Measurement Of Electrical Parameters Of GHz Solenoid Microcoil

In response to the need for percutaneous wireless energy supply for micro devices embedded in the body,midfield wireless energy transmission uses millimeter-sized microcoils in the body for energy reception.The operating frequency of the system is increased from MHz to GHz.The efficiency of energy transmission depends on the coupling coefficient and impedance matching degree of the coil.Therefore,measuring the electrical parameters(including high-frequency resistance,inductance,high-frequency capacitance,resonance frequency,and quality factor)of the solenoid microcoil used for energy reception is very critical to the system design.For the measurement of electrical parameters of solenoid microcoils under laboratory conditions,this thesis studies two methods: scale-up method and TRL(Thru,Reflect and Line)de-embedding.This thesis analyzes the midfield wireless energy transmission system using the coupled mode theory and the multi-layer tissue model of the human body.It is concluded that the conditions for obtaining the maximum energy transmission efficiency are the GHz optimal frequency and impedance matching.On this basis,this thesis proposes to use the scale-up method to measure the electrical parameters of the millimeter-sized solenoid microcoil,that is,to measure the electrical parameters of the coil proportionally enlarged by the geometric size,and calculate the electrical parameters of the solenoid microcoil according to the measurement model.In order to establish the measurement model of the scale-up method,the analytical model of the relationship between the electrical parameters and the amplification factor is first established through the mathematical derivation of the empirical formula,and then the electrical parameters of the coil are extracted by HFSS and Q3 D software for the solenoid coils with different amplification factors.On this basis,curve fitting is performed to obtain a regression model of the relationship between the electrical parameters and the amplification factor.The results show that the two models are basically the same.In order to compare the measurement results of the scale-up method,this thesis uses the more mature TRL de-embedding method to measure the electrical parameters of the solenoid microcoil,deduces the de-embedding calculation process,and designs a high-frequency-resistant de-embedding device.The purpose of TRL de-embedding is to eliminate the influence of the fixture on the electrical parameter measurement of the solenoid microcoil.The network parameters obtained by multiple fixtures are used for matrix exchange to obtain the electrical parameters of the micro-coil.Two methods are used to measure the electrical parameters of the solenoid microcoil.Compared with the electrical parameters of the micro coil extracted by HFSS and Q3 D,the experimental measurement results show that the errors of the scale-up method are: high frequency resistance 1061.2%,inductance-8.6%,High frequency capacitance-25.8%,resonance frequency 19.8% and quality factor-90.4%;the errors of TRL de-embedding method are: high frequency resistance 2.7%,inductance-4.5%,high frequency capacitance 2.2%,resonance frequency-0.1% and quality factor-5.9%.The results show that the TRL de-embedding method can be used to measure the electrical parameters of the micro-coil under laboratory conditions,while the low-cost scale-up method is not suitable for the measurement of resistance and quality factor due to large measurement errors.