Reducing PAPR of SC‐FDMA Signals through Simple Amplitude Predistortion

A novel peak‐to‐average power ratio (PAPR) reduction method is proposed for single‐carrier frequency‐division multiple access (SC‐FDMA) signals. The proposed method deliberately distorts the amplitude values of a few of the complex modulated symbols that cause peaks beyond a predetermined threshold in the samples of the output signal. The method then marks the location indices of the distorted symbols by using a pilot block at the transmitter without transmitting side information. At the receiver, the method is then able to recover the distorted amplitude values through the marked location indices. Computer simulation results show that when compared to conventional SC‐FDMA signals, the proposed scheme can effectively reduce the PAPR of SC‐FDMA signals with asymptotically consistent bit error rate (BER) performance.     

一种室内可见光通信亮度控制方法

为了解决室内无线可见光通信中照明光源亮度不稳定的问题,提出了一种新型的以脉冲宽度调制（PWM）波形作为载波的编码调制方法,设计了基于该方法的发射器和接收器。PWM波形在逻辑1和逻辑0时的载波占空比相同,频率分别为38 kHz和7 kHz。发射端采用高亮度白光LED作为光源,接收端采用PIN光电二极管和低噪声放大器作为前...     

Significance of image representation for face verification

In this paper we discuss the significance of representation of images for face verification. We consider three different representations, namely, edge gradient, edge orientation and potential field derived from the edge gradient. These representations are examined in the context of face verification using a specific type of correlation filter, called the minimum average correlation energy (MACE) filter. The different representations are derived using one-dimensional (1-D) processing of image. The 1-D processing provides multiple partial evidences for a given face image, one evidence for each direction of the 1-D processing. Separate MACE filters are used for deriving each partial evidence. We propose a method to combine the partial evidences obtained for each representation using an auto-associative neural network (AANN) model, to arrive at a decision for face verification. Results show that the performance of the system using potential field representation is better than that using the edge gradient representation or the edge orientation representation. Also, the potential field representation derived from the edge gradient is observed to be less sensitive to variation in illumination compared to the gray level representation of images.     

脉冲激光沉积法制备的PZT铁电薄膜的残余应力

根据压电本构方程和细观力学统计平均法，采用X射线衍射（XRD）测量Pb（Zr0.52Ti0.48）O5（PZT）铁电薄膜的残余应力。考虑激光沉积生长过程中，薄膜相变应力、热应力和本征应力对自由能的贡献，分析薄膜晶胞在晶体坐标系上的应力应变状态。由坐标转换将晶胞残余应力从晶体坐标系转换到样品坐标系得到任意取向晶粒的残余应力，通过取向平均得到薄膜样品坐标系上的残余应力。用脉冲激光沉积法（PLD）制备了不同厚度的PZT薄膜。利用X射线衍射分别采用细观力学统计平均法和传统sin^2φ法测量了PZT薄膜的残余应力。结果表明，两种结果在数值上是比较接近的（绝对差范围0．3～16．6MPa），残余压应力随着膜厚的增加从96MPa左右减少到45MPa左右。最后讨论了细观力学统计平均法的优缺点。     

不同产地信息茶叶的红外光谱分析

通过规范化的标准检测, 制备样品并获取样品的标准红外光谱, 分别得到了几种中国名茶的标准红外光谱图。为了更全面地了解这些茶叶的整体地域特征, 建立了红外光谱分析的平均偏离方法, 对光谱图进行了的直观分析, 而且还探讨了平均偏离大小与茶叶产地纬度的关系。研究表明, 产地纬度相近的茶叶, 平均偏离小; 产地纬度相差大的茶叶, 平均偏离大。因此茶区的海拔高度和纬度与茶叶的产地信息有着密切关系, 平均偏离有可能成为分析茶叶产地信息的强有力的方法。     

A novel search method to reduce PAPR of an OFDM signal using partial transmit sequences

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak‐to‐average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. As ordinary PTS technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub‐blocks. In this paper, we propose a novel PTS technique with reduced complexity that each level inverts twice of phase factor bits from previous level. Then we also use initial random phase sequence to find the better search way of PAPR reduction. Numerical results show that the proposed method can achieve significant reduction in search complexity with little performance degradation. Copyright © 2006 John Wiley & Sons, Ltd.     

一种计算缩减级型广义洗牌网络平均跳距的算法

简单介绍了广义洗牌网络（ＧＳＮ）的结构和分类,着重分析缩减级型ＧＳＮ的平均跳距性能,并提出一种计算平均跳距的算法     

多普勒激光雷达运动测风数据降噪处理

车载测风激光雷达在进行移动测量时,激光雷达在各个方位的累积时间变短,另外还有天空背景光、大气湍流、机械振动的干扰以及暗噪声、电子学噪声的影响,回波信号的信噪比会因此降低,从而限制激光雷达的探测范围。在风廓线的反演过程中利用窗口大小随距离变化的滑动平均滤波器和中值滤波器可将12~15 km的平均信噪比提高2.8倍,因而可有效提高探测距离。     

影响LED显示屏视觉质量的诸要素辨析

本文在此介绍部分容易混淆的重要视觉参数,为高质量LED显示屏设计提供依据,包括：亮度与感知亮度、灰度视觉感受、影响亮度的环境要素、色温的心理感受、色度校正、逐点校正、逐点色度校正、逐点校正的作用等,供大家参考。     

基于锁相放大器的万能试验机采集系统研制

基于STM32、STM8处理器,设计完成了万能试验机的多个功能模块。为了提高小信号的采集精度与速度,用多处理器设计了一种混合式的锁相放大器,并运用数字处理进行进一步处理,具有很高的性价比。在位移信号采集中,运用STM8S实现了低成本的设计。实验表明,本系统在速度与精度上满足万能试验机要求,总体性价比高。