Computer Simulation and Research of RF Circuit Effect on Communication System Performance of OFDM System

• Main Author: 蔡壬勝
• Other Authors: 林福林
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/72139618226280535339

碩士 === 南台科技大學 === 電子工程系 === 92 === Orthogonal frequency division multiplexing (OFDM) is a promising transmission technology for high data rate communications in the future. However, the OFDM signal is more sensitive to the nonlinear effect of power amplifier, phase noise in oscillator and I-Q imbalance. Therefore, this thesis presents detailed analysis and the computer simulation by Matlab for above three imperfect effects. First, we study the improvement by the clipping method to IEEE 802.11a standard with nonlinear power amplifier and predict the error vector magnitude (EVM) by computer simulation. Secondly, we concern the influence of the I-Q imbalance in an OFDM receiver. The receiver architectures, such as direct conversion, super-heterodyne and low-IF, may be used for the front-end in an OFDM system. The direct conversion architecture will become popular since it offers one important advantage over a heterodyne counterpart, that is, the problem of image is circumvented and no image filter is required. However, this approach suffers from some impacts such as DC offset and I-Q imbalance. The second part in this thesis, we try to analyze the influence of I-Q imbalance with IEEE 802.11a standard. Finally, we focus on the phase noise. The considerations of the distortion can be separated into two parts, the common phase error and the ICI error. The former can be corrected by the pilot, so we only consider the effect of the ICI error. The simulation is based on the multi-band OFDM system, which is made by the UWB standard committee (802.15.3a task group) in 2003 and may be adopted as UWB communication standard. These simulation methods and numerical results are very useful for RF circuit/system designers in OFDM system.