Capacitive micromachined ultrasound transducers (CMUTs) have broad application prospects in medical imaging, flow monitoring, and nondestructive testing. CMUT arrays are limited by their fabrication process, which seriously restricts their further development and application. In this paper, a vacuum-sealed device for medical applications is introduced, which has the advantages of simple manufacturing process, no static friction, repeatability, and high reliability. The CMUT array suitable for medical imaging frequency band was fabricated by a silicon wafer bonding technology, and the adjacent array devices were isolated by an isolation slot, which was cut through the silicon film. The CMUT device fabricated following this process is a 4 × 16 array with a single element size of 1 mm × 1 mm. Device performance tests were conducted, where the center frequency of the transducer was 3.8 MHz, and the 6 dB fractional bandwidth was 110%. The static capacitance (29.4 pF) and center frequency (3.78 MHz) of each element of the array were tested, and the results revealed that the array has good consistency. Moreover, the transmitting and receiving performance of the transducer was evaluated by acoustic tests, and the receiving sensitivity was −211 dB @ 3 MHz, −213 dB @ 4 MHz. Finally, reflection imaging was performed using the array, which provides certain technical support for the research of two-dimensional CMUT arrays in the field of 3D ultrasound imaging.
Abstract:Estimating the precision of a multichannel telemetry data system accurately and efficiently is important because of the high cost of flight experiments and the complexity of telemetry data. System precision is significantly determined by the crosstalk effect. This paper proposes an efficient precision estimation method for data acquisition system based on multichannel phase-shift rectangular waveforms. The experiments are conducted to test the precision of the multichannel data acquisition system. Experimental results show that the proposed approach can estimate the precision of the acquisition system accurately; this finding was further validated by comparing the results with those of the IEEE Std 1057-2007 method. In addition, the measurement time of the proposed method was significantly shorter. In contrast to the existing method, the proposed method can locate faulty signal channels rapidly and estimate system precision effectively and efficiently.
The telemetry data are essential in evaluating the performance of aircraft and diagnosing its failures. This work combines the oversampling technology with the run-length encoding compression algorithm with an error factor to further enhance the compression performance of telemetry data in a multichannel acquisition system. Compression of telemetry data is carried out with the use of FPGAs. In the experiments there are used pulse signals and vibration signals. The proposed method is compared with two existing methods. The experimental results indicate that the compression ratio, precision, and distortion degree of the telemetry data are improved significantly compared with those obtained by the existing methods. The implementation and measurement of the proposed telemetry data compression method show its effectiveness when used in a high-precision high-capacity multichannel acquisition system.
Based on the analysis of pattern matching algorithm and data compression algorithm, this paper develops a kind of common and fast real-time monitoring software model according to high cohesion and low coupling design principles of software engineering. This model carries out data compression in the process of pattern matching for monitoring data, which can effectively reduce system time consumption and ensure the real-time performance of monitoring system, and meanwhile it can be applied to different application environments after being configured by configuration module, improving the reusability of software..
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