| Capsule endoscope is the most effective method to obtain the image of the entire digestive tract.High-quality diagnosis requires the multifunctionality of the endoscope,which imposes higher requirements on the energy supply of the capsule endoscope.Because,the power capacity of existing batteries is limited and cannot meet the long-term application,wireless power transfer is an effective method to solve this problem.In the existing energy supply systems for capsule endoscope,the volume of power receiver is too large,the power transfer efficiency is low,and its stability is poor.How to use a small power receiver to achieve efficient and stable energy supply for capsule endoscopes remains a problem.Energy supply and high-rate data transmission for implanted medical devices are realized through wireless power transfer antennas and implantable RF antennas,the existing wireless power transfer and implantable antennas are structurally independent,resulting in a relatively large volume,this is not suitable for human implants.How to achieve an integrated structure with both functions in a smaller volume is a research hotspot of implanted medical devices.Firstly,this thesis conducts a theoretical research on the efficient wireless power transfer based on magnetic field focusing and proposes a magnetic field focusing method based on the maximum transmission power.Wireless power transfer of a fixed target is analyzed theoretically,Matlab calculation and electromagnetic full wave simulation are adopted to verify its high-efficiency.To solve the problem of mobile capsule location in magnetic field focused wireless power transfer,a method based on computed tomography human model reconstruction and time difference of arrival(TDOA)algorithm has been proposed.Based on the reconstructed human torso model,the arrangement and size of the transmitting coil are analyzed.Finally,an overall structure of wireless power transfer system with high stability is proposed.Secondly,a wireless power transfer verification system composed of a power receiving coil in capsule and an extracorporeal power transmitting system is designed.The proposed system consists of a receiving coil,a transmitting coil array,a power distribution network,phase shifters and variable gain amplifiers.A wireless power transfer verification system working at 13.56 MHz for mobile target is designed,which is based on magnetic field focusing.The variation of the transmission coefficients of the wireless power transfer system is measured when the capsule endoscope moved and rotated.The actual measured results show that the stability of the system reaches up to 89%.Thirdly,an implantable structure integrated with wireless power transfer and RF radiation is proposed,which is based on the magnetic resonant coupled wireless power transfer structure.The magnetic resonant coupled wireless power transfer system is analyzed based on the equivalent circuit model,and the design method of magnetic resonant coupled wireless power transfer system with high transmission efficiency is provided.Considering the speciality of the environment in human body,the constraints of the implantable design of magnetic resonant coupled wireless power transfer is proposed.An implantable integrated structure with power transfer and RF radiation is proposed,which is based on the basic structure of magnetic resonance coupled wireless power transfer system.The receiving coil in wireless power transfer system is reused as the radiator of RF radiation.A prototype with complete design process is proposed to verify the feasibility of the integrated structure.Finally,the experimental tests of the integrated structure on wireless power transfer operating at 40 MHz and RF radiation operating at 2.45 GHz ISM band are carried out.Experimental results proved the compatibility,stability and security of the integrated design.The measured results show that when it is applied to implanted medical devices,the integrated structure has significant advantages as compared to the published works. |
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