多载波RRU系统的设计和研究

RRU多载波通信系统,具有抑制频率选择性衰落和频谱利用率等优点,在目前数字接收发射机中复杂度较高。但该系统在实际的使用中,多个载波由于存在较大的峰均比,导致系统在实际环境中,效率较低,也难以满足多载波情况下的额定输出。在设计中,以软件无线电的系统原理背景,分析了数字处理中载波成型的过程,同时,根据多载波系统的峰均比特性,结合链路的AGC和ALC功能,以及先进的功放线性化技术,提出了一种解决多载波在峰均比同样存在的情况下也满足最大输出的设计方法。     

MPEG-2和DVB-T信号的测量

均峰比(Crest Factor)是反映发射机质量的一个重要的参数,在本文中,将重点讨论均峰比的确定及中功率DVB-T发射机的功率测量方法。     

一种降低OFDM系统PAPR的TR方法及其FPGA实现

针对正交频分复用(OFDM)系统的高峰均功率比问题,介绍了一种改进的载波保留(TR)方法,该算法应用时域核函数构造时域核函数矩阵并进行缩放参数优化,迭代过程复杂度低且性能良好.设计了一种简化的OFDM发射机方案以验证该算法在实际系统中的有效性,给出了在FPGA上实现该方案的整体架构及关键模块.硬件测试结果表明该OFDM发射机的峰均比得到了有效抑制,验证了该TR算法的正确性,证明其有较好的应用前景.     

CMMB发射机OFDM射频调制方案的设计

概述了OFDM物理层射频调制的CMMB(中国移动多媒体广播)发射机的系统结构.OFDM多载波调制存在峰均比过高的缺陷,会直接恶化功率放大器的效率.作为唯一和CMMB发射系统相匹配的峰均比抑制方案,削波结合星座图扩展的技术,以其结构简单,节约频谱资源的优势,是目前工程实现的热点.设计的CMMB发射机射频调制方案就是以成熟...     

一种新的降低MIMO-OFDM信号峰均比的方法

一、引言 在未来宽带无线通信系统中，面临的两个最大的困难：多径衰落和带宽利用效率。多入多出正交频分复用系统（MIMO-OFDM）以其高效的频谱利用率和良好的抗多径衰落性能成为4G宽带无线通信系统的热门候选传输方案。但是，与OFDM系统一样，MIMO-OFDM系统本质上也是多载波结构，仍然存在高峰均功率比（PAPR）的问题。     

次优化SLM法降低OFDM系统PAPR

正交频分复用（OFDM）系统的主要缺点是发射机输出信号的高峰均功率比（PAPR）。选择性映射（SLM）法能有效地降低OFDM信号的PAPR概率,但它需要一组逆快速傅立叶变换（IFFT）来产生候选传输信号,这将导致高的计算复杂度。本文给出一种低复杂度的次优化SLM算法。仿真结果表明该次优化SLM算法在降低PAPR相似的情况下,具有更小的计算复杂度。     

对数字预失真的一种改进

为了弥补传统数字预失真方法在收敛速度和稳定性方面的不足,采用了一种根据输入信号功率的统计特性,将其分成不同等级的处理方法,并对提出的方法进行了分析和仿真。从仿真结果看,所提出的方法跟传统方法相比,将ACLR改善了7dB。     

降低OFDM系统中PAPR的次优化PTS算法

正交频分复用(OFDM)系统的主要缺点是峰均功率比(PAPR)增大会严重地降低了发射机中高功率放大器(HPA)的效率.部分传输序列(PTS)算法能有效地降低OFDM信号的PAPR概率,但随着PTS中分割子块的增多也带来了高的计算复杂度.为此,文中提出一种新的PTS算法,该算法比传统的穷尽搜寻法具有更佳的性能.仿真结果表明,文中所提PTS算法在降低PAPR相似的情况下,具有更小的计算复杂度.     

降低PAPR的PTS算法比较

正交频分复用（OFDM）是一种有效降低符号间干扰的高速数据调制技术。在技术实现过程中若峰均比（PAPR）过高,发射机和接收机内部放大器线性要求就会很高,从而限制了OFDM调制技术的实际应用。部分传输序列（PTS）算法可以有效地降低峰均比。在此通过介绍几种改进型的部分传输序列方法,并且在峰均比降低性能、计算复杂度和其他性能指标几个方面做出了分类对比,这对今后降低PAPR的研究有一定的指导意义。     

对合成干扰信号峰均比的研究

合成干扰信号的峰均比对发射机发射信号功率有较大的影响,直接关系到干扰效果的优劣。因此在有多路干扰合信号合成时,分析其峰均比的分布以及如何降低峰均比至关重要。文中用互补累计概率分布函数分析峰均比的特性,用峰值截断法和随机相位叠加法来降低合成信号峰均比。     

Tribune/WGN DTV field test

Tribune Broadcasting Corporation, owner of 18 broadcast stations spread throughout the United States, including WGN-TV in Chicago, is dedicated to bringing DTV service to its viewers. On March 25, 1998, Tribune's WGN-TV became the first TV station to begin DTV field testing in Chicago, Illinois. The Advanced Television System Committee (ATSC) signal was successfully received first in the northwest suburb of Mount Prospect, and then subsequently received around the entire Chicago-land area during three weeks of testing. This marks the first time a DTV field test was performed using a transmitter site situated in a major city from atop a large building in the center of the city. Previous tests utilized a transmitter that was located outside the major city of coverage. This provided information about the various types of multipath that occurs when DTV signals bounce off large building structures close to the transmitter. Also of interest was the performance of DTV when transmitting through an existing RF NTSC system (HPA, coaxial feedline, and narrow-band antenna) using a side-mounted antenna from a lower height transmitter tower (compared to the Sears and Amoco buildings). This report describes the testing methods, data results, and analysis of this Chicago DTV field test. Two phases of testing were performed and completed: March 25-29, 1998, and May 13-23, 1998. Both outdoor and indoor testing were performed, the results of which are described     

Transmitter identification using embedded pseudo random sequences

A transmitter identification system for DTV distributed transmission network using embedded pseudo random sequences is investigated. Different orthogonal pseudo random sequences and their suitability for transmitter identification are discussed. Code generators are developed to study the auto-correlation and cross-correlation properties of the Kasami sequences. To speed up the identification process, the embedded pseudo random sequence is preferred to be time-synchronized with the DTV frame structure. Therefore, the length of the identification code has to be truncated before it is fitted into each field of the ATSC DTV signal. The impact of truncation noise and in-band DTV interference on transmitter identification is also investigated. It is shown that the auto-correlation and cross-correlation properties are only slightly affected by truncation. It is also found that the dominant interference to the transmitter identification is the in-band DTV signal. The signal to truncation noise ratio and signal to DTV interference ratio in the correlation output are derived, and verified via simulation. It is further recognized that in-band DTV interference can only be mitigated by increasing the code length or by time-domain averaging technique to smoothen out the in-band interference.     

A Novel Data Transmission Scheme for ATSC Terrestrial DTV Systems

In Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) systems, additional very low‐rate data can be transmitted by modulating the amplitude and polarity of the transmitter identification (TxID) signal. Although the additional data transmission scheme offers reliable transmission and has a very large coverage area, it has a limitation on the data rate. In this paper, we propose a novel additional data transmission scheme based on the TxID sequences of the ATSC DTV system and Walsh modulation. The proposed scheme not only increases the data rate significantly, but also offers a virtually identical coverage area compared to a conventional scheme.     

DTV repeater emission mask analysis

Terrestrial digital television (DTV) requires careful planning in the allocation of RF channels, especially during the transition period when intermixing both analog and digital signals in the same coverage area. One important issue to consider is adjacent channel interference, which limits the number of RF channels utilized in any given area. This issue is important in the deployment of not only full service stations, but also of secondary stations such as translators, on-channel repeaters, and low power television stations. Full service stations have FCC rules that limit the amount of adjacent channel splatter by requiring the splatter energy to remain below a rigid emission mask. Currently there are no FCC rules for translators and low power television stations. The paper discusses typical DTV transmitter splatter sidebands and their causes, as well as specific methods for interference analysis from adjacent channel DTV splatter into adjacent NTSC or DTV signals. Two rigid emission masks ("simple" and "stringent") are proposed and evaluated. Several filter designs are computer simulated and analyzed for minimizing adjacent channel splatter interference as well as in-band DTV signal degradation. Linear pre-correction techniques are analyzed for various length (15-tap and 31-tap) transversal filter equalizers. The simulation is verified by measuring and evaluating DTV system performance for two hardware band-pass filters individually placed at the output of a low power (30 W average) transmitter.     

有线网络开展3DTV技术方案与应用研究

提出了有线网络开展3DTV直播、点播、节目注入和有线网络传输、机顶盒解码显示等系列技术方案,介绍了3D影像的技术路标,给出了有线网络开展3DTV技术方案,包括3D电视直播、点播平台以及3DTV传输格式与信道编码.对设计方案进行了应用验证,同时对开展3DTV的商用性进行了分析.     

数字电视测试接收机MER和EVM校准方法研究

根据MER和EVM的测量原理,得出MER和EVM与信噪比、IQ幅度不平衡、IQ正交误差之间的关系.此外,提出数字电视测试接收机MER和EVM参数的校准方法,并给出MER和EVM理论值的计算方法.最后,使用R&S公司SFU数字电视测试发射机和ETL数字电视测试接收机对该校准方法进行了验证,验证结果与理论值基本一致,达到了...     

数字电视发射机功放的预失真技术研究

介绍了一种可识别HPA记忆效应的数字预失真器的结构、特点,以Hammerstein预失真器为例仿真了可识别功放记忆效应的基带数字预失真器,并在数字电视发射机功放线性化中加以应用,结果表明记忆效应预失真结构应用在数字电视发射机功放的线性化中可以取得令人满意的效果.     

DTV reception quality field tests for portable outdoor reception in a single frequency network

This paper presents a field measurement campaign developed to study the influence of the special features of a Single Frequency Network (SFN) reception in the C/N thresholds applicable to portable DTV reception. The measurements presented here were performed inside coverage areas of the nationwide SFN which broadcasts DTV (COFDM 8 K mode) services in Spain. The aim of this paper is to present some network planning reference values for portable reception in urban environments where both multipath and multiple transmitter reception have to be taken into account to ensure a good quality of service.     

Small-world brain functional network altered by watching 2D/3DTV

With the development of display technology, the healthy problems caused by watching 2D/3DTV have received more and more attention. This paper utilized resting-state functional magnetic resonance imaging to study the changes of small-world brain network before and after one-hour 2D/3DTV watching, and explored the brain fatigue mechanism caused by watching 2D/3DTV. We conclude that one-hour watching of 2DTV will not increase the burden of brain. On the contrary, one-hour watching of 3DTV requires the brain to regulate the efficiency of brain areas, such as temporal lobe and occipital lobe, which may explain the fact that watching 3DTV can easier cause brain fatigue than watching 2DTV.