Research On High Performance RF MEMS Switch And Power Divider

Transmit/Receive(T/R)modules are one of the key components of the Radio Frequency(RF)radar systems and communication systems.Its performance and size affect the whole performance of the radar systems and communication systems directly.It can improve the performance and efficiency of the RF radar and communication systems while reducing its cost if RF Micro-Electro-Mechanical System(MEMS)switches are applied to T/R modules,However,through investigations,high driving voltage and reliability issues are the main factors in the development of RF MEMS switches.In addition,the RF power divider,as an indispensable component of the radar systems and communication systems,is mainly used to distribute RF signals.Then,through investigations,high insertion loss and reliability issues greatly affect the performance and size of the RF systems.Therefore,in response to the above problems,a RF MEMS switch with reconfigurable driving voltage and inline self-detection MEMS microwave power divider are explored,which can not only well meet the application of T/R modules in RF radar systems and communication systems,but also provide a technical idea for the design of new RF circuits.The main research contents of this paper include:(1)A RF MEMS switch with reconfigurable driving voltage has been presented,which solves the problem of excessively high driving voltage of the traditional electrostatic drive type RF MEMS switch.In the structure,by intentionally injecting an appropriate amount of charges into the dielectric layer on the driving electrode,the stable built-in potential can be formed in the dielectric layer,so that the driving voltage of the RF MEMS switch is reduced without changing the structural parameters.On the model,a mathematical analysis model of the RF MEMS switch is established based on the parallel plate capacitor theory,the influence of charge injection on the driving voltage is analyzed,and the correctness of the model is verified by finite element software.On the simulation,a built-in potential of 70 V is formed by optimizing the charging injection,which reduces the driving voltage of the RF MEMS switch from 84.6 V to 15.4 V.In addition,the reconfiguration of the driving voltage is researched when DC voltage excitation and RF power excitation exist at the same time,and the RF power excitation model under DC pre-bias voltage is constructed.Through the model,the relationship between the RF power required to drive the RF MEMS switch and the DC pre-bias voltage are analyzed under different application conditions,which lays a theoretical foundation for its application in near-zero RF sensor wake-up systems.(2)An inline self-detecting RF MEMS power divider based on MEMS power divider and inline MEMS power sensor is proposed,which can realize the real-time inline self-detecting power of RF MEMS power divider under broadband operation.In the structure,the use of a circular asymmetric coplanar strip line as the transmission line can reduce the electromagnetic coupling of signals between adjacent transmission lines and reduce the area of the chip.The use of the air bridge can realize the connection of separate ground wires and adjust the length of the transmission line to optimize the size of the chip by designing the structural parameters.The inline RF MEMS power sensors are installed at the ports of the RF MEMS power divider,which can realize real-time inline monitoring of the RF power at each port.On the simulation,for the Ka band,the return loss is less than-30 d B at the center frequency of 35 GHz,while the insertion loss is about-4.7 d B,in the whole Ka band,return loss is about less than-15 d B,while the isolation is less than-15 d B;at the same time,for the low frequency band from 0.1 to 10 GHz,the return loss is-25 d B at the center frequency of 5.8 GHz,and the insertion loss is about-4.3 d B,in the frequency range of 4 to 7 GHz,the return loss and isolation are both less than-15 d B.The results show that the design theory of the inline self-detecting RF MEMS power divider can be applied to different working frequency bands to meet the needs of the RF system.(3)The experimental research on the RF MEMS switch with reconfigurable driving voltage and the inline self-detecting RF MEMS power divider is carried out.Multiple RF MEMS switch samples are manufactured and tested,according to the test results,the feasibility of the designed RF MEMS switch with reconfigurable driving voltage based on the charge injection mechanism is verified initially;In the test where DC voltage excitation and RF power excitation exist at the same time,the DC pre-bias voltage is set to multiple values close to the driving voltage.It is observed that the RF power required to drive the RF MEMS switch is reduced from-9 d Bm to-27.8 d Bm,which verifies the possibility of the application of RF MEMS switches in RF sensor wake-up systems.Based on the Ga As Microwave Monolithic Integrated Circuit(MMIC)process,an inline self-detecting RF MEMS power divider is manufactured,and the size is about 2.5×2 mm~2.The RF and sensing performance of the divider have been tested.Experiments show that the return loss,isolation and insertion loss at the center frequency of 35 GHz are-24 d B,-28 d B and-5 d B respectively,in the frequency range of30.6 to 40 GHz,the return loss is less than-10 d B,while in the frequency range of 33.2 to 37.5 GHz,the return loss is less than-10 d B,in the whole Ka band,the isolation is less than-15 d B.The measured output thermal voltages at port 1,port 2 and port 3 are approximately linear with the input power,and their sensitivities are 2.50,0.65 and 0.80?V/m W respectively,which verifies the effectiveness of the inline self-detecting RF MEMS power divider for real-time inline detecting of RF power.The experimental tests show that it is feasible to apply the designed RF MEMS switch with reconfigurable driving voltage and inline self-detecting RF MEMS power divider to T/R modules.