基于FPGA+DSP的双模兼容导航接收机设计

现有的商业化接收机由于其集成式、固化式设计已不能满足当前科研领域的研究需求,针对世界上多种卫星导航系统同时并存的状态,文章介绍了一种基于FPGA+DSP的双模兼容导航接收机系统设计方案。由天线及前端射频模块完成GPS L1和GLONASSL1频点信号的接收、下变频及A/D采样,充分利用FPGA和DSP实现接收机的基带相关运算、信号处理、导航定位解算,系统间各部分的接口设计。系统测试结果表明文章所设计的接收机具有功耗低、体积小、集成度高、可重复开发的特点。     

多模多频卫星导航接收机数据处理技术研究

卫星导航系统的不断升级完善加快了导航接收机的更新换代,导航接收机数据处理技术也需要进行不断完善。针对多模多频导航接收机数据处理技术中的多模多频导航定位技术、数据输出技术和远程加载技术进行了深入研究。多模多频导航定位技术中提出了采用"高内聚、低耦合"定位处理流程,所有通用处理方法不进行系统区分,实现了各处理方法独立无耦合;针对卫星导航系统频点的增加导致观测信息数据协议包较长的问题,设计了一种伪距增量的方式进行数据传输协议;针对多模多频导航接收机含有多FPGA和多DSP芯片的特点,设计了一种基于CRC校验方式进行远程加载,具备加载速度快和成功率高等优点。     

导航信号的射频直接采样方法与实现

针对传统导航接收机采用模拟射频前端存在的缺陷,提出一种基于直接射频采样技术的导航接收机实现方法。根据当前公开的导航频段,将1.2 GHz和1.5 GHz的导航信号视为2个整体的带通信号,通过带通采样原理,选择可以兼容多频段导航信号的采样频率。为了解决射频采样后数据速率较高的问题,设计了一种基于抽取滤波和多相混频的数字下变频信号处理结构,可实现任意频点导航信号的降速、下变频和分离。该方法通过软件模块修改配置参数就可以实现多频点信号接收,极大地提高了系统的灵活性。通过Matlab对GPS L1的信号进行了仿真验证,结果表明该方法有效。     

多频GNSS射频采样接收机设计与实现

针对多频GNSS接收机采用模拟射频前端存在的缺陷,研究基于直接射频采样技术的多频GNSS接收机设计与实现。根据当前公开导航频段,设计了一种可配置、可兼容的前端数字信号处理结构,将模数转换器件紧接在天线后端,直接在射频域对导航信号进行数字化,射频以下的所有处理功能全部采用软件模块来实现,使接收机通过参数设置就可以兼容多种导航系统。对采样频率选择、本振频率选择、抽取滤波等关键技术进行了分析,基于可编程片上系统平台给出一种射频采样GNSS接收机的实现方案,分析了其中各功能模块的实现框图与工作流程,通过测试给出接收机的性能指标。      

基于SIP的低噪放电路模块小型化方案设计

文章介绍了一种基于SIP技术,展望了未来低噪放电路芯片化可行性,在北斗B3频点,带宽为20 MHz,在已验证可靠的卫星导航接收机射频前端低噪放电路模块上,验证了SIP技术的可行性,该设计具有小型化、低功耗、高性能的优势,在未来卫星导航接收机中具有广阔的应用前景。     

一种基于0.18μm CMOS工艺低功耗多频点兼容GNSS卫星导航系统接收机射频前端模块设计

本文介绍了一种全集成的L波段多频点全球卫星导航系统(Global navigation satellite system, GNSS)接收机的射频前端模块的设计和实现.该模块采用了低中频,单射频通道的设计,包括一级低噪声放大器,一级下变频器以及多相滤波器和求和电路.其中低噪声放大器采用改进的带有源极负反馈的共源共栅极结构,并保证多频点兼容且共用片外匹配网络,并通过开关进行不同工作频点的切换.另外重新设计了可用于宽带的双平衡混频器作为下变频器,其在增益,噪声和线性度等方面进行了改进.采用TSMC 0.18μm 1P4M RF CMOS进行流片,对兼容1.27GHz和1.575GHz双模低中频射频前端模块结构进行相关设计的验证.相关测试表明,对于两个工作频点,本模块可以分别提供约45dB或43dB增益,噪声系数为3.35dB或3.9dB.同时,该模块在1.8V电压下电流为11.8mA到13.5mA. 射频模块的面积仅为1.91×0.53 mm²而整体芯片面积为2.45×2.36 mm².完全满足卫星导航接收机的应用需求.     

基于软件无线电的S频段通用化TDRSS用户终端

介绍了一种S频段通用化跟踪与数据中继卫星系统(Tracking&Data Relay Satellite System,TDRSS)用户终端的实现方案,重点论述了射频通道的通用化设计和数字处理模块的实现。对70 MHz中频信号直接欠采样数字化后,利用FPGA完成中频处理的所有流程,实现了一个硬件平台满足不同通信频点、扩频伪码和信息速率的需求。系统具有体积小、重量轻的特点,适合应用于微小卫星平台。测试结果表明,能满足常规中继测控通信指标要求。     

北斗卫星导航系统应用终端检测技术探究

北斗导航系统主要采用GNSS接收机来接收信号,接收机一般由射频前端、基带数字信号处理模块和定位导航运算模块构成。主要介绍了北斗导航卫星系统技术原理和网络架构体系;分析了应用接收端的主要功能实现以及以及主要性能参数指标的测试分析;通过建立的GNSS接收机兼容性以及性能仿真测试平台,对应用终端相关参数性能进行仿真检测,通过实时仿真评估分析,确保应用端各项指标符合设计要求,满足用户需求。     

GPS L1C信号模拟器设计实现

多体制全星座卫星导航射频信号模拟器,能够同步实时模拟多个星座多种信号体制的卫星导航信号,为卫星导航系统仿真验证和接收机测试提供高效支持。本文旨在设计实现GPSL1C信号模拟器,着重研究了基于FPGA和DSP的L1C信号的数字合成问题,包括信号特性及生成模型、信号通道结构及各模块设计:最后通过与L1C接收机的对接测试结果,验证了模拟器生成的L1C信号的性能。     

GPS/Galileo卫星导航接收机射频前端设计

本文阐述了 GPS/Galileo 卫星导航接收机射频前端的设计方法。首先提出了卫星导航接收机射频前端设计中的几个关键指标,然后详细说明了射频前端具体电路的设计方法,最后给出了实际电路的测试结果。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.