A new blind frequency offset estimation method based on cyclic prefix and virtual subcarriers in coherent optical orthogonal frequency division multiplexing （CO-OFDM） system is presented. It is able to estimate the ...A new blind frequency offset estimation method based on cyclic prefix and virtual subcarriers in coherent optical orthogonal frequency division multiplexing （CO-OFDM） system is presented. It is able to estimate the fractional part and integral part of frequency offset at the same time. Its estimation range is about [-3.5 GHz, 3.5 GHz]. The influence of the integral frequency offset is comprehensively analyzed in COOFDM system. Its performances in the additive white Gaussian noise （AWGN） channel and the dispersive channel are investigated, respectively. Simulation results indicate that even in the dispersive channel, when the optical signal-to-noise ratio （OSNR） is low, it can still work very well.展开更多
The signal-to-noise ratio may be increased by the cross-range coherence integration so as to detect the moving target in low signal-to-noise ratio （SNR） condition.But, the radial velocity, acceleration and the chang...The signal-to-noise ratio may be increased by the cross-range coherence integration so as to detect the moving target in low signal-to-noise ratio （SNR） condition.But, the radial velocity, acceleration and the change of acceleration due to the maneuvering motion of target may induce serious range migration and cross-range high-order phase terms leading to the unfocused cross-range image, the reduction of signal-noise ratio and the invalidation of target detection.Therefore, in order to solve these problems, this paper proposes a new method based on the adjacent correlation and scale transform methods for detection, parameters estimation and imaging of maneuvering targets in wide-band signal.This method can align the range and remove the cross-range high-order phase terms induced by the radial motion of target, enabling us to detect the target and estimate its moving parameters better.Finally, the simulated target is used to confirm that the method proposed by this paper can perfectly detect the maneuvering target in low signal-to-noise ratio condition, estimate its motion parameters and obtain an ISAR image of target.展开更多
为了扩大盲信噪比SNR的估计范围,同时降低计算的复杂性,提出了一种新的基于样本的协方差矩阵的信号子空间方法和联合信息标准(Combined information criterion,CIC)的盲信噪比估计算法。算法中采用的CIC克服了AIC(Akaike information cr...为了扩大盲信噪比SNR的估计范围,同时降低计算的复杂性,提出了一种新的基于样本的协方差矩阵的信号子空间方法和联合信息标准(Combined information criterion,CIC)的盲信噪比估计算法。算法中采用的CIC克服了AIC(Akaike information criterion)惩罚度较小和MDL(Minimum description length)惩罚度较大的缺点,并且推导出了CIC的最大似然形式。算法不需要信号调制方式、波特率和载波的先验知识。计算机仿真结果表明,该算法可以用小样本对在加性白高斯噪声和Rayleigh衰落信道下常用的数字调制方式进行盲估计,在SNR从-10 dB^25 dB范围内平均估计误差小于1 dB。展开更多
基金supported in part by the National Natural Science Foundation of China (No. 60932004)the National "863" Program of China (Nos. 2009AA01Z256,2009AA01Z253, and 2009AA01A345)the National"973" Program of China (No. 2007CB310705).
文摘A new blind frequency offset estimation method based on cyclic prefix and virtual subcarriers in coherent optical orthogonal frequency division multiplexing （CO-OFDM） system is presented. It is able to estimate the fractional part and integral part of frequency offset at the same time. Its estimation range is about [-3.5 GHz, 3.5 GHz]. The influence of the integral frequency offset is comprehensively analyzed in COOFDM system. Its performances in the additive white Gaussian noise （AWGN） channel and the dispersive channel are investigated, respectively. Simulation results indicate that even in the dispersive channel, when the optical signal-to-noise ratio （OSNR） is low, it can still work very well.
基金Supported by the National Natural Science Foundation of China (Grant No 60502044)the Program for New Century Excellent Talents in University (Grant No NCET-06-0861)
文摘The signal-to-noise ratio may be increased by the cross-range coherence integration so as to detect the moving target in low signal-to-noise ratio （SNR） condition.But, the radial velocity, acceleration and the change of acceleration due to the maneuvering motion of target may induce serious range migration and cross-range high-order phase terms leading to the unfocused cross-range image, the reduction of signal-noise ratio and the invalidation of target detection.Therefore, in order to solve these problems, this paper proposes a new method based on the adjacent correlation and scale transform methods for detection, parameters estimation and imaging of maneuvering targets in wide-band signal.This method can align the range and remove the cross-range high-order phase terms induced by the radial motion of target, enabling us to detect the target and estimate its moving parameters better.Finally, the simulated target is used to confirm that the method proposed by this paper can perfectly detect the maneuvering target in low signal-to-noise ratio condition, estimate its motion parameters and obtain an ISAR image of target.
文摘为了扩大盲信噪比SNR的估计范围,同时降低计算的复杂性,提出了一种新的基于样本的协方差矩阵的信号子空间方法和联合信息标准(Combined information criterion,CIC)的盲信噪比估计算法。算法中采用的CIC克服了AIC(Akaike information criterion)惩罚度较小和MDL(Minimum description length)惩罚度较大的缺点,并且推导出了CIC的最大似然形式。算法不需要信号调制方式、波特率和载波的先验知识。计算机仿真结果表明,该算法可以用小样本对在加性白高斯噪声和Rayleigh衰落信道下常用的数字调制方式进行盲估计,在SNR从-10 dB^25 dB范围内平均估计误差小于1 dB。
