Carbon dioxide (CO2) gas sensor using surface acoustic wave (SAW) device based on Zinc oxide (ZnO) was developed and fabricated in this paper. The center frequency of SAW device is 203.528 MHz. The input and two output interdigital transducers (IDT) apodized by Morlet wavelet function can improve the side lobe rejection compared with uniform IDT. The ZnO film sensitive to CO2 gas was fabricated in measurement acoustic track of SAW device. Experiments results confirm that the CO2 gas sensor using SAW device based on ZnO film has good response characteristics to different concentrations CO2 gas. Furthermore, the CO2 gas sensor using SAW device based on ZnO film has good stability and linearity.
In order to track the ballistic re-entry target, a new kind of ballistic target tracking algorithm, square-root quadrature Kalman filter (SRQKF) algorithm, was proposed. The proposed algorithm is the square-root implementation of the quadrature Kalman filter (QKF). The quadrature Kalman filter is a recursive, nonlinear filtering algorithm developed in the Kalman filtering framework and computes the mean and covariance of all conditional densities using the Gauss-Hermite quadrature rule. The square-root quadrature Kalman filter propagates the mean and the square root of the covariance. It guarantees the symmetry and positive semi-definiteness of the covariance matrix, improved numerical stability and the numerical accuracy, but at the expense of increased computational complexity slightly.
In order to preserve the coverage and ensure the efficiency of Wireless Sensor Networks (WSNs), a distributed coverage-hole repair algorithm towards nodes failure is proposed in this paper. Every node has a energy threshold, if node’s energy is lower than its threshold, it sends a failure message to the nearest node and appoints it as the head node, the head node consideres all the neighbors of the failure node are preparatory boundary nodes at first, then judges every preparatory boundary nodes whether be a non-boundary node through the intersection angle with the failure node. In the last, the head node activates the redundant node within the sensing range of failure node which has the most boundary nodes as neighbor nodes. Analyzes and simulation on Matlab platform indicate that this algorithm has a low time complexity and the repair efficiency has a grate relation with node density and node sensing radius.
To solve complex measurement and difficult remote operation in the test for frequency response characteristic of SAW device, an automatic test system for frequency response characteristic of SAW device based on vector network analyzer is proposed. The system consists of the vector network analyzer, the crossover cable, the computer, the fixtures and the SAW device. The user interface of test system is developed with the VB language. By means of calling the VISA-COM library, the SCPI commands can send to the vector network analyzer. Many functions of the automatic test system for frequency response characteristic of SAW device include the settings of measurement parameters, the measurement calibration, the data storage, the data display, the data transmission, the marker analysis and the data output. By the actual measurement of a SAW device with the center frequency at 101.764MHz, the experimental results show that the transmission loss of SAW device is-27.532dB, and the reflection loss is-7.715 dB.
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