Research On Quantization Noise Shaping Technology Of OFDM System Based On ?? Modulation

Orthogonal frequency division multiplexing is not only a kind of modulation technology,but also can be regarded as a kind of multiplexing technology.Because of its advantages of high bandwidth efficiency and robustness against frequency selective fading ability has been widely attention and application,which solves the problem of high speed information transmission in wireless channel,and has become the core technology in the field of broadband wireless communications.In this thesis,the data converter based on sigma-delta modulator is studied for multi-band OFDM communication system,which provides a new effective scheme for OFDM signal conversion.Based on the basic structure principle and noise shaping characteristics of sigma-delta modulator,the performance of two kinds of existing sigma-delta modulator are compared and analyzed in detail for multi-band OFDM system.In addition,two quantization noise shaping algorithms are proposed for multi-band OFDM systems with sigma-delta modulation:Quantization noise shaping algorithm of sigma-delta modulation OFDM system based on all phase FFT method and quantization noise shaping algorithm of sigma-delta modulation OFDM system based on new cascade structure.Aiming at the application of the existing single-zero and multi-zero sigma-delta modulator in OFDM system,this thesis gives the theoretical analysis by deducing the quantization noise and the quantized signal-to-noise ratio,and obtains the multi-zero sigma-delta modulator has not been able to achieve the ideal state of eliminating quantization noise in OFDM system,and has given proof and simulation to improve the modulation scheme of the above two kinds of modulator in OFDM system.The application based on all phase FFT method in frequency offset compensation,channel estimation and other related fields,it will be introduced to the OFDM system to solve the problem of quantization noise shaping,with combining the basic principle of OFDM and all phase FFT,we have carried out theoretical and simulation analysis in the case of considering the quantization noise of sigma-delta modulation structure and obtains the quantization noise shaping algorithm for OFDM system using all phase FFT method.Under the precondition of preserving the advantages of the original structure,the split-architecture sigma-delta modulator is improved to get better noise shaping performance for OFDM system,the derivation and simulation analysis between the cascade structure before and after improvement are given,which obtains the quantization noise shaping algorithm for OFDM system using proposed sigma-delta modulator.