Ka频段10 W自适应射频预失真线性化固态功放研制

射频功率放大器的特性会随信道切换、环境温度、工作状态等多种因素发生变化,为了保证功率放大器的优良工作特性,具有自适应性能的预失真系统就显得非常重要。提出了一种自适应反馈检测方法,以减小放大器输出信号的幅度失真和相位失真作为系统自适应的优化目标,〖JP2〗采用多方向搜索优化算法对预失真系统进行优化调整,使系统始终处于最优工作状态。研制了工作于Ka频段10 W自适应射频预失真线性化固态功放原理样机,当工作温度为-40℃～+60℃时,在3 GHz的工作带宽内,三阶交调指标优于-32 dBc。测试结果表明该功放具有工作频带宽、温度适应性广等特点。     

零中频接收机及其AGC方法的研究与实现

实现了基于LT5506下变频器和Cyclone IV FPGA的零中频接收机,采用射频、基 带一体化架构,尺寸仅为8 cm×6 cm×1.5 cm,重量仅为45 g,功耗仅为 800 mW,满足小型化 、低功耗的要求。针对零中频接收机中射频信号检波困难和传统AGC的调节时间受输入信号 幅度影响的缺点,由Cyclone IV完成信号检波,增加对数运算环节并改进环路滤波器的结构 ,配合LT5506中的可变增益放大器仿真并实现固定调节时间的AGC,用8 MHz采样时钟对 1 MHz正弦波进行幅度控制,调节时间恒定为53 μs,不受输入信号幅度影响。     

自适应陷波器在连续波引信噪声抑制中的应用

为提高连续波多普勒无线电引信在噪声干扰环境中的工作可靠性,分析了噪声干扰对 连续波多普勒无线电引信的影响。根据连续波引信信号的单频率特点,将单频率自适应陷波 器应用到引信中,用来对引信通带内的噪声干扰进行抑制,分析了噪声抑制原理,并对噪声 抑制效果进行了仿真。仿真结果表明,信噪比为-10 dB时,利用单频率自适应陷波器仍 然可以达到很好的噪声抑制效果。     

双模噪声背景下自适应小波阈值去噪

在分析双模噪声模型统计特性的基础上提出自适应小波阈值算法。新算法中设计改进的阈值函数和控制函数,克服了传统硬、软阈值法的不足,并且自适应得到最佳控制因子。该算法对加入双模噪声的信号进行闭环反馈处理：小波分解、阈值量化处理、小波逆变换重构信号、控制函数寻优。Matlab 2012a仿真结果表明,该算法相对于传统硬、软阈值法,去噪图形曲线清晰、光滑、连续性好,信噪比分别提高9 dB和4 dB。在双模噪声背景下,自适应小波阈值去噪有效、可行,拓展了小波阈值算法的应用。     

卫星广播信号上重叠发射导航增强信号的方法

提出了一种在卫星广播信号上重叠发射卫星导航增强信号的方法,将差分校正数据经过扩频后发射出去,与卫星广播信号进行频谱重叠,一起经卫星转发。通过参数设计和性能仿真可知,差分增强信号对广播信号的接收解调影响很小,差分接收机可以通过串行干扰抵消的方法从混合信号中提取出差分增强信号,实现解扩与辅助测距,解扩得到的差分校正数据可直接用于差分定位。当混合功率比为26 dB时,捕获概率达99.99%,测距精度为10.67 m,表明了此方法的可行性。     

最小能量框架的跟踪干扰识别和去噪算法

讨论了基于离散信号空间上的最小能量（小波）框架的跟踪干扰信号识别和去噪算法。利用一组框架对采用相位调制的接收信号进行分解，如果受到跟踪干扰，则未干扰区信号和干扰区信号的3个分解子信号将呈现明显不同的能量分布特征，据此提出了一种跟踪干扰信号识别和自适应阈值去噪算法。理论分析和仿真结果表明，识别算法具备低虚警率和漏警率性能，而去噪算法有效抑制了干扰信号能量，10-2 误包率时，BPSK+1/2 Turbo信号中1/16尾部信号受到干信比值10 dB的高斯噪声干扰后，去噪算法获得了约4 dB的增益；而QPSK+1/2 Turbo信号中1/8尾部信号受到干信比值10 dB的高斯噪声干扰后，去噪算法可以把误包率性能从1降低至约0.67的水平。     

一种欠完备自编码器调制识别技术

基于信号特征进行模式识别的调制识别方法需要先计算信号的高阶特征、高阶累积量再进行模式识别，整体设计复杂，特征不易计算。机器学习技术由于其强大的特征提取能力和分类能力，被广泛应用到模式识别领域中。针对调制识别问题，提出了一种基于欠完备自编码器的调制识别技术，使用欠完备自编码器进行调制信号的特征自动提取，再使用神经网络分类器进行分类识别。整体模型更为简洁，运算复杂度较低，有利于部署在硬件上进行实时识别。对常见的BPSK、QPSK、2ASK、2FSK、16QAM数字调制方式进行的识别实验表明，算法在信噪比10 dB时平均识别率高于0.97，并且在信噪比为0 dB时仍然有0.92以上的平均识别率。     

数字调制信号制式识别新方法

通过分析数字调制信号功率谱及高阶谱特征，对高阶谱的求取方法作了改进，并在此 基础上提出新的特征参数，结合瞬时统计特征，采用支持向量机分类器，实现了AWGN信道下 数字通信信号的制式自动识别。仿真表明，所提取的特征参数具有较好的抗噪性能，对调制 参数的变化具有稳健性。考虑脉冲成形的影响，在信噪比大于12 dB时，单种信号最低 正确识别率大于985%，平均识别率达995%以上。     

用于旋转映射信号的多天线联合Turbo均衡算法

旋转映射信号将编码比特旋转移位后映射为符号，同时采用了隐性交织、加扰等技术，具有交织复杂度低、信道效率高等特点，是一种典型且使用较为广泛的短波通信信号。针对第三方接收条件下，频率选择性衰落造成该类信号难以有效接收的问题，推导了该类信号的软符号解映射、映射方法，提出了一种针对该类信号的多天线联合Turbo均衡算法，实现了软信息在均衡与译码之间的迭代交换。典型短波信道下的仿真结果表明，迭代4次后的两天线联合Turbo均衡在10-5误码率时相对两天线硬判决译码提供了约4 dB的增益，相对两天线软判决译码提供了约1 dB的增益，在10-4误码率时相对单天线Turbo均衡提供了约5.5 dB的增益。     

一种自适应增强谱线算法的优化设计与实现

自适应谱线增强（ALE）算法能够提高高动态、低信噪比信号的 载波频率估计精度。针对实际应用中该算法消耗硬件资源多、结构复杂、使用效率低等问题 ,提出了结合可编程逻辑门阵列（FPGA）优化的ALE算法结构方法,简化了ALE硬件电路。设 计结果表明,改进ALE方法后,可实现信噪比为0～20 dBHz、最大多普勒动态为800 H z/s的测控信号载波频率准确估计。     

Public Financial Expenditure——A Reflection of the Livelihood Improvement

In recent years.China's public finance put social construction high on the agenda and attaches more importance on livelihood insurance and improvement.The 2003-2007 public financial expenditure reflects a fact that the government isputting more emphasis on livelihood andissues concerning the people.     

Voices from the MPC and CPPCC

"Crucial for economic growth.energy utilization has its role in all economic sectors and every aspect of people's daily life.Now we are in dire need of a new profession,namely energy manager.We not only need to have passion and responsibility,but also a scientific approach to conserve energy and cut emissions.APpropriate legislation should be in place.and a special profession should be introduced to ensure the implementation of these laws and regulations."     

Slowdown Trade Surplus Growth

According to Ma Kai＇s economic planning report submitted to the NPC session on March 5th,（Ma Kai is the Minister in charge of the National Development and Reform Commission）,the government has listed the slowdown in trade surplus growth and the steady expansion of external investment as major tasks for 2008.     

Ouyang Riping： A Hero Besides Entrepreneur

A bout fifty years ago. a baby＇s cry broke the sky of quietness, in a small and beautiful town of Hunan province, which surroundcd by green hills and clear water. Though his .birth brought his family great happiness and hope just as any new life, nobody knew that the little boy would get great achievement when he grow up. even start his business oversea, and earn international honor. Let＇s share with you the entrepreneur Ouyang Riping＇s story, which may insights thcsc people who want to succeed and complete oneself in favorite condition or adversity rather leave things to so-called fate.     

Belarus, A Chinese Fort in Europe

＂In recent years, we＇ve found increasing interest from Chinese investors in the Belarus economy. Please let China know, Belarus is always ready to be a true friend to China. We have built a fort in Europe for China,＂ the President of Belarus, Alexander Lukashenko told Zhou Xiaochuan, President of the Bank of China, during his visit to the capital of Minsk, on January 8th, he expressed his high praise and firm confidence in the development of Sino-Belarusian relations.     

What＇s Behind Spring Festival？

Similar to what the Christmas Day means for the westerners,the Spring Festival is the most important celebration for Chinese people.This big event according to Chinese traditional lunar calendar relaxes and pleases the whole country as the happiest gathering time of the year.National-wide crusade for going back home,too-difficult-to-get train tickets,generous family-going-out shopping,Miaohui laundering,New Year Eve reunion dinner,visiting friends and relatives,watching annual TV gala......each piece of clue reminds us of the smell of Chinese Spring Festival.     

KEY WDRDS for Foreign Investment in China

FDI(Foreign Direct Investment),a component of a country's national financlal accounts,is investment of foreign assets into domestic structures,equipment,and organizations.It does not include foreign investment into the stock markets,concession and subcontract.FDI iS thought to be more useful to a country than investments in the equity of its companies because equity investments are potentially "hot money"which can leave at the first sign of trouble,whereas FDI is durable and generally useful whether things go well or badly.     

Brown＇s Blossom in Britain-China

The overall strategic relationship between U.K. and China is ＂better than ever＂, China- Britain relations have maintained good momentum, with increased high-level exchanges and the reinforcement of strategic mutual trust, with more room for growth in the future.     

Challenge and Opportunity Go Hand in Hand——What Global Economic Agitation Brings to the China's Economy?

Domino effects of the global finance agitation As the origin of the subprime crisis,US financial institutions lost USS45 billion last year,accounted for over half of the total US,EU & Japan loss.Since January 15th,Chtigroup released its financial statement of the 4th quarter,showing a net deficit of USS9.83 billion,which marked the hisoric high of its quarterly deficit.     

Consumption, New Protagonist in 2007 GDP

Not long ago, the National Bureau of Statistics released its 2007 Macro Economy Index. Social consumption retail sales reached RMB 8.9 billion, increased by 16.8 percent over the previous year, or 3.1 percentage points higher; the whole investment in social fixed assets was valued RMB 13.7 billion, a year-on-year increase of 24.8 percent, that is 0.9 percentage points higher; and trade surplus amounted to RMB 24.7 billion, rising by 47.7 percent compared with the same period last year, 26.3 percentage points falling over the increasing speed last year. According to preliminary estimates, GDP for the year was RMB 24.67 trillion, up by 11.4 percent from the previous year,