| In recent years, with the development of micro-electronic technologies, communication technologies particular wireless communication have a surprising development. Furthermore, as the important part of wireless communication, people pay more and more attentions to RF front-end.This paper focuses on the wide-band digital RF front-end, refers to a large number of domestic and foreign literatures on the basis of RF, discusses and researches the basic principles of wide-band digital RF front-end in theory. This design uses the super heterodyne secondary frequency architecture, combining frequency synthesis technology and automatic gain control technology and so on. It achieves a wide-band digital RF front-end with large dynamic range.The methods and technologies used in this front-end are innovative and original. In design, local oscillators select the direct digital frequency synthesizer (DDS) and phase-locked loop (PLL) frequency synthesizer. The DDS has the merits of super fine frequency resolution, high frequency accuracy, very fast frequency hoping and so on. The PLL has a favorable narrow-band tracing filter character, presents high quality wide band local oscillator source and super small frequency hoping step. While making use of technology of PC control combining DSP control, the design notably improves the selectivity and anti-interference of the wide-band digital RF front-end.This wide-band digital RF front-end has characters of high sensitivities, low noises, changeable IF frequencies, IF outputs and so on. It can be used in receiving and detecting the short wave and super-short wave. It also can be used as the front-end of SDR system, in order to provide receiving channels and hardware for the base-band processing parts. |
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