基于判决反馈的OFDM载波频率同步环路
A Decision-Directed OFDM Carrier Frequency Synchronization Loop
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摘要: 对OFDM系统中一种基于接收时域信号重构的载波频率盲估计算法进行了进一步的研究，分析了在这种方法中影响估计精度的4个方面的因素。为了减少载波频率估计的剩余误差，通过在频率补偿时增加反馈因子，提出了一种基于判决反馈的载波频率同步环路结构。通过调整同步环路的环路增益，可以获得更好的频率跟踪性能。如果信噪比达到9dB，即使存在较大的频率漂移，剩余频偏也被限制在子载波间隔的1%以内。Abstract: Further investigation is given to a kind of carrier frequency offset (CFO) blind estimation algorithm based on time domain received signal reconstruction in OFDM systems, and the four aspects that affect the estimation accuracy are analyzed. For minimizing the residual carrier frequency offset, a kind of decision-directed carrier frequency synchronization loop is given by introducing a feedback factor into the frequency compensation. Better carrier frequency tracking performance can be gotten by adjusting the loop gain. The residual frequency offset can be restricted within 1% of the carrier spacing even if lager frequency drift exists, if bit SNR reaches 9dB.
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