K. Murakami

Thin film cloth-structured inductor for magnetic integrated circuit

A thin-film cloth-structured inductor for MAGIC (magnetic integrated circuit) operation in the high-frequency range is described. To achieve high inductance in a small area, magnetic core arrays with low demagnetizing factor are utilized. To increase the frequency, which is limited by the resonant frequency, the magnetic-strip core arrays are divided into three parts and each core array is excited out of phase; that is, the inductor is composed of three unit inductors connected in series with low mutual coupling. Thus, the resonant frequency of the integrated inductor is high, and high-frequency operation is possible. The experimental inductor is 3*3 mm/sup 2/ in size. The inductance is about 300 nH at 100 MHz, which is about eight times as large as that of the air-core inductor. High inductance can be easily achieved by increasing the number of strip cores with high permeability. >

Temperature-sensitive amorphous magnetic flakes for intratissue hyperthermia

Abstract For intratissue hyperthermia, we have developed capsules contained temperature-sensitive amorphous metal flakes, which can also release anticancer agents. By applying an alternating magnetic field, the amorphous flakes continue to generate heat until the temperature reaches the Curie point. The maximum temperature of the capsule is controlled automatically within an accuracy of ±0.5 °C. In animal experiments, the capsules generate sufficient heat or intratissue hyperthermia with the enhanced release of the anticancer agent. By using the capsules, richly vascularized tumours, such as kidney or liver cancers, are considered to be treated by a multifunctional procedure consisting of embolization therapy, hyperthermia and chemotherapy.

A planar transformer utilizing a parametric oscillation

This paper describes a new magnetic device consisting of a 12 mm/spl times/12 mm planar magnetic path-type transformer utilizing a parametric oscillation. The device is formed from a stack of 50% Ni-Fe laminations or Fe/sub 3/Co/sub 70/Si/sub 15/B/sub 10/ laminations, and is composed of magnetic paths with three legs and two parallel paths connecting the ends of those legs. Rectangular slots are made in the centers of the outside edges of the parallel paths, to cause a parametric oscillation in the device. The device operates as a parametric transformer and has an excellent voltage regulation with respect to load variation.

A new planar inductor with ring-connected magnetic core

A planar inductor employing a ring-connected magnetic core has been devised. By connecting small planar ring cores in a matrix array, the magnetoresistance of the magnetic circuits in the core is reduced, and high inductance, which is about 1.5 times that of the conventional ring-core inductance, is achieved. By exciting the core with two coils arranged orthogonally, the stray capacitance, which restricts the upper limit of the useful frequency band, is decreased. The inductor is suitable for a microinductor operating at high frequency. The ring-connected core can be also used as a transformer with high coupling coefficient and low stray capacitance. >

Performance of a miniaturized planar parametric transformer having an excellent voltage regulation

The fundamental performance characteristics of a 5 mm/spl times/7 mm sized planar parametric transformer fabricated by the wire-electric discharge machine are investigated. An excellent voltage regulation which is less than 0.9% at the rated value is obtained, when the supply frequency f is equal to 500 kHz. The capability of a multi-output-type parametric transformer is clarified.

Planar Coil Inductor with Closed Magnetic Circuit

A break in the electrical or the magnetic path in a conductor or magnetic core is a serious problem for the fabrication of inductors. A planar-coil inductor with a closed magnetic circuit is proposed, and its characteristics are described. The conductor of the planar-coil inductor is patterned on a plane, in order to prevent the occurrence of disconnections in the conductor. To decrease the magnetic resistance, the cross-sections of core junctions, at which there is the risk of disconnection, are regulated. A trial-fabricated inductor consisted of one hundred magnetic cores, each of size 180 ¿m × 180 ¿m. The inductor dimensions were 2.3×2.3 mm2. The inductance of the device was 50 nH, and the resonance frequency was about 400 MHz.

A Laminated Core Type Parametric Induction Motor

A new type of a parametric motor using a laminated iron core is proposed in this paper. The structure and the fundamental performance characteristics of the motor are discussed. It is clarified that the output and efficiency of the trial motor are comparable to conventional single phase induction motors. The behavior of the magnetic flux in the stator core of the motor is also studied to understand the operating mechanism of the motor.

Studies on Frequency Characteristics of Micro Inductors

We performed analyses of the frequency response of cloth inductors and thin-film inductors using an amorphous core, applying both to miniature dc-dc converters. Because these inductors are used in high-frequency bands from 1 to 100 MHz, the frequency dependence of the inductance L, capacitance C and resistance R in the inductors cannot be disregarded. The undetermined coefficients in a least-squares calculation were found by expressing L, C and R in terms of the coefficients of an expansion in powers of the frequency. In examining the coefficients of the first and second powers of the frequency, the hysteresis loss can be distinguished from the eddy current loss in the inductors. Moreover, the difference between the iron loss and the copper loss can be clarified. The maximum value of the quality factor is obtained at a frequency at which the iron loss is equal to the copper loss. The results calculated using this procedure are in approximate agreement with experiment.

Solenoid-Type Thin-Film Micro-Transformer

In order to miniaturize magnetic devices, the operating frequency must be raised. We have studied thin-film microin-ductors with the aim of achieving a high operating frequency and reduced iron loss. In this paper, we propose a thin-film microtransformer with a high operating frequency, achieved by use of a multilayered magnetic film as the core. The magnetic core was made of amorphous CoFeSiB mono-layer film or CoFeSiB/SiO2 multilayered film. The induced magnetic anisotropy was controlled such that the coil exciting direction is along the hard axis. The total thickness of the magnetic layer was 3 ¿m, and the size of the core was 0.6×2.3 mm. The experimental transformers revealed that a multilayered core is useful for improving the transmission loss of transformers at high operating frequencies. A thin-film transformer was developed with a transmission loss of 2.7 dB between 100 MHz and 250 MHz, a value smaller than the 5.3 dB loss of a mono-layer-core device.

Some Considerations on the Directional Control of a Linear Parametric Motor

This paper describes two methods for the directional control of a linear parametric motor. The first uses a circuit-changing switch. The direction of this linear parametric motor can be controlled by exchanging the power supply circuit and tuning the capacitor circuit. In the second method, which we call separately excited control, the linear motor has two power supplies, and the velocity or direction of the mover can be easily controlled by regulating the primary voltage phase difference. The experimentally ascertained features of these two methods are described.