Omnidirectional Inductive Powering for Biomedical Implants / Analog Circuits and Signal Processing (PDF)

In the year 2000, a capsule endoscope was introduced on the market for diagnosis of small bowel diseases. This pill, about one centimeter in diameter, takes images of the gastric track and transmits them wirelessly to the outside world. Since the capsule is battery powered, the limited energy budget restricts both the amount and the quality of images that can be shot. To resolve this limitation, Omnidirectional Inductive Powering for Biomedical Implants investigates the feasibility of inductive powering for capsule endoscopy and freely moving systems in general. The main challenge is the random position and orientation of the power receiving system with respect to the emitting magnetic field. Where classic inductive powering assumes a predictable or fixed alignment of the respective coils, the remote system is now free to adopt just any orientation while still maintaining full power capabilities. Before elaborating on different approaches towards omnidirectional powering, the design and optimisation of a general inductive power link is discussed in all its aspects. Useful rectifier and inverter topologies are presented, including a class E driver that copes with coil deformations. Special attention is paid to the interaction of the inductive power link with the patient's body. Putting theory into practice, the implementation of an inductive power link for a capsule endoscope is included in a separate chapter.