Research Of The Indirectly-Heated Terminating Type MEMS Microwave Power Sensor

Nowadays, there are several types of microwave power sensors. In this paper, the indirectly-heated type microwave power sensor is introduced. The indirectly-heated type microwave power sensor is composed of the CPW, the thermocouple contacts, the resistive terminations and the thermopile. A low-loss 50Ω micromachining coplanar waveguide transmission line provides the input connection to the matched resistive load which converts the incident RF energy into heat. The 50Ω matched resistive load is made up of two 100Ω shunt-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.The purpose of this paper is to design the indirectly-heated type microwave power sensor with high performances in sensitivity and responsivity. We hope the sensor have the following indices. The sensitivity of the sensor is 10mV/mW, the power range is 0.01-10mW, the frequency range is 3-20GHz and the burnout power is over 50mW.First, the structure is built in the paper. The basic principle of the indirectly-heated type microwave power sensor is researched and the relations between the performances and the sizes are confirmed. The structure of the sensor is optimized by analyzing the heat transfer, and heat distribution of the sensor is simulated by Coventorware and ANSYS. Three structures of the microwave power sensor are all simulated, and according to the results, the best one is chosen to be the final structure of the sensor. Because the sensor is used in high frequency, the existing of the thermopile and the pads will influence the frequency range of the sensor. In this paper, this is simulated using HFSS software by calculating the return loss.At last, on the basis of the structure, layout and the fabrication of the sensor are designed according to the GaAs process of No. 55 institute of Ministry of Information Industry.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.