Showing papers on "Inductor published in 1998"

On-chip spiral inductors with patterned ground shields for Si-based RF ICs

Abstract: This paper presents a patterned ground shield inserted between an on-chip spiral inductor and silicon substrate. The patterned ground shield can be realized in standard silicon technologies without additional processing steps. The impacts of shield resistance and pattern on inductance, parasitic resistances and capacitances, and quality factor are studied extensively. Experimental results show that a polysilicon patterned ground shield achieves the most improvement. At 1-2 GHz, the addition of the shield increases the inductor quality factor up to 33% and reduces the substrate coupling between two adjacent inductors by as much as 25 dB. We also demonstrate that the quality factor of a 2-GHz LC tank can be nearly doubled with a shielded inductor.

Analysis, design, and optimization of spiral inductors and transformers for Si RF ICs

Abstract: Silicon integrated circuit spiral inductors and transformers are analyzed using electromagnetic analysis. With appropriate approximations, the calculations are reduced to electrostatic and magnetostatic calculations. The important effects of substrate loss are included in the analysis. Classic circuit analysis and network analysis techniques are used to derive two-port parameters from the circuits. From two-port measurements, low-order, frequency-independent lumped circuits are used to model the physical behavior over a broad-frequency range. The analysis is applied to traditional square and polygon inductors and transformer structures as well as to multilayer metal structures and coupled inductors. A custom computer-aided-design tool called ASITIC is described, which is used for the analysis, design, and optimization of these structures. Measurements taken over a frequency range from 100 MHz to 5 GHz show good agreement with theory.

RF-CMOS oscillators with switched tuning

Abstract: Fully integrated CMOS oscillators are of great interest for use in single-chip wireless transceivers. In most oscillator circuits reported to date that operate in the 0.9 to 2 GHz frequency range, an integrated spiral inductor sets the frequency. It is generally believed that an LC oscillator, even when it uses a low-Q inductor, displays a lower phase noise than a ring oscillator. However, due to the absence of a good varactor compatible with CMOS technology, the integrated LC oscillator suffers from a very limited tuning range. Although this tuning range may encompass the limited frequency agility required in an RF oscillator, for instance to span the modulation bandwidth in a transmitter, it will seldom cover the much larger lot-to-lot process variations manifest as spreads of up to 20% in capacitance. Fortunately, the self-inductance of a metal spiral does not suffer spreads, because it depends on a precise number of turns and on the geometry of metal traces which is little affected by fluctuations in lithography. This work addresses the practical problem of how to design RF CMOS oscillators with a wide enough tuning range to reliably cover process variations, without compromising current drain or phase noise. Prototypes were developed in the 0.6 /spl mu/m MOSIS CMOS process to oscillate at up to 1.8 GHz with a sub-3V supply. The tuning method exploits digital capabilities and MOS analog switches.

RF circuit design aspects of spiral inductors on silicon

Abstract: The design and optimization of spiral inductors on silicon substrates, the related layout issues in integrated circuits, and the effect of the inductor-Q an the performance of radio-frequency (RF) building blocks are discussed. Integrated spiral inductors with inductances of 0.5-100 nH and Q's up to 40 are shown to be feasible in very-large-scale-integration silicon technology. Circuit design aspects, such as a minimum inductor area, the cross talk between inductors, and the effect of a substrate contact on the inductor characteristics are addressed. Important RF building blocks, such as a bandpass filter, low-noise amplifier, and voltage-controlled oscillator are shown to benefit substantially from an improved inductor-Q.

Micromachined electro-mechanically tunable capacitors and their applications to RF IC's

Abstract: Micromachined electro-mechanically tunable capacitors with two and three parallel plates are presented. Experimental devices have been fabricated using a standard polysilicon surface micromachining process. The two-plate tunable capacitor has a measured nominal capacitance of 2.05 pF, a Q-factor of 20 at 1 GHz, and achieves a tuning range of 1.5:1, The three-plate version has a nominal capacitance of 4.0 pF, a Q-factor of 15.4 at 1 GHz, and a tuning range of 1.87:1. The tuning ranges achieved here are near theoretical limits. Effects due to various physical phenomena such as temperature, gravity, and shock are examined in detail. An RF voltage-controlled oscillator with an integrated inductor and a micromachined tunable capacitor is also demonstrated. The active circuit and the inductor have been fabricated in a 0.5 /spl mu/m CMOS process. The voltage-controlled oscillator has been assembled by bonding together the CMOS and the micromachined parts. The 1.35 GHz voltage-controlled oscillator has a phase noise of -98.5 dBc/Hz at a 100 kHz offset from the carrier.

System and method for the wireless sensing of physical properties

Abstract: Several sensors are provided for determining one of a number of physical properties including pressure, temperature, and other physical conditions. In general, the sensors feature a resonant circuit with an inductor coil which is electromagnetically coupled to a transmitting antenna. When an excitation signal is applied to the antenna, a current is induced in the sensor circuit. This current oscillates at the resonant frequency of the sensor circuit. The resonant frequency and bandwidth of the sensor circuit is determined using an impedance analyzer, a transmitting and receiving antenna system, or a chirp interrogation system. The resonant frequency may further be determined using a simple analog circuit with a transmitter. The sensors are constructed so that either the resonant frequency or bandwidth of the sensor circuit, or both, are made to depend upon the physical properties such as pressure, temperature, presence of a chemical species, or other condition of a specific environment. The physical properties are calculated from the resonant frequency and bandwidth determined.

Micromachined planar inductors on silicon wafers for MEMS applications

Abstract: This paper describes three micromachined planar inductors (a spiral type, a solenoid type, and a toroidal meander type) with electroplated nickel-iron permalloy cores which have been realized on a silicon wafer using micromachining techniques. The electrical properties among the fabricated inductors are compared and the related fabrication issues are discussed, with emphasis on the low-temperature CMOS-compatible process, the high current-carrying capacity, the high magnetic flux density, the closed magnetic circuits, and the low product cost. The micromachined on-chip inductors can be applied for magnetic microelectromechanical systems devices, such as micromotors, microactuators, microsensors, and integrated power converters, which envisages new micropower magnetics on a chip with integrated circuits.

System, method, and sensors for sensing physical properties

Abstract: Several sensors are provided for determining one of a number of physical roperties including pressure, temperature, chemical species, and other physical conditions. In general, the sensors feature a resonant circuit with an inductor coil which is electromagnetically coupled to a transmitting antenna. When an excitation signal is applied to the antenna, a current is induced in the sensor circuit. This current oscillates at the resonant frequency of the sensor circuit. The resonant frequency and bandwidth of the sensor circuit is determined using an impedance analyzer, a transmitting and receiving antenna system, or a chirp interrogation system. The resonant frequency may further be determined using a simple analog circuit with a transmitter. The sensors are constructed so that either the resonant frequency or bandwidth of the sensor circuit, or both, are made to depend upon the physical properties such as pressure, temperature, presence of a chemical species, or other condition of a specific environment. The physical properties are calculated from the resonant frequency and bandwidth determined.

AC powered light emitting diode array circuits for use in traffic signal displays

Abstract: An LED array circuit includes a number of series connected LED pairs, each pair including two parallel connected oppositely polarized LEDS. The array is coupled to a standard AC voltage source in series with an inductor L having Q>5 and a reactance which is equivalent to the resistance of a current limiting resistor. The use of an inductor in place of a resistor increases the efficiency of the array to approximately 80%. The efficiency of the array is increased even further by coupling a capacitor parallel to the array and by tuning the inductor and capacitor to the frequency of the AC voltage source. According to one embodiment of the invention, a somg;e retro-fittable unit is provided wherein an inductor, a capacitor, and an array of LEDs are contained in a housing having substantially the same size and shape as a standard incandescent bulb or the lens/filter used in a traffic signal display. According to another embodiment of the invention, a single module is provided with a plurality of LED arrays, with each LED array having its own capacitor coupled in parallel thereto, and its own series coupled switch. The module is coupled to and across the AC voltage source, with one node of the module coupled to the AC voltage source by an inductor.

Study of the ground bounce caused by power plane resonances

Abstract: We describe Delta-I noise caused by power plane resonances in multilayer boards. First, we study the effect of power plane resonances on the ground bounce of the system by performing finite-difference time-domain (FDTD) simulations. We simulate the voltage fluctuations at one point of the printed circuit board (PCB) due to a current surge between the power planes in a different point. Next, two methods to prevent this ground bounce effect are investigated. The first method consists of adding lumped capacitances to the design. The effect of one large capacitor is compared to the effect of adding a "wall" of smaller capacitors. A second approach is to isolate the chips by etching a slot around the sensitive integrated circuits (ICs) and connecting both sides by a small inductor. Both methods provide excellent protection against power plane resonances.

DC-to-DC converter with inductor current sensing and related methods

Abstract: A DC-to-DC power converter includes at least one power switch, a pulse width modulation circuit for generating control pulses for the at least one power switch, an output inductor connected to the at least one power switch, and a current sensor connected in parallel with the inductor for sensing current passing through the inductor. The current sensor preferably includes a resistor and a capacitor connected together in series. The current sensor is connected to a peak current control loop circuit cooperating with the pulse width modulation circuit for controlling the at least one power switch responsive to the current sensor. The resistor and capacitor preferably have respective values so that the current sensor is a substantially instantaneous current sensor. The output inductor has an inductance and a direct current (DC) resistance defining a first time constant. In one embodiment, the resistor and capacitor of the current sensor define a second time constant within a predetermined range of each other. In another embodiment, the resistor and capacitor of the current sensor define a second time constant substantially equal to the first time constant.

Monolithic transformers and their application in a differential CMOS RF low-noise amplifier

Abstract: A 900 MHz low-noise amplifier (LNA) utilizing three monolithic transformers to implement on-chip tuning networks and requiring no external components has been integrated in 2.88 mm/sup 2/ in a standard digital 0.6 /spl mu/m CMOS process. A bias current reuse technique is employed to reduce power dissipation, and process-, voltage-, and temperature-tracking biasing techniques are used. At 900 MHz, the LNA dissipates 18 mW from a single 3 V power supply and provides 4.1 dB noise figure, 12.3 dB power gain, -33.0 dB reverse isolation, and an input 1-db compression level of -16 dBm. Analysis and modeling considerations for silicon-based monolithic transformers are presented, and it is shown that a monolithic transformer occupies less die area and provides a higher quality factor than two independent inductors with the same effective inductance in differential applications.

Estimation Methods for Quality Factors of Inductors Fabricated in Silicon Integrated Circuit Process Technologies

Abstract: By examining uses of quality ( ) factors for in- ductors in silicon integrated circuit design, new methods for estimating quality factors are proposed. These methods extract factors by numerically adding a capacitor in parallel to measured data of an inductor, and by computing the fre- quency stability factor and 3-dB bandwidth at the resonant frequency of the resulting network. These parameters are then converted to effective quality factors using relationships for simple parallel RLC circuits. By sweeping the numerically added capacitance value, effective quality factors at varying frequen- cies are computed. These new techniques, in addition to being more relevant for circuit design, provide physically reasonable estimates all the way up to the self-resonant frequencies of inductors. At moderate to high frequencies, the commonly used definition can significantly underestimate and can even give unreasonable results. Data obtained using the new methods suggest that quality factors remain high and integrated inductors remain useful all the way up to their self- resonant frequencies, contrary to the behavior obtained using . These indicate that the commonly used technique can lead to improper use and optimization of integrated inductors.

Control of inductive power transfer pickups

Abstract: Secondary resonant pickup coils (102) used in loosely coupled inductive power tranfser systems, with resonating capacitors (902) have high Q and could support large circulating currents which may destroy components. A current limit or 'safety valve' uses an inductor designed to enter saturation at predetermined resonating currents somewhat above normal working levels. Saturation is immediate and passive. The constant-current characteristic of a loosely coupled, controlled pickup means that if the saturable section is shared by coupling flux and by leakage flux, then on saturation the current source is terminated in the saturated inductor, and little detuning from resonance occurs. Alternatively an external saturable inductor (1101, 1102) may be introduced within the resonant circuit (102 and 902), to detune the circuit away from the system frequency. Alternatively DC current may be passed through a winding to increase saturation of a saturable part of a core. As a result, a fail-safe pickup offering a voltage-limited constant-current output is provided.

An economical single-phase passive power-factor-corrected rectifier: topology, operation, extensions, and design for compliance

Abstract: This paper describes a novel passive power-factor correction circuit that ensures the compliance of the capacitively filtered single-phase rectifier with the EN61000-3-2 norm at a cost much lower than the known solutions The circuit can be used to about 300 W The additional components are a small inductor, a small capacitor and a diode

Inductive power transfer across an extended gap

Abstract: Inductive power transfer across an extended gap (100) from a primary conductor (119) is provided by means of a resonant intermediate loop comprised of capacitor (118) with inductor (117) - perhaps simply a non-coiled wire - carrying a larger resonating current, that can in turn generate an inductive field to be collected by a pickup coil (120). This loop may increase the transfer rate or reduce the alignment accuracy required of an IPT system, useful for vehicles as well as for lighting and display purposes, and also offers frequency-stabilising features. An electroluminescent advertising panel may be powered from a sine-wave oscillator at 1.2 kHz; its DC power at 50 volts collected by a controlled secondary pickup coil tuned to a system frequency of 15 kHz and placed near to an intermediate pickup coil; also resonant at the system frequency and which is driven by inductive coupling from a primary conductor fed with alternating current at the system frequency.

A Q-factor enhancement technique for MMIC inductors

Abstract: An increase of 50% in the peak Q-factor and a wider operating bandwidth for monolithic inductors is achieved by exciting a microstrip structure differentially. Conventional excitation of a 8 nH spiral inductor fabricated in a production silicon IC technology resulted in a peak (measured) Q-factor of 6.6 at 1.6 GHz, while the differential connection showed a maximum Q-factor of 9.7 at 2.5 GHz. These experimental results compared favorably with the behaviour predicted from simulation.

Plural parallel resonant switching power supplies

Abstract: A plurality of converter circuits A and B are provided. The converter circuits A and B have circuit structures that are identical to each other. In the converter circuit A, a resonant capacitor 31, a resonant inductor 32 and a primary winding 51 of a transformer 5 are connected in series, with the two ends of the serial circuit thus achieved connected between the connecting point of switching elements 11 and 12 and one end of a source 10. The output ends of output rectifier smoothing circuits 7 and 8 are connected commonly. Resonant circuits 3 and 4 of the converter circuits A and B are connected with each other.

Switched-capacitor inverter with high power density and enhanced regulation capability

Abstract: A DC-AC inverter containing no inductors or transformers is presented. The role of the magnetic devices is played by a switched-capacitor (SC) circuit, formed by two subcircuits. Each SC-subcircuit contains 15 basic cells, each one formed by one capacitor, two MOSFETs and two diodes. The sinusoidal output waveform is realized in a staircase, formed by 64 steps. To achieve each step, the inverter operates like a step-up DC-DC converter: by using a certain number of SC-cells, the input voltage is boosted to the voltage required by the step in consideration. Each step is implemented in a large number of switching cycles. In each cycle, the inverter goes through four phases; according to a designed switching sequence, some of the capacitors of the SC-cells involved in the respective step are in a charging process from line, while the others are in a discharging process to the load. The phases 2 and 4 have a regulation role only. A duty cycle control is used. A Fourier analysis evidences the clean AC output waveform. The inverter exhibits low weight, high power density, and enhanced regulation for large changes in line and load.

Surface micromachined solenoid inductors for high frequency applications

Abstract: As operation frequencies and performance requirements of wireless devices increase, the resultant demands on the performance of passive components also increase. Miniaturization of inductive components for high frequency has been a key research area to address this issue; however, in general, miniaturized integrated inductors can suffer from low Q factors and/or self-resonant frequencies when compared to their discrete counterparts. In this research, a modified geometry of a solenoid type inductor using a surface micromachining technique is proposed. This inductor has an air core and an electroplated copper coil to reduce the series resistance, and its low temperature process is suitable for various packaging applications. An important feature of the proposed inductor geometry is the introduction of an air gap between the substrate and the conductor coil in order to reduce the effects of the substrate dielectric constant. This air gap can be realized using a polyimide sacrificial layer and a surface micromachining technique. Therefore, the resulting inductor can have less substrate-dependent magnetic properties, less stray capacitance, and higher Q-factor. The measurement result shows that this inductor has high Q-factor and stable inductance over a wide range of operating frequency. Also, various effects of geometrical factors have been investigated. Various inductors with the inductance varying from 1 to 20 nH and maximum Q-factor from 7 to 60 have been fabricated and measured.

Printed circuit boards with integrated passive components and method for making same

Abstract: A multi-layered printed circuit board having a plurality of burried passive elements and a method for producing the circuit board wherein the passive elements can include resistors, capacitors and inductors. The method includes the steps of manufacturing individual layers of the multi-layer printed circuit board with electrical circuits thereon and subsequently screening polymer inks having resistive, dielectric or magnetic values to form the resistors, capacitors and inductors. Each layer of the circuit board is cured to dry the polymer ink and thereafter the individual layers are bonded together to form the multi-layer board.

Tunable-trimmable micro electro mechanical system (MEMS) capacitor

Abstract: A high Q MEMS capacitor that can be continuously tuned with a large tuning ratio or reversibly trimmed using an electrostatic force. The tunable capacitor has a master/slave structure in which a control voltage is applied to the master (control) capacitor to set the capacitance of the slave (signal) capacitor to which an RF signal is applied via a suspended mechanical coupler. The master-slave structure reduces tuning error by reducing the signal capacitor's surface area and increasing its spring constant, and may eliminate the need for discrete blocking inductors by electrically isolating the control and signal capacitors. The trimmable capacitor provides an electrostatic actuator that selectively engages a stopper with teeth on a tunable capacitor structure to fix the trimmed capacitance.

Progress in RF inductors on silicon-understanding substrate losses

Abstract: The recent progress in the integration of inductors on silicon substrates is reviewed first. The substrate losses, which present the main difference to the well-established inductor integration on quasi-ideal GaAs or printed circuit boards, are then investigated through specific experiments to support the inductor optimization and modeling. Metal ground shield structures, that potentially isolate the spiral inductor coil from the lossy silicon, are evaluated as well.

DC-DC converter with fast transient response and high efficiency for low-voltage microprocessor loads

Abstract: The paper describes a DC-DC power converter for use with low voltage microprocessor loads. The control method is a hysteretic current-mode control in the continuous conduction mode which has fast transient response. At light loads, the power converter operates in the discontinuous conduction mode using a peak current control method which causes the switching frequency to be proportional to load current, thus maintaining high efficiency in a very wide range of loads. The control method implementation, transient response and output inductor design equations, and equations for designing an input filter to reduce input current di/dt are provided. An inductor current estimator which provides higher efficiency, good transient response, and current limiting, is presented. Experimental results for a 5.0 V input, 3.1 V output, 13 A DC-DC converter are included to verify the theoretical information.

Deactivateable resonant circuit

Abstract: A resonant tag (58) used with an electronic article surveillance system for detecting the tag within a surveilled area utilizing electromagnetic energy at a predetermined detection frequency includes a resonant circuit (66, 68) capable of resonating at the predetermined detection frequency. The resonant circuit (66, 68) includes an inductor (66) formed at least in part on a surface of a dielectric substrate of the tag (58). The inductor (66) is formed with a discontinuity or gap (74) causing an electrical open circuit. The open circuit is closed with a fuse (36) secured proximate to the gap (74) and wirebonded (40, 42) to the portions of the inductor (66) proximate to the gap (74). The fuse (36) is melted by a current greater than a predetermined level flowing therethrough. Such a high current may be induced in the inductor (66) by an external electromagnetic field. Melting of the fuse (36) causes an open circuit condition, which alters the frequency at which the tag (58) resonates.

High pulse rate pulse power system

Abstract: A high pulse rate pulse power source (20) for supplying controlled high energy electrical pulses at rates of 2000 Hz or greater. The source (20) includes a pulse generating circuit (30) including a charging capacitor (42), a solid state switch (46) and a current limiting inductor (48). Pulses generated in the pulse generating circuit (30) are compressed in at least two pulse compression circuits (61, 65) and a step-up pulse transformer (56) increases peak voltage to at least 12,000 volts. A very fast regulated power supply is provided for charging the charging capacitor (42) in less than 400 microseconds and a pulse control system including a programmed processor (102) controls the charging of the charging capacitor (42) to an accuracy of less than about one percent at a rate of at least 2000 charges per second.

AC/DC flyback converter with improved power factor and reduced switching loss

Abstract: A new single stage, single switch input current shaping circuit features substantially reduced turn-on switching losses of the switch in the flyback-converter. In this technique, the turn-on switching losses due to the discharge of the output capacitance of the switch are reduced by turning on the switch when its voltage is minimal or close to the minimal. To achieve the turn-on loss reduction for a wide range of line and load conditions, the flyback-converter stage is continuously operated at the boundary of the CCM and DCM by employing a variable-frequency control. In this technique the boost inductor can work either in the DCM or the CCM. The wide-bandwidth, variable-frequency control is implemented by detecting the onset of the DCM/CCM boundary and, subsequently, turning the switch on at the minimum switch voltage. The switch is turned off when the increasing primary current reaches a reference level set by the output-voltage feedback control circuit.

Coupled-inductor current-doubler topology in phase-shifted full-bridge DC-DC converter

Abstract: The paper proposes and analyses the coupled-inductor version of the current-doubler rectifier. The analysis shows that coupling of the inductors can reduce losses both in transformer and inductor windings. Practical design procedure of the coupled-inductor and experimental results for a 1900 W telecom rectifier are included.

A vector control scheme for EV induction motors with a series iron loss model

Abstract: Electric vehicle (EV) motors are characterized by their low inductance and high current density, so that they run at high speed and produce a high starting torque. Due to the low inductance coil design, the current ripple caused by pulsewidth modulation (PWM) switching makes a significant amount of eddy-current loss and hysteresis loss, especially in high-speed operation. If one simply neglects the iron loss, the overall vector controller is detuned, resulting in an error in the torque control. The iron loss is modeled, in general, by a parallel resistor R/sub M/ to the magnetizing inductor L/sub M/. The authors propose a series R-L model that accounts for the effects of the iron loss. A major advantage of the series model is that it does not increase the number of state variables in developing a vector control. In this paper, they derive a rotor-flux-oriented flux error, orientation angle error, and torque error caused by iron loss. Finally, they demonstrate the effectiveness of the proposed control method through computer simulation and experimental results.

Cold plasma coagulator

Abstract: A cold plasma coagulator clots blood bleeding from tissue during surgical operation in an effective manner, by applying unipolar cold plasma to the blood. The cold plasma coagulator has a high frequency power supply, gas dynamic block and plasmotron. The power supply has a rectifier, capacitor storage and voltage inverter. The said plasmotron is assembled in a hermetically sealed case and in which resonance inductor and dielectric tube are located coaxially. One end of the dielectric tube is connected to the gas dynamic block, another end is positioned to eject plasma through output nozzle. A needle corona electrode is located along the axis of the dielectric electrode. The coils of the resonance inductor has a low voltage and high voltage section, the low voltage section of resonance coils being connected to output of the voltage inverter. One pin of the high voltage section is isolated and another one is connected to the needle corona electrode.