Design of wireless power supply optimized structure for capsule endoscopes

Wireless power transmission is an important method for powering wireless capsule endoscopes, but its efficiency is low, especially when the devices move freely in random positions and orientations. To improve the stability and efficiency of the endoscope in vivo, this study designed an optimization method for planar spiral coils utilized in wireless power transfer for capsule endoscopes. An optimized structure using six planar spiral coils was first proposed as the transmitting coil, and the efficiency of a series-parallel wireless power transmission model was analyzed. A theoretical model was then examined for the magnetic field vector distributions of the spiral-type transmitting coil by using an elliptic coordinate system. The relationship between the position of the receiving coil and the coupling coefficient was determined when the position and attitude changed. Finally, the experimental device of the wireless power supply system of the endoscope was designed with a class-E amplifier and Liz coil. The simulation and experimental results showed that the proposed method can generate high intensity magnetic field uniform, which can improve the efficiency of the wireless power transmission in the case of axial deviation and angular misalignment. The experimental results also indicated that the proposed scheme can meet the needs of the power supply of wireless endoscopes.