伪码测距中码跟踪环的FPGA实现

码跟踪环的设计是伪码/载波相位联合测距系统的一个关键环节.分析了伪码跟踪环路的结构,利用查表法、二阶环路分别对NCO和环路滤波器等关键部分进行了设计,并给出了相应的电路结构.系统仿真与FPAG片上测试结果表明,实现了伪码准确、实时跟踪,跟踪到的伪码相位误差小于载波相位的周期长,设计的跟踪环具有一定工程应用价值.     

非相干扩频接收机伪码跟踪环设计及FPGA实现

伪码跟踪环的设计是实现非相干扩频接收机的关键环节。为了实现非相干扩频接收机的伪码跟踪,设计了能量归一化的延迟锁定跟踪环,给出了环路的实现结构及环路参数的计算方法。分析了非相干扩频的特点,指出环路设计的关键点,在此基础上阐述了码环鉴别器、环路滤波器、超前滞后码发生器的设计及实现方法,并给出一套具体的实现参数。Modelsim仿真结果及FPGA实测数据表明所设计的环路能对伪码进行精确跟踪。     

一种基于再生伪码测距的遥测信号测距方法

为了简化深空探测器无线测量系统设计,解决下行系统受功率、带宽等因素限制遥测信号和测距信号权衡设计问题,在再生伪码测距技术的基础上,提出了一种基于遥测信号测距的新方法,以遥测数据符号代替测距伪码的功能,利用地面跟踪环路对遥测信号的跟踪测量实现下行测距,减少了独立的下行测距信号。分析和仿真结果表明:新方法简化了下行信号形式,降低了系统实现复杂度,在遥测码速率为100 kbit/s左右时,随机测距误差优于传统再生伪码测距模式,且随着遥测码速率的增加测距精度进一步改善。     

航天测控系统中伪码测距精度分析

伪码测距以其较长的无模糊距离和较高的测量精度的显著优势,广泛应用于航天测控系统中。依据伪码测量原理,并结合工程经验数据,通过分析星地伪码测距系统的具体实现结构,研究了系统中各误差源引入的随机误差和系统误差,其中以星地伪码测距设备引入的测量误差作为重点,并对主要误差源伪码跟踪环路进行了较为深入的剖析。     

中频数字化直接序列扩频接收机的实现

给出了统一信道直接序列扩频通信系统的中频数字化接收机的实现方案。采用该方案所实现的直接序列扩频通信系统的载波与伪随机码的捕获分别采用了FFT辅助捕获技术,载波的跟踪采用了数字CPAFC环路牵引,数字COST-AS环路精确跟踪技术,伪码跟踪采用的是数字DLL环路实现。系统中I通道采用可编程GOLD扩频,Q通道采用截断m序列直扩,并置截断m序列与GOLD码具有相同速率、倍周期的关系,以简化系统伪码的同步电路设计。最后,讨论了该系统应用于扩频测距时,测量数据的"置中值"处理方法。     

基于IR-UWB码相关测距研究

研究了伪随机码测距技术在IR—UWB体制中的应用,阐述了码相关测距工作原理,对测距过程进行了仿真,并给出了系统实现框图。通过误差分析,指出伪码自相关旁瓣以及相关运算步长对码相关测距精度影响较大。     

DVB-T中伪随机序列扰码器的FPGA实现

伪随机序列在伪码测距、导航、数字数据扰乱器、噪声产生器、通信加密中有着广泛的应用。在这些实际应用中,常常利用现场可编程门阵列（FPGA）来产生伪随机序列,这便于系统设计和测试的实现。针对数字地面电视广播（DVB-T）标准,以线性反馈移位寄存器电路为基础,设计了一种并行伪随机序列产生方法,该方法简单而高效地实现DVB-T系统码流数据的扰码。实验结果表明,MATLAB扰码算法结果与FPGA扰码模块仿真结果和硬件实现结果一致,该设计方法切实可行。     

基于FPGA的伪码测距电路的设计与实现

介绍了基于伪码测距的某定位系统的设计方案，简要分析了伪码测距的原理，研究了和FPGA实现伪码的捕获与跟踪的方法。     

伪码测距雷达中的伪码跟踪环路设计

提出了一种适用于伪码测距雷达的伪码跟踪环设计方法,重点对伪码跟踪环的跟踪精度和动态性能进行了分析,讨论了一种最小跟踪误差意义下的最优环路带宽确定方法。仿真结果表明伪码跟踪环跟踪精度高,对动态运动的适应能力强。     

直接序列扩频通信系统中PN码相位的精确测量方法

本文提出了一种精确测量本地PN码和输入PN码相位差的方法,这种方法结合了数值分析算法和数字信号处理技术,通过对鉴相单元输出值的处理得到很高的测量精度,并且由于这种方法为全数字方法,可以用FPGA、DSP等处理芯片方便地实现。文中给出了计算机仿真的结果,并根据仿真结果分析了此方法的准确度和抗噪声性能。这种方法在伪码测距、高精度伪码捕获跟踪、差分定位等领域中有很大的应用价值。     

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.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

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.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

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.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.