| This paper presents a new type of RF MEMS microwave power sensor, and have an in-depth theoretical study and design analysis.The RF MEMS microwave power sensor is introduced. The RF MEMS microwave power sensor is composed of the CPW, the resistive terminations and the thermopile. A low-loss 50Ωmicromachining coplanar waveguide transmission line provides the input connection to the matched resistive load,which converts the incident RF energy into heat. The 50Ωmatched resistive load is made up of two 100Ωshunt-wound resistors. The terminal resistors absorb the energy and convert it into heat, then, the temperature of the hot junction is increased, and at the cold regions, volts d. c. can be got, thus, we attain the relation between the output and the incident power. Si has some shortcomings in high frequency, so the microwave power sensor can't be made on the substrate of Si directly.GaAs is chosen to be the substrate. Thus, the sensor can not only have good characteristics, but also be compatible with the MMIC standard process.In order to design a new kind of RF MEMS microwave power sensor, which have a better performance than the existing microwave power sensors. I have researched a lot of microwave power sensors. So I hope the sensor have the following indices. The power range is 10uW～100mW,the sensitivity of the sensor is 3～4mV/mW; the frequency range is2～70GHz;the response time is4～6ms.In order to achieve the above-mentioned requirements, I did the following work:First, the basic structure of the RF MEMS microwave power sensor is designed.Second, studied the basic theory of RF and microwave, analyzed the electromagnetic fields and electromagnetic wave propagation characteristics of the CPW.Third, studied the working principle and the components of the RF MEMS power sensor; selected the materials,the geometric model and the performance parameters.Fourth, analyzed the heat transfer model of the sensor, optimized the entire structure of the sensor,and ultimately got the structure and calculated the performance parameters.Fifth, because the sensor is used in high frequency, using the high-frequency electromagnetic finite element analysis software ANSOFT HFSS, simulated the electromagnetic field distribution of the CPW and the condition of the resistor to absorb the electromagnetic waves. Based on the results of the simulation to optimize the structure of the sensor.Sixth, using the finite element analysis software ANSYS to get the the voltage and temperature's distribution of the thermocouple, in order to verify the SEEBECK effect, and to optimize the size of the thermocouple.Seventh, using the MEMS processing technology to produce the sensor, briefly introduce and analyze the processing technology.Compared to the known microwave power sensors, the senor designed in this paper has some good performances such as high sensitivity, fast responsivity and compatibleness with the MMIC standard process. |
