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This communication investigated the dust effect on microelectromechanical system (MEMS) thermal wind sensors, with an aim to evaluate performance in practical applications. An equivalent circuit was established to analyze the temperature gradient influenced by dust accumulation on the sensor's surface. The finite element method (FEM) simulation was carried out to verify the proposed model using COMSOL Multiphysics software. In experiments, dust was accumulated on the sensor's surface by two different methods. The measured results indicated that the output voltage for the sensor with dust on its surface was a little smaller than that of the sensor without dust at the same wind speed, which can degrade the measurement sensitivity and accuracy. Compared to the sensor without dust, the average voltage was reduced by about 1.91% and 3.75% when the dustiness was 0.04 g/mL and 0.12 g/mL, respectively. The results can provide a reference for the actual application of thermal wind sensors in harsh environments. [ABSTRACT FROM AUTHOR]

An analytic model of dual-layer-structure (DLS) microelectromechanical system (MEMS) thermal wind sensor was proposed in this article. Heat conduction and heat convective theory were applied to obtain the temperature difference between upstream and downstream under different wind speeds and directions. Simulation by finite element method (FEM) was performed to verify the proposed model. The DLS MEMS wind sensor was fabricated by commercial foundry with two polysilicon layers and one metal layer. After being packaged, the wind sensor was tested based on front surface sensing mode in the wind tunnel up to 33 m/s. The results demonstrated that the wind speed measurement agrees with the proposed model well and the average error of output voltage was no more than 8 mV. Moreover, the measured wind direction increased with the actual value marked on the base from 0° to 360°, which was consistent with the established model. Moreover, the average error was close to 3.7° and the maximum value was no more than 6.38°, which may be caused by asymmetry in scribing and packaging. [ABSTRACT FROM AUTHOR]

Modeling of the packaged wind sensor operating on constant power (CP) mode is proposed in this paper. The proposed model is based on the theory of heat conduction and forced convection. The presented model indicates that the total output dc voltage is proportional to the square root of the wind speed, and ${V}_{x}$ , as well as ${V}_{y}$ , varies with the wind direction based on cosine function. The wind sensor is fabricated by microelectromechanical systems (MEMS) technology and packaged with the glue. The test is performed in the wind tunnel and the measured results indicate an agreement with the presented model. The relative error of voltage for the wind speed is less than 14% up to 30 m/s, while that for the wind direction is no more than 10.7% from 0° to 360°. [ABSTRACT FROM AUTHOR]

A self-heated double Wheatstone bridge configuration for a 2-D wind sensor is presented. Without a central heating element, eight thermistors are symmetrically arranged in two orthogonal directions, and four of them in each direction make up a Wheatstone bridge. The eight thermistors simultaneously act as the heating sources and temperature sensing elements. By applying the constant current supply to the bridge, the terminal voltage across the bridge and the bridge output voltage are utilized to measure the wind speed and direction, respectively. The 2-D wind sensor has been simulated numerically and fabricated directly on the ceramic substrate. Experiments demonstrate that the measured speed varies from 0 to 40 m/s with an error less than ±2 m/s while the measured direction spans from 0° to 360° with an error less than ±3° after calibration. The double bridge configuration greatly simplifies the measurement and control circuits for the 2-D wind sensor. [2018-0171] [ABSTRACT FROM AUTHOR]

In this paper, we present a robust, low-power and wide-range MEMS thermal wind sensor, which is based on a glass reflow process. A general analytical model is first proposed for obtaining the heater's temperature and the temperature distribution on the sensor surface. Based on this model, the effect of the sensor's geometry and package on the sensor's performance is investigated. These results demonstrate how the measurement range and the sensitivity of the sensor can be optimized with a change in structural geometries. Besides, it has shown that the package structure of the sensor is also important for obtaining the required performance. Then, calculated results are validated with 2-D finite element method (FEM) solver CMOSOL. It is found that although there is some deviation between theoretical and simulation results, the model can have good reference value for latter MEMS thermal wind sensor design. Finally, the sensor is characterized in a wind tunnel. At a constant heating power of 14.5 mW, measurement results show that the sensor can detect airflow speeds of up to 33 m/s, with an accuracy better than 0.5 m/s at low speeds and 5% Full-Scale at high speeds. Airflow direction can be determined in a 360° range with an accuracy better than 5°. In addition, the sensor also shows a good repeatability. [ABSTRACT FROM AUTHOR]

The cascaded power sensor, including terminating-type one and capacitive-type one is modeled in this paper. The electric-heat-electric conversion model in the terminating-type power sensor is based on Fourier conduction equation, and the electric-force-electric conversion model in the capacitive-type power sensor is based on strain equation. Experiments are performed to verify the model. For the incident power from 1 to 100 mW, the measured sensitivity of the terminating-type is 0.124 mV/mW and the sensitivity of the model is 0.135 mV/mW. For the incident power from 100 to 150 mW, the sensitivity of the capacitive-type sensor is about 0.156 fF/mW, while the calculated sensitivity of the model is 0.165 fF/mW. The comparison demonstrates that the related error of the voltage is less than 9% and the related error of the capacitance change is less than 6%. [ABSTRACT FROM PUBLISHER]

This paper reports a high dynamic range power sensor based on GaAs process and MEMS technology. The proposed sensor consisted of the terminating-type sensor and the coupling-type sensor. The former measures low power while the latter is for high power detection. This device is designed and fabricated by GaAs MMIC process. In order to optimize microwave performance, impedance compensating technology by increasing the slot width of the CPW transmission line is developed. Related calculation and simulation are also presented in this paper. The microwave performance test reveals that the return loss is close to −28 dB@8 GHz, −27 dB@10 GHz and −26 dB@12 GHz, respectively. The microwave power response experiment is investigated from 1 mW to 150 mW. For the incident power less than 100 mW, the terminating-type sensor operates and the measured sensitivity is about 0.095 mV/mW@8 GHz, 0.088 mV/mW@10 GHz and 0.084 mV/mW@12 GHz, respectively. Related lumped equivalent circuit models of the loaded resistors are developed to explain the loss induced by the frequency of the signal. For the incident power with the improved dynamic range from 100 mW to 150 mW, the coupling-type sensor is adopted and the measured sensitivity is about 9.2 μV/mW@8 GHz, 8.6 μV/mW@8 GHz and 9.0 μV/mW@12 GHz, respectively. [ABSTRACT FROM AUTHOR]

A 2-D MEMS wind sensor based on $\Delta \text{P}$ (power difference) thermal feedback control is presented. The sensor consists of four outlying heaters and four inlying thermistors in two orthogonal directions on ceramic substrate. A $\Delta \text{P}$ thermal feedback control system is applied to eliminate the flow-induced temperature difference between upstream and downstream so as to achieve a temperature-balanced mode. This applied power difference among the four heaters is a measure for the wind speed and direction. Experimental results demonstrate that the measured speed varies from 0 to 40 m/s with an error less than ±0.5 m/s while the measured direction spans from 0° to 360° with an error less than ±2°. [2017-0286] [ABSTRACT FROM AUTHOR]

In this paper, a novel in-line type frequency detector is proposed based on a MEMS membrane for X-band applications. In this design, the MEMS membrane stands above the signal line of the CPW transmission line and acts as a coupling capacitance. A certain percentage of the incident power, as a function of the frequency, is coupled to the microwave power sensors. Finally, the frequency of the incident RF signal is able to be deduced by measuring the output thermovoltage of the microwave power sensor based on the Seebeck effect. The design, lumped equivalent circuit model and simulation are presented. The in-line type power sensor is fabricated by the GaAs MMIC process based on MEMS technology. The measured return loss is less than −13 dB and the insertion loss is better than 1.3 dB over the frequency band of 8–12 GHz. The RF frequency measurement demonstrates that the output thermovoltage increases from 0.22 to 0.35 mV when the frequency varies from 8 to 12 GHz under the input power of 10 dBm. [ABSTRACT FROM AUTHOR]

An 8-12 GHz microwave frequency detector is presented, which is based on MEMS power sensors, by sensing the phase delay of two separated signals in two different tracks. The phase delay, proportional to frequency of the input microwave signal, leads to variation of the output power. Two different kinds of MEMS power sensors, a thermoelectric microwave power sensor and a MEMS capacitive power sensor, are adopted to measure the variation. The former is used for measuring the lower power while the latter for the higher one. The presented detector has been designed, optimized and fabricated successfully using the GaAs MMIC process. For the microwave signals of 10, 15 and 20 dBm, the measured result shows that the output thermovoltage decreases with the frequency based on the thermoelectric microwave power sensor and sensitivities of the detector better than 0.033, 0.110 and 0.343 µVMHz-1 are measured, respectively. Furthermore, the sensitivity of detector is directly proportional to the power of the input microwave signal. For the microwave signals of 24 dBm, the measured result shows that the capacitance decreases with the frequency based on the MEMS capacitive power sensor and the sensitivity of 0.013 fF MHz-1 is measured. The frequency measurement demonstrates the validity of the presented design. [ABSTRACT FROM AUTHOR]

In this letter, a new cascaded terminating-type and capacitive-type power sensor is proposed for −10- to 22-dBm application. The terminating-type power sensor is designed for the low-power detection, while the capacitive-type power sensor is for high-power detection. This device is based on microelectromechanical systems (MEMS) technology and fabricated by GaAs monolithic microwave integrated circuit process. The tested return loss is about −23 dB at 8 GHz, −21.5 dB at 10 GHz, and −20 dB at 12 GHz. For the incident power from 1 to 100 mW, the terminating-type sensor operates, and the measured sensitivity is close to 0.132 mV/mW at 8 GHz, 0.124 mV/mW at 10 GHz, and 0.125 mV/mW at 12 GHz, respectively. For the incident power from 100 to 150 mW, the capacitive-type sensor works, and the measured sensitivity is about 0.160 fF/mW at 8 GHz, 0.156 fF/mW at 10 GHz, and 0.145 fF/mW at 12 GHz, respectively. [ABSTRACT FROM AUTHOR]

• Finite element simulation of miniaturized housing structure for 3D packaged MEMS thermal wind sensor model. • Experiments are also done firstly, an agreement between simulation and experiment is obtained. • Provide a reference for the design and manufacture of MEMS thermal wind sensor miniaturization package. [Display omitted] This paper, for the first time, investigates the effects of miniaturized housing structure with various parameters on micro-electro-mechanical systems (MEMS) thermal wind sensors by simulation and experiments. Pillar diameter, number, height and curve-shaped top cover with different radian are considered to find out their influence on sensors performance. In the simulation, finite element method (FEM) software COMSOL is applied to simulate the 3D packaged sensor model. Then sensors with different housing parameters are tested in the wind tunnel based on thermal calorimetric principle, which uses flow-induced temperature gradient between symmetrically distributed thermistors to represent wind speed. An agreement between simulation and experiment is obtained, and the results demonstrate that the device's performance can be improved with smaller pillar diameter, more pillar number, and smaller pillar height. Moreover, the curved roof is designed, which provides a possibility for high wind speed measurement. [ABSTRACT FROM AUTHOR]