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Sensors 2014, 14(12), 23843-23870; doi:10.3390/s141223843

Automatic Frequency Controller for Power Amplifiers Used in Bio-Implanted Applications: Issues and Challenges

Department of Electrical, Electronic & Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor, Malaysia
Department of Electrical and Electronic Engineering, University of Technology-Iraq, Baghdad 35010, Iraq
Author to whom correspondence should be addressed.
Received: 8 October 2014 / Revised: 6 November 2014 / Accepted: 24 November 2014 / Published: 11 December 2014
(This article belongs to the Section Biosensors)
View Full-Text   |   Download PDF [1216 KB, uploaded 11 December 2014]   |  


With the development of communication technologies, the use of wireless systems in biomedical implanted devices has become very useful. Bio-implantable devices are electronic devices which are used for treatment and monitoring brain implants, pacemakers, cochlear implants, retinal implants and so on. The inductive coupling link is used to transmit power and data between the primary and secondary sides of the biomedical implanted system, in which efficient power amplifier is very much needed to ensure the best data transmission rates and low power losses. However, the efficiency of the implanted devices depends on the circuit design, controller, load variation, changes of radio frequency coil’s mutual displacement and coupling coefficients. This paper provides a comprehensive survey on various power amplifier classes and their characteristics, efficiency and controller techniques that have been used in bio-implants. The automatic frequency controller used in biomedical implants such as gate drive switching control, closed loop power control, voltage controlled oscillator, capacitor control and microcontroller frequency control have been explained. Most of these techniques keep the resonance frequency stable in transcutaneous power transfer between the external coil and the coil implanted inside the body. Detailed information including carrier frequency, power efficiency, coils displacement, power consumption, supplied voltage and CMOS chip for the controllers techniques are investigated and summarized in the provided tables. From the rigorous review, it is observed that the existing automatic frequency controller technologies are more or less can capable of performing well in the implant devices; however, the systems are still not up to the mark. Accordingly, current challenges and problems of the typical automatic frequency controller techniques for power amplifiers are illustrated, with a brief suggestions and discussion section concerning the progress of implanted device research in the future. This review will hopefully lead to increasing efforts towards the development of low powered, highly efficient, high data rate and reliable automatic frequency controllers for implanted devices. View Full-Text
Keywords: bio-implanted devices; bio-telemetry systems; power amplifiers; automatic controller; inductive coupling link bio-implanted devices; bio-telemetry systems; power amplifiers; automatic controller; inductive coupling link

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Hannan, M.A.; Hussein, H.A.; Mutashar, S.; Samad, S.A.; Hussain, A. Automatic Frequency Controller for Power Amplifiers Used in Bio-Implanted Applications: Issues and Challenges. Sensors 2014, 14, 23843-23870.

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