An Adjustable Wireless Power Transfer Design for Capsule Endoscopes

This paper presents a novel Wireless Power Transfer (WPT) system design employing a one-dimensional coil as receiver and consequently choosing a three-dimensional coil array as the transmitter for wireless capsule endoscopes (WCEs). The receiving coil (RC) is designed to be a one-dimensional solenoid to save space. The transmitting coil array (TCA) consists of several planar spiral coils arranged on the surface of human torso. The feeding amplitude and phase of each transmitting coil unit (TCU) in the TCA can be adjusted to change the magnetic field at the position of the RC. Thus, when the position and orientation of the RC is given, the power transfer efficiency (PTE) can be maximized based on the proposed optimization theory. To verify the proposed method, an example of WPT system operating at 13.56 MHz is established and simulated, and the minimum PTE (about3.18%) for various possible positions and orientations can be obtained.