Resonance frequency analysis of a dual-frequency capacitive micromechanical ultrasonic transducer for detecting high and low pressures simultaneously with high sensitivity and linearity

Abstract

A novel design of a dual-frequency capacitive micromechanical ultrasonic transducer (CMUT) that is capable of detecting two pressure ranges is proposed in this paper. The linear relationship between the pressure and the resonance frequency of the CMUT is exploited to achieve pressure detection within low and high pressure ranges, whereas the tendencies of the frequency response in the two cases are opposite. A dual-frequency CMUT array with two resonance frequencies is utilized to detect vacuum pressure ranges of 0–10 kPa and 20 kPa–101 kPa using frequency shifts around 200 kHz and 180 kHz, respectively, achieving good linearity and sensitivity in the two pressure ranges. The finite element method is utilized to optimize the structural dimensions, and then a dual-frequency CMUT sensor is fabricated by wafer bonding technologies. The experimental results show good agreement with the finite element model and demonstrate that the sensor features a high sensitivity of 441.08 Hz kPa−1 in the pressure range of 20–101 kPa and 50.57 Hz kPa−1 in the pressure range of 0–10 kPa. According to the theoretical analysis and finite element method, the structural parameters of the dual-frequency CMUT array can be altered to measure another two different pressure ranges. Furthermore, the detection of multiple pressure ranges may be realized by designing multi-frequency CMUT array, which is of great significance in the field of aviation, industrial control or other occasions where the detection of multiple pressure ranges is necessary.

Research on Novel CMUTs for Detecting Micro-Pressure with Ultra-High Sensitivity and Linearity

“…It is worth noting that these studies effectively reduced the stiffness of the membrane, through the method of grooving the membrane, and achieved an increase in the displacement of the membrane, which caused a reduction of the collapse voltage and an improvement of the measurement sensitivity. Among them, the structure of the pressure sensor made in [21] is the same as that of the traditional CMUT in this paper. Therefore, the sensitivities of the two are similar, and the difference of parameters is mainly caused by the parameters of the membrane.…”

“…In addition, a temperature compensation method was proposed to eliminate the negative influence of the external ambient temperature [20]. Zhang et al [21] developed a CMUT array which featured a sensitivity of 50.57 Hz/kPa in the pressure range of 0-10 kPa and 441.08 Hz/kPa in the pressure range of 20-101 kPa. Later, a novel dual-frequency CMUT that can simultaneously detect pressure and humidity was proposed for the first time by the group, which had good experimental performance [22].…”

Investigation of New Accelerometer Based on Capacitive Micromachined Ultrasonic Transducer (CMUT) with Ring-Perforation Membrane

“…Among many MEMS accelerometers, resonant accelerometers have the advantages of high measurement accuracy, strong antiinterference ability, and better long-term stability than other types of sensors. They have been extensively researched in recent decades [3][4][5], including medical devices, consumer electronics, aerospace, and automotive electronics [2,4,6].…”

A dual-frequency piezoelectric micromachined ultrasound transducer array with low inter-element coupling effects

“…Instead, micromachined ultrasonic transducer (MUT) technology provides a possible solution for DFUT array, in which the low and high frequency MUT cells can be interlaced on a scale smaller than the shortest wavelengths of the array, offering the promise of DFUT arrays with minimal deleterious grating and side lobes [10]. Compared to Capacitive MUTs (CMUTs) [11][12][13], Piezoelectric MUTs (PMUTs) do not need high bias voltage or small gap to ensure the transducer sensitivity [14]. Moreover, PMUTs exhibit larger capacitance, which means that the influence of system parasitic capacitance on coupling and sensitivity is not as significant as that of CMUT [15][16][17].…”