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Based on the basic principle of the phase locked loop, analyzes the structural characteristics of the loop filter technology and ADF4350; secondly, design and analysis of two order passive low pass filter, three order passive low pass filter, two order active low-pass filter, with parameters such as bandwidth, phase margin ADF4350 PLL, selection the loop filter is suitable for the actual situation; using ADIsimPLL software to determine the parameters and realize the optimization of S parameters on circuit simulation, optimized and then use ADS software to observe. Finally, according to the results of analysis to adapt to the situation three kinds of filter structure of ADF4350phase locked loop.

To meet the requirements of a large-scale soil moisture monitoring system, this dissertation developed a new type of capacitive soil moisture sensor based on the detection and amplification of the singal peak-to-peak value named PA-1 sensor. PA-1 sensor was calibrated and evaluated under static laboratory conditions. A new type of soil moisture sensor named PA-1 is developed, which is based on the relationship between soil moisture and soil relative permittivity. Circuit design, operating features and exterior design of the sensor are introduced. PA-1 is calibrated in solution samples using the standard calibration method. Calibration experiment results show that PA-1 has a very linear measurement curve. The performance of PA-1 is studied and compared to the widely used Decagon Company’s EC-5 capacitive soil moisture sensor. Experiment results show that PA-1 has advantages of high sensitivity, low temperature drift, strong tolerance to electromagnetic interference and low power consumption. Keywords: sensor, Precision Agriculture, low temperature drift, low power consumption.

In view of debris flow monitoring for complicated mountainous terrain, network topology is impacted by environmental change, this paper designing a structure-free network topology to enhance network robustness. While applying the weighted resampling algorithm, to avoid monitoring data loss, make sure fairness transmission sensor nodes. To solve the problem of energy consumption and the time delay in wireless sensor networks, a real-time data aggregation algorithm proposed to reduce the redundant information transmission, to improve the energy efficiency. The simulation results show that adopted the network model of data aggregation is effective in reducing the energy consumption and improves the quality of network communication, while meeting the requirements of real-time monitoring.