Showing papers on "Electromagnetic coil published in 2003"

Remotely powered and remotely interrogated wireless digital sensor telemetry system

Abstract: An electronic system includes a reader and a remotely powered and remotely interrogated sensor transponder. The sensor transponder includes a coil or an antenna, a switched reactance circuit, a processor, and a sensor. The sensor transponder receives power radiated from the reader to the coil or antenna. The sensor uses the power for sensing. The sensor transponder is capable of processing sensor data in the processor and transmitting the sensor data to the reader using the switched reactance circuit. In one embodiment, the receiver coil or antenna is part of a resonant tank circuit which includes an impedance matching circuit. The impedance matching circuit is connected to the receiver coil or antenna to provide greater current to the sensor or other power-using device than would be available to the sensor or other power-using device if the sensor or other power-using device were connected between the first and second end. The impedance matching circuit can be two or more taps to the coil or antenna.

Power supply system

Abstract: A power supply system is provided, having: a primary side coil; a power transmission apparatus having a primary side circuit for feeding a pulse voltage resulted from switching a DC voltage which is obtained by rectifying and smoothing a commercial power supply to the primary side coil; a secondary side coil magnetically coupled to the primary side coil; and power reception equipment having a secondary side circuit for rectifying and smoothing voltage induced across the secondary side coil, wherein there is provided a power adjusting section for adjusting a level of power to be transmitted according to power required by the power reception equipment. The power adjusting section has, in the primary side circuit, a carrier wave oscillation circuit for supplying a carrier wave to the primary side coil, a demodulation circuit for demodulating a modulated signal transmitted from the secondary circuit and received by the primary side coil, and a power change-over section for selecting a level of power to be transmitted according to an information signal from the power reception equipment and demodulated by the demodulation circuit. The power adjusting section has, in the secondary side circuit, a modulation circuit for modulating the carrier wave fed from the carrier wave oscillation circuit and received by the secondary side coil with the information signal from the power reception equipment and transmitting the modulated signal.

Inductive power adapter

Abstract: An inductive power systems transfers energy by inductively coupling a source coil on a power source to a receiver coil on a power portion of a power adapter. The source current is received in the power adapter and converted to direct current for transmission to a computer system. Wireless communication between a power source and the power adapter is provided. A wireless communication arrangement provides for authentication of devices that are allowed by a source to be powered.

Inductive battery charger

Abstract: An inductive charging system transfers energy by inductively coupling a source coil on a power source to a receiver coil for a battery charger. Source current may be received in the battery charger and converted for charging a battery pack. A wireless communication arrangement may also provide for authentication of devices that are allowed by the source to be powered or otherwise charged.

On the design of RF spiral inductors on silicon

Abstract: This review of design principles for implementation of a spiral inductor in a silicon integrated circuit fabrication process summarizes prior art in this field. In addition, a fast and physics-based inductor model is exploited to put the results contributed by many different groups in various technologies and achieved over the past eight years into perspective. Inductors are compared not only by their maximum quality factors (Q/sub max/), but also by taking the frequency at Q/sub max/, the inductance value (L), the self-resonance frequency (f/sub SR/), and the coil area into account. It is further explained that the spiral coil structure on a lossy silicon substrate can operate in three different modes, depending at first order on the silicon doping concentration. Ranging from high to low substrate resistivity, inductor-mode, resonator-mode, and eddy-current regimes are defined by characteristic changes of Q/sub max/, L, and f/sub SR/. The advantages and disadvantages of patterned or blanket resistive ground shields between the inductor coil and substrate and the effect of a substrate contact on the inductor are also addressed in this paper. Exploring optimum inductor designs under various constraints leverages the speed of the model. Finally, in view of the continuously increasing operating frequencies in advancing to new generations of RF systems, the range of feasible inductance values for given quality factors are predicted on the basis of optimum technological features.

Low-power, high-modulation-index amplifier for use in battery-powered device

Abstract: An external transmitter circuit drives an implantable neural stimulator having an implanted coil from a primary coil driven by a power amplifier. For efficient power consumption, the transmitter output circuit (which includes the primary coil driven by the power amplifier inductively coupled with the implanted coil) operates as a tuned resonant circuit. When operating as a tuned resonant circuit, it is difficult to modulate the carrier signal with data having sharp rise and fall times without using a high power modulation amplifier. Sharp rise and fall times are needed in order to ensure reliable data transmission. To overcome this difficulty, the present invention includes an output switch that selectively inserts a resistor in the transmitter output coil circuit in order to de-tune the resonant circuit only during those times when data modulation is needed. Such de-tuning allows sharp rise and fall times in the data modulation without the need for using a high power modulation amplifier. Because data modulation is typically needed for only a small percent of the time that a carrier signal is present, it is thus possible using the present invention to achieve reliable data modulation, transmission and reception without having to use a high power modulation amplifier in the transmitter.

Ultimate intrinsic signal-to-noise ratio for parallel MRI: electromagnetic field considerations.

Abstract: A method is described for establishing an upper bound on the spatial encoding capabilities of coil arrays in parallel MRI Ultimate intrinsic signal-to-noise ratio (SNR), independent of any particular conductor arrangement, is calculated by expressing arbitrary coil sensitivities in terms of a complete set of basis functions that satisfy Maxwell's equations within the sample and performing parallel imaging reconstructions using these basis functions The dependence of the ultimate intrinsic SNR on a variety of experimental conditions is explored and a physically intuitive explanation for the observed behavior is provided based on a comparison between the electromagnetic wavelength and the distance between aliasing points Imaging at high field strength, with correspondingly short wavelength, is shown to offer advantages for parallel imaging beyond those already expected due to the larger available spin polarization One-dimensional undersampling of k-space yields a steep drop in attainable SNR for more than a 5-fold reduction of scan time, while 2D undersampling permits access to much higher degrees of acceleration Increased tissue conductivity decreases baseline SNR, but improves parallel imaging performance A procedure is also provided for generating the optimal coil sensitivity pattern for a given acceleration, which will serve as a useful guide for future coil designs

Infusion device and driving mechanism and process for same with actuator for multiple infusion uses

Abstract: A drive mechanism for delivery of infusion medium a coil capable of being electrically activated to provide an electromagnetic field. The coil surrounds a piston channel extending in an axial direction. An armature is located adjacent the coil, on one side of the axial channel. The armature is moveable toward a forward position, in response to the electromagnetic field produced by activation of the coil. A piston is located within the piston channel and is moveable axially within the channel to a forward position, in response to movement of the armature to its forward position. The armature and piston are moved toward a retracted position, when the coil is not energized. The armature may be configured with a reduced diameter by including a coil cup for supporting the coil including a shelf portion defining at least a portion of a pole surface of the coil cup.

Enhanced RF wireless adaptive power provisioning system for small devices

Abstract: An apparatus to provide wireless powering of a mobile device comprising a pad having an embedded coil, the coil driven by a power oscillator and is controlled by a controller, to provide a narrow-band resonance coupling.

Wired pipe joint with current-loop inductive couplers

Abstract: A robust, low-loss wired pipe joint is provided for service as a component of a wired pipe string for transmitting measurement data to a surface station from locations in a borehole in oil well drilling and oil well operations. Conductive layers reduce signal energy losses over the length of the drill string by reducing resistive losses and flux losses at each inductive coupler. The wired pipe joint is robust in that it remains operational in the presence of gaps in the conductive layer. A wired pipe joint includes an elongate tubular shank having an axial bore, a threaded box-end, and a threaded pin end. A first annular coil, fixedly mounted to the box-end is partially surrounded by a first high-conductivity, low-permeability layer, and a second annular coil fixedly mounted to the pin-end is partially surrounded by a second high-conductivity, low-permeability layer, such that when the box-end of a first wired pipe joint is coupled for operation with the pin-end of a second wired pipe joint, the first and second high-conductivity, low-permeability layers form at least a portion of a toroidal path enclosing the first annular coil of the first wired pipe joint and the second annular coil of the second wired pipe joint. Coil windings of the first and second coils of the wired pipe joint are electrically coupled.

Medical device with deflecting shaft and related methods of manufacture and use

Abstract: Various embodiments of a medical device having a deflecting shaft and related methods of manufacture and use are disclosed. For example, the device may include a proximal handle, a distal assembly for performing a medical procedure, and a wire coil connecting the proximal handle to the distal assembly, wherein actuation of the proximal handle may cause the distal assembly to perform the medical procedure. The wire coil may have a proximal portion comprised of a first wire and a distal portion comprised of a second wire. The second wire may have a diameter less than a diameter of the first wire so that the distal portion of the wire coil may have a flexibility greater than a flexibility of the proximal portion.

Compact electrical machine

Abstract: An electrical machine comprises a combined magnetic gearbox and electrical generator. A first set of permanent magnets (30) are arranged on a rotor (16) to produce a spatially variable first magnetic field. A second set of permanent magnets (32) are arranged on a rotor (40,41,43), stationary pole pieces (36) are positioned between the first set of permanent magnets (30) and the second set of permanent magnets (32) to interfere with the first magnetic field. Rotation of the rotor (16) relative to the pole pieces (36) produces a second magnetic field which rotates the second set of permanent magnets (32). A stator (42) has windings (46) to transduce a changing second magnetic field produced by the rotation of the second set of permanent magnets (32) into an electrical voltage. The electrical machine is useful for a wind turbine generator. Alternatively the arrangement may be modified to produce an electrical motor.

Conditioning of coupled electromagnetic signals on a lead

Abstract: A method and an apparatus for reducing coupled electrical energy resulting from an electromagnetic field. Embodiments of the present invention provide for an elongate body having a proximal end portion, a middle portion, and a distal end portion and at least one coil wound about at least one of the proximal end portion, the middle portion, and the distal end portion, the coil to provide for filtering of radio frequency (RF) signal-coupled electrical energy.

Computation of electric and magnetic stimulation in human head using the 3-D impedance method

Abstract: A comparative, computational study of the modeling of transcranial magnetic stimulation (TMS) and electroconvulsive therapy (ECT) is presented using a human head model. The magnetic fields from a typical TMS coil of figure-eight type is modeled using the Biot-Savart law. The TMS coil is placed in a position used clinically for treatment of depression. Induced current densities and electric field distributions are calculated in the model using the impedance method. The calculations are made using driving currents and wave forms typical in the clinical setting. The obtained results are compared and contrasted with the corresponding ECT results. In the ECT case, a uniform current density is injected on one side of the head and extracted from the equal area on the opposite side of the head. The area of the injected currents corresponds to the electrode placement used in the clinic. The currents and electric fields, thus, produced within the model are computed using the same three-dimensional impedance method as used for the TMS case. The ECT calculations are made using currents and wave forms typical in the clinic. The electrical tissue properties are obtained from a 4-Cole-Cole model. The numerical results obtained are shown on a two-dimensional cross section of the model. In this study, we find that the current densities and electric fields in the ECT case are stronger and deeper penetrating than the corresponding TMS quantities but both methods show biologically interesting current levels deep inside the brain.

System for spatially adjustable excitation of leadless miniature marker

Abstract: A system for generating a magnetic field for excitation of a leadless marker assembly. The system of at least one embodiment includes a source generator that generates a plurality of alternating electrical signals each having an independently adjustable phase. A plurality of excitation coils are configured to simultaneously receive a respective one of the alternating electrical signals at a selected phase to generate a magnetic field. The phase of the alternating electrical signal for each excitation coil is independently adjustable relative to the phase of the alternating electrical signal for the other excitation coils so as to adjust the magnetic field from the respective coil. The magnetic fields from the excitation coils combine to form a spatially adjustable excitation field for excitation of the remote leadless marker assembly.

Summary, assessment and implications of the ITER Model Coil test results

Abstract: Testing of the five International Thermonuclear Experimental Reactor (ITER) model coils is nearly complete and it is possible to produce an overall summary of the conductor performance assessment. The interpretation is supported by a large database of tests on components (especially strand) and by analysis of the two main phenomena that influence the strand performance in the cable (current non-uniformity and mechanical loads). Individually, interpretation of individual coils is difficult but taken together the results enable conclusions to be drawn about the expected behaviour of conductors in the ITER coils. The conductor design has successfully resolved many of the problems of stability and pulsed current behaviour associated with large multi-strand cables, and the performance is better than expected in these areas. The current sharing behaviour is below expectations, probably due to an extra unexpected strain effect in the Nb3Sn strands arising from the local magnetic loads, and the paper concentrates on this issue. Design modifications are required to recover the performance and updated design criteria to implement these are proposed.

Method for making high speed, high areal density inductive write structure

Abstract: An inductive write element is disclosed for use in a magnetic data recording system. The write element provides increased data rate and data density capabilities through improved magnetic flux flow through the element. The write element includes a magnetic yoke constructed of first and second magnetic poles. The first pole includes a pedestal constructed of a high magnetic moment (high Bsat) material, which is preferably FeRhN nanocrystalline films with lamination layers of CoZrCr. The second pole includes a thin inner layer of high Bsat material (also preferably FeRhN nanocrystalline films with lamination layers of CoZrCr), the remainder being constructed of a magnetic material capable of being electroplated, such as a Ni—Fe alloy. An electrically conductive coil passes through the yoke between the first and second poles to induce a magnetic flux in the yoke when an electrical current is caused to flow through the coil. Magnetic flux in the yoke produces a fringing field at a write gap whereby a signal can be imparted onto a magnetic medium passing thereby.

System and method for inductive charging a wireless mouse

Abstract: A system for using inductive coils to transfer energy to a wireless mouse thereby allowing the wireless mouse to refresh its rechargeable batteries while at the same time being operated over the surface containing the sending inductive coil or coils.

Inductive write head having high magnetic moment poles and low magnetic moment thin layer in the back gap, and methods for making

Abstract: The present invention provides a write element for use in magnetic data recording system such as a computer disk drive. The write head utilizes the advantageous properties of high magnetic moments while overcoming the corrosion problems engendered by such materials. The write element includes a magnetic yoke constructed of first and second magnetic poles joined to one another at a back gap. While the majority of the poles are constructed of a high magnetic moment material a layer of relatively low magnetic moment material is provided on the first pole at the back gap portion of the first pole. The relatively low magnetic moment material prevents corrosion of the first pole during subsequent manufacturing of the write head. An electrically conductive coil passes through the magnetic yoke and is insulated there from. By passing an electrical current through the electrical coil, a magnetic flux is generated in the yoke. This magnetic flux then generates a magnetic fringing field in at a write gap of the yoke. The fringing field imparts magnetic data onto a recording medium passing thereby.

Detection element for objects and detection device using the same

Abstract: A body detecting element is buried in the ground together with a body such as a metal body and includes a magnetic member acting as a magnetic core, an antenna coil wound around the magnetic member and a capacitor connected to both the ends of the antenna coil for forming a resonance circuit together with the antenna coil. The antenna coil is mounted on the body integrally therewith through an electromagnetic shield member with the outer peripheral surface thereof confronting the outer surface of the body. A body detecting element includes an RFID circuit connected to the antenna coil and mounted on a body integrally therewith such that the outer peripheral surface of the antenna coil confronts the outer surface of the body through an electromagnetic shield member. Even if the body detecting element is mounted on the body such as the metal pipe integrally therewith, it can accurately detect the body because a resonant frequency and the Q value of the coil are not changed. There is almost no possibility that detecting element is broken or moved even if a body other than the above body is dug.

Micro-mechanical capacitive inductive sensor for wireless detection of relative or absolute pressure

Abstract: A micro-mechanical pressure transducer is disclosed in which a capacitive transducer structure is integrated with an inductor coil to form a LC tank circuit, resonance frequency of which may be detected remotely by imposing an electromagnetic field on the transducer. The capacitive transducer structure comprises a conductive movable diaphragm, a fixed counter electrode, and a predetermined air gap between said diaphragm and electrode. The diaphragm deflects in response to an applied pressure differential, leading to a change of capacitance in the structure and hence a shift of resonance frequency of the LC tank circuit. The resonance frequency of the LC circuit can be remotely detected by measuring and determining the corresponding peak in electromagnetic impedance of the transducer.

Cochlear implant sound processor with permanently integrated replenishable power source

Abstract: A cochlear implant sound processor is powered by a rechargeable battery that is permanently integrated into the sound processor. The sound processor contains an inductive coil that may be tuned to an external charging coil for battery recharging. The electronic circuits and coil of the sound processor are housed in a material transparent to RF signals. The sound processor may be placed in a recharging base station in which the sound processor is positioned in a space surrounded by the inductive charging coil embedded in a material transparent to RF signals. The inductive charging coil sends power to the coil inside the processor and thereby recharges the battery. An alternative embodiment utilizes contacts in the sound processor case and aligned terminals in the recharging base station that allow direct charging of the battery.

Design of large air-gap transformers for wireless power supplies

Abstract: This paper addresses the design of two-dimensional large air gap transformers for wireless power transmission. A theoretical analysis of the optimum shape and arrangement of the primary coils is presented. The magnetic field created by such a system is discussed and optimised. The effects of shielding of the secondary coils are discussed. The optimum coil arrangement for one example design is derived.

Method and system for providing induction charging having improved efficiency

Abstract: A battery charging system (250) for use with an induction charger (210). The battery charging system can include a secondary coil (252) having a plurality of turns for receiving magnetic flux produced by a primary coil (220) of the induction charger, and a control circuit (254) for controlling a number of turns of the secondary coil that are used in generating an output voltage for charging a cell (264). For example, the secondary coil can include a plurality of taps (291, 292, 293, 294), each of the taps providing an electrical connection to the coil at a different point, and thus providing a variety of selectable output voltages.

Disk drive monitoring a supply current to protect motor driver circuits

Abstract: A disk drive is disclosed comprising a spindle motor for rotating a disk and a voice coil motor (VCM) for actuating a head over the disk. The spindle motor comprises a plurality of windings, and the VCM comprises a voice coil. If the current flowing from a supply voltage exceeds a threshold, the windings are disconnected from the supply voltage, the voice coil is disconnected from the supply voltage, and the first and second ends of the voice coil are connected to ground.

3-D magnetic tracking of a single subminiature coil with a large 2-D array of uniaxial transmitters

Abstract: A novel system and method for magnetic tracking of a single subminiature coil is described. The novelty of the method consists in employing a large, 8 /spl times/ 8 array of coplanar transmitting coils. This allows us to always keep the receiving coil not far from the wide, flat transmitting array, to increase the signal-to-noise ratio, and to decrease the retransmitted interference. The whole transmitting array, 64 coils, is sequentially activated only at the initiation stage to compute the initial position of the receiving coil. The redundancy in the transmitters number provides fast and unambiguous convergence of the optimization algorithm. At the following tracking stages, a small (8 coils) transmitting subarray is activated. The relatively small subarray size allows us to keep a high update rate and resolution of tracking. For a 50-Hz update rate, the tracking resolution is not worse than 0.25 mm, 0.2/spl deg/ rms at a 200-mm height above the transmitting array's center. This resolution corresponds to an /spl sim/1-mm, 0.6/spl deg/ tracking accuracy. The novelty of the method consists as well in optimizing the transmitting coils' geometry to substantially (down to 0.5 mm) reduce the systematic error caused by the inaccuracy of the dipole field approximation.

Variable stiffness coil for vasoocclusive devices

Abstract: The variable stiffness vasoocclusive coil is given variable stiffness along the length of the coil by selectively heat treating certain segments of a primary or secondary coil. The primary coil can be selectively heat treated to form soft or deformable segments along the length of the coil, and can then be shaped into a secondary shape that is set by a heat treatment process. Distal regions of the coil can also be heat treated to make the distal ends of the coil softer, more deformable, or less traumatic.

Model and design of PCB parallel winding for planar transformer

Abstract: In today's high-frequency low-profile switching-mode power converters, paralleling winding in planar transformers is needed, especially for low voltage and high current applications. Although this practice is believed to be effective to increase the current handling capacity of the windings, the effect might be offset due to the unequal current sharing within parallel layers if the winding layers are not properly arranged and connected. In this work, the particular problems raised from parallel winding are addressed and modeled based on a one-dimensional field model. The factors affecting winding losses with parallel connection are analyzed. Software to predict the current density distribution and AC loss for planar windings has been developed.