DESIGN A DIGITAL-DOWN CONVERTER FOR OFDM SYSTEM

• Main Authors: Chang, Cheng-Chun, 張正春
• Other Authors: Hen-Wai Tsao
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/77588275305061140081

碩士 === 國立臺灣大學 === 電信工程學研究所 === 91 === Orthogonal frequency division multiplex (OFDM) becomes one of the promising techniques because it can efficiently combat multipath propagation and provide high-rate data transmission. And many Standards, such as IEEE802.11a, DVB etc., have adopted the attractive technique. Intrinsically, OFDM signals are sensitive to subtle changes in phase and magnitude. Any wireless transceiver front-end impairment may lead to system performance degradation. In this thesis, we set up an OFDM link in Matlab Simulink to analyze the front-end requirement. First, we focus on relationship of digital clipping and transmit symbol wordlength. Second, we study the non-ideal front-end effects, such as amplifier nonlinearity, oscillator phase noise and IQ-imbalance. On the other hand, we utilize Filter-bank theory and multirate signal processing skills to investigate digital IF receiver architecture based on OFDM system. We propose both “CP-saving” and “windowing” Digital-Down Converter (DDC) architecture and suggest a DDC FIR filter design method to improve system performance. Finally, we complete a 4-IF DDC architecture RTL design by using VHDL.