T. Takura

Impedance Matching Method About Multiple Contactless Power Feeding System for Portable Electronic Devices

By the spread of portable electronic devices which need to charge own battery, it have an increased need for contactless power feeding system. To build a convenient desktop feeding system, it is necessary to feed wide area and adapt many kinds of devices. Because of this reason, our group researches a contactless power feeding system using electromagnetic induction on the low coupling between primary and secondary coil. It has only one primary coil, and secondary circuit has resonator made with inductor and capacitor. This resonator can work out wide feeding area and impedance matching for each load.

Basic evaluation of signal transmission coil in transcutaneous magnetic telemetry system for artificial hearts

In implantable medical devices such as artificial hearts, it is important to communicate device control and monitoring signals across the skin for its stable operation. Using the signal transmission coil pairs we have proposed, we studied through measurements and experiments the best carrier frequency, based on the frequency characteristics of the L/C resonance circuit that inherits in the coil geometry.

Improvement of communication area for implantable signal transmission system with ferrite chip core

Transcutaneous power and signal transmission system are useful for artificial hearts. The signal transmission system is important to control the implanted device and to monitor the inside condition. They do not have lines penetrating through the skin. The signal transmission coils are set on the power transmission coils. We have proposed integrated power and signal transmission system utilizing eight-figure coils. Using the signal transmission coil pairs we have proposed, we studied through measurements and experiments the communication area for implantable signal transmission system with a ferrite chip core.

Parameter Design for High-Efficiency Contactless Power Transmission Under Low-Impedance Load

Recently, demand for contactless power transmission techniques has been growing in various industrial fields. Electromagnetic induction is able to transfer high power with high efficiency. Power transmission circuits typically consist of a paired coil and capacitance for improving the efficiency. The coil frequency and configuration that gives a high quality factor is essential for high-efficiency transmission because the maximum efficiency depends on the product of the coupling coefficient between the two coils and the quality factor of the coils. However, the matching with the load resistance also needs to be discussed. We therefore propose a circuit constructed by inserting a short-circuited LC into the receiving circuit, which we call the LC-booster method. This method is highly practical because it allows one to use coils with high quality factors and to adjust the circuit to match the load resistance. We examine the relationship between the capacitance in the short-circuited LC and the power transmission efficiency.

Wireless power transfer by low coupling electromagnetic induction — LC booster

There are currently various proposals for method of wireless power transmission. Electromagnetic induction method has been known as a relatively efficient transmission method for a wide variety of application. Here we report the results of recent investigations about the “LC booster method,” a new electromagnetic induction-based system. This method make it possible to using Hi-Q Coil and load-matching, and enables power transmission in bands of several hundred kilohertz under low coupling condition.

Stabilization of input impedance for wireless power supply circuit

A wireless power supply transmits electrical energy from a power source to a load without the use of a connecting wire. There are a number of wireless power supply techniques including electromagnetic induction, electromagnetic radiation, and electrical conduction. Here, we have investigated methods that use electromagnetic induction. Typically, for electromagnetic induction, we assume that the load resistance will fluctuate during battery charging due to variations in the battery voltage. Therefore, to stabilize the electrical power supply, a steady input impedance of the transmission circuit is preferable such that the influence of load resistance fluctuations is minimized. To this end, we suggest a “series-parallel resonant circuit” for the transmission circuit that has this characteristic.

Development of wireless communication system in real-time internal radiation dose measurement system using magnetic field

In radiation therapy, excessive radiation occurs because the actual delivered dose to the tumor is unknown. To overcome this problem, we need a system in which the delivered dose is measured inside the body, and the dose data are transmitted from the inside to the outside of the body. In this study, a wireless communication system, using magnetic fields was studied, and an internal circuit for obtaining radiation dose data from an x-ray detector was examined. As a result, a communication distance of 200 mm was obtained. An internal circuit was developed, and a signal transmission experiment was performed using the wireless communication system. As a result, the radiation dose data from an x-ray detector was transmitted over a communication distance of 200 mm, and the delivered dose was determined from the received signal.

Miniaturization of Micro Implantable Devices With Thermosensitive Ferrite for Soft-Heating Hyperthermia

The soft heating method is one technique utilized in hyperthermia treatment. The heater that consists of thermosensitive ferrite is implanted into the body, and heated by high-frequency magnetic field. This study applies the soft heating method. A complex type of heater composed of thermosensitive ferrite wound on a metallic ring is created. This complex type of heater produces heat due to losses of hysteresis and inductive current than thermosensitive ferrite alone. Further, this heater can control the temperature of the heater by using the Curie-point. For this technique, it is necessary to miniaturize the heater and provide safety high performance. We applied the method of miniaturization to plating. The effect of plating is examined. As a result, we have approximated to the optimal thickness of the metallic ring.

Bidirectional Communication System for Magnetic Direct Feeding FES

Functional electrical stimulation (FES) is a type of therapy used for paralyzed patients. In FES, the implant direct feeding method is an ideal stimulus method. In this method, small stimulators are implanted in the paralyzed limbs, and magnetic coupling is used to simultaneously power the implants and enable digital communication with the mounted system. To realize this method, we have developed an implant antenna (magnetic connective dual-resonance antenna) that can transmit as well as receive signals and a mounted communication system that is responsible for supplying power and communication from outside the body to the implanted antenna inside of the body. However, to guarantee safe stimulation, this system requires the closed-loop control function. For this purpose, we have proposed a communication protocol that is inexpensive, and a new communication system that supports bidirectional communication. In this paper, we present the new protocol, the composition and mechanisms of the proposed system, and the experimental results that verify the efficiency of this system.

Assessment of Superimposed Signal and Power Transmission System in Implanted TES

Therapeutic electrical stimulation (TES) is electrical stimulation to treat disorders caused by abnormalities in nerves. We have been researching implanted TES that stimulates objective nerves directly inside the body. Prior to this, separate coils were used in implanted TES to transmit power and signals. However, the two-coil system presents several problems. For example, it is necessary to carefully design both coils because the one for power transmission is more powerful than the one for signal transmission, and the power magnetic field interferes with the signal magnetic field. That makes it extremely difficult to design these coils flexibly. To solve this problem, we have begun research on establishing a different method that would increase the flexibility with which coils could be designed. The concept underlying this new approach was to transmit power and signals simultaneously with the same magnetic field. To achieve this, we superimposed the signal on the power. In the first step in this research, we ascertained that this superimposed system of transmission could drive the system for implanted TES.