The Uhf Band Wireless Transceiver Rf Front-end Design

Nowadays,the higher and higher requirements are raised to the wireless transceiver with the rapid development of mobile communications,such as low voltage, low power, low-cost, high integration and high reliability and so on,which forces people to make an appropriate improvement.Microwave transceiver has been used in all aspects of telecommunication.Therefore, its reseach becomes a hot spot. Based on these key points, this paper designs a UHF-band RF front-end for transceiver.First of all, in the paper, the characteristics of UHF are introduced and the importance of the design of RF front-end is emphasized.Then several structures of transceiver in popular and their parameters are researched,and the theory and characteristics of frequency synthesis technology are analyzed.Then according to the requirements of tasks, a system configuration of receiver based on superheterodyne and transmitter based on two-step approach is proposed,and LO is realized by DDS driving PLL.Finally,by designing the system and showing the test results, the feasibility of this system configuration has been proved.In the system, some integrated chips are adopted to reduce the complexity of the system.Some simulations are made which fit the demands basically and the final test results also fit the requirments.The output IF is 69.99 MHz,the emission frequency is 875 MHz.The narrow receiving band is 1.25 MHz,gain is 30~60 dB, NF<5 dB;the wide band is 10 MHz, gain is 20~80 dB, NF<3 dB.At the end of this paper, some measures are provided to improve the shortcomings of this system.Some methods proposed in the paper have considerable value for the future research.