S. Yabukami

A new permeance meter based on both lumped elements/transmission line theories

We have developed a new permeance meter in the 1 MHz-1.5 GHz range using either a microstrip pickup coil or a shielded loop pickup coil. Both pickup coils and the driving plates are free from LC resonance due to impedance matching. In the MHz range we must consider signal-to-noise ratio of the pickup coil. In the GHz range we must eliminate the voltage induced by the electric field, and an electromagnetic higher order mode in the driving plates.

Motion capture system of magnetic markers using three-axial magnetic field sensor

We have developed a magnetic motion capture system consisting of up to two magnetic markers (Nd-Fe-B magnet) and four three-axial sensors. The position and orientation of the magnetic markers (dipole) are detected by measuring the magnetic field of markers. Position accuracy of one marker is about 3 mm when a marker is located 150 mm from a sensor, position accuracy of two markers is about 20 mm when the markers are located 150 mm from sensors. The most common error source is crosstalk between the cores of three-axial sensors.

A new 1 MHz-2 GHz permeance meter for metallic thin films

We have developed a permeance meter in the 1 MHz-2 GHz range using a shielded loop type pickup coil. The effect of grounding between drive coil and pickup coil was analyzed using time domain reflectometry (TDR). The grounding increased the output voltage and eliminated the multiple reflections in the drive coil. Using the grounding, magnetic thin film permeance can be measured accurately over a wide frequency range. The complex permeance is shown of a l /spl mu/m thick Co/sub 85/Nb/sub 12/Zr/sub 3/ film.

Numerical Study on the Improvement of Detection Accuracy for a Wireless Motion Capture System

A detection technique having an accuracy of better than 1 mm is required for body motion analysis in the field of medical treatment. A wireless magnetic motion capture system is one such effective detection technique. We propose a candidate system using an LC resonant magnetic marker (LC marker). Previous studies have showed that the system is capable of repeatable position detection accuracy of better than 1 mm if the system has an adequate signal-to-noise (S/N ratio). However, there are some cases in which the detection results include unignorable errors because some approximations, e.g. a magnetic dipole assumption of the LC marker, are applied to solve the inverse problem to determine the position and orientation of the LC marker. Therefore, a numerical analysis is employed to realize a motion capture system having a high detection accuracy. To elucidate the problem of detection error, the influence of variations in the sizes of the LC marker and the pick-up coil are considered in the numerical simulation. After studying the analysis, the main cause of detection error is determined to be the size of the pick-up coil rather than the size of the LC marker. It was also is found that a pick-up coil measuring 10 mm in diameter with a wound coil width of 1 mm achieves a detection accuracy of better than 0.1 mm.

A high frequency carrier-type magnetic field sensor using carrier suppressing circuit

A highly sensitive high frequency carrier-type magnetic field sensor based on the giant magnetoimpedance effect has been developed. It has been combined with a high frequency carrier suppressing circuit to reduce carrier phase noise dramatically. Highly sensitive magnetic field resolution of 8.8/spl times/10/sup -7/ Oe (8.8/spl times/10/sup -11/ T) was demonstrated.

Development of multilayer planar flux sensing coil and its application to 1 MHz–3.5 GHz thin film permeance meter

Abstract We have developed a new planar flux sensing coil using multilayer printed wiring board fabrication technique. The coil is useful for high frequency magnetic flux sensing because the coil is sensitive to the magnetic field and insensitive to the electric field. A 1 MHz–3.5 GHz broad bandwidth thin-film permeance meter is developed by using parallel plates with short plate and shielded loop pickup coil combination. We investigated the upper frequency limit of permeance measurement is given by the minimum value of standing wave position at the center of pickup coil.

Noise analysis of a 1 MHz–3 GHz magnetic thin film permeance meter

We analyzed the permeability measurement error of a low permeance thin film. We clarified that the noise voltage was excited by a current loop which is composed of the coaxial cable and the ground plane. The current loop should be removed for high sensitivity of the permeameter. The permeability of a high electrical resistivity film (CoFeHfO) has been demonstrated 1 MHz–3.5 GHz.

Wireless Magnetic Position-Sensing System Using Optimized Pickup Coils for Higher Accuracy

With the aim of improving the detection accuracy of a wireless magnetic position-sensing system using an LC resonant magnetic marker, a pickup coil with an optimal size (10 mm in diameter × mm thick), as calculated by a previous simulation study, was used and tested in this paper. Our study confirmed that positional errors were reduced to a submillimeter order in the area within y=120 mm from the pickup coil array. On the contrary, in the area outside y=130 mm from the pickup coil array, the errors increased by about 0.5-2 mm compared to the results for the previous pickup coil size (25 mm in diameter × 2 mm thick). Regardless of the size of the pickup coil, however, compensation can be made for these positional deviations, including the influence of the mutual inductance between the LC marker and the exciting coil. After application of the compensation process, the detection results were corrected approximately to the actual positions of the LC marker.

Development of real-time and highly accurate wireless motion capture system utilizing soft magnetic core

Highly accurate wireless motion capture system using LC resonant magnetic marker has been developed. The marker consists of soft magnetic core with wound coil and a chip capacitor without battery or electric wires, driven wirelessly by the action of electromagnetic induction. The system realized the position accuracy is less than 1 mm within the space of 150 mm from the pickup coil array. Compared with dc magnetic system, the proposed system is applicable for precision motion-capturing under optically isolated space without magnetic shielding because the system is not influenced very much by the earth field noise.

Wireless Magnetic Motion Capture System—Compensatory Tracking of Positional Error Caused by Mutual Inductance

A wireless magnetic motion capture system using an LC resonant magnetic marker was developed and has been studied. The positional error of the system caused by mutual inductance between the exciting coil and the LC marker was examined. It has been found that the impedance change of the exciting coil due to a resonance of the LC marker perturbs the strength of the magnetic field which is used for marker excitation. The more a marker approaches the exciting coil, the larger it becomes. This fluctuation induces an error in the marker signal which is measured by the pickup coils and is necessary for positional calculation. Then, the compensatory process in consideration of the mutual inductance has been employed for positional calculation in order to improve the positional accuracy. From the compensation, the absolute positional accuracy is less than 2 mm within 140 mm of the pickup coil array