Research Of In-line Microwave Power Detection System And Its Theoretical Model

Now,the MEMS microwave power detection system mainly includes two forms: terminal type and in-line type.The in-line microwave power detection system is widely concerned because it can realize the in-line measurement of microwave power without depleting the power to be measured.However,due to the influence of microwave performance,the coupling capacitance is relatively small and the sensitivity is not high.The yield rate is lower in the fabrication of MEMS beam.In order to solve the problems above,a parallel double MEMS beam structure is proposed in this paper,and based on the parallel double MEMS beam structure,the capacitance in-line and coupling in-line microwave power detection system are designed,respectively.The sensitivity of the in-line microwave power detection system and the yield rate in the process of MEMS beam fabrication are both improved based on structure design.The corresponding theoretical model is established to guide the design of the in-line microwave power detection system,and the theoretical model is verified with the finite element simulation.The main research contents of this work are as follows:(1)The theoretical models of microwave performance and coupling factors of MEMS beams are established and the influencing factors are studied.A double MEMS beam structure in parallel is proposed.The theoretical model of microwave performance and coupling factor of parallel double MEMS beams is established,and the effects of impedance value and electric length of coplanar waveguides between double MEMS beams on microwave performance and coupling factor are studied.It is found that the structure of parallel double MEMS beams is suitable for capacitive in-line and coupling in-line microwave power sensors.(2)Based on the parallel double MEMS beam structure,the capacitive in-line microwave power detection system and the coupling in-line microwave power detection system are designed.The microwave performance model,sensitivity model and overload power model of capacitive in-line microwave power detection system are established.The microwave performance model,sensitivity model and heat transfer model of the coupling in-line microwave power detection system are established.The influence of different structural parameters on the performance of the in-line microwave power detection system is discussed.The capacitive in-line microwave power sensor and coupling in-line microwave power detection system are optimized according to the theoretical model.Finite element simulation is used to verify the feasibility of the optimization scheme,and an in-line microwave power detection system with optimized structure is designed.(3)The fabrication process of in-line microwave power detection system is studied.Two kinds of in-line microwave power detection system are fabricated and their microwave performance and sensitivity were tested.The simulation results show that the reflection loss of the capacitive in-line microwave power detection system before optimization is less than-20 d B,and less than 1% of the microwave power will be reflected.The reflection loss of the capacitive in-line microwave power detection system is less than-34.4d B,and less than one thousandth of the microwave power will be reflected.The maximum temperature of the load resistance of the coupling in-line microwave power detection system before optimization is 316.818 K,and the temperature difference of thermopile is 5.374 K.The maximum temperature of load resistance of the optimized coupling in-line microwave power detection system is 321.15 K,and the temperature difference of thermopile is 9.866 K.The experimental results show that the reflection loss of capacitive in-line microwave power detection system is less than-11.5d B in the frequency range of 8-12 GHz.The insertion loss is better than-3.7d B in the frequency range of 8-12 GHz.The reflection loss of the coupling in-line microwave power detection system is less than-9.3d B in the frequency range of 9-11 GHz.The insertion loss is better than-2.9d B in the frequency range of 9-11 GHz.The sensitivity of the coupling in-line microwave power detection system is 1.1m V/W,1.45 m V/W and 0.85 m V/W at 9,10 and 11 GHz,respectively.The linearity of the coupling in-line microwave power detection system 99.82%,99.85%and 98.87% at 9,10 and 11 GHz,respectively.