多频道通信程控多环式频率综合器

为适应多频道通信的需要,在采用的频率综合技术中,锁相多环式频率综合可同时满足信号频谱纯、频道多且间隔小、换频速度快等要求。本文利用典型的带电流源鉴频鉴相器的锁相环,推导了其环路数学模型,并对其稳定性进行了讨论。最后,结合大规模集成销相环,给出一个三环式多频道频率综合器的原理框图及主要性能指标,并讨论了低噪声压控振荡器等具体电路的设计。     

一种基于CORDIC算法的高速高精度数字鉴相器

提出了一种基于CORDIC算法的高速、高精度数字鉴相器。该数字鉴相器根据正交解调原理测相,采用高速全流水线结构在FPGA上实现,利用CORDIC算法实现了数字下变频(DDC)和相角的计算。本方法不需要正交本振信号与参考信号严格同步,并且允许输入信号的频率与DDC的NCO频率存在一定频偏,便于工程实现。经时序仿真验证,系统工作时钟可达100 MHz,在30 dB的信噪比条件下,测相误差小于0.004 rad,样本标准差小于0.03 rad。     

实用锁相环的门限限制

锁相环经常在高噪声环境中用作恢复信号信息的门限扩展装置。在采用低噪声低偏移的滤波器和相位抖动很小的压控晶振的频带很窄的锁相环电路中,鉴相器在输入信噪比很低时的不良工作会限制电路的有效门限的扩展。本文讨论噪声对鉴相器工作的有害影响,并比较几种电路在低输入信噪比时的性能。文中推导了以不同的设计参数估算每种鉴相器门限值的公式。     

最佳解调用的数字锁相环

本文研究了深埋在高斯噪声中的随机角调制信号的离散时间解调。首先借助于离散卡霍奈—罗也夫(Karhunnen—Loeve)展开式表示了,在适当的条件下,特殊的非均匀取样数字锁相环(DPLL)从最大后验意义上来说不过是一种近似最佳数字解调器。有意义的是这种数字环路的鉴相器只由取样器组成;在环路输出端不需要数字乘法器。其次是对上述一阶环路的输入出现随机相位调制的情况使用近似非线性分析。用模拟实验证实了这些结果。最后利用卡尔曼滤波法推导出相位和频率调制信号的最佳解调器,并介绍了它们的性能。     

数字摄录一体机的新进展

简要叙述ＤＶ数字摄录机的记录格式、主要性能及优点,并重点就最近一年来取得的主要进展如摄录机的数字接口、无带数字摄录机以及摄录像与照相一体机进行了介绍     

AD9858在捷变频频率合成器设计中的应用

系统地介绍了一种低杂散、低相位噪声、快速捷变频频率合成器的实现途径,用TMS320VC5409控制AD9858得到宽带、低相噪、高SFDR(无杂散动态范围)的输出信号.文中详细阐述了高性能DDS芯片AD9858的主要性能及其应用方法,着重说明了AD9858时钟电路的设计、调试方法,并给出了用PN9000相位噪声仪测试的结果.该数字频率合成器通过编程可方便地实现单点频、线性调频和调相功能, 经过实际应用达到了比较满意的效果.     

一种同播发射机的基准频率源设计

根据同播系统对同播发射机的要求,提出了一种利用GPS秒时钟修正晶体振荡器频率 漂移,实现高稳定度基准频率源的方法。该方法根据数字锁相原理,采用CPLD作数字鉴相器 ,通过测量GPS秒时钟与压控晶体振荡器(VCXO)时钟间的相位差,并将其转变为直流电压控 制晶振频率,取得了频率稳定度优于2×10-9的成果,已成功应用于同播发射机中。     

同步通信中的软件鉴频与锁相技术

本文介绍了一种利用软件产生同步通信中同步时钟信号的方法,论述了软件鉴频与锁相技术的基本思想,论证了软件鉴频与锁相技术的可靠性,并以实例说明了软件鉴频与锁扣技术的实际应用.软件鉴频与锁相技术较之硬件实现具有适应性强,经济性好,实现简便等优点.     

一种基于AD6620的中频数字解调方案

AD6 6 2 0是美国AD公司推出的功能强大的数字下变频信号处理器 ,本文提出了一种基于该芯片设计的中频数字正交解调方案 ,实验结果表明该方案结构简单 ,易于实现 ,且精度高、误差小。     

大动态PCM/FM遥测信号的非相干解调

针对大动态低码率PCM/FM遥测信号的可靠接收问题展开研究,给出了一种基于连续相位调制（CPM）信号原理的载波频偏矫正及差分序列检测的非相干接收方案。针对限幅鉴频、多符号检测及差分序列检测等3种非相干解调算法,介绍了各自应用于PCM/FM信号的算法原理,并比较了3种算法的解调性能及对大动态环境的适应能力。计算机仿真表明,在无残留频偏情况下,2符号相位差分序列检测性能最好;但在0.05倍码速率的残留频偏下,1符号相位差分序列检测的性能更好,优于2符号相位差分序列检测、限幅鉴频检测和多符号非相干检测。对PCM/FM信号的讨论包含了几种典型的非相干解调,对大动态环境下的PCM/FM接收有重要的参考价值。     

一种基于DDS芯片AD9850的信号源

直接数字合成 (DDS)是一种重要的频率合成技术 ,具有分辨率高、频率变换快等优点 ,在雷达及通信等领域有着广泛的应用前景。文中介绍了一种高性能DDS芯片AD985 0的基本原理和工作特点 ,阐述了如何利用此芯片设计一种频率在 0～ 5 0kHz内变化、相位正交的信号源 ,给出了AD985 0芯片和MCS5 1单片机的硬件接口和软件流程     

一种基于AD9954和AD8349的宽带线性调频信号源的设计

介绍了一种基于AD9954和AD8349的宽带线性调频信号源的设计。通过正交调制上下边带互换原理,信号的带宽可拓展为原来的2倍,实现宽带信号源。另外,还提出了一种利用DDS的可编程特性对信号的相位进行分段补偿从而获得高边带抑制比的方法。     

AD9858在超短波无线电通信领域中的一种应用

介绍了AD9858在超短波无线电通信领域中的一种应用.基于AD9858设计一种频率合成器,该频率合成器采用"DDS 倍频"的方案,具有相噪低、跳速快等优点,可用于超短波无线电通信系统.     

Anti‐dumping: A Growing Problem in International Trade

This paper discusses the issue of anti‐dumping (AD) proliferation. AD is used more frequently, by more countries, and against more products than ever in its history. I review AD filing patterns with an emphasis on the scope of countries and industries seeking protection. Recent trends suggest that the widespread embrace of AD protection makes the prospect for AD reform increasingly unlikely. AD is no longer being used solely by high‐income developed countries. It is increasingly being used by middle‐income and even lower‐income countries. New users have chosen to use AD very intensively. Per dollar of imports the new users have filed AD cases up to 15–20 times more frequently than the traditional AD users such as the US and EU. The evolving set of AD users complicates AD negotiations. In the near term, strong opposition by the US and EU makes reform a highly unlikely outcome. In the longer run, rising use of AD against the US and EU could conceivably weaken their support for AD; yet, the same trends that might finally cause the US and EU to realise AD is a failed policy will likely make reform impossible.     

Accounting for Stylised Facts about Recent Anti‐dumping: Retaliation and Innovation

Recent work has found certain stylised facts about anti‐dumping (AD) actions. (i) AD actions are mostly between industrial and developing countries; (ii) developing countries use AD to retaliate against industrial countries; and (iii) AD is concentrated in R&D‐intensive industries. This study develops an analytical framework that can account for these empirical findings. The model suggests that market expansions and/or improvement in R&D capability in the South are essential in avoiding AD wars with the North. Interestingly, stricter enforcement of intellectual property rights in the South has little effect on stopping AD wars between the North and the South.     

高性能DDS芯片-AD9852的应用研究

本文介绍了一种高性能DDS芯片－AD9852应用的研究结果。该合成器的DDS芯片选用AD公司最新推出的AD9852，其宽带杂散优于60dBc，频率捷变时间小于200ns。本文在讨论AD9852级成与功能的基础上，对其在频率混合、波形合成和跳频通信系统中的应用进行了研究。     

East Asia's Anti‐dumping Problem

East Asia accounts for a large and growing share of worldwide anti‐dumping (AD) activity. East Asian countries have long been the main targets of AD actions, accounting for about one‐third of all AD actions during the 1980s, more than 40 per cent of all AD actions during the 1990s, and almost 50 per cent of all AD actions in recent years. After controlling for factors that might influence filings such as the exchange rate and trade volume, it is found that East Asian countries are subject to about twice as many cases as either North American or Western European countries. Moreover, the trend in filings against East Asian countries is increasing, meaning that in recent years the propensity for countries to direct their AD filings against East Asian countries is growing. One concern is that the growing intensity of AD use against East Asia is driven by China‐PRC. Importantly, but a rising propensity is found even excluding China‐PRC.     

Anti‐dumping's Happy Birthday?

The purpose of this paper is to highlight and discuss recent developments in the worldwide use of anti‐dumping (AD) policy as a possible strategic counterpoint to trade liberalisation. First, we review briefly the original intended purpose of AD policy, and reflect on its secondary position on the agenda of current international trade negotiations. Second, we discuss the escalating – and perhaps strategic – use of AD policy, particularly in the developing world, and highlight the roles of both interest groups and the state in determining policy outcomes. Next, we review the state of affairs of AD policy with the world's most active user, the US. In particular, we introduce and discuss the latest important development, the implementation of the ‘Continued Dumping and Subsidy Offset Act of 2000’, which incorporates monetary compensation for petitioners, potentially offering more opportunities for strategic policy behaviour by firms, industries and the state. We conclude the article with a short discussion of directions for future research and some general concerns about the use of AD policy.     

The First Review of European Union Antidumping Reviews

The literature on antidumping (AD) has documented various aspects of this protectionist tool. However, a peculiar feature of AD has not received much attention: these measures are endogenous to the behaviour of the exporting firms, which can adjust the dumping margin by changing their export price and ask the authority to amend the AD measures accordingly. The objective of this paper is to fill part of this gap in the literature by analysing the AD reviews conducted by the European Union for affirmative petitions initiated in 1980–2009. To this end, a novel data set of all such reviews has been assembled. Summary statistics reveal that more than a third of all petitions concluded with the imposition of AD measures are reviewed at least once before their expiration, and most reviews lead to lower AD duties (although, almost 20 per cent of the firms investigated through interim reviews see their duties increase). There are significant differences in the outcome of the reviews depending on the party requesting them (i.e. reviews lodged by European producers are less likely to lead to lower duties). These conclusions are confirmed by the econometric analysis, which also shows that Chinese firms see their duties reduced significantly less than those of firms from other countries.