Composite Cathode Bi1.14Sr0.43O2.14-Ag for Intermediate-temperature Solid Oxide Fuel Cells

Composites consisting of strontium stabilized bismuth oxide (Bi1.14Sr0.43O2.14 SSB) and silver were investigated as cathodes for intermediate-temperature solid oxide fuel cells with doped ceria electrolyte. There were no chemical reactions between the two components. The microstructure of the interfaces between composite cathodes and Ce0.8Sm0.2O1.9 (SDC) electrolytes was examined by scanning electron microscopy (SEM). Impedance spectroscopy measurements show that the performance of cathode fired at 700℃ is the best. When the content of Ag2O is 70wt%, polarization resistance values for the SSB-Ag cathodes are as low as 0.2Ωcm2 at 700℃ and 0.29Ωcm2 at 650℃. These results are much smaller than some of other reported composite cathodes on doped ceria electrolyte and indicate that SSB-Ag composite is a potential cathode material for intermediate temperature SOFCs.     

数字式单边带调制的关键及实现方法

分析了传统模拟方法实现单边带调制的不足，给出了用数字信号处理方法实现单边带调制的实现方法，并分析了其中的正交调制、内插技术等关键技术，在此基础上设计并实现了一个以TI TMS320芯片为核心的数字式单边带调制系统．与模拟调制法相比，该电路结构简单，性能稳定可靠。     

光子学射频移相器的研究及进展

本文介绍了光实时延迟线移相器、光学外差SSB射频移相器和基于矢量和技术的光子学射频移相器,并对其各自的工作原理和技术特点做了分析.     

基于集成频率合成器的锁相环设计

本文介绍了采用直接数字频率合成器(DDS)和集成锁相频率合成器PE3236设计2.4G-4.4G Hz本振信号源的新方法,与传统采用小数分频的设计方法相比,具有电路简单、功耗低、体积小等优点,经制作实验电路板验证,试验电路的单边带相位噪声和频率分辨率都达到了预先的设计要求,试验取得了预期的效果.     

频率可调带宽可选的VLBI多相数字基带转换器

VLBI数据采集终端是VLBI台站的重要设备,近年来随着数字硬件设备例如ADC、DSP、FPGA的快速发展,数字基带转化器代替模拟基带转换器成为现实。现有采用多相滤波器实现DBBC的方法不可避免存在盲区,且频率、带宽均不可调。提出一种通用的基于多相结构的宽带数字下变频方法,将多速率信号处理和并行处理方法应用在其中,成功实现了VLBI多个通道的单边带数字基带转换,且能实现中频中心频率可调、带宽可选。硬件测试结果表明VLBI数字基带转换器频率设置正确,带宽选择正确,且数字基带转换器带通特性好于模拟基带转换器。     

ROF系统中的色散分析及抑制

ROF（RadioOverFiber）系统中光纤的色散是影响系统性能最主要的因素。传统的光载波双边带调制会引起严重的色散问题。光学单边带调制（OSSB）是最普遍的的方法，SSB能有效地抑制色散带来的能量损耗，并延长信号的传输距离。另外提出了一种改进的SSB调制方法，能够克服载波和边带引起的色散，传输距离也比普通的单边带调制更长。     

改进的基于多倍频的单边带调制ROF全双工系统

利用单边带调制技术,设计了一种改进的毫米波光纤传输系统,进行了系统色散分析及仿真实验.该系统在中心站通过设置相位调制器的偏置电压,使调制器产生的奇数边带被抑制,采用滤波器滤出其中的一个二阶边带.基带信号经过中频调制形成副载波,再将此副载波通过单边带调制到二阶边带上;在基站,通过带通滤波器滤出上行链路所需的光载波.用该单...     

Analysis of mismatch impact on image rejection ratio for passive polyphase filters

Passive polyphase filters (PPFs) are useful symmetric RC networks for processing analog quadrature signals. Passive polyphase filters are also used to implement differential‐quadrature or quadrature‐differential converters. The quality of these quadrature signals is essential to achieve good performance in modern communication systems. However, mismatch effects can produce notable degradation in the PPF frequency response, and this results in an important reduction in quadrature signal quality, being amplitude balance and phase offset notably affected. Both these errors could be summarized and evaluated together considering image rejection ratio as a figure of merit. This work deepens in the analysis of mismatch impact on PPF, studying image rejection ratio degradation for 2 PPF types, and a systematic method is proposed to obtain the worst case of mismatch in PPFs with any number of stages. It has been validated in a 65‐nm CMOS technology.     

成形网最新制造技术及相关产品

介绍了国外各大成形网制造商如Tamfelt、Heimbach和Albany等公司先进的成形网制造技术及其应用高新科技所生产出的先进的SSB成形网产品.并对其生产的成形网的特点从结构和实际应用效果上进行了分析和比较.     

SSB无线传输中加性高斯噪声对TTIB处理的影响

本文分析了SSB TTIB系统的性能,并根据TTIB处理原理,通过数学分析肯定了导音提取过程中噪声性能恶化亦可导致门限效应,确定了导音电平、TTIB处理门限与FFSR导音处理模块的输入信噪比关系,为更好地运用TTIB技术进行数据传输提供了理论参数,试验结果与理论分析较为吻合。