Sensor Networks, Rf Front-end Research

Wireless sensor network is a kind of data-centered self-organization wireless network. The node in the network is intensive, huge quantity and covering a large area, and the network topology is dynamic, and was self-organization and self-modulation. The node has a lot of characteristics, such as low cost, small volume, but the energy, computing ability, memory, and communication ability are limited. The energy of the node is the most vital factor of designing node.Currently, the research on wireless sensor network primarily concentrates in the protocol stack, data frame form, the uniform interface definition between difference layers and each layer's regular management are considered fewer. Certainly, the development of hardware overseas in designs and in the techniques is at the leading position. The function of chip is getting stronger, as the quantity of the channel gets larger and larger, the transmission rate is getting higher.RF Front end of the sensor is important part of the wireless transmission system. Receiver front end amplifies the weak signal with low noise amplifier, then use the bandpass filter to prevent the noise out of the useful signal, then amplify it to the level that can be accepted by the ADC. In the transmitter front end, QPSK signal firstly filtered by BPF in order to prevent the noise out of the useful band, and then amplified to the standard level, lastly launched through the switch.The front-end is composed by low noise amplifier, amplifier with AGC, power amplifier, single pole double throw switch (SPDT), the sound surface wave filter (SAW), the operating frequency is 300MHz-400MHz. To meet the needed power gain, the receiving end uses two cascaded LNA, an amplifier with AGC, a MMIC power amplifier was used in the transmitting end. Also has selected the small SAW filter, lower the volume, facilitates has carried.Based on design and selection the good each separation component, becomes their cascade to be possible finally the practical application system. Between the theory and the actual application always has the disparity, good theory may not obtain good application effect. The hardware is proposed, and the detailed test data has given out. Through the test data, we can see that the target requirements have been met.