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| 1 | Pseudo-noise preamble based joint frame and frequency synchronization algorithm in OFDM communication systems显示文摘Frame and frequency synchronization are essential for orthogonal frequency division multiplexing(OFDM) systems. The frame offset owing to incorrect start point position of the fast Fourier transform(FFT) window, and the carrier frequency offset(CFO) due to Doppler frequency shift or the frequency mismatch between the transmitter and receiver oscillators, can bring severe intersymbol interference(ISI) and intercarrier interference(ICI) for the OFDM system. Relying on the relatively good correlation characteristic of the pseudonoise(PN) sequence, a joint frame offset and normalized CFO estimation algorithm based on PN preamble in time domain is developed to realize the frame and frequency synchronization in the OFDM system. By comparison, the performances of the traditional algorithm and the improved algorithm are simulated under different conditions. The results indicate that the PN preamble based algorithm both in frame offset estimation and CFO estimation is more accurate, resourcesaving and robust even under poor channel condition, such as low signaltonoise ratio(SNR) and large normalized CFO. | Qingfeng Jing Ming Cheng Yuping Lu Weizhi Zhong Hongwei Yao | 2014 | Journal of Systems Engineering and Electronics2014，25，1： | 4 |
| 2 | 基于伪随机序列前导码的OFDM系统帧同步算法显示文摘在正交频分复用(orthogonal frequency division multiplexing,OFDM)系统接收端,错误估计快速傅里叶变换窗口起始点会导致OFDM帧偏差,从而造成严重的符号间干扰(inter symbol interference,ISI)以及子载波间干扰(inter carrier interference,ICI)。首先建立一个带有帧同步的OFDM系统模型,然后通过理论推导得到帧偏差对OFDM系统的影响。利用伪随机序列自身较好的相关特性,设计了一种基于伪随机序列前导码的帧同步算法,并分析了3种基于循环前缀(cyclic prefix,CP)的传统帧同步算法。通过仿真实验,结果表明所提出的基于伪随机序列前导码的帧同步算法与传统算法相比,即使在较差的信道条件下,如在较低的信噪比或存在较大的载波频率偏移(carrier frequency offset,CFO)时,其帧偏差估计结果更为准确、稳定以及节省资源。 | 井庆丰 陆宇平 仲伟志 严晓菊 | 2013 | 系统工程与电子技术2013，35，2： | 3 |
| 3 | 基于FFT与PLL相结合的载波同步方法研究显示文摘针对无线通信系统中的载波恢复问题,提出了基于FFT和PLL相结合的载波同步方法。该方法首先将接收信号通过非线性平方器和带通滤波器的预处理,然后用FFT恢复出未知载波的频率,并用该频率控制PLL振荡器产生的正弦信号频率,最后通过PLL环路的自适应算法实现载波相位的动态跟踪,达到了载波同步的目的。通过以4-PAM信号为例,建立了全数字化的MATLAB仿真模型,并深入分析了系统的性能,仿真实验表明,该方法有良好的载波同步性能和相位的动态自适应性。 | 李清泉 彭昌睿 蒲杰 钟俊 | 2010 | 技术与市场2010，17，9： | 2 |
| 4 | NLMS自适应滤波器的FPGA实现显示文摘目的采用FPGA芯片实现NLMS算法,从而生成高性能的自适应滤波器来滤除通信信号中时变、未知的干扰信号,得到高质量的通信信号.方法通过对LMS及其改进算法的原理讨论及比较,确定适合于FPGA芯片上实现的NLMS算法,并对算法的具体实现方法进行论述.采用分段移位的方法实现除法运算,从而提高运算速度.结果通过对输出信号的频谱分析,当信号带宽为200 kHz,频率偏离中心频率0.087 5 MHz时,衰减达到了99.21 dB.结论本设计能高速度、高质量地滤除通信信道中的干扰信号,并很好地处理了FPGA的资源与速度的关系,能满足高速信号处理的要求. | 戴敬 赵延洲 张辉 田越 白浠霖 | 2011 | 沈阳建筑大学学报(自然科学版)2011，27，1： | 2 |
| 5 | 基于功率谱的非均匀子带自适应滤波显示文摘根据输入信号的功率谱特征,非均匀滤波器组能够动态调整子带滤波器的带宽和位置,可以获得比均匀滤波器组更好的收敛性能.根据子带最小均方(least mean square,LMS)自适应算法的收敛特性,以提高其收敛速度为目标,提出了一种基于功率谱信息的非均匀子带自适应滤波方法,并详细讨论了非均匀滤波器组实现结构和信号重建性能.计算机仿真实验和分析表明,与现有的均匀和非均匀滤波器组设计方法相比,在子带数目相同的条件下,本文提出的方法能有效地降低子带信号的最大特征值扩散度,而信号重建性能基本相同. | 许小东 张炜 戴旭初 | 2012 | 中国科学技术大学学报2012，42，2： | 2 |
| 6 | Blind estimation of phase offset in OFDM subcarrier for coherent demodulation显示文摘An adaptive algorithm named low complexity phase offset estimation (LC-POE) is proposed for orthogonal frequency division multiplexing (OFDM) signals. Depending on the requirement, the estimation procedure is divided into several scales to accelerate the adaptive convergence speed and ensure the estimation accuracy. The true phase offset is estimated through shrinking the detection range and raising the resolution scale step by step. Both the convergence performance and complexity are discussed in the paper. Simulation results show the effectiveness of the proposed algorithm. The LC-POE algorithm is promising in the application of OFDM systems. | Jian Chen Long Yang Ming Li | 2012 | Journal of Systems Engineering and Electronics2012，23，4： | 0 |
| 7 | Novel method for radial velocity difference estimation of moving targets with wideband signals显示文摘For the frequency difference of arrival(FDOA) estimation in passive location, this paper transforms the frequency difference estimation into the radial velocity difference estimation,which is difficult to achieve a high accuracy due to the mismatch between the sampling period and the pulse repetition interval. The proposed algorithm firstly estimates the point-in-time that each pulse arrives at two receivers accurately. Secondly two time of arrival(TOA) sequences are subtracted. And finally the radial velocity difference of a target relative to two stations with the least square method is estimated. This algorithm only needs accurate estimation of the time delay between pulses and is not influenced by parameters such as frequency and modulation mode. It avoids transmitting a large amount of data between two stations in real time. Simulation results corroborate that the performance is better than the arithmetic average of the Cramer-Rao lower bound(CRLB) for monopulse under suitable conditions. | Hui Di Yu Liu Jian Yang | 2014 | Journal of Systems Engineering and Electronics2014，25，2： | 0 |
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