wireless communication is highly evident. Thus, a new electronically reconfigurable stub topology-based BSF is proposed. The response of the BSF filter can be switched from single to dual-band. The switching is achieved by a silicon PIN diode (BAP70-03) and a biasing network. When the switch is OFF, it gives a single-band bandstop response with the bandwidth of 1.70GHz -5.74GHz. When the switch is ON, it offers dual-band bandstop response with the bandwidth of 1.42GHz -1.59GHz & 4.82GHz – 5.73GHz, and between both stopbands, the passband of 1.96GHz – 4.56GHz facilitates mobile communication (3G, 4G, and 5G). Validation of the |S| parameter of the proposed reconfigurable filter is carried out using the filter’s transmission line model (TLM) for both the ON and OFF state of the PIN diode. Consequently, even and odd mode impedance is calculated analytically, and a lumped equivalent circuit model of the proposed BSF filter is extracted. The simulation results of electromagnetic (EM)/distributed model, equivalent lumped circuit model, and measured results of fabricated prototype reconfigurable BSF filter are in good agreement.

Full Lumped Element-Based Equivalent Circuit Model for Connected Slot Antenna Arrays

A full lumped element-based equivalent circuit model for connected slot antenna arrays (CSAA) is proposed with three configurations of the CSAA being considered: infinite, semi-infinite, and finite slots. First, an equivalent circuit model was developed from the available Green’s Function (GF) based analytical expression of the active impedance of CSAA. It was demonstrated that by combining PI or T networks with parallel RLC resonant circuits and modeling the higher order modes via the series inductor, the active impedance and the reflection characteristics of the CSAA can be represented in an efficient and accurate manner. Secondly, utilizing the proposed equivalent circuit model, a generalized design procedure was developed to assist the design and analysis of arbitrary configurations of CSAA at both microwave and millimeter wave (mm-wave) bands. Finally, the effectiveness and accuracy of the proposed approach are validated by several numerical and measured results. A 2x2 CSAA prototype was fabricated at 3 GHz to validate the proposed equivalent circuit model. For the finite slot case, the proposed RLC+T network outperforms both the available transmission line-based equivalent circuit model and the proposed RLC+PI network, in describing the resonance frequencies and the values of the impedances of the finite slot. It was demonstrated that the proposed equivalent circuit model had a maximum of 4.55% and 5.27% average errors for the real and imaginary parts of the impedances, as compared with the full-wave simulator, while the computational time was reduced by more than two orders of magnitude.

Fast identification method for thermal model parameters of Lithium-ion battery based on discharge temperature rise

An accurate thermal model of lithium-ion battery is extremely important for the safe operation of electric vehicles. The entropy coefficient is a key thermal characteristic of the battery, which is usually measured in advance. However, traditional measurement methods require a long test time or expensive equipment. In this paper, a novel thermal model parameter identification method with fast and continuous entropy coefficient identification is proposed, in which thermal parameters are obtained with lower time and equipment costs. First, a lumped thermal equivalent circuit model is established to describe the dynamic behaviors of battery temperature. Second, the thermal model parameters are identified based on experiments and calculations. The entropy coefficient is calculated based on temperature rise responses with different discharge currents. Finally, the identification results of the entropy coefficient are compared with traditional methods, which are found to be in good agreement. Furthermore, the thermal models are thoroughly verified under both galvanostatic discharge tests and dynamic profiles over the temperature range from 0 °C to 40 °C. Three kinds of thermal models with different entropy coefficient treatments are compared in terms of temperature errors, which indicates the superiority of the model with dynamic entropy coefficient, especially at high temperatures.

An improved electrochemical‐based model to estimate battery equivalent circuit parameters for pulsed discharge scenarios

AbstractLithium‐ion batteries (LIBs) power almost all consumer electronics products these days. High‐energy density and low cost are some of the reasons behind LIBs being used to electrify all modes of transportation. Battery equivalent circuit models enable estimation of the state of battery energy and power. These models also assist in the capturing dynamic and transient operation of electric vehicles (EVs). Researchers have used lumped equivalent circuit models in the past which fail to capture the transient variation of battery capacity during pulsed charging scenarios. In this article, we approach the estimation of battery equivalent circuit parameters from an electrochemical model‐based approach. This is the first research work to employ the single particle model that considers the electrolyte behavior to derive battery equivalent circuit parameters. We evaluate this approach using three different batteries of varying cell capacities. This technique not only improves the accuracy of these models but enables a complete understanding of the transient load operation of these batteries.

Broadband Bandpass Filter for UWB Networks with Multiple In-Band Transmission Zeros

Proposed in this manuscript is a broadband bandpass filter (BPF) with dual in-band transmission zeros (TZs) and elongated stopband for application in ultra-wideband (UWB) networks. The basic structure is developed on the principle of broadside coupling of microstrip-to-coplanar waveguide (CPW). Semi-elliptical microstrips on the top are arranged in back-to-back manner and coupled to the open circuited CPW in the ground. The basic BPF is of 3rd order with good insertion/return loss. To this basic BPF structure multiple defected ground structures (DGS) in the shape of complimentary split ring resonator (CSRR) are appended to place dual Tzs within the passband and later dumbbell-shaped DGS are engraved in the CPW to widen the stopband. Also, an approximate equivalent lumped element circuit model is developed and its frequency characteristics matched against full-wave EM simulation. The proposed dual notched BPF is finally fabricated and is found to occupy a compact area of 13.6 × 6.75 mm2.

Mechanically coupled clamped circular plate resonators: modeling, design and experimental verification

Mechanically coupled resonators usually require a mechanical coupling element; this introduces additional complexity to the picture. We propose a novel modeling and design approach, followed by experimental verification, for mechanically coupled clamped circular plate resonators in which no additional coupling element is present. In our study, the flexural mode clamped circular plate resonators overlap to an extent, and their clamps at the overlap region are removed to generate a freely moving coupling boundary between the resonators. The practical measure of the overlapping is small enough to preserve the characteristics of each resonator. This result enables modeling the coupled resonators based on the clamped circular plate resonator model. A physics-based lumped element equivalent circuit model is developed where dimensions, bias voltage, and material properties are controllable variables. Each of the model parameters is expressed as the corresponding single resonator model parameter multiplied by a function of the amount of overlap. Analytical derivations and finite element method simulations are used to extract the dependency of the model parameters on the amount of overlap. Closed-form expressions for center frequency, bandwidth, and termination impedance of the coupled resonator are derived using the developed model. A design procedure is introduced to determine dimensional parameters and bias voltage. The proposed coupled-resonator offers up to 5% fractional bandwidth. For a typical design using a polysilicon plate with 100 nm gap height, the ratio of the termination impedance to the center frequency is calculated to be 158 Ω MHz−1. This result indicates that on-chip intermediate frequency filters can be implemented at center frequencies up to several 100 MHz using this type of coupled resonators. A coupled resonator is designed and realized for a proof of concept demonstration. The measurement results of the coupled resonator show good agreement with the equivalent circuit model simulations.

High selectivity and sharp roll-off filtenna array for Ku-band application

ABSTRACT A (1 × 2) filtenna array inspired by an inter-digital-based bandpass filter is presented in this paper for simultaneous radiation and filtration. The feed line of the proposed antenna array resonating at 14 GHz with fractional bandwidth of 5.72% is modified in such a way that it acts like an inter-digital-based bandpass filter. The equivalent lumped circuit model of the proposed structure is analysed and detail synthesis procedure is presented. To study the impact of dimensional variations on the performance of proposed filtenna array, various parametric studies of filtenna and corresponding antenna array are performed and compared. The design strategy involves (N-1) filter circuits for realising a (1 × N) element filtenna array. The proposed array exhibits advantageous features such as low circuit complexity, compact size and low operational power over other reported filtenna arrays. The presented filtenna possesses fractional bandwidth and peak gain of 3.85% and 8.14 dB respectively at resonating frequency of 14 GHz, which covers the standards of Ku-band. The physical size of the filtenna array in terms of free space wave length is 1.96λ0 × 1.96λ0 × 0.073λ0 at 14 GHz. The radiation patterns are omni-directional in E-plane and nearly omni-directional in nature at H-plane at resonance frequency of 14 GHz.