集成锁相环MC145146在频率合成器中的应用及频率控制码的算法

本文结合集成锁相环MC145146在频率合成器中的应用,推荐了一种较优的频率控制码的算法。最后,给出了一个典型的应用实例。     

解析无线通信网络频率规划的要点

随着科学技术的不断进步,无线通信技术正在不断更新完善,当今社会是网络信息化的社会,通信技术的好坏直接影响着一个国家的发展水平,决定着社会的进步程度.在城市化进程不断加快的今天,进一步完善无线通信网络频率规划有着非常现实的意义.本文就对网络信道的基本分配方法及其手段进行分析,并对无线通信网络频率规划的要点进行分析.     

一种基于扩展卡尔曼滤波器的频率及频率斜率估计算法

提出一种实用扩展卡尔曼滤波器(EKF),用于极低信噪比、高动态信号的频率及频率斜率捕获.考虑滤波器的收敛性、发散抑制、捕获时间及稳态误差等指标,提出了扩展卡尔曼滤波器的参数化设计方法.计算机仿真分析了滤波器的捕获效果,结果表明,应用该设计方法,可以使频率估计具有更低的信噪比门限和更短的捕获时间.     

一种新的平滑频率扫描方式及其实现

工程中常用的匀速频率扫描方式在频率拐点处的瞬时频率变化率 较大,针对此缺点,提出了一种新的频率扫描方式——平滑频率扫描,并推导出平滑扫描的 数学表达式。利用MATLAB进行建模仿真表明,平滑频率扫描可以有效减少扫描在频率拐点处 的瞬 时频率变化率,提高接收端的捕获概率。实际工程应用证明,该平滑频率扫描方式有效可行 。     

多频道通信程控频率合成器

本文以大规模锁相环集成电路为中心,提出了一种可程控的频率合成技术。探索了多频道无线通信频率切换的方法,并给出了电路设计参数,图表以及微机接口的硬件和软件流程。有效地解决了多频道通讯中的程控频道切换的问题。     

一种基于PE3236的L频段频率合成器设计

设计了一种L频段频率合成器,该频率合成器采用大规模锁相集成芯片PE3236构成锁相环电路,外加电压预置电路对VCO控制电压进行快速预置,大大缩短了频率捷变时间,并运用相噪最优理论设计环路参数,实现了低杂散、低相噪、快速频率捷变的性能要求.另外,电路设计可靠性高,具有较大的实用性.     

日本移动通信频率选择技术动向

本文介绍日本在移动通信中频率选择的技术动向以及开展移动通信频率资源的几项措施。     

频率选择性慢衰落信道下的快速频率估计

给出了在频率选择性慢衰落信道下适用于突发传输的两种快速频偏估计算法。针对慢衰落选择性信道下的频率估计问题，两种算法均给出了一个简单的闭式解，且算法实现无需任何信道幅度信息。第一种算法要求用于频率估计的训练序列的自相关矩阵具有对角特性，第二种算法使用周期的训练序列，两种算法所需的运算量大大低于最大似然估计算法。仿真结果显示，在较高信噪比下两种算法均具有较好的估计性能。     

GSM系统频率同步的实现

在GSM系统中提出一种简单的频率同步算法,利用系统频率校正信道（FCCH）的信 号特征估计接收信号的频率偏移,并通过频率补偿实现系统频率同步。仿真结果表明,该算 法丢包率低,信噪比为8 dB时就可完全检测到FCCH;频偏估计和补偿效果好,降低了系 统误 码率。与传统的基于频域FCCH检测算法和最大似然匹配检测算法相比,所提算法基于 时域信号处理,不需进行频域分析,其性能好且简单实用。     

快速跳频雷达频率合成器的实现

本文结合实际工程,基于频率数字变换（Ｆ／Ｄ）锁相环路辅助捕获方法,提出了一种实用的由单片机控制的缩短频率转换时间的有效技术途径,以宝贝人有快速跳频能力的雷达频率合成器。     

一种新型电子对抗通道声光微波信号处理技术

本文简要论述了一种新型电子对抗通道声光微波信号处理技术，它有别于目前常用的电子对抗技术。该技术实现了多通道声光微波信号处理，对未来战场上实施对敌多路载频信号的电子对抗，对发展雷达预和毫米波制导武器系统有着实用价值。     

Capital controls on inflows, exchange rate volatility and external vulnerability

We use high frequency data and a new econometric approach to evaluate the effectiveness of controls on capital inflows. We focus on Chile's experience during the 1990s, and investigate whether controls on capital inflows reduced Chile's vulnerability to external shocks. We recognize that changes in the controls will affect the way in which different macro variables relate to each other. In particular, we consider the case where controls co-exist with an exchange rate band aimed at managing the nominal exchange rate. We develop a methodology to deal explicitly with the interaction between these two policies. The main findings may be summarized as follows: (a) a tightening of capital controls on inflows depreciates the exchange rate and (b), we find that a tightening of capital controls increases the unconditional volatility of the exchange rate, but makes it less sensitive to external shocks.     

Interest rate liberalization and pass-through of monetary policy rate to bank lending rates in China

We examine whether the effectiveness of the monetary policy rate transmission differs before and after interest rate liberalization in China using the autoregressive distributed lag (ARDL) bound test and an error correction model (ECM). The results show that after liberalization the mark-up is lower, and both the long-run and shortrun interest rate pass-through has become faster and more complete. We attribute our findings to the ongoing reforms of China’s banking system, which has improved the competitiveness of Chinese commercial banks.     

Formal business networking and SME growth

This paper provides new empirical evidence on the impact of formal business networking on small and medium-sized enterprise (SME) growth. Using a large, unbalanced panel data set of Flemish SMEs over the period 1992–2008, we examine whether participation in a government-supported program aimed at providing small business managers with structured formal networking contacts is associated with SME growth. Our results suggest that formal business networking is significantly positively correlated with net asset and added value growth.     

Market microstructure effects on volatility at the TAIFEX

This study examines whether changes in the frequency of market clearing or changes in trading hours on competing exchanges that use different auction systems affect the volatility of futures prices. In particular, this study exploits a natural experiment in the frequency of market clearing of stock index futures contracts traded on the Taiwan Futures Exchange (TAIFEX) to assess whether successive increases in the frequency of market clearing are associated with changes in the volatility of futures prices. The impact of changes in the trading hours on the TAIFEX and on the competing Singapore Exchange (SGX) where a similar Taiwanese stock index futures contract trades under a continuous auction market regime is also examined. The evidence for the impact of an increase in the frequency of market clearing on volatility is mixed. However, the introduction of simultaneous opening times for the TAIFEX (which batches orders at the open) and the SGX (which does not) is associated with a significant reduction in the volatility in SGX Taiwanese stock index futures prices. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:1219–1243, 2007     

未来防空系统综合化对抗体系发展展望

在介绍全球主要现役防空系统的基础上,结合网络通信、人工智能技术在军事装备中 的逐步推广以及商用货架产品用于军事装备的特点,预测了未来防空系统的发展趋势,分析 了基于联合组网和自动控制的智能化防空系统给目前广泛采用的基于信号层的压制和欺骗式 雷达对抗所带来的挑战,针对未来防空系统的特点给出了综合化对抗体系发展的三个层面并 建立了对应的应用模式。最后得出网络对抗、智能反辐射以及传统传感器电子对抗综合化是 未来防空系统对抗体系主要发展方向的结论。     

具有闭环跟踪的连续波雷达动态目标模拟器设计

为满足连续波雷达任务联试、设备功能检查和人员跟踪训练需要,设计了具有闭环 跟踪的动态目标模拟器。根据目标理论弹道和天线角度,完成信号幅度、多普勒频率和初始 相位的精确估计,采用FPGA+DSP构架实现动态目标的射频和差信号产生。经试验验证,该模 拟器产生的信号经过接收机解调后送至伺服,驱动天线电轴始终对准目标,实现动态目标的 闭环跟踪。     

Adolescents’ attitudes towards organic food: a survey of 15‐ to 16‐year old school children

Adolescents are the consumers of tomorrow; therefore policies aimed at increasing organic food consumption should address the needs of this group. To discover their attitudes towards organic food and their knowledge of the subject, a survey among almost 700 school children aged 15–16 years was conducted. Four main groups of questions were used: adolescents’ knowledge of organic food, attitudes, whether they bought organic food and the perceived influences they exerted on the buying patterns of their parents. From the survey it can be concluded that adolescents’ attitudes towards organic food are positive, but their knowledge of and their willingness to buy it are low. Campaigns aimed at encouraging the purchasing of organic food targeted at adolescents should particularly emphasize those characteristics of organic foods that they can relate to their interests and ethical preferences, for example, animal welfare and environmental considerations.     

How organizational identification among retail employees is affected by advertising

This paper investigates whether the organizational identification among retailer employees can be influenced by advertising aimed at consumers. The results of an experimental study of employees at a large grocery retailer show a positive impact of advertising exposure on organizational identification. Employee perceptions of advertising effectiveness (and not their feelings of pride with regards to the advertising) are found to explain this effect. The results suggest that advertising can serve an important human resource role tool by helping retailers build organizational identification amongst its employees. Further managerial implications are discussed in the paper.     

中国城市化对流通业发展影响的实证研究

从历史演进和逻辑分析相结合的角度看,城市的经济职能在于其作为集中的交换场所促进了交易频率的提高和流通业的不断发展.因此,旨在检验城市化与流通业发展关系的实证研究无疑是锦上添花.中国经济的快速增长使得多数宏观经济变量表现出非平稳特征,而协整以及建立在协整关系基础上的误差修正模型为研究非平稳变量之间的定量关系奠定了理论基础.本文利用1960～2003年中国的城市化率和流通业发展的年度数据,通过自回归分布滞后模型的方法建立了一个对应的误差修正模型,以此作为定量分析城市化对流通业发展影响的基础.研究表明,从长期看,城市化水平每增长1个百分点促使流通业增长2.436个百分点.