An improved high efficiency 500 kilowatt short wave broadcasttransmitter with novel features

Some of the changes in international broadcaster's HF (high-frequency) transmitter needs are addressed, along with some adaptations in HF transmitter design to reflect those needs. The authors identify three fundamental changes in the emphasis of international broadcast transmitter requirements: due to increasing energy costs, more emphasis has been placed on equipment power efficiency; due to increasing labor costs, more attention is being paid to automation and ease of maintenance, i.e. manpower efficiency; and, third, because of spectrum crowding, improved spectral occupancy has become a concern, particularly with respect to transmitted signal purity, and spectral-efficient modulation modes. Several developments designed to meet these needs of broadcasters are described. The issue of power efficiency has been met with improved transmitter RF and modulator circuits. RF efficiency has been improved in part by lowering losses in RF output coupling circuits. This improvement is afforded by better network design, and better automatic tuning, i.e. tuning for best efficiency. More efficient RF output tubes have also been developed     

A high power solid-state medium wave broadcast transmitter

The factors leading to the choice of an all-solid-state 50-kW medium-wave broadcast transmitter are examined, and its advantages over vacuum-tube-type transmitters of the same power are discussed. The installation and operation of the transmitter are described. The transmitter has demonstrated high levels of performance and reliability. Energy savings and reduction of maintenance times have been achieved     

DF100A型100kW短波发射机中和电路的维护

DF100型100KW短波发射机是电台的重要设备,为维护发射稳定,电路维护工作应受到高度重视.本文先分析了不良极间电容的影响,并给出了解决方法,然后选择中和电路,针对DF100型100KW短波发射机出现的问题进行了分析.     

DF500A型500KW短波发射机射频末级电子管的全寿命管理

作为发射机的核心器件,射频末级电子管工作的稳定性直接影响到发射机稳定运行,本文针对DF500A型500KW短波发射机的射频末级电子管的验收测试、入库存储、环境控制和后期管理的整个过程以及在各阶段涉及的注意事项进行了系统的阐述,为相关领域中射频末级电子管的维护管理提供参考。     

500kW PSM短波发射机可编程控制功率模块的研制

500kWPSM短波发射机可编程控制功率模块,是瑞士ThalesBroadcast&MultimediaAG公司TSW2500型500kWPSM短波发射机调制器的主要组成部分,每部发射机装有26块。此种机型在同类产品中有显著的先进性,成为我们对外广播的主力机型。可编程控制功率模块的研制,是为了解决该机型备件国产化而进行的研发项目之一。该项目于2001年底立项开始研制,2002年9月第一块样品上机试验,2003年完成小批量生产试用获得成功。现已通过标准计量产品鉴定,并获总局科技进步一等奖。     

一种高精度红外地球波算法与硬件实现

红外地球敏感器是卫星姿态测量的关键部件之一.在研制过程中,需要红外地球波信号源为其提供电激励信号,组成闭环测试系统,从而完成对红外地球敏感器的地面测试与标定.针对红外地球敏感器研制过程中逻辑功能验证、精度测试、可靠性环境寿命试验等需求,提出一种高精度的模拟式红外地球波算法.在对算法的精度、实时性等进行仿真分析的基础上,设计了一种红外电地球波模拟器的硬件实现方案,并研制了样机.试验结果表明,该算法及系统能够满足红外地球敏感器地面测试中的实时性和高精度需求.     

A 1 kW 500 kHz front-end converter for a distributed power supplysystem

The analysis, design, and performance of a prototype high-power-density converter suitable for use in the front-end of a distributed power supply system is presented. It delivers 1 kW to a regulated 40 V distribution bus from the rectified utility. Its switching frequency is 500 kHz, and it uses a phase-shifted PWM (pulsewidth modulation) technique to avoid primary side switching losses     

中短波广播发射台电磁干扰问题的控制方式探析

文章针对中短波广播发射台产生电磁干扰的成因与类型进行详细介绍,并结合其干扰形式的不同提出针对性控制方式,以期为我国中短波广播的发展提供有价值的参考意见。     

高速ADC在短波宽带接收系统中的应用

文章论述了基于高速A/D转换芯片LTC2209应用的电路设计。系统应用结果表明基于LTC2209的短波宽带接收系统能够同时接收处理2 MHz带宽内的短波信号。系统指标满足设计要求。     

谈大功率短波宽带天线的收发开关

本文首先研究和探讨了大功率短波宽带天线和大功率短波宽带天线收发开关设计的意义和价值,并对一种大功率短波宽带天线收发开关的设计展开研究和探讨,为大功率短波宽带天线收发开关的研究和设计提供资料参考.     

PSM 500kW短波发射机高末屏压自升自降故障分析与维护

PSM短波发射机出现高末屏压自升自降故障是比较常见又很难判断处理的故障,通过对420C型500kW PSM短波发射机出现的2种高末屏压自升自降故障现象,结合发射机高末屏压产生的原理进行深入分析,同时给出了解决问题的方法,对提高发射机稳定工作提供了一种思路。     

短波通信选频中的电离层同化短期预报方法

为实现短波通信链路可用频率的短期预报,提出了一种基于卡尔曼同化技术的电离层特征参数短期预报方法.该方法以电离层观测网实时测量值为基础,对未来1~24 h的电离层参量foF2进行预报.通过对不同太阳活动期、不同季节中国区域预报的分析,结果表明：该方法短期预报均方根误差在0.57~0.72 MHz之间,相对误差在9%~12%之间;且中高纬地区的预报精度优于低纬地区.     

500kW／380V国产大功率变频器在钻机上的应用

针对国外变频器价格昂贵、调试周期和维修周期长等特点，我公司自主研发了可替代进口机的高性能钻机国产专用变频器。该变频器能够从零开始调速。当钻井卡钻时，能及时断开电动机，在低速提升时，能最大限度地发挥电动机的动力特性，提供220％的转矩输出。变频器具有易安装、调试、维护，性能稳定。应用中据实测数据显示，采用变频改造后，打1口井可节省柴油15t。     

采用高性能谐振控制器的12kW雷达电源

伴随着变换器型电源技术的飞速发展，各种集成化电源专用控制电路也不断推出。本文介绍了MC33066高性能谐振控制器原理及其在大功率雷达发射机逆变电源中的应用，探讨了工程实践中应注意的问题和采取的措施。     

Content-adaptive deblocking for high efficiency video coding

In this paper, a content-adaptive deblocking method is proposed to improve the visual quality of block-based DCT compressed videos. We find that the edge information obtained through the global orientation energy edge detection (OEED) on an initially deblocked image provides a robust partition of local directional features (LDFs). Based on this partition, for the directional featured region, we design corresponding filter orientation and thresholds to best preserve image details while reducing blocking artifacts; for the consecutive non-featured region, we impose extra smoothing to suppress the visually severe blocking artifacts. Experimental results demonstrate that our method effectively improves the visual quality while well maintaining the objective fidelity of block-based DCT compressed videos, compared with the H.264/AVC deblocking method and other existing directional deblocking methods.     

An NRD-fed dielectric rod antenna for the short millimeter wave band

A simple E-plane tapered rectangular dielectric rod fed by NRD guide is used as a millimeter wave antenna. This class of aerial features attractive radiation patterns with relatively low sidelobes and moderate gain. The measured results show that such an antenna and mounting structure can be exploited as effective radiating element in the short millimeter wave frequency band.     

小功率中短波发射台站防雷措施

雷电对于发射台站系统运行的不良影响是多方面的.本文通过分析雷电对小功率中短波发射台站的危害以及对当前防雷措施存在缺陷的研究,明确小功率中短波发射台站防雷工作方面存在的不足之处,并结合小功率中短波发射台站的特点,介绍了提高防雷性能的相关措施与方法.     

一种新的短帧交织器设计

分析了交织器的自交织距离与互交织距离对译码性能的影响,建立了交织距离的目标函数,提出了交织器优化设计的设计准则。在此基础上,给出了一种线性迭代的交织器设计方法,仿真结果表明该交织器具有优良的性能。