Power Amplifiers for Electronic Bio-Implants

Healthcare systems face continual challenges in meeting their aims to provide quality care to their citizens within tight budgets. Ageing populations in the developed world are perhaps one of the greatest concerns in providing quality healthcare in the future. The median age of citizens in economically developed regions is set to approach 40 years by the year 2050, and reach as high as 55 years in Japan. This trend is likely to lead to strained economies caused by less revenue raised by smaller workforces. Another effect of ageing populations is the need of further care in order to remain healthy. This care varies from frequent check-ups to condition monitoring, compensation for organ malfunction and serious surgical operations. As a result of these trends, healthcare systems will face the task of servicing more people with more serious and expensive health services, all using less available funds. Effort is being focused on running cheaper and more effective healthcare systems and the development of technology to assist in this process is a natural research priority

Wireless Power Technology for Biomedical Implants

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Biomedical Engineering, Trends in Electronics, Communications and Software

Rapid technological developments in the last century have brought the field of biomedical engineering into a totally new realm. Breakthroughs in material science, imaging, electronics and more recently the information age have improved our understanding of the human body. As a result, the field of biomedical engineering is thriving with new innovations that aim to improve the quality and cost of medical care. This book is the first in a series of three that will present recent trends in biomedical engineering, with a particular focus on electronic and communication applications. More specifically: wireless monitoring, sensors, medical imaging and the management of medical information

Biomedical Engineering, Trends in Materials Science

Rapid technological developments in the last century have brought the field of biomedical engineering into a totally new realm. Breakthroughs in materials science, imaging, electronics and, more recently, the information age have improved our understanding of the human body. As a result, the field of biomedical engineering is thriving, with innovations that aim to improve the quality and reduce the cost of medical care. This book is the second in a series of three that will present recent trends in biomedical engineering, with a particular focus on materials science in biomedical engineering, including developments in alloys, nanomaterials and polymer technologies

Class-E self-oscillation for the transmission of wireless power to implants

This paper develops the concept of Class-E self oscillation for wireless power delivery to implantable sensors with the comparison of several topologies. Power amplifiers and oscillators are considered as two separate blocks in wireless power transmission. By combining these topologies into a self-oscillating power transmitter, greater efficiency can be achieved. Various topologies are compared with measured hardware results, determining that a crystal feedback network provides both accuracy and high power output. A new crystal feedback Class-E self oscillator has been implemented by transmitting power through 2 cm-thick biological tissue. The paper includes a second order modelling and design process that can be used to design a Class-E self oscillator as an inductive power transmitter as well as measured results

Class-E oscillators as wireless power transmitters for biomedical implants

This paper presents the use of Class-E oscillators as inductive power transmitters for implanted telemetry devices that transmit information sensed by biosensors. Several Class-E oscillators are compared with an equivalent Class-E amplifier, showing higher efficiency while maintaining frequency clarity, stability and accuracy. Energy has been successfully transferred to a receiving inductor 1.5 cm away, which has been rectified to produce a 1 V_DC signal

Harmonics-based bio-implantable telemetry system

Miniaturization is a key focus for medically implantable electronics such as Cochlear and Retinal prosthesis, and medical monitoring and recording applications. The need for low power dissipation is equally important, and power-hungry crystals and oscillators are commonly used to produce and control the implant's carrier transmission frequency. This paper presents a new harmonics-based method that allows this transmission frequency to be varied and controlled externally, while also minimizing the size and power requirements of certain implanted devices

Stacked spirals for use in biomedical implants

A new type of wireless transmission coil is proposed for biomedical implants. By stacking several spirals above one another, the space required for an implantable coil is miniaturised, the self-resonant frequency (SRF) of the spiral is reduced, as is the required power transmission frequency for the implanted device. A four-layer 15 mm x 15 mm spiral coil of seven turns was simulated in CST Microwave Studio (TM), and constructed and successfully tested in hardware

Practical considerations for high-frequency inductive links

Inductive power links are a popular method of wirelessly transferring power to small devices. High efficiency power transmitters such as the Class-E transmitter are the preferred choice for frequencies up to the low MHz range, however at frequencies above 100 MHz, the circuit does not produce a high enough efficiency. This paper investigates the consideration of parasitic elements of the transmission coils in the circuits, showing an improvement in the circuit’s performance

Ultra low frequency FM sensing of piezoelectric strain voltage

A new method of piezoelectric strain sensing is proposed, allowing measurements at lower frequencies than previously possible. Piezoelectric devices generally exhibit highpass characteristics when loaded, which causes difficulty in measuring at low frequencies using traditional methods. The method proposed in this article converts changes in the piezoelectric device's strain voltage to changes in capacitance with a high impedance varactor diode. The varactor diode forms part of a feedback network in a Colpitts oscillator, converting variations in capacitance to variations in frequency. The frequency variations are then demodulated using an FM demodulator, and demodulated signals down to 15mHz were achieved. Due to the high impedance of the varactor diode at low frequencies, this method allows the measurement of ultra low frequency variations, and holds the potential for a wireless link between the actuator and a demodulating receiver