一种改进结构的数字混频正交变换法

数字正交解调器是软件无线电（SDR）接收机的重要部件,数字混频正交变换法是实现正交解调器的常用算法。本文针对软件无线电中传统数字混频正交变换法算法,根据理论推导,提出一种适用于多频段中频信号的改进结构的数字混频正交变换法。该改进算法将正交解调与低通滤波两个过程结合在一起实现,并且每输入M个输入采样值做一次输出滤波。通过分析和在可编程器件FPGA上的实验表明,该新结构完全实现了数字混频正交变换法,且能较大地减少所占用的FPGA上的RAM和乘法器资源,在相同的FPGA资源条件下,可以较大地提高中频数字正交解调器的邻道隔离性能,或者大幅度提高所允许的前端模数采样器（ADC）的采样频率。      

用于CATV双向网的全数字BPSK／QPSK解调器

介绍一种全数字ＰＳＫ解调器ＳＴＥＬ－２１０５，它采用相干正交解调，芯片内包括了为此所需的全部功能单元如下变频、载波恢复和位时恢复等，本文简单介绍了此解调器的功能，结构以及使用方法。     

直接数字频率合成杂散抑制方法的研究

在理想条件下分析了直接数字频率合成（DDFS）输出信号的主频谱，在此基础上，引入了延时叠加法来减少其杂散分量，本文也讨论了DDFS线路中器件本身的非理想特性引起的量化噪声及减小量化噪声的方法，采用上述这些方法后，DDFS输出信号的频谱中的杂散和噪声得到了较大的改善，如要进一步抑制DDFS的杂散和噪声，则应考虑应用DDFS＋PLL方案。     

一种适用于数字视频编码器的高性能直接数字频率合成器

提出了一种适用于数字视频编码器的直接数字频率合成器DDFS(DirectDigitalFrequencySynthesizer)新结构.通过采用相位截断噪声整形技术,使所需要的ROM面积下降为传统结构的1/8.同时采用了其它优化策略进一步减少了ROM的面积,整个DDFS仅需要1152bit的ROM.DDFS输出在PAL制式下信噪比为69dB,NTSC制式下为70.7dB.     

一种基于非均匀分段线性插值的直接数字频率合成器

提出了一种基于非均匀分段线性插值的直接数字频率合成器（DDFS）的设计方法．在所设计的DDFS的相位幅度转换模块中．通过对正弦函数的0到π/2段进行非均匀分段，然后在每一段中采用线性插值近似实现．采用此方法。在八分段、十四分段情况下DDFS的无杂散动态范围（SFDR）值分别达到64．7dB、73．3dB。     

基于FPGA的超声信号数字正交解调器

利用FPGA设计用于检测微弱超声信号的数字正交解调器.将经高速A/D采样的数字信号分为两路正交的基带信号,通过数字混频、低通滤波和数据抽取,最后从两路正交基带信号中提取出超声回波信号的幅度信息.本文对数字正交解调进行了理论分析,并分别利用FPGA中的内建RAM实现数控振荡器,内嵌乘法器实现数字混频,IP核实现低通滤波器,及宏模块实现数学运算.对玻璃杯的扫描成像实验结果,证明了设计的正确性.     

一种适用于数字视频编码器的高性能直接数字频率合成器

提出了一种适用于数字视频编码器的直接数字频率合成器 DDFS(Direct Digital Frequency Synthesizer)新结构 .通过采用相位截断噪声整形技术 ,使所需要的 ROM面积下降为传统结构的 1/ 8.同时采用了其它优化策略进一步减少了 ROM的面积 ,整个 DDFS仅需要 115 2 bit的 ROM.DDFS输出在 PAL 制式下信噪比为 6 9d B,NTSC制式下为 70 .7d B     

津沈数字微波电路调制／解调器原理及故障分析

津沈数字微波电路调制／解调器原理及故障分析天津市长途电信局微波站王洪良天津至沈阳的电路使用的是四次群、大容量的数字微波系统，采用了意大利Ｔｅｌｅｔｔｒａ公司的１４０Ｍｂ／Ｓ调制／解调设备，其集成度较高，结构较简单，有调制器、解调器（终端站和背对背双端...     

同洲CDVB981M数字卫星接收机故障处理

同洲CDVB981M数字卫星接收机由TUNER前端解调器（信道解调器）、MPEG-2解调器、音频DAC和视频编码器、主控制电路和用户控制接口电路（从控制电路）等5大部分组成，如图1所示。     

低功耗调谐器可用于数字卫星付费电视系统

ZL10037卫星调谐器可用于付费电视（PayTV）系统中的标准清晰度和高清晰度数字卫星电视接收机，与ZL10313卫星解调器结合使用，提供了一种高性能低功耗的QPSK（四相相移键控）卫星接收机解决方案。与8-PSK解调器一起使用时，ZL10037调谐器还可提供HD标准的性能。     

Design of a mechanism for biaxial rotation of a wing for a hovering vehicle

This paper presents a novel mechanism to actuate the wings of a hovering micro air vehicle (MAV). The mechanism uses a single actuator, but each wing can rotate about two orthogonal axes. The goal of this work is to design a light-weight compact mechanism that flaps the wings, inspired from the wing motion of hummingbird and hovering insects, to generate enough lift for the vehicle to hover. This paper explains in detail the proposed mechanism and its working prototypes. Also, the paper presents a dynamic simulation of the mechanism. The proposed dynamic simulation is used to predict the theoretical lift of the ornithopter. Further, the theoretical model is supported by actual experimental data collected from the prototype. The experimental data shows that the vehicle has the potential to develop enough lift to hover.     

An adaptive technique for determining a reduced model for a system

A reduced or sparse system model is discussed that will contain only the most significant components, as opposed to a complete finite impulse response (FIR) model which may not be very accurate with the requirement of only a few components. The technique presented uses an adaptive delay filter to provide the sparse model and compares it to the model obtained with the standard adaptive filter     

Interleaving and decoding scheme for a product code for a mobiledata communication

We propose a new ordered decoding scheme for a product code for mobile data communications. The ordered decoding scheme determines the order of decoding for both row and column component codewords according to the probability of decoding the component codeword correctly. Component codewords are decoded independently. To randomize burst errors in both row and column codewords, a diagonal interleaving scheme is used for code symbols in the codeword. It is shown that the ordered decoding scheme combined with diagonal interleaving improves the performance of a product code with reasonably long code length for mobile data communications     

Wavelets for a vision

Early on, computer vision researchers have realized that multiscale transforms are important to analyze the information content of images. The wavelet theory gives a stable mathematical foundation to understand the properties of such multiscale algorithms. This tutorial describes major applications to multiresolution search, multiscale edge detection, and texture discrimination     

Building a virtual community for a tele-learning environment

This article presents the results of a research project that requires students and faculty to evolve a virtual community in a university class. The concepts, requirements, and importance of a virtual community are discussed, along with the skill requirements necessary for students to participate effectively in a virtual community. The Web sites and class assignments that form the basis of a virtual community are described. Finally, the importance of enriching the learning experience and humanizing the learning process through the use of a virtual community is also discussed     

高性能数字电视QAM均衡器VLSI结构设计

本文设计了一种适用于高清晰数字电视(HDTV)接收芯片的全数字正交幅度调制器(QAM)的均衡器。该均衡器由前馈滤波器、误差判别电路和系数更新电路以及后馈滤波器构成。该均衡器采用了常模算法(CMA)和判决导引最小均方算法(DD-LMS)相结合的算法。重点给出了均衡器的VLSI实现、两种算法间切换的依据、步长的选择以及抽头系数的确定。同时在电路上采用了逻辑简化、重编码、电路时分复用等简化和优化方法来实现性能、面积和功耗的折衷。     

高性能数字电视QAM均衡器的VLSI结构设计

设计了一种适用于高清晰数字电视(HDTV)接收芯片的全数字正交幅度调制器(QAM)的均衡器.该均衡器由前馈滤波器、误差判别电路和系数更新电路以及后馈滤波器构成.该均衡器采用了常模算法(CMA)和判决导引最小均方算法(DD-LMS)相结合的算法.重点给出了均衡器的VLSI实现、两种算法间切换的依据、步长的选择以及抽头系数的确定.同时在电路上采用了逻辑简化、重编码、电路时分复用等简化和优化方法来实现性能、面积和功耗的折衷.