A wideband 8-12 GHz inline type microwave power sensor, which has both working and non-working states, is presented. The power sensor measures the microwave power coupled from a CPW line by a MEMS membrane. In order to reduce microwave losses during the non-working state, a new structure of working state transfer switches is proposed to realize the two working states. The fabrication of the power sensor with two working states is compatible with the GaAs MMIC （monolithic microwave integrated circuit） process. The experimental results show that the power sensor has an insertion loss of 0.18 dB during the non-working state and 0.24 dB during the working state at a frequency of 10 GHz. This means that no microwave power has been coupled from the CPW line during the non-working state.
A Fourier equivalent model is introduced to research the thermal transfer behavior of a terminating-type MEMS microwave power sensor.The fabrication of this MEMS microwave power sensor is compatible with the GaAs MMIC process.Based on the Fourier equivalent model,the relationship between the sensitivity of a MEMS microwave power sensor and the length of thermopile is studied in particular.The power sensor is measured with an input power from 1 to 100 mW at 10 GHz,and the measurement results show that the power sensor has good input match characteristics and high linearity.The sensitivity calculated from a Fourier equivalent model is about 0.12,0.20 and 0.29 mV/mW with the length at 40,70 and 100μm,respectively,while the sensitivity of the measurement results is about 0.10,0.22 and 0.30 mV/mW,respectively,and the differences are below 0.02 mV/mW. The sensitivity expression based on the Fourier equivalent model is verified by the measurement results.
The design, fabrication, and experimental results of an MEMS microwave frequency detector are presented for the first time. The structure consists of a microwave power divider, two CPW transmission lines, a microwave power combiner, an MEMS capacitive power sensor and a thermopile. The detector has been designed and fabricated on GaAs substrate using the MMIC process at the X-band successfully. The MEMS capacitive power sensor is used for detecting the high power signal, while the thermopile is used for detecting the low power signal. Signals of 17 and 10 dBm are measured over the X-band. The sensitivity is 0.56 MHz/fF under 17 dBm by the capacitive power sensor, and 6.67 MHz / μV under 10 dBm by the thermopile, respectively. The validity of the presented design has been confirmed by the experiment.
A terminating type MEMS microwave power sensor based on the Seebeck effect and compatible with the GaAs MMIC process is presented. An electrothermal model is introduced to simulate the heat transfer behavior and temperature distribution. The sensor measured the microwave power from –20 to 20 dBm up to 20 GHz. The sensitivity of the sensor is 0.27 mV/mW at 20 GHz, and the input return loss is less than –26 dB over the entire experiment frequency range. In order to improve the sensitivity, four different types of coplanar waveguide （CPW） were designed and the sensitivity was significantly increased by about a factor of 2.
A terminating type MEMS microwave power sensor based on the Seebeck effect and compatible with the GaAs MMIC process is presented.An electrothermal model is introduced to simulate the thermal time constant. An analytical result,about 160 ms,of the thermal time constant from the non-stationary Fourier heat equations for the structure of the sensor is also given.The sensor measures the microwave power jumping from 15 to 20 dBm at a constant frequency 15 GHz,and the experimental thermal time constant result is 180 ms.The frequency is also changed from 20 to 10 GHz with a constant power 20 dBm,and the result is also 180 ms.Compared with the analytical and experimental results,the model is verified.
