基于FPGA的QPSK高速解调器的设计与实现

根据无人机系统对数据链路的高速率、低误码的需求,分析比较了QPSK数字中频解调与零中频解调2种方案。针对本系统的特点,采用FPGA及DSP设计实现了一种高速QPSK数字零中频解调器,同时简要分析了高速数字解调器的工作原理,并介绍了高速解调器的硬件与软件实现。     

基于FPGA的全数字低中频QPSK调制解调器实现

本文给出了一种基于FPGA的全数字低中频四相相移键控(QPSK)调制解调器实现方案，通过硬件实现证明了本方案的可行性。     

CDMA2000数字中频的设计

在CDMA2000系统中,信道是经过QPSK正交调制传输的。数字中频与模拟中频相比能产生严格幅相平筝的正交信号,处理时能保证严格的线性相位。本文介绍了CDMA2000系统数字中频调制解调的实现方案,并对其中抗混叠滤波器、数字频率合成器的设计方法作了详细探讨。最后给出了基于FPGA的实现结果。     

CDMA2000数字中频的设计

在CDMA2000系统中，信道是经过QPSK四相扩频正交调制传输的，数字中频与模拟中频相比能产生严格的幅相平衡正交信号，处理时能保证有严格的线性相位，为此介绍了CDMA2000系统数字中频调制解调实现的方案，对其中抗混叠滤波器，数字频率合成器的设计方法进行了详细的讨论，最后给出了用基于高密度逻辑门电路可编程集成片编辑器（FPGA Compiler)实现的结果。     

基于FPGA的小型化微波发射系统设计

针对小型飞行器在飞行过程中工作状态参数的测试需求,设计了一种基于FPGA的小型化宽带零中频微波发射系统。该系统以FPGA为主控单元,接收飞行器上传感器的参数,通过正交上变频模块,实现QPSK调制,完成对所需频段微波信号的输出。经测试,该发射机输出的调制信号频率可达到4 000 MHz,功率可达到10 dBm,各项参数满足设计要求,能够实现数据的高速传输。     

一种基于优化IP核的数字中频接收机

随着现场可编程门阵列（FPGA）的出现,基于软件无线电的数字中频技术目前被广泛地应用到3G基站中。结合多速率信号处理理论,采用分级实现的方法对码分多址扩频复用（WCDMA）基站中的数字中频接收系统进行优化设计,提出一种基于FPGA硬件的IP核实现方案。仿真结果表明,IP核简洁的图形化界面保证设计可靠性的同时优化了硬件资源的配置,极大地减少了计算量进而显著缩短了设计时间。     

ILS与VOR分析仪数字中频处理技术研究与实现

本文对仪表着陆与全向信标分析仪中航向信标信号基于FPGA的数字中频处理技术进行了研究,提出了一种基于数据分离滤波的数字中频处理方案。与传统的数字中频处理方案相比,对LOC多频调制信号进行了分离测量,提高了测试的精度,对仪表着陆与全向信标分析仪广泛应用于机场校飞、日常监测和设备维护有着重要的意义。     

基于FPGA的数字中频信号发生器硬件设计

QPSK作为一种先进的数字调制方式,特别适用于数字卫星通信系统。而近年来DSP,FPGA等数字芯片的高速发展,使全数字式调制得到广泛应用。介绍一种适用于卫星通信,基于FPGA,采用QPSK全数字式调制的中频信号发生器的硬件设计方案,给出了工作原理和系统组成、主要元器件说明、以及电路板设计和制作中若干注意事项。     

一种过零脉宽检测QPSK全数字解调器及其FPGA实现

根据现代通信系统中调制解调技术全数字化的发展趋势和FPGA的广泛应用,文章提出并实现了一种采用过零脉宽检测方法、以FPGA为硬件载体的全数字QPSK解调器实现方案,并通过软件仿真和硬件测试验证了该方案的正确性和可行性.     

四阵元GNSS抗干扰天线的设计与实现

提出了一种GNSS自适应实时抗干扰天线的设计实现方案。该方案基于Cholesky分解计算最小功率算法的最优权系数,提高了抗干扰处理的实时性,并且中频调零的算法实现简化了数字上下变频模块设计,在数字基带处理中仅采用一片FPGA可以进行所有运算。实际场地测试结果验证了该方案设计天线的抗干扰能力。     

慢波结构SIR双频带通滤波器设计

本文通过分析阶梯阻抗谐振器（SIR）和慢波结构谐振器的特性,提出了利用SIR谐振器的寄生通带产生第二通带的双频带通滤波器设计方法,以达到滤波器小型化的目的;并基于0°馈电结构获取传输零点的原理对滤波器阻带性能进行优化。最后结合ADS仿真软件设计了一个中心频率在2.4GHz和5.2GHz的微带双频带通滤波器。仿真结果表明滤波器具有良好的带内带外特性。本文所设计的滤波器尺寸小,性能好,具有很好的实用价值。     

Root-of-unity based signals

A generalisation of the linear root-of-unity (LRU) filtering process is discussed. It is shown that any signal based on roots of unity, or filtered with the LRU filtering technique, will exhibit analytical properties under certain conditions. The theory is illustrated by an example using complex polyphase spreading sequences     

Landmark‐based device calibration and region‐based modeling for RSS‐based localization

During the past decades, many fingerprint‐based indoor positioning systems have been proposed and have achieved great success. However, uncontrolled effects of device diversity, signal noise, and dynamic obstacles could recognizably degrade the performance of modern fingerprint‐based indoor localization systems. In this paper, to amend the variations in radio signal strengths (RSSs) caused by device diversity, we proposed an automatic device calibration process. Because of device diversity, the sensed RSS would deviate from the trained radio map and thus leads to poor positioning. An RSS transform function could be adopted to calibrate the RSS variation between different devices and overcome the device diversity problem. However, to train the transform function, a data collection process is required. Unlike conventional calibration methods requiring manual data collection, we proposed a landmark‐based automatic collection process. Based on the detection of Wi‐Fi landmarks, our system could automatically collect pair‐wise RSS samples between devices and train the RSS transform function without extra human power. In addition, to well represent the effects of signal noise and dynamic obstacles, a region‐based RSS modeling method was also proposed. The proposed modeling method allows our system to perform region‐based target localization and utilize more robust region information for localization. Experiments in various environments demonstrate that our system could give a better positioning performance by properly handling the RSS variation caused by signal noise, dynamic environment, and device diversity. Copyright © 2015 John Wiley & Sons, Ltd.     

基于3G网络移动设备位置服务的应用

为了使3G网络架构的性能为移动设备定位提供更好的服务，现介绍一种在J2ME开发平台下，运用Mobile SVG规范开发的，移动GIS中定位技术的应用。分析了Mobile SVG在开发移动GIS中的优势，并且提出如何运用J2ME和SVG Tiny技术来构造3G手机位置服务的终端应用平台。     

Local appearance based face recognition method using block based steerable pyramid transform

In this paper, an efficient local appearance feature extraction method based on Steerable Pyramid (S-P) wavelet transform is proposed for face recognition. Local information is extracted by computing the statistics of each sub-block obtained by dividing S-P sub-bands. The obtained local features of each sub-band are combined at the feature and decision level to enhance face recognition performance. The purpose of this paper is to explore the usefulness of S-P as feature extraction method for face recognition. The proposed approach is compared with some related feature extraction methods such as principal component analysis (PCA), as well as linear discriminant analysis LDA and boosted LDA. Different multi-resolution transforms, wavelet (DWT), gabor, curvelet and contourlet, are also compared against the block-based S-P method. Experimental results on ORL, Yale, Essex and FERET face databases convince us that the proposed method provides a better representation of the class information, and obtains much higher recognition accuracies in real-world situations including changes in pose, expression and illumination.     

Current conveyor based or unity gain cells based two integrator loop oscillators

Four alternative families of oscillators are considered in this paper, three of the families employ CCII or ICCII or combination of both and each family has sixteen oscillator circuit members. The fourth family uses unity gain cells and has four circuit members. Two alternative transformation methods are used in this paper for the generation of oscillators. The first one uses the adjoint circuit theorem to obtain a new family of current mode oscillators from a voltage mode oscillator circuit. The second transformation method uses the nodal admittance matrix (NAM) expansion to generate a grounded passive element oscillator family from an oscillator circuit, which employs a virtually grounded resistor. Although this paper has a tutorial nature it includes two new families of oscillators; one of them provides both current and voltage outputs and the other provides voltage outputs and is based on the use of voltage, current followers and inverters. Simulation results are included to support the analysis.     

NAT和IPSec相容性研究

随着Internet的飞速发展,NAT和IPSec应用越来越广泛,两者不兼容已成为一个备受关注的问题。论文给出的改进UDP封装法和实现规范化描述不仅有助于更好地解决IPSec和NAT之间的冲突问题,还有利于在已有的IPSec平台的基础上进行实施。     

Reaction based robot control

A formalized approach to reaction based control of robots equipped with sensors is presented. In the case of reaction based control a goal that is to be achieved and a single layer of actions (called reactions), that are executed when sensors detect appropriate conditions, are distinguished. Unlike the pure behavioural approach, where the partitioning of the system is intuitive, a formal method was followed. First the sensor reading space was partitioned into sub-spaces, and a reaction was associated with each of these sub-spaces. If during the realization of the goal the sensor readings “enter” a sub-space associated with a certain action, then the realization of the global goal is interrupted and the action is executed. As the sensor reading space, robot reactions and the global goal can be described formally, a formal specification of the robotic controller was obtained. It was later used as the basis for coding the software of controllers tailored to the execution of specific tasks.     

ATM based multimedia servers

Next-generation multiprocessors will be deployed as servers in a multimedia environment. Current servers cannot handle multimedia traffic internally and effectively deliver the network's high bandwidth to the processing and storage subsystems. Three proposed scalable, subsystem-based, multimedia server architectures use ATM to tackle this problem     

基于FPGA的设计安全考虑

现代商业产品设计中,针对设计安全的问题往往考虑不足,这容易引发知识产权纠纷,产品设计被篡改,产品被仿制等诸多问题.为了提高产品的设计信息的安全性,文中介绍了几种方法,可以降低甚至消除产品设计信息被窃取的风险.