Lumped-element Circuit Model Research Articles

Compact low‐pass filters with deep and ultra‐wide stopband using tri‐ and quad‐mode resonators

On the basis open stub-loaded tri- and quad-mode resonators, two compact microstrip low-pass filters (LPFs) with deep and ultra-wide stopband are presented. Modal characteristics of the tri- and quad-mode resonators are analysed by even–odd-mode method. Multimode resonator can be modelled as multiple LC resonant circuits and the lumped-element equivalent circuit models of the proposed LPFs are presented. The tri- and quad-mode resonators have strong slow-wave and bandstop effects, which can achieve ultra-wide and deep stopband and size reduction in the design of LPFs. For the proposed low-pass filter using tri-mode resonators, the 3 dB cutoff frequency is 2.5 GHz and the stopband with 40 dB suppression is from 4.5 to 17.7 GHz. The low-pass filter based on quad-mode resonators has a 3 dB cutoff frequency of 2.2 GHz and the stopband with 30 dB suppression is from 4.1 to 18 GHz.

The role of ion transport phenomena in memristive double barrier devices.

In this work we report on the role of ion transport for the dynamic behavior of a double barrier quantum mechanical Al/Al2O3/NbxOy/Au memristive device based on numerical simulations in conjunction with experimental measurements. The device consists of an ultra-thin NbxOy solid state electrolyte between an Al2O3 tunnel barrier and a semiconductor metal interface at an Au electrode. It is shown that the device provides a number of interesting features such as an intrinsic current compliance, a relatively long retention time, and no need for an initialization step. Therefore, it is particularly attractive for applications in highly dense random access memories or neuromorphic mixed signal circuits. However, the underlying physical mechanisms of the resistive switching are still not completely understood yet. To investigate the interplay between the current transport mechanisms and the inner atomistic device structure a lumped element circuit model is consistently coupled with 3D kinetic Monte Carlo model for the ion transport. The simulation results indicate that the drift of charged point defects within the NbxOy is the key factor for the resistive switching behavior. It is shown in detail that the diffusion of oxygen modifies the local electronic interface states resulting in a change of the interface properties.

Improvement in Cavity and Model Designs of LDMOS Power Amplifier for Suppressing Metallic Shielding Cover Effects

Some key technical issues are addressed for improving electromagnetic compatibility (EMC) design of metallic shielding cavity for achieving better RF performance of LDMOSFET-based power amplifier (PA). With the help of an Automation Testing Bench, its input–output responses are at first measured and compared, where an interactive influence between the PA and PCB is studied in detail. The internal and outer matching structures of LDMOSFET on the PCB are simulated using the commercial full-wave software HFSS. Perturbation theory is used to analyze the shielding cover effects with different package sizes and cavity heights sensitivity considered. Some guidelines for selecting suitable inner shielding structure and cavity height are given, and an improved model for both LDMOSFET and PA module is proposed and analyzed. Furthermore, it is integrated with the lumped-element circuit model of die and cosimulated using the software ADS 2013, and good agreement between the simulated and measured results is obtained. The most sensitive feedback path of electromagnetic interference inside the shielding cavity is characterized and a metallic isolation wall is introduced between the input (gate) and output (drain) of the LDMOSFET die for suppressing inner coupling effects. This research should be useful for the development of compact and miniaturized PA modules with our desired EMC performance.

Influence of Parasitic Capacitance on Single and Dual 2-D Magnetic Recording Read Head Performance

The parasitic capacitance of the reader affects performance through signal-to-noise ratio (SNR) in single readers and through crosstalk in dual 2-D magnetic recording readers. In a single reader, the majority of the capacitance is not from shield-to-shield capacitance but instead from lead-to-shield capacitance. The low-pass filtering of the reader circuit leads to an equalized SNR that depends on the parasitic capacitance. In a dual reader, the capacitance between the outer shields must be considered in addition to the capacitance between the inner shields in order to model accurately the crosstalk. Finite-element electromagnetic models and lumped element circuit models are validated with RF experiments on real heads.

Highly selective wideband bandpass filter using combined microstrip/coplanar waveguide structure

A highly selective wideband bandpass filter using a combined coplanar waveguide (CPW) and microstrip structure is proposed. The CPW section is responsible for creating a 4–8 GHz bandwidth. The microstrip split ring resonators and shorted coupled lines are used to sharpen the transitions between the passband and the stopband at lower and upper edges. The CPW section is fed by a microstrip host line and consists of two symmetrical coupled stepped-impedance resonators to limit the bandwidth of the desired filter. A lumped element circuit model is presented and comparisons with experimental and simulation results confirm great compatibility and performance. The measurement results confirm a return loss larger than 15.3 dB in the passband, an out-of-band rejection greater than 15 dB.

Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator.

We present a design for a tunneling-current-assisted scanning near-field microwave microscope. For stable operation at cryogenic temperatures, making a small and rigid microwave probe is important. Our coaxial resonator probe has a length of approximately 30 mm and can fit inside the 2-in. bore of a superconducting magnet. The probe design includes an insulating joint, which separates DC and microwave signals without degrading the quality factor. By applying the SMM to the imaging of an electrically inhomogeneous superconductor, we obtain the spatial distribution of the microwave response with a spatial resolution of approximately 200 nm. Furthermore, we present an analysis of our SMM probe based on a simple lumped-element circuit model along with the near-field microwave measurements of silicon wafers having different conductivities.

Direct Synthesis and Design of a General Sequentially Coupled Wideband Bandpass Filter With -Transmission Zeros

This paper presents a general sequentially coupled wideband bandpass filter and its direct synthesis and design theory. The filter can achieve the same number of controllable transmission zeros (TZs) as that of resonators above the passband. Each resonator consists of a pair of shunt connected capacitively loaded stub and a grounded inductive stub. Resonators are connected through a short section of transmission line with designated electric length. The short connecting lines allow the filter a wide spurious free stopband. For given specifications and prescribed TZs, the elementary lumped element circuit model can be directly synthesized. Three basic lumped element circuit building blocks are approximated by legitimate distributed element circuits with which the wideband distributed element circuit can be systematically obtained. To demonstrate the performance of the proposed filter configuration and the effectiveness of the developed theory, a fourth and an eighth order of filter prototypes were designed and measured, showing the promising potential for practical applications.

Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

The terahertz (THz) region of the electromagnetic spectrum holds great potential in many fields of study, from spectroscopy to biomedical imaging, remote gas sensing, and high speed communication. To fully exploit this potential, fast optoelectronic devices such as amplitude and phase modulators must be developed. In this work, we present a room temperature external THz amplitude modulator based on plasmonic bow-tie antenna arrays with graphene. By applying a modulating bias to a back gate electrode, the conductivity of graphene is changed, which modifies the reflection characteristics of the incoming THz radiation. The broadband response of the device was characterized by using THz time-domain spectroscopy, and the modulation characteristics such as the modulation depth and cut-off frequency were investigated with a 2.0 THz single frequency emission quantum cascade laser. An optical modulation cut-off frequency of 105 ± 15 MHz is reported. The results agree well with a lumped element circuit model developed to describe the device.

Compact continuous tunable low-pass filter with high selectivity and wide stopband

This letter presented a novel compact continuously tunable low-pass filter (LPF) using varactor-loaded coupled rhombic stubs. The proposed LPF demonstrated excellent roll-off selectivity, wide stopband range as well as good cut-off frequency tunability. This LPF consisted of three varactor-tuned coupled rhombic stubs loaded on a section of high-impedance microstrip line symmetrically and two coupled line LPFs which could further improve the stopband performance. A detailed explanation of the tuning mechanism was illustrated by adopting lumped-element equivalent circuit model. The measured results showed not only a wide cut-off frequency tuning range of 56% from 350 to 800 MHz, but also an excellent steepness factor of less than 1.14. Additionally, a rejection level of greater than 20 dB up to 8 GHz (>10 fc) was observed in the stopband. The proposed ideas were verified by the measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1641–1644, 2016

Numerical Modeling of Dielectric Barrier Discharge Plasma Actuation

A computational method has been developed to couple the electrohydrodynamic (EHD) body forces induced by dielectric barrier discharge (DBD) actuation with unsteady Reynolds-Averaged Navier–Stokes (URANS) model or large eddy simulation (LES) for incompressible flows. The EHD body force model is based on solving the electrostatic equations for electric potential and net charge density. The boundary condition for net charge density on the dielectric surface is obtained from a space–time lumped-element (STLE) circuit model or an empirical model. The DBD–URANS/LES coupled solver has been implemented using a multiple-domain approach and a multiple subcycle technique. The DBD plasma-induced flow in a quiescent environment is used to validate the coupled solver, evaluate different EHD body force models, and compare the performance of the actuator driven by voltage with various waveforms and amplitudes.

Use of Mutual Coupling to Decrease Parasitic Inductance of Shunt Capacitor Filters

In this paper, we propose and study several new designs of a shunt capacitor filter with two surface-mount technology capacitors. These designs make use of mutual inductance effects to increase the attenuation provided by the filter in the range of high frequencies where the filter behaves inductively. We provide lumped element circuit models for the proposed designs that allow identification of the key inductive parameters that determine the high-frequency performance of these filters. We obtain the equations relating these parameters to the effective inductance of the filter, which can be used to compare the high-frequency behavior of different filter designs. We have fabricated and measured several compact shunt capacitor filters with improved performance at high frequencies. We have found that, compared with a shunt capacitor filter with one capacitor, a proper filter design with two capacitors can easily increase in 15–20 dB the high-frequency attenuation provided by the filter. This design also outperforms by 10–15 dB a traditional shunt capacitor filter with two capacitors closely placed. Moreover, this improvement is obtained with no increase in size, cost, or time of design of the filter.

A Dynamically Adaptable Impedance-Matching System for Midrange Wireless Power Transfer with Misalignment

To enable the geometrical freedom envisioned for wireless power transfer (WPT), fast dynamic adaptation to unpredictable changes in receiver position is needed. In this paper, we propose an adaptive impedance-searching system that achieves good impedance matching quickly. For fast and robust operation, the proposed method consists of three steps: system calibration, coarse search, and fine search. The proposed WPT system is characterized using distance variation and lateral and angular misalignment between coils. The measured results indicate that the proposed method significantly reduces searching time from a few minutes to approximately one second. Furthermore, the proposed system achieves impedance matching with good accuracy. The robust impedance-searching capability of the proposed system significantly improves power transfer efficiency. At 6.78 MHz, we achieve a maximum efficiency of 89.7% and a high efficiency of >80% up to a distance of 50 cm. When the center-to-center misalignment is 35 cm, the efficiency is improved from 48.4% to 74.1% with the proposed method. At a distance of 40 cm, the efficiency is higher than 74% for up to 60° of angular rotation. These results agree well with the simulated results obtained using a lumped-element circuit model.

Thermal characterization and modeling of ultra-thin silicon chips

Manufacturing ultra-thin chip is an emerging field in semiconductor technology that is driven by 3-D integrated circuits and flexible electronics. Unlike bulk silicon (Si) chips with thickness greater than 400μm, the thermal management of ultra-thin Si chips with thickness smaller than 20μm is challenging due to the increased lateral thermal resistance implying stringent cooling requirements. Therefore, a reasonable prediction of temperature gradients in such chips is necessary. In this work, a thermal chip is implemented in an ultra-thin 0.5μm CMOS technology to be employed in surface steady-state and transient temperature measurement. Test chips are either packaged in a Pin Grid Array (PGA) ceramic package or attached to a flexible polyimide substrate. The experimental results show an on-chip temperature gradient of ∼15°C for a dissipated power of 0.4W in the case of the PGA package and ∼30°C for the polyimide substrate. The time constants are ∼50s and ∼1s for the PGA and the polyimide packages respectively. The measurements are complemented by FEM simulations using ANSYS 14.5 workbench and spice simulations using an equivalent lumped-component thermal circuit model. The lumped-element thermal circuit model is then used for the surface temperature prediction, which is compared to measurement results.

Investigation of Armature Capture Effect on Synchronous Induction Coilgun

To obtain high velocity and high energy conversion efficiency on a synchronous induction coilgun, the armature capture effect which is the inherent characteristic for the synchronous induction coilgun needs to be analyzed. The reason for the armature capture effect is first deduced and analyzed using the lumped element circuit model and then quantificational result is obtained based on the field-circuit coupled model. According to the analytical result, the method to minimize the armature capture effect is proposed from the viewpoint of the magnetic coupling between the driving coil and the armature. Several ways are analyzed through the finite-element simulation. The simulation results show that adjusting the power parameters, such as increasing the capacitance or initial voltage, and decreasing the crowbar resistance, and adjusting the armature parameters, such as decreasing the mass or adopting the solenoid armature, can minimize the armature capture effect and increase the conversion efficiency. These methods are validated through a four-stage induction coilgun. We compare the simulation results with the experimental results and show that by adjusting the armature parameters, we can minimize the armature capture effect. It provides valuable reference for synchronous induction coilgun design.

Analysis of transmission lines loaded with pairs of coupled resonant elements and application to sensors

This paper is focused on the analysis of transmission lines loaded with pairs of magnetically coupled resonators. We have considered two different structures: (i) a microstrip line loaded with pairs of stepped impedance resonators (SIRs), and (ii) a coplanar waveguide (CPW) transmission line loaded with pairs of split ring resonators (SRRs). In both cases, the line exhibits a single resonance frequency (transmission zero) if the resonators are identical (symmetric structure with regard to the line axis), and this resonance is different to the one of the line loaded with a single resonator due to inter-resonator coupling. If the structures are asymmetric, inter-resonator coupling enhances the distance between the two split resonance frequencies that arise. In spite that the considered lines and loading resonators are very different and are described by different lumped element equivalent circuit models, the phenomenology associated to the effects of coupling is exactly the same, and the resonance frequencies are given by identical expressions. The reported lumped element circuit models of both structures are validated by comparing the circuit simulations with extracted parameters with both electromagnetic simulations and experimental data. These structures can be useful for the implementation of microwave sensors based on symmetry properties.

The relationship between local field potentials (LFPs) and the electromagnetic fields that give rise to them.

The relationship between local field potentials (LFPs) and the electromagnetic fields that give rise to them.

Estimation of the accuracy of the microwave FET equivalent circuit using the quasi-hydrodynamic model of electron transport

Computational methods are considered for the time- and frequency-domain simulations of a microwave power amplifier with a transistor built on a diamond-like semiconductor. The first method is based only on a two-dimensional model of the intrinsic transistor that includes the quasi-hydrodynamic model of electron transport and electric field equations. The second method, which is less accurate but much more computer-time-saving, is based on the intrinsic transistor large-signal lumped-element equivalent circuit model with the parameters and spline characteristics calculated by means of the abovementioned two-dimensional model. Using these two methods, the microwave parameters of the amplifier are calculated for frequencies varying from 15 to 90GHz. When using the equivalent circuit at frequencies of up to 60GHz, the calculation error (equal to the difference between the results of the time- and frequency-domain simulations) does not exceed 5% for the input impedance and 0.6dB for the transducer power gain.

Finite Element Model of a Superconducting Fault Current Limiter Calibrated by Hardware-in-the-Loop Measurements

A bench top model of an inductive superconducting fault current limiter (iSFCL) has been designed based on wide tape of second generation high temperature superconducting (2GHTS) coated conductor. The tape forms a ring shielding a reduced size ferromagnetic core. The design was optimized using a finite element model, which was calibrated and refined by impedance measurements and power hardware-in-the-loop testing of the bench top iSFCL. The finite-element model was coupled with a lumped element circuit model that simulates the electric power grid. Usefulness of such coupled models for design optimization studies and for reduction of uncertainty in transient simulation models is demonstrated.

Conversion of electromagnetic energy in Z-pinch process of single planar wire arrays at 1.5 MA

The electromagnetic energy conversion in the Z-pinch process of single planar wire arrays was studied on Qiangguang generator (1.5 MA, 100 ns). Electrical diagnostics were established to monitor the voltage of the cathode-anode gap and the load current for calculating the electromagnetic energy. Lumped-element circuit model of wire arrays was employed to analyze the electromagnetic energy conversion. Inductance as well as resistance of a wire array during the Z-pinch process was also investigated. Experimental data indicate that the electromagnetic energy is mainly converted to magnetic energy and kinetic energy and ohmic heating energy can be neglected before the final stagnation. The kinetic energy can be responsible for the x-ray radiation before the peak power. After the stagnation, the electromagnetic energy coupled by the load continues increasing and the resistance of the load achieves its maximum of 0.6–1.0 Ω in about 10–20 ns.

Electrical Modeling of Three-Dimensional Carbon-Based Heterogeneous Interconnects

One three-dimensional (3-D) carbon-based heterogeneous interconnect scheme, consisting of a couple of horizontal multilayer graphene transmission lines (MLG-TL) and vertical through silicon carbon nanotube bundle vias (TS-CNTBV), is proposed and investigated theoretically. For its realization, some metallic bumps are used to integrate MLG-TLs with TS-CNTBVs, and contact resistance among them are characterized and compared. The lumped-element circuit model of a couple of MLG-TLs is also combined with that of TS-CNTBVs, with anomalous skin effect treated in an appropriate way. Numerical studies are performed for capturing distributed parameters as well as transmission characteristics of MLG-TLs, TS-CNTBVs, and whole 3-D interconnects at different operating frequencies. It is believed that this study can provide some useful information about carbon-based heterogeneous interconnects, where both graphene and carbon nanotube advantages can be exploited for the future 3-D ICs.