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Wireless sensor network is a data-centric self-organizing wireless network. Nodes in the network -intensive, huge and deployed in a very wide area ; dynamic network topology and network with self- organizing and self-tuning features. The network node with low cost , small size , energy is very limited computing power, storage and communication capabilities with limited features. Node energy to focus on the design process is one of the key factors to consider . Abroad for wireless sensor networks mainly focused on MAC algorithm , routing algorithms, data fusion location algorithm and algorithms . In the protocol stack separated into functional definition, hierarchy data frame format , the interface between the layers , each layer specification management are considered small. Of course, the hardware development abroad in the design and technology are in a leading position. Increasing function of the chip , channel more and more, faster and faster transfer rates . RF front-end sensor for wireless transmission system is an important component. Antenna receiver front-end to a weak signal through low-noise amplifier, and then, with a band -pass filter to filter out the noise , then the signal is amplified , to the extent permitted ADC . Transmitting end is QPSK modulated signal by the band -pass through the filter will filter out the noise band , then the signal is amplified , the required power , the signal emitted by the switch . Entire RF front end by a low -noise amplifier , controllable gain amplifier , power amplifier, single-pole double -throw switch (SPDT), surface acoustic wave (SAW) filters , working frequency is 300M-400MHz. In order to achieve the required power gain , the receiver uses two low-noise amplifier , a controllable gain amplifier , transmitter using a MMIC power amplifier . Are also made of the surface acoustic wave filter of smaller size , the volume was further miniaturization , convenient to carry. Based on the design and selection of good individual discrete devices, eventually they can cascade into a practical application of the system . The design process of a real circuit , and gives a detailed test data. As can be seen through the test data designed to meet the targets of this requirement .
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