Research On Key Technologies Of RF MEMS Switch Attenuator

The attenuator is a common microwave device whose main function is to realize the level amplitude control of the microwave signal and realize the step attenuation of the microwave signal level by power attenuation.Mainly used in microwave spectrum analyzers,vector network analyzers,signal generators,power meters and other microwave test instruments.Because RF MEMS switches have good linearity,excellent RF performance and minimal power loss,MEMS switch-based attenuators can meet the requirements of miniaturization,high performance and low power consumption of modern microwave test systems.In this thesis,through the integrated research and design of MEMS switch and TaN resistor,the microwave performance and manufacturing process of the device are researched,and a 3-bit step attenuator based on MEMS switch is designed and manufactured.The paper firstly designed the overall structure of the attenuator,and then designed and optimized the RF MEMS switch,attenuation resistor network,power divider and direct corner respectively.A straight-plate RF MEMS switch,horn-type power divider structure and ?-shaped attenuation resistor network based on coplanar waveguide are designed.Through the HFSS simulation software,the attenuation performance of the attenuator is verified that the center value of insertion loss is better than 1.35 dB,the VSWR is less than 1.08 dB in DC ~ 20 GHz band and the attenuation accuracy is better than ± 1.6dB in the range of 0~70dB.these instruments have a wide range of applications in military defense and automated test equipment.For example,the signal generator is applied to the comprehensive performance evaluation of electronic systems such as radar,electronic warfare,and communication equipment.Aiming at the problem of traditional attenuator insertion loss and attenuation precision,a 4-bit RF MEMS attenuator design scheme is proposed.The paper studies the manufacturing process of RF MEMS attenuators.The TaN thin film resistor preparation process,electroplating gold process and polyimide sacrificial layer process were studied.The TaN thin film resistor preparation process,electroplating gold process and polyimide sacrificial layer process were studied.In the preparation process of TaN thin film resistors,the influence of power and partial pressure ratio on the resistance of the thin film was studied.In the sacrificial layer process,the sacrificial layer high-level spin coating method is mainly studied,which effectively improves the yield of the attenuator.The coplanar waveguide made by the Au plating process and the upper electrode of the switch have higher flatness.Finally,wafer level packaging of RF MEMS devices was studied.