摘 要
本論文的目的，是基於探討電磁波在室內傳播的效應，架設一套QPSK的基頻調變系統。而其傳輸的資料速度5Mbits/s，載波頻率為65MHz，並配合著前端5.3GHz的射頻電路，整合為一組5.3GHz的無線傳輸系統，以利日後替換模組測試之用。
針對本系統的製作，首先從理論推導到模擬系統，最後到選擇美商Analog Device出的AD9853這顆QPSK modulator，以滿足本文所要求的系統規格。
AD9853具備的功能包括Preamble，Randomizer，Reed-Solomom Encoder及FIR Digital Filter，其載波的頻段可調，data rate 的速度可調等等，均是透過I2C的介面控制來完成，本論文藉由單晶片的控制來達成。

Abstract
In this thesis，we propose the design and implementation
of a QPSK modulator for a wireless Lan system which’s carrier frequence is 65MHz ,data rate is 5MHz。And then Intergrate baseband modulator with IF and RF module。Due to the modulization design method,this system provides a test platform for the individual IC design module in the future.
To implement the QPSK system，base on system simulation，we choose a chip AD9853 which is manufactured by Analog Device to achieve our system。
The AD9853 integrates a high speed direct-digital synthesizer (DDS), a high performance, high speed digital -to-analog converter (DAC), digital filters and other DSP functions onto a single chip, to form a complete and flexible digital modulator device.
The function of AD9853 can be programmed，We setup it according to its and program it by I2C communication algorithm which uses PIC(peripheral interface controller)16F877 to implement。

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