| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 99 === The transmit signal in Orthogonal Frequency Division Multiplexing (OFDM) systems is known to have high peak-to-average power ratio (PAPR). Due to this property, the power amplifier (PA) of the system must operate in a wide linear region, making it the most power-hungry device in the RF circuit. The linear-amplification-with-nonlinear-component (LINC) technique has been developed to reduce the power consumption in high-PAPR systems. By using the LINC architecture, nonlinear PAs with high power efficiency can be used to linearly amplify the input signal. However, a critical component in LINC transmitter, named power combiner, is difficult to design and implementation. To avoid the use of the combiner, a combinerless LINC system is later proposed. Unfortunately, the performance of the system is poor in some non-ideal channel conditions. In this thesis, we study the combinerless LINC-OFDM system and propose a new maximum likelihood (ML) detection algorithm to improve its performance. With the proposed algorithm, the LINC-OFDM system can be effectively operated in non-ideal channel environments. Simulations show the proposed algorithm can significantly enhance the performance of the combinerless LINC-OFDM systems. In most cases, the proposed algorithm can even outperform the conventional OFDM systems. We also propose several methods to reduce the computational complexity of the ML algorithm.
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