General Electric Company

Sayed-Amr A El-Hamamsy

Joseph C Borowiec

William A Edelstein

Victor D Roberts

Ronald Dean Watkins

Mustansir Hussainy Kheraluwala

Robert James Thomas

Michael M Secen

Charles L Dumoulin

Charles S Korman

Robert Adolph Ackermann

Robert Arvin Hedeen

Rayette Ann Fisher

Mark E Duffy

Gerald E Duffy

Louis Robert Nerone

Raymond Albert Fillion

Kenneth Gordon Herd

Eddy Benjamin Boskamp

Steven Marc Gasworth

David Joseph Kachmarik

Otward M Mueller

Paul Shadforth Thompson

Constantine A Neugebauer

George A Farrall

Alexander J Yerman

Eric J Wildi

John F Schenck

Harald L Witting

Robert Michael Vavrek

Mark Lloyd Miller

James F Burgess

David E Dean

Christopher P Yakymyshyn

Scott Thomas Mansell

Bruce Campbell Amm

John P Cocoma

John Andrew Mallick

Edward John Thomas

Perry S Frederick

Randy Otto John Giaquinto

James Domenic Mieskoski

Timothy A Taubert

Richard Philip Mallozzi

David O Wharmby

Dewain Anthony Purgill

George Jernakoff

John Peter Fura

Michael W DeVre

Roman I Dachniwskyj

Gerald W Ludwig

Icko Eric Iben

Mike James Radziun

John W Blackmore

Kenneth J Downton

Robert S Scott

Icko Eric Timothy Iben

A low noise imaging apparatus for producing Magnetic Resonance (MR) images of a subject and for substantially minimizing acoustic noise generated during imaging is provided. The imaging apparatus comprises a magnet assembly, a gradient coil assembly, and a rf coil assembly, wherein at least one of the magnet assembly, the gradient coil assembly and the rf coil assembly are configured to reduce the generation and transmission of acoustic noise.

Low noise MRI scanner

A quadrature coil suitable for use with an open frame MRI system provides crossing pairs of arrays of parallel conductor elements, respectively. Compact configuration is provided through use of an isolating circuit for incorporating parasitic capacitances at the resonance frequency of the coil into a blocking parallel resonance. Termination of the parallel conductor elements may be accomplished by equal impedance node connectors formed from branching pairs of conductors or a triangular least resistance connection form. RF shields are provided by pairs of conductive sheets containing eddy current reducing slots aligned with the parallel conductors elements of the coil.

Radio frequency coil for open magnetic resonance imaging system

A sweep generator,applies a range of frequencies to an rf coil,to detect the resonant frequency of a field generated by a magnet,. A frequency to current converter,applies an auxiliary magnetic field to tune an MRI apparatus to the resonant frequency of the rf coil. A flexible coil of one turn (,) or two or more turns (,) has a plurality of segments (,). One of the belt has a contact k,, (k,&prime;), which is electrically connectable to one or more contacts k,, (k,&prime;), k,, (k,&prime;), etc. located between the ends of the segments. For each connection to successive contacts, the length of the coil and its inductance increases by the added impedance DL,between contacts k,and k,. That increase of inductance is nullified by capacitors DC,located between segments.

Method to automatically tune MRI RF coils

An MR magnet assembly includes a cylindrical vessel for housing a superconducting magnet and having a vacuum between its inner and outer walls. The vessel defines a magnet bore for receiving a patient to be imaged. A gradient coil assembly is mounted in the bore adjacent the inner wall of the magnet assembly. To reduce gradient coil noise, the inner wall is constructed of a non-conductive material which does not support eddy currents.

MRI magnet assembly with non-conductive inner wall

A sweep generator 230 applies a range of frequencies to an rf coil 140 to detect the resonant frequency of a field generated by a magnet 125a,b. A frequency to current converter 220 applies an auxiliary magnetic field to tune an MRI apparatus to the resonant frequency of the rf coil. A flexible coil of one turn (300) or two or more turns (500) has a plurality of segments (301-307; 501-513). One of the belt has a contact k0, (k0'), which is electrically connectable to one or more contacts k1, (k1'), k2, (k2'), etc. located between the ends of the segments. For each connection to successive contacts, the length of the coil and its inductance increases by the added impedance .DELTA.L.sub.ij between contacts k.sub.i and k.sub.j. That increase of inductance is nullified by capacitors .DELTA.C.sub.sij located between segments.

Several complete fingerprint coils are attached to a support. The support is then rolled into a cylindrical shape such that a ray connecting the centers of each of pair of coils aligns with a component of a magnetic desired to be minimized or eliminated. In order to create this alignment, the support must have a length larger than the circumference of the cylinder which it forms, thereby causing a predetermined overlap. Since the coils are complete, there is no need to solder half-turns of coils to make a complete coil as was the case in previous coils. Since there are no solder points which are typically weaker than the remaining coil, the coil assembly is more resilient and less prone to breakage, making it more reliable.

Solderless `fingerprint` RF shield

An amalgam is accurately placed and retained in an optimized location in the exhaust tube of an electrodeless SEF lamp for operation at a mercury vapor pressure in the optimum range from approximately four to seven millitorr by forming a dimple in the exhaust tube and using a dose locating member to locate and retain the amalgam on the side of the dimple away from the core of the lamp after filling the lamp. As an alternative, two dimples may be situated on opposite sides of the exhaust tube for performing the same function as, but with less depth than, the single dimple. In another alternative embodiment, first and second dimple configurations are formed in the exhaust tube after tip-off thereof, each dimple configuration including either one or two dimples. The second dimple configuration is spaced apart from the first dimple configuration along the length of the exhaust tube. In this way, the amalgam may be initially positioned farther from the tip-off region, thereby avoiding problems during tipping off of the exhaust tube, such as loss of mercury from the lamp, or quenching of the tip which could cause stress cracks. After tip-off, the second dimple configuration allows for placement of the amalgam closer to, or preferably in contact with, the tip of the sealed exhaust tube, i.e., the coolest location in the exhaust tube.

Accurate placement and retention of an amalgam in a electrodeless

An electrically controllable variable capacitor includes the interelectrode capacitance of at least one power MOSFET, a capacitance connected in series with the MOSFET and having one terminal connected to the drain or source thereof (the series capacitance), and bias control circuitry for controlling the bias voltage applied to the MOSFET. The voltage rating of the MOSFET, the peak amplitude of the applied ac signal, and the value of the series capacitance determine the range of dc bias voltages over which the MOSFET can be operated, and hence the capacitance range of the variable capacitor. Such a variable capacitance is useful as a tuning capacitor in an electrodeless HID lamp ballast.

Electronically controllable capacitors using power MOSFET's

Power semiconductor device structures and assemblies with improved heat dissipation characteristics and low impedance interconnections include a thermally-conductive dielectric layer, such as diamondlike carbon (DLC) overlying at least portions of the active major surface of a semiconductor chip, with vias formed in the dielectric layer in alignment with contact pads on the active major surface. A patterned metallization layer is formed over the thermally-conductive dielectric layer, with portions of the metallization layer extending through the vias into electrical contact with the chip contact pads. A metal structure is electrically and thermally coupled to selected areas of the patterned metallization, such as by solder bonding or by a eutectic bonding process. In different embodiments, the metal structure may comprise a metal conductor bonded to the opposite major surface of another power semiconductor device structure, a heat-dissipating device-mounting structure, or simply a low-impedance lead.

Direct stacked and flip chip power semiconductor device structures

A modified valley fill circuit, including a main ballasting inductor for supplying an electrolytic capacitor, has an additional charging winding on the main ballasting inductor for charging the electrolytic capacitor to a predetermined voltage which maximizes the power factor of the input current by optimizing the conduction angle of the input current. In a discharge lamp ballast, the modified valley fill circuit reduces the lamp current crest factor by controlling the frequency with a lamp current control loop.

Modified valley fill high power factor correction ballast

A multi-resonant boost power factor correction circuit includes a full-wave rectifier; a high frequency filter capacitance coupled across the input terminals of the full-wave rectifier; a series half-bridge converter; a diode connected between the output of the rectifier and the dc bus voltage such that its cathode is connected to a dc bus; a capacitance coupled between the output of the rectifier and the junction between the series-connected switching devices of the half-bridge converter; a resonant load circuit connected to the junction between the switching devices, including a resonant inductor, a resonant capacitor and a load, such as a fluorescent discharge lamp; and a driver circuit for alternately switching the switching devices via a dead time control for selecting a dead time after one of the devices switches off and the other device switches on. The multi-resonant boost high power factor circuit meets the IEC standard for low harmonic content on input current, thus operating with a very high power factor, and operates with a minimal number of circuit components. In addition, the circuit meets lamp current crest factor specifications for fluorescent discharge lamp ballasts and requires lower voltage power devices.

Multi-resonant boost high power factor circuit

A fixed duty ratio, variable frequency, square wave generator includes an astable multivibrator having a pair of resistors coupled in series between a supply voltage terminal and a capacitor, such as of a type implemented with a 555 timer, and further includes a JFET connected between the capacitor and ground. In a current-controlled version, the anode of a diode is connected to the gate of the JFET, and the cathode of the diode is connected to a sensing resistor for sensing current in a load. The multivibrator generates a ramp voltage across the capacitor which varies between predetermined fractions of the supply voltage with a fixed duty ratio. The capacitor of the multivibrator charges and discharges through the series connection of the resistors and the JFET channel resistance with charging and discharging times that vary with the input voltage to the JFET, thereby varying the generator frequency.

Variable frequency generator for resonant power feedback

A simulated load circuit for measuring the impedance of the arc discharge of an electrodeless discharge lamp of the type having an arc tube and an excitation coil for exciting the arc discharge in an ionizable fill contained therein includes: a secondary coil spaced apart from the excitation coil by a distance which is varied in order to vary the coupling coefficient between the secondary coil and the excitation coil; a fixed load resistance coupled to the secondary coil; and a variable matching network coupled in series or parallel with the load resistance, the impedance of the matching network being varied in order to vary the ratio of reactance to resistance of the load circuit. The distance between the secondary coil and the excitation coil is varied, and the impedance of the matching network is varied, until the input impedance of the load circuit is substantially equivalent to the operating impedance of the lamp. The simulated load circuit is useful for designing and testing ballast circuits for electrodeless discharge lamps and for providing measurements of arc discharge power and excitation coil efficiency.

Simulated load circuit for simulating the arc impedance of an

The resolution .DELTA.C of a binary capacitance ladder having a plurality of N branches is precisely determined by appropriately selecting the value of a fixed capacitor in each branch relative to the parasitic capacitance of a corresponding series-connected switch. The capacitance of each respective branch varies by 2.sup.n-1 .DELTA.C, where n is the number of the branch, adjacent branches being numbered sequentially. The total capacitance is variable between C.sub.Total and C.sub.Total -(2.sup.N -1).DELTA.C in steps of .DELTA.C, where C.sub.Total is the sum of the capacitances in the ladder with all switches closed, and C.sub.Total -(2.sup.N -1).DELTA.C is the capacitance of the ladder with all switches open. For any particular branch of the ladder, the switch capacitance may be further controlled by adding a fixed capacitance in parallel with the respective switch. Such a variable capacitance is useful as a tuning capacitor in an electrodeless HID lamp ballast.

Variable capacitor with very fine resolution

An electrodeless lamp (e.g., an electrodeless fluorescent lamp) includes a dielectric housing shaped to conform to a portion of a lamp envelope, which housed portion is opposite to a portion through which light is emitted. The dielectric housing includes a continuous conductor, i.e., a shorted turn, situated between the dielectric housing and the lamp envelope which conforms to at least a portion of the dielectric housing. The configuration of the shorted turn, in terms of the location and amount of surface area occupied thereby, is optimized to minimize interaction between the excitation coil and any metallic fixture and to avoid interfering with lamp starting and light output.

Virtual fixture for reducing electromagnetic interaction between an

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Schenectady, NY, United States of America

Sayed-Amr A El-Hamamsy