基于压缩量化的非正弦时域正交调制信号预失真方法

针对基于椭圆球面波函数的非正弦时域正交调制信号峰均功率比较高,因而受功率放大器非线性失真影响较大的问题,该文设计了一种基于波形训练的非迭代查询表预失真结构。由于所选量化方法直接决定了查询表预失真器的精度,通过分析调制信号的幅值分布特性,提出一种综合考虑功率放大器特性及信号幅值分布特性的压缩量化方法。对采用所提预失真方法前后信号的带内带外失真特性进行了仿真,并与采用幅度均匀量化方式的性能进行了比较。结果表明,该文方法有效改善了非正弦时域正交调制信号功率谱及系统误码率特性,减小了功率放大器给信号带来的非线性失真。     

统计过程控制(SPC)技术在紫外像管制作中的应用

采用统计过程控制(SPC)技术对关键工序进行监控是保持产品生产线稳定、减少质量波动的有效方法.可以提高产品的成品率和可靠性.在现有工序状态下,通过采集封接温度、真空度等数据,计算和分析关键工序的工序能力指数,进行工艺调整和改进,直到工序能力指数Cpk≥1.33.通过选择控制图,对数值进行监控.若发现工序失控时,分析原因...     

基于ARM7的太阳能控制器的设计与现实

本文阐述了太阳能光伏电池的工作原理以及伏安特性,提供了一套完善的太阳能控制器电路.该电路采用了目前最流行的ARM芯片为控制核心,来实时监控光伏两端电压、蓄电池两端电压以及充电电流和放电电流.从而控制整个电路的工作状态.     

A low jitter, low spur multiphase phase-locked loop for an IR-UWB receiver

A low jitter,low spur multiphase phase-locked loop(PLL) for an impulse radio ultra-wideband(IR-UWB) receiver is presented.The PLL is based on a ring oscillator in order to simultaneously meet the jitter requirement, low power consumption and multiphase clock output.In this design,a noise and matching improved voltage-controlled oscillator(VCO) is devised to enhance the timing accuracy and phase noise performance of multiphase clocks.By good matching achieved in the charge pump and careful choice of the l...     

Fast mode decision algorithm for H.264 inter-prediction

A fast mode decision algorithm for H.264/AVC inter-prediction to reduce computational complexity of the H.264 encoder is presented. Experimental results show that the algorithm can save the entire encoding time by 77% on average while introducing only negligible loss in PSNR value and small increment of bit rate.     

DDS相位舍位杂散信号的频谱分析

杂散特性限制着直接数字频率合成（DDS）技术的应用和发展,其中相位舍位、幅度量化和DAC的非理想特性等是影响DDS输出频谱质量的主要杂散源。文中主要研究相位舍位对DDS输出频谱的影响,首先通过离散傅里叶变换将任意的频率控制字转化为频率控制字为1来对DDS的输出信号进行频谱分析,然后由DDS的输出序列入手深入研究了相位舍位时DDS输出频谱的特性,得到的DDS输出频谱的数学模型精确、简单。     

基于电子管SRPP电路的高保真耳机放大器设计

以电子管微变等效电路分析为基础,设计了一款以驱动高保真耳机为目的的耳机放大器.该放大器以共阴极放大器为输入级,SRPP放大器为输出级,驱动耳机工作.分析了该放大器的开环和闭环参数,并采用客观测量和主观评价的方式对该放大器的品质进行评价.     

Modification of Energy Level Alignment for Boosting Carbon-Based CsPbI2Br Solar Cells with 14% Certified Efficiency

Hole transfer material (HTM)-free, carbon-based all-inorganic perovskite solar cells (C-PSCs) are promising alternatives to conventional organic–inorganic hybrid PSCs in addressing thermal and moisture instability issues. However, the energy level mismatch between the inorganic perovskite and carbon electrode coupled, together with the incapability of the carbon electrode to reflect incident light for reabsorption, limits the power conversion efficiency (PCE) of C-PSCs. To address these issues, herein, a new strategy of a hexyltrimethylammonium bromide (HTAB)-modified CsPbI₂Br perovskite surface is devised to reduce this energy offset from 0.70 to 0.32 eV and increase the built-in potential by 70 mV for the final devices. Additionally, a CsPbI₂Br perovskite film with a thickness of up to 800 nm is realized via a hot-flow-assisted spin coating approach in an ambient atmosphere with humidity of less than 80%. Reduced energy offset coupled with suppressed charge recombination and thick perovskite layer boosts the champion PCE of CsPbI₂Br C-PSCs to 14.3% (J_sc = 14.1 mA cm⁻², V_oc = 1.26 V, and fill factor = 0.806), and the average PCE to 13.9% under one sun illumination. A new certified efficiency record of 14.0% is obtained for HTM-free inorganic C-PSCs. Meanwhile, the moisture-resistant barrier from the alkyl chain in HTAB improves the stability of the final devices.     

On centralized and distributed algorithms for minimizing data aggregation time in duty-cycled wireless sensor networks

We study the problem of minimizing data aggregation time in wireless sensor networks (WSNs) under the practical duty-cycle scenario where nodes switch between active states and dormant states periodically for energy efficiency. Under the protocol interference model, we show that the problem is NP-hard and present a lower bound of delay for any data aggregation scheme. To solve the problem efficiently, we then construct a routing tree based on connected dominator set and propose two aggregation scheduling algorithms, which are the centralized Greedy Aggregation Scheduling (GAS) and the distributed Partitioned Aggregation Scheduling (PAS), so as to generate collision-free transmission schedules for data aggregation in duty-cycled WSNs. To minimize the total delay, GAS tries to achieve maximal concurrent transmissions in each time-slot during each frame by using global information, while PAS leverages a network partition based strategy and local information to ensure the largest degree of channel reuse across space and time domains. Theoretical analysis indicates that each algorithm consumes at most \(O(R+\varDelta)\) frames and achieves nearly constant factor approximation on the optimal delay. Here R and \(\varDelta\) are the network radius and the maximum node degree, respectively. We also evaluate the practicability of our algorithms by extensive simulations under various network conditions and the results corroborate our theoretical analysis.