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The self-heating of micro-machined spiral inductors operated under high-power conditions is studied. The studies have shown that the self-heating of suspended coil can be improved by deploying thick highly conductive metals.

This paper reports the theoretical and experimental studies of high-Q suspended microinductors produced by flip-chip assembly for multigigahertz RF integrated-circuit applications. The effects of device and substrate parameters on the Q factor of the inductor devices are studied by numerical simulation using Ansoft's High Frequency Structure Simulator electromagnetic field simulation package. Suspended inductor devices are realized using a flip-chip assembly method ill which the inductor structures with the supporting pillars are fabricated on a low-cost polyimide thin-film carrier and then assembled onto a low resistivity (3-4 [OMEGA] * cm) silicon substrate by flip-chip bonding. Individual and 2 x 2 arrays of meander and spiral inductor designs have been successfully fabricated with air gap heights ranging from 15 to 31 [micro]m. Maximum Q factors of ~15 and ~13 at ~1 GHz have been achieved for meander and spiral suspended inductor devices before pad deembedding. It is shown that the optimal air gap between the inductor and substrate surface is ~15 [micro]m beyond which no further enhancement in the Q factor can be obtained for devices on low-resistivity substrates. The experimental results are in excellent agreement with that of theoretical simulation. The inductor assembly method requires minimal chip/wafer processing for integration of high-Q inductors. Index Terms--Flip-chip assembly, high Q, microelectromechanical systems (MEMS), modeling, passive inductor, polyimide film, silicon RF integrated circuit (RFIC).

Abstract: Electro-inductive devices have recently been introduced to implement passive control schemes in special classes of structures. Their fascinating feature is the feasibility of large devices, to be installed, for [...]

The magnetic hysteresis phenomenon plays an important role in the ferroresonance behavior of a transformer. However, most existing transformer models for the analysis of the ferroresonance phenomenon either ignore the hysteresis effects or represent it based on the hysteresis major loop and scale it for lower current levels. Such a modeling approach does not reflect the actual physical behavior of the magnetic core with respect to the ferroresonance phenomenon. This paper, based on Preisach theory, introduces an accurate model of hysteretic inductor to represent a single-phase transformer for the investigation of the ferroresonance phenomenon. Based on the developed model, time-domain simulation studies show that even in the case of a single-phase transformer where no magnetic coupling exists between the three-phases, all known types of ferroresonance, including fundamental, sub-harmonic, quasi-periodic and chaotic modes, may occur. The effects of hysteresis and its initial conditions, grading capacitors and transformer winding capacitance on occurrence of ferroresonance and its change of mode are also discussed. Index Terms--Ferroresonance, grading capacitor, hysteresis, initial conditions, power transformer, Preisach theory.

This paper begins with the definition of ideal coupler, the justification of negative inductance concept and the establishment of various equivalences between circuits. Then, an energy-based recursive method for designing for the equivalent circuit of an n-input magnetic system is presented and the leakage transformer concept is introduced. The obtained circuits allow easy checking of inequalities that inductance matrix elements must satisfy. Advantage is then taken from winding identity and dominant coupling to simplify circuit design. This new knowledge is applied to design equivalent circuits for a three-phase inductor and a three-column six-winding transformer. Finally, key points of a strategy intended to experimental identification of all circuit elements are given. Index Terms--Equivalent circuit, identification, magnetic coupling, transformer.

In this paper, a photovoltaic (PV) module integrated converter is implemented with a current fed two-inductor boost converter cascaded with a line frequency unfolder. The current source is a sinusoidally modulated two-phase buck converter with an interphase transformer. The boost cell operates at a fixed duty ratio and has an integrated magnetic structure. The two inductors and the transformer are integrated into one magnetic core. Passive lossless snubbers are employed to recover the energy trapped in the transformer leakage inductance and to minimize the switching losses. The two-inductor boost converter output interfaces with the mains via an unfolding stage, where the MOSFETs are driven by the PV gate drivers. Experimental results are provided for a 100-W converter developing a single phase 240-V 50-Hz output. Index Terms--Integrated magnetics, lossless snubber, two-inductor boost converter.

Advances in high-power-density batteries have rekindled interest in using inductive store as a pulse compression system. Although these batteries are considered very power dense, they lack over an order of magnitude of power density to drive a deployable electric gun. However, one can add an inductive circuit to a battery bank to make a hybrid system that has a much higher power density titan batteries alone. A battery-inductor hybrid pulsed-power supply boasts several advantages over pulsed alternators, as inductors are static and relatively easy to cool. Inductors are potentially more energy dense than capacitors, making a battery-inductor hybrid pulsed-power supply an attractive alternative to capacitor-based pulsed-power supplies. The opening switch has been a major obstacle in previous inductive store projects, but in simulation, a new circuit topology--the Slow Transfer of Energy Through Capacitive Hybrid (STRETCH) meat grinder--greatly attenuates the problem. This paper discusses the design, construction, and testing of a small-scale STRETCH meat grinder system, which was successfully used to power a miniature railgun. Index Terms--Battery, capacitor, inductor, pulsed power, railgun.

Full-wave analysis of deep-trench isolation patterning (DTP) is presented for substrate coupling reduction and Q-factor improvement. Effects of the buried layer (BL) doping level and grounding mechanisms on substrate coupling are analyzed. Influences of induced depletion regions on substrate coupling are investigated. Q-factor improvement of on-chip RF inductors resulting from the interruption of BLs and part of the lossy substrate by DTP to limit electric and magnetic energy dissipation is studied. The combination of DTP with topological optimization demonstrates high Q-factor enhancement. Distributed capacitances and resistances resulting from the BL and substrate grating are evaluated. Coupling between inductors and limits of representations by lumped-element equivalent circuits to account for distributed effects are discussed. Comparison of obtained results with two-and-one-half- and three-dimensional-based commercial electromagnetic tools and with measurement data for reference structures are presented. Index Terms--Deep-trench isolation patterning (DTP), depletion regions, eddy current, floating ground plane, local and global ground reference, Q factor, RF inductors, seal ring, substrate coupling, transverse wave formulation (TWF).

By utilizing a differential tunable active inductor for the LC-tank, a wide tuning-range CMOS voltage-controlled oscillator (VCO) is presented. In the proposed circuit topology, the coarse frequency tuning is achieved by the tunable active inductor, while the fine tuning is controlled by the varactor. Using a 0.18-[micro]m CMOS process, a prototype VCO is implemented for demonstration. The fabricated circuit provides an output frequency from 500 MHz to 3.0 GHz, resulting in a tuning range of 143% at radio frequencies. The measured phase noise is from -101 to -118 dBc/Hz at a 1-MHz offset within the entire frequency range. Due to the absence of the spiral inductors, the fully integrated VCO occupies an active area of 150 x 300 [micro][m.sup.2]. Index Terms--Differential active inductors, frequency tuning range, miniaturization, multistandard transceivers, phase noise, voltage-controlled oscillators (VCOs), wideband.

A computationally efficient physics-based wideband predictive inductor compact model is presented that is capable of evaluating the impact on inductance and quality factor of dummy metal fill-ceils. In a modern integrated-circuit process, high amounts of these fill-cells are required to meet metal density rules and guarantee adjacent circuit integrity. The predictions made with this model are shown to be in agreement with data measured on symmetrical octagonal inductors realized in a 90-nm CMOS process with varying amounts of dummy metal fill-cells. We further provide all inductance equations, list additional sources of eddy current losses, and discuss layout modifications, which would further improve the performance of the integrated inductors. Index Terms--Dummy metal fill-cells, integrated circuits (ICs), on-chip inductors, on-wafer microwave measurements, tiling.

A new self-adjusting current-fed push-pull parallel inverter (SA-CFPPRI) is presented and tested by simulation and experimentally. The power source includes a soft switching control circuitry and a controllable inductor. The SA-CFPPRI can drive a capacitive load at any frequency within the design range. It will maintain zero voltage switching of the main transistors and follow the input frequency signal even when the resonant elements and/or the load vary. Possible range of applications for the proposed power source is: piezoelectric transformers and motors, ac bus for a distributed power system and other loads that need to be fed by a sinusoidal waveform. The experimental results of the laboratory unit (160 Vrms at 93 kHz and nominal output power of 5 W) verify the analytical analysis and proposed design procedure. Index Terms--Phase comparator, push-pull parallel resonant inverter (PPPRI), sinusoidal power source, variable inductor.

For integrated radio-frequency applications, tunable magnetic inductors are expected. A tunable magnetic inductor, based on magnetoimpedance effect, is presented in this paper. The proposed inductor is constructed with a magnetic inductor body, wound by an insulated coil, inducing a longitudinal dc bias magnetic field when a dc control current is flowing through. Formed by a conductive core coated by a high-permeability magnetic layer, the magnetic inductor body can be realized by either a thin-film structure or a composite wire. The reluctance models for both thin-film and composite wire structures are studied. A prototype tunable magnetic inductor, using a composite wire element, has been characterized. The results show that by varying the dc control current, the inductance L of the magnetic inductor can be tuned. The tunable range depends on the frequency of the current flowing through the inductor. A relative variation of inductance [DELTA]L/[L.sub.o], up to 18% at low frequency (around 5 MHz), is achieved by applying a bias current of magnitude merely up to 15 mA. The quality factor varies from 5 to 17 in the measured frequency range. The proposed tunable inductor may be further optimized for high-frequency applications and has the potential to be realized in micro-electromechanical systems technology. Index Terms--Inductors, magnetic films, magnetoimpedance, tunable circuits and devices.

A method to extract low-order dynamic models of nonlinear magnetic devices from a high-order physics-based model is presented. The model includes saturation, skin effect, and eddy current. The physics-based model is derived from finite-element analysis, using only geometry and materials data. A nonlinear model order reduction method based on the Krylov subspace projection is used to extract the low-order model. A linear system is set up at each interpolation point along a training trajectory. Each linear system is reduced by the corresponding projection matrix. The resulting reduced linear systems are used to approximate the original system within each region, yielding accurate local simulation results. Good global properties are achieved by the use of piecewise simulation and weighting. Simulation results demonstrate that the original, nonlinear high-order system can be represented by a set of connected low-order, piecewise-linear systems with satisfactory agreement. This method can be automated and should provide a foundation for more complicated magnetic devices, such as multiphase coupled inductors, actuators, and rotary machines. Index Terms--Finite element analysis (FEA), inductor, Kryiov subspace, model order reduction (MOR).

In this paper, the Watkins-Johnson (WJ) converter was found to best step down the future automotive 42-V power network to 3 V or lower for the supply of microcontrollers and semiconductors. The particularity of the WJ converter is that it only employs a tapped-inductor and three other components. The use of a tapped-inductor is well-known and gives an extra-degree of freedom by the insertion of the winding ratio of the tapped-inductor into the transfer function of the WJ converter. It also permits the duty cycle to be adjusted to a value at which the efficiency of the converter is improved. The converter can be slightly modified and used as a multiple output converter while employing few components, diminishing the weight, size, cost, and complexity of a system. Practical test results for the single-output WJ converter are presented. Index Terms--Duty cycle, multiple output converter, tapped-inductor, Watkins-Johnson (WJ) converter.

Size reduction for spiral inductors is investigated. We reveal bidirectional ferromagnetic inductors with an ~30% to 135% increase in L over the air-core value. This is advantageously realized by using single deposition. The realization uses above-IC techniques and high-magnetization FeHfN laminated films. We also report a quality factor of ~10 at 1.5 GHz, which is mitigated while realizing high FMR frequency (up to 6 GHz). This leads to considerations on nonmagnetic excess losses. Finally, a surface reduction of 25% to 50% for conventional spirals is demonstrated. Index Terms--FMR, high magnetization, inductance.

In many radio frequency (RF) microelectromechanical systems (MEMS) applications, currents are confined to the outermost portions of conductors due to the skin effect. Conductors consisting of polymer cores coated with metal, the so-called polymer-core conductor, are appropriate to consider for these applications, and in many instances are easier to fabricate than their solid-metal-core counterparts. Implementation of polymer-core conductors using an SU-8 epoxy-core patterning and subsequent metal electrodeposition is reported. The SU-8 core approach allows for relatively simple formation of extremely high-aspect-ratio columns for inductor sidewalls. In addition, an SU-8 bridge fabrication technique has been realized using a double exposure and single develop scheme. The bridge thickness has been characterized as a function of the optical dose and the post bake time in an oven. Three-dimensional, high-aspect-ratio, high Q-factor, solenoid-type RF inductors are fabricated and tested to demonstrate the feasibility of the polymer-core conductor approach for RF applications. A single, vialess metallization over SU-8 back-bone structure provides the complete conducting paths of the inductor. A single turn inductor that is 900 [micro]m in height and 600 [micro]m in lateral extension shows a maximum Q-factor of 84 and an inductance of 1.17 nH at 2.6 GHz. [1382] Index Terms--Double-exposure-single-development, epoxy-core conductor, high-aspect-ratio solenoid inductor, polymer-core conductor, radio frequency (RF) microelectromechanical systems (MEMS), SU-8 bridge fabrication.

We have designed and fabricated a radio-frequency (RF) planar integrated inductor using Permalloy-Si[O.sub.2] granular film as the magnetic core. By controlling the composition and microstructure, we produced a granular film with excellent soft magnetic properties and high electrical resistivity. The inductance L of the inductor with granular Permalloy-Si[O.sub.2] magnetic film increased 6% to 15%, compared to that of an air-core inductor, and the quality factor Q value was high, approaching 10 in the frequency range of 2-3 GHz. The controllable anisotropy of the granular film generated in deposition process gives the magnetic inductor a very high self-resonance frequency peak--over 6 GHz. Index Terms--Magnetic thin film devices, soft magnetic materials, thin film inductors.

A robust micromachined spiral inductor with a cross-shaped sandwich membrane support and fabricated with full CMOS compatible post processes for radio frequency integrated circuit (RFIC) applications are proposed. The results show the robust inductor can have similar electrical performance to the as-fabricated freely suspended inductor, which has five times Q (quality factor) improvement than the inductor without the substrate removal.

A new approach to RF thin-film inductors with an integrated magnetic core has been investigated. A toroidal inductor design was realized in thin-film technology aiming at small-signal applications in the frequency range from 10 MHz to 1 GHz. The magnetic core consists of a multilayer of sputter deposited soft magnetic FeCoBSi. The individual magnetic films were deposited in a way to realize a crossed magnetic anisotropy in the core. High-frequency measurements of the multilayers already illustrated the advantages of the unique magnetic geometry. The influence and benefit of such a magnetic core on the toroid microinductor is discussed. The results show that such crossed anisotropy microinductors are a very promising alternative to common planar spiral inductors in the RF range. Index Terms--Anisotropy, inductor, magnetic devices, magnetic cores, permeability.

An improved version of an inductor-switching fast-response dc-dc converter is presented that will provide the requirements and features of the new generation of microprocessor and digital systems. Lower output voltage, higher output current, and smaller output voltage ripple requirements have greatly increased the difficulty of the power supply design. To further increase the problem, power-saving 'stop-clock' modes of the microprocessor has demanded faster and more stable transient response from the dc-dc converter. A novel method of inductor switching is applied to a dc-dc converter, and it provides the prominent features of current amplification and absorption during the heavy burden of load transients. The design and simulation of the concept is verified by experiment with a 12-V input and 3.3-V/30-A output converter. Index Terms--Analog circuit, dc-dc power conversion, inductor switching, voltage control.

The design of high-frequency power converter is very difficult because the leakage inductance of the transformer affects the performance. With consideration of the high-frequency eddy current, the flux linkage due to the eddy-current reaction field using a proposed summation calculation method is computed. The leakage inductance of a high-frequency transformer is therefore characterized. An optimum design method of the transformer can be obtained. Experimental results confirm the affectivity of the calculation method. Index Terms--Inductor, power conversion, transformer.

In this paper, a systematic methodology is proposed for the full-wave time-domain analysis of planar loaded transmission-line (TL)-based negative-refractive-index (NRI) media. Lumped inductors and capacitors are incorporated in a finite-difference time-domain (FDTD) mesh via an 'extended FDTD' approach, combining Maxwell's equations with lumped-element voltage--current characteristics. The analysis is facilitated by periodic boundary conditions that restrict the simulated domain to a single unit cell of the periodic loaded TL grid. Thus, fast numerical characterization of the NRI structures under study is attained. The proposed technique is successfully compared to measured results and is proven to consist of an effective tool for the rigorous explanation of experimental observations through the dispersion analysis and computation of modal patterns and relative strengths of the types of waves supported by an NRI medium. Index Terms--Dispersion, finite difference time domain (FDTD), negative refractive index (NRI).

This paper describes a new wireless differential protection system for detection of turn-to-turn faults in air-core inductors. The proposed system is composed of a pair of floating magnetic field sensors placed at opposite ends of an air-core inductor, which wirelessly communicate their measurements to a remote receiver. The receiver compares the magnetic field measurements from the sensors and triggers an alarm or circuit interruption system if the mean-squared field difference exceeds a specified threshold. The main contributions of this paper are a description of a specific realization of this differential air-core inductor protection system with several novel features and experimental results that demonstrate the sensitivity and latency of the proposed protection system. Our results suggest that deployment of the proposed system in shunt-connected inductors could help to prevent catastrophic damage resulting from turn-to-turn faults by detecting and arresting these faults in their incipient stages. Index Terms--Communication systems, inductors, protection, transformers.

This paper presents an integrated magnetic isolated two-inductor boost converter. All magnetic components are integrated into one magnetic assembly. Two inductor windings are intrinsically coupled to allow input current to increase only when both primary switches are closed. The operation principle, start-up, and protection mechanisms are detailed. A prototype converter has been built. Experimental and simulation results verify the analysis. Index Terms--Boost converter, integrated magnetics, magnetic assembly.

A new trend in power converters is to design planar magnetic components that aim for low profile. However, at high frequencies, ac losses induced in the planar inductor and transformer windings become significant due to the skin and proximity effects. A planar litz conductor can be constructed by dividing the wide planar conductor lengthwise into multiple strands and weaving these strands in much the same manner as one would use to construct a conventional round litz wire conductor. Each strand is then equally subjected to the magnetic fields in the winding window, thereby equalizing the flux linkage and improving the current distribution. Three-dimensional finite-element modeling was performed for simple models. The simulation results showed that the planar litz conductor can result in lower ac resistance than a solid conductor over a specific frequency range. The performance of the planar litz winding was also verified with measurements on two experimental prototypes. Index Terms--Finite-element modeling (FEM), planar litz conductor.

The impedance errors remaining after applying the industry standard 'open-short,' a 'pad-open-short,' and a 'open-short-load' deembedding scheme on a 0.43-nH 20-GHz high-Q single-loop inductor test structure are investigated using real S-parameter data taken up to 50 GHz. Since the latter two deembedding schemes both correct for all parasitic elements of the test structures, they are, at least in principle, error free. The accuracy of the 'open-short-load' deembedding scheme, however, critically depends on how well the reactive part of the load resistance is accounted for. This issue makes the more simple 'pad-open-short' deembedding scheme an attractive choice because the required split between external and internal capacitances is easy to make, either based on process and layout information or from measurements done on a 'pad' dummy structure. Index Terms--Calibration, deembedding, integrated circuits, on-chip inductors, on-wafer microwave measurements.

In this paper, a systematic design procedure based on key factor analysis of the Q curve has been proposed. In addition to inductor design, we also present a technique that combines optimized shielding poly, and proton implantation treatment is utilized to improve the inductor Q value. The shielding effect of poly-silicon and the semi-insulating characteristics of proton-bombarded substrate have added a 37% and 54% increment to the Q value of the inductors, respectively. The combination of the two means has created a multiplication of their individual contribution rather than addition. The dramatic improvement of the Q value resulted from the doping level and film thickness optimization of a poly shield layer combined with a proton implantation treatment. A phenomenal Q-value increment as high as 122% of 4-nH spiral inductors can be realized. This technique shall become a critical measure to put inductors on a silicon substrate with satisfactory performance for Si-based RF integrated-circuit applications. Index Terms--Poly shield, proton implant, Q value, RF integrated circuit (RFIC), spiral inductor.

Silicon planar and three-dimensional inductors and transformers were designed and characterized on-wafer up to 100 GHz. Self-resonance frequencies (SRFs) beyond 100 GHz were obtained, demonstrating for the first time that spiral structures are suitable for applications such as 60-GHz wireless local area network and 77-GHz automotive RADAR. Minimizing area over substrate is critical to achieving high SRF. A stacked transformer is reported with [S.sub.21] of -2.5 dB at 50 GHz, and which offers improved performance and less area (30 [micro]m x 30 [micro]m) than planar transformers or microstrip couplers. A compact inductor model is described, along with a methodology for extracting model parameters from simulated or measured y-parameters. Millimeter-wave SiGe BiCMOS mixer and voltage-controlled-oscillator circuits employing spiral inductors are presented with better or comparable performance to previously reported transmission-line-based circuits. Index Terms--Inductors, millimeter wave, mixer, self-resonance frequency (SRF), stacked inductors, transformers, voltage-controlled oscillator (VCO).

We describe the implementation of a knowledge-based system for designing iron core inductors. We identify the underlying issues related to the implementation of such a system. We employ a recursive design methodology based on imitating an expert human designer that is suitable for embedding in the knowledge-based system. A hybrid knowledge base, using both frame-based and rule-bused paradigms, together with assertions and procedural attachment, captures inductor-oriented design expertise. The paper establishes a general framework whereby dedicated knowledge-bused systems for electromagnetic design can be built. It presents results that illustrate the performance of the developed system, particularly in comparison to the standard design procedure found in the literature. Index Terms--Design methodology, electromagnetic devices, inductors, knowledge-bused systems.

The electromagnetic behavior of circular spiral inductors on layered substrates is analyzed by using the concentric ring approximation. The problem is formulated in terms of mixed-potential volume integral equations. The latter are semianalytically solved within the quasi-one-dimensional approximation. The result is a fast computationally efficient model, which takes into account substrate RF loss, as well as nonuniform current density distribution across inductor windings. The results are in good agreement with experimental data from various inductors on both low- and high-resistivity silicon substrates. Index Terms--Eddy currents, mixed-potential integral-equation (MPIE) method, monolithic inductors, spiral inductors, substrate RF loss.

We propose a model with frequency-dependent lumped parameters to represent the behavior of laminated iron-core inductors that are used in switching converters, i.e., for excitation frequencies above several kilohertz. The model applies to laminated iron cores with air gaps. We show that the core parameters can be calculated by using the same analytical expressions as those valid for gapless cores if a properly defined equivalent magnetic permeability is introduced instead of the iron sheet permeability. We compare the inductor model parameters calculated as functions of frequency with those obtained by measurements for two test inductors. The behavior of the inductors showed that the effects due to the eddy currents in the laminated iron core and the turn-to-turn and turn-to-core stray capacitances become significant in different frequency ranges. Index Terms--Coupling reactors, eddy currents, inductor high-frequency models, inductors, laminated iron magnetic cores, power filters, proximity effect, skin effect.

The impact of two different types of floating patterns on spiral inductors was investigated. Both patterned trench isolation with a floating pin junction and floating metal poles were implemented underneath reference spiral inductors. All three types of inductors have an identical spiral geometry. Combination of patterned trench isolation with a floating pin junction increases maximum quality factor ([Q.sub.max]) by 17% compared to the reference inductors. The floating metal poles enable adjustment of the frequency at [Q.sub.max] ([f.sub.max]) without hampering the [Q.sub.max]. A ladder-type lump-element model was employed to analyze inductor performance after it was demonstrated to precisely capture behavior of all three inductors. Enhancement of the quality factor due to patterned trench isolation with a floating p/n junction was found to result from an increment of effective resistivity in substrates. Reduction of the frequency [f.sub.max] due to the floating metal poles was caused by increasing effective coupling capacitance between the spiral inductors and substrate. Index Terms--Floating structures, inductor, metal pole, model, patterned trench isolation.

A study of the stability and numerical dissipation of the finite-difference time-domain technique including passive and active lumped elements has been reported recently by Thiel and Katehi. In particular, three different formulations for lumped inductors were analyzed: the explicit, semi-implicit, and implicit schemes. The implicit scheme was identified to be the same as the formulation previously introduced by Piket-May et al., and its dissipative nature was modeled by a series resistor. In this paper, we perform a numerical dispersion analysis of the above-mentioned schemes, which has not been reported thus far. Other numerical properties of these schemes such as the stability are also discussed. The dispersion analysis allows the numerical impedance of the lumped inductor to be defined or, alternatively, to show that a region of lumped inductors can be interpreted as a dielectric material with a frequency-dependent permittivity. Special attention is given to the implicit scheme. For this scheme, three main conclusions are drawn, i.e., 1) the formulation introduced by Piket-May et al. does not correspond to the implicit scheme, but to the explicit one, 2) the implicit scheme is unconditionally stable for a range of inductance values, and 3) by means of the dispersion analysis, it is shown that the dissipative nature of the implicit scheme is more naturally modeled by a parallel resistor. Index Terms--Finite-difference time-domain (FDTD) methods, lumped inductors, numerical dispersion, stability.

This paper presents a new modified-T model for three-dimensional inductors embedded in the multilayer low-temperature cofired-ceramic substrate with a remarkably large bandwidth. This model combines a core circuit, a five-element modified-T model, to include the effects of a transmission line with an electrical length up to [pi], and several resonators to consider the effects due to coil coupling and the finite ground plane. It is emphasized that most of the elements in this equivalent-circuit model can be extracted directly from the measured S-parameters. Compared to the conventional PI-section model that is valid only up to the fundamental self resonant frequency (SRF), this model can include more higher-order SRFs and ground resonant frequencies effectively, which results in several times larger bandwidth. Index Terms--Embedded inductor, inductor model, low-temperature cofired-ceramic (LTCC) inductor, three-dimensional (3-D) inductor.

Design and equivalent circuit of an inductor with ferromagnetic film is described. High-frequency circuit simulation including inductances is carried out by two methods: 1) a SPICE-based simulation in which the distributed linear circuit is converted into GCRL equivalent circuit and 2) a harmonic balance method in which the nonlinear active part of the circuit is solved in terms of sinusoidal harmonics in frequency domain. High-frequency circuits including inductors and active elements such as low noise amplifiers are analyzed by these methods. Index Terms--Equivalent circuit, finite element method, harmonic balance method, MMIC, simulation, thin film inductor.

The thin-film power amplifier module for wide-band code division multiple access was designed and fabricated using the magnetic thin film as magnetic core of choke inductors. CoFeSiO--Si[O.sub.2] multilayer granular films showing high resistivity and good magnetic properties were applied to the module. Inductance value increased about 30% by application of magnetic films, and occupation area and series resistance were also reduced by 20%. The obtained module size was 3.0 mm x 3.5 mm, which was much smaller than the conventional power amplifier module, since the bias circuit was formed on the same silicon substrate. Index Terms--Choke inductor, magnetic film, power amplifier module, thin-film inductor.

This paper gives an overview of recent advances in applying magnetoelastic thin films in inductive high-frequency devices. Single and multilayer films were fabricated and optimized with respect to application in stress-sensitive inductors, which are operated at high frequencies. These films require high magnetic permeability, high ferromagnetic resonance frequency, low losses, and a high inverse magnetostrictive effect. A thin-film LC circuit with incorporated magnetic thin films, sensitive to applied external magnetic field and/or applied stress, is presented. It operates at a frequency of about 0.5 GHz and has a quality factor of 8, allowing wireless interrogation, e.g., by inductive coupling. Applied strain in a range Index Terms--High frequency, inductors, magnetoelastic multilayers, stress sensors.

A full-bridge converter which employs a coupled inductor to achieve zero-voltage switching of the primary switches in the entire line and load range is described. Because the coupled inductor does not appear as a series inductance in the load current path, it does not cause a loss of duty cycle or severe voltage ringing across the output rectifier. The operation and performance of the proposed converter is verified on a 670-W prototype. Index Terms--Coupled inductor, full bridge converter, phase shift control, zero voltage switching.

In this paper, we developed a simple wide-band inductor model that contains lateral substrate resistance and capacitance to model the decrease in the series resistance at high frequencies related to lateral coupling through the silicon substrate. The model accurately predicts the equivalent series resistance and inductance over a wide-frequency range. Since it has frequency-independent elements, the proposed model can be easily integrated in SPICE-compatible simulators. The proposed model has been verified with measured results of inductors fabricated in a 0.18-[micro]m six-metal CMOS process. We also demonstrate the validity of the proposed model for shielded inductors. The proposed model shows excellent agreement with measured data over the whole frequency range. Index Terms--Inductor, inductor model, series resistance, substrate capacitance, substrate modeling, substrate resistance, wide-band.

We present a parametric investigation of various groups of on-chip asymmetrically octagonal inductors on silicon substrates. The inductors have different numbers of turns, strip widths, spacings, outer dimensions, and inner radii. Using two-port S parameters measured by a deembedding technique, we derive some local scalable formulas for extrapolating Q factor, resonance frequency, inductance, overlapping, and oxide capacitances of these octagonal inductors with different geometries. The effects of all geometric parameters on Q factor and so forth are explored, analyzed, and compared with each other in detail. Index Terms--Inductance, on-chip asymmetrically octagonal inductors, Q factor, resonance frequency, scalable formulas.

Inductors play a key role in dc-dc converters, but few options exist for implementing on-chip inductors for highly miniaturized, monolithic power converters. Microinductors constructed by standard microelectronic fabrication techniques with magnetic films as the core material have been investigated during the past 20 years with mixed results. A 13-[mm.sup.2] microinductor based on a spiral geometry, and having L = 3.2 [micro]H and Q = 1.3 at 1 MHz is reported here. Key issues regarding microinductor design and performance are discussed. Index Terms-Distributed power electronics, integrated passive components, microinductors.

A theory is proposed to explain spectral behaviors in proton-enhanced high-Q inductors.

This paper presents a new efficient multiline model for monolithic inductors. A preliminary model was developed by Huynen, which divided the spiral in sections of coupled transmission lines whose parameters are calculated by a variational principle. This model has been improved for inductors with high trace width-to-gap ratios and it has been demonstrated to be adequate for predicting S-parameters characterizing the inductor over a wide frequency band, even above its self-resonant frequency. This new design tool is shown to be useful for analyzing and optimizing inductor topologies built on both insulating and semiconducting substrates. Index Terms--Inductor model, integrated circuit (IC) modeling, substrate loss.

This paper addresses the possibility of integration of an induction machine rotor fault monitoring technique into batch tests. Conventional monitoring techniques are designed for operating conditions near nominal speed and load. Generally, load torque is not available at batch test as the test sample should not or cannot be clutched. However, at standstill, shaft torque and rotor currents are big enough to enable rotor monitoring. Therefore, short-circuit tests are applicable for diagnostic purposes. This application will be demonstrated by means of the Vienna Monitoring Method, which is a model-based torque evaluation technique. Index Terms--Batch test, diagnostics, faulty rotor bars, induction machine, rotor-cage monitoring, short-circuit test, squirrel cage, standstill.

A method is developed to take foil winding inductors into account in the frame of the magnetic vector potential magnetodynamic formulation, in 2-D and 3-D. The definition of the foil voltage as a continuous unidirectional spatially dependent global quantity enables to express the elementary foil circuit relations, relating currents and voltages. A convenient form of these circuit relations is developed and its continuous extension is shown to weakly define the constraints on currents peculiar to foil windings, i.e., allowing skin effect in the direction of the height of the foils while maintaining a constant current in each elementary foil. Index Terms--Electric circuit, finite-element method, foil winding, inductors, magnetodynamics.