| This subject derives from the project, which is supported by Yunnan province and Chongqing University technological joint foundation. The objective of the project is to capture infrared video and transmit the data to headquarter with encryption techniques. Based on requirements of Direct Sequence Spread Spectrum, the dissertation discusses the scheme to accomplish the RF front-end for 2.4GHz ISM band.The difficulties of the scheme are the broadband matching and wide dynamic range. By means of a skillful method, the designer achieves the goal at last. In designing process, the designer adopts a new circuit design method: First, bring out a budget for the system based on experience and project requirements. Then, select the components and their typical application circuits. Third, design circuits with the selected components, simulated with EDA software, and optimize the circuits to gain finest results. At last, test the PCBs, analyze the results and propose the final suggest. The RF front-end circuits achieve the project requirements by using generic heterodyne receiver architecture, including Up/down-mixers, 2.38GHz local oscillator, RF power amplifier, low-noise amplifier, IF/RF band pass filters, IF automatic gain control and so on.At the end of this paper, the author brings forward methods for improving system performance based on the test results. And the follow task is proposed too. |
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