Research On Inline MEMS Microwave Standing Wave Meter

With the rapid development of microwave communication and radar technology in the 21st century,the existence of standing waves has caused great harm to microwave communication and radar systems,not only increasing the loss of the transmission line,reducing the energy transmission efficiency,and even damaging the components in the system under special circumstances.Therefore,it is necessary to use a standing wave meter to detect whether the microwave communication and radar systems achieve impedance matching.With the rapid development of microwave radar and communication systems,modules such as microwave transceiver components will become more highly integrated and their self-detection tests will become more important and frequent.However,most of the existing microwave standing wave meters have the disadvantages of large size,high power consumption,and low integration.Therefore,in order to meet the self-detection requirements of microwave high-density integrated micro-systems and microwave radar systems,it is of great significance to design a microwave standing wave meter that meets the requirements of miniaturization,low power consumption,integration,low cost,and controllable working states.Based on the above-mentioned background and requirements,an inline MEMS microwave standing wave meter research is proposed,the main content of which is as follows.In terms of structure,the basic structure of an inline MEMS microwave standing wave meter is proposed.First,the MEMS microwave directional coupler is used in the MEMS microwave standing wave meter to extract the incident power and the reflected power to the coupling port and the isolation port.This thesis studies three kinds of MEMS microwave directional couplers,which use MEMS air bridges instead of bonding wires to achieve interconnection.Then,at the coupling port and isolation port of the MEMS microwave directional coupler,electrostatically driven MEMS microwave switches is designed.When the MEMS microwave standing wave meter is in the non-detecting state,almost no microwave power in the MEMS microwave directional coupler is coupled to the coupling port and the isolation port,while most of the microwave power is transmitted to the output port,reducing unnecessary loss.Finally,thermopile-based MEMS microwave power sensors is designed at the ends of the coupling port and the isolation port.The microwave power transmitted to the coupling port and the isolation port are respectively converted into DC output thermoelectric potential,and the standing wave ratio can be obtained by measuring and analyzing the output thermoelectric potential.In terms of models,construct a microwave system-level model of a MEMS microwave standing wave meter that includes lumped S parameters,microwave power-thermal-electric conversion mechanism,and electric-force-electromagnetic wave coupling mechanism,explore the sensing and control mechanism,and analyze the impact of key parameters(distance between main and secondary transmission lines and coupling line length)on the S-parameter performance of the standing wave meter.In terms of simulation,based on the structure parameters calculated by the above model,the mechanical properties of the MEMS microwave switch and the thermal performance of the MEMS microwave power sensor are optimized through simulation software such as ANSYS,to determine the structure parameters of the MEMS microwave switch and the MEMS microwave power sensor.The electromagnetic distribution and microwave performance of the MEMS microwave directional coupler and the MEMS microwave standing wave meter are optimized through simulation software such as HFSS,to achieve their low reflection loss,low insertion loss,high isolation,and stable coupling output performance.In terms of process,a manufacturing process of a MEMS microwave standing wave meter compatible with Ga As MMIC process is developed.An inductively coupled plasma dry method is used to etch the back of the substrate to form the substrate membrane of the MEMS microwave standing wave meter,which increases the thermal resistance and thereby improves its sensitivity.An oxygen plasma dry etching process is used to remove the photosensitive polyimide sacrificial layer to form a high-quality MEMS fixed-fixed beam.In terms of experiment,design the test method of the inline MEMS microwave standing wave meter and build test platforms to test and analyze the prepared chip.It can be obtained through experiments that when the MEMS microwave standing wave meter is in the detection state,the reflection loss S₁₁ in the Ka band is less or equal to-18.9 d B,and the minimum value appears at 31.7 GHz,which is-40.6 d B,and the insertion loss S₂₁ is in the range of-0.8?-1.5 d B.When the MEMS microwave standing wave meter is in the non-detection state,in the Ka band,the measured reflection loss S₁₁ is less or equal to-18.5 d B,and the minimum value appears at 32.2 GHz,which is-59.9 d B,and the insertion loss S₂₁ is in the range of-0.7?-1.4d B.When the MEMS microwave standing wave meter switches from the detection state to the non-detection state,in the Ka band,the reflection loss does not change much,and the absolute value of the insertion loss becomes small,indicating that the MEMS microwave standing wave meter has realized the state conversion function and inline measurement.When the input microwave power is between 0 and 500 m W,the output thermoelectric potential measured at the coupling port and the isolation port of the MEMS microwave standing wave meter has a good linear relationship with the input microwave power,indicating that the MEMS microwave standing wave meter can work normally at a higher power.When the output port of the MEMS microwave standing wave meter is connected to a microwave load with a standing wave ratio of 1.2 and 3.0 respectively,the sensitivity measured at the coupling port and the isolation port will increase with the increase of the standing wave ratio,verifying the validity of the design of the MEMS microwave standing wave meter.Therefore,this thesis proposes a complete set of design theory and implementation method of inline MEMS microwave standing wave meter,which can basically meet the current inline self-detection requirements of microwave communication and radar systems.And laid a theoretical and experimental foundation for the research of other related MEMS microwave devices.