接收机

0617477超快宽调谐突发模式10Gbit/s收发信机的实现=I m-plementation of ultrafast widely-tunable burst-mode10Gbit/s transceiver〔刊,英〕/S.Rubin,E.Bui movich//Electronics Letters.—2002,38(23).—1462(E)0617478GPS中频接收机同步的实现〔刊,中〕/陈勇//电子科技.—2006,(3).—5-8(D)介绍了一种GPS接收机的同步实现仿真过程,由于捕获部分采用FFT变换方法,大大缩短了捕获时间,码跟踪采用数字延迟相环(DPLL),载波跟踪采用数字锁相环(DPLL),位同步采用了一种计算所有可能比特跳变位能量的最大似然位同步算法,可以在极低…     

一种新型高速数字锁相环的研究

本文针对传统方法实现的数字锁相环(DPLL)工作速率低的问题,通过对一种典型的DPLL的分析,找出影响其工作速率的主要因素,研究并提出了一种全新的高速实现方法,并在实验室进行了数据传输位同步提取实验。     

一种大频偏和低信噪比条件下的全数字锁相环设计

全数字锁相环设计是相干解调全数字接收机载波同步和位同步的关键技术,而大频偏和低信噪比分别从两个方面增加了环路设计的难度.该文在此背景下,以捕获时间和跟踪性能为指标,从模拟环路分析出发,给出一种适用于大频偏和低信噪比条件的全数字锁相环设计.     

先进的深空应答机数字基带基线结构的初步设计和实现

本文阐述了先进的深空应答机的数字基带基线结构的设计和实现。对适于模数转换器（ADC）比特数选择的研究以及最佳取样方法进行了阐述。此外,还详细分析了推荐的最佳取样方法,论述了数字基带（或数字前端）以及载波跟踪的数字锁相环（DPLL）的实现。     

基于FPGA的数字锁相环实现与性能分析

在数字通信系统中,对传输数据的位同步信号提取非常重要.在基于FPGA的数字系统中,通常是设计一个数字锁相环(DPLL)来解决这些问题.文章设计一种新的利用bang-bang鉴相器实现的DPLL,bang-bang鉴相器能直接从接收数据流中提取位时钟信号,且在减少抖动、侪频、时钟恢复和数据同步有很好的优越性.分析了,整个数字锁相环在无高斯白噪声环境下的性能,最后给出了整个锁相环的波形仿真.     

软件接收机中DSB-SC信号载波同步的一种算法

本文提出了软件妆收机中抑制载波双边带调幅（DSB-SC）信号载波同步的一种算法，根据下变频后的基带信号估计出收发载波的频差，并经卡尔曼滤波后结合数字锁相环以达到载波捕获范围宽、跟踪速度快、环路噪声小的特点。文章最后给出了一个具体实例的仿真结果。     

直扩导航系统中数字科思塔斯环的FPGA设计与实现

引言 扩频接收机载波的同步包括捕获和跟踪两个过程,载波捕获即多普勒频移的粗略估计通常包含在伪码同步过程中,而精确的载波相位及多普勒频移则通过FLL（锁频环）和PLL（锁相环）跟踪来实现。锁频环直接跟踪载波频率,而锁相环则直接对载波相位进行跟踪。锁相环具有较高的跟踪精度,但对通信链路干扰的容忍能力差,特别是受载体动态引入的多普勒频移影响较大;而锁频环具有较好的动态性能,但跟踪精度较低。     

星座组网中直扩信号快速同步改进算法

基于直扩体制的时分多址(TDMA)卫星星座组网,信号帧前导段长度越短、净荷长度越长,数据传输的效率就越高.但是,直扩体制信号帧前导段长度越短意味着接收信号捕获增益就越低,捕获概率就越低.另外,前导段长度越短要求锁相环信号跟踪收敛速度越快.星座组网整网数据传输效率受到卫星信号同步算法性能的制约.为了提高直扩信号同步算法的性能,从捕获与跟踪两个部分对同步算法进行了改进,提出了一种直扩信号快速同步改进算法.针对捕获部分,分析了前置低通滤波器带宽对扩频信号的自相关函数的影响,通过选择滤波器参数在保证相关主峰无明显恶化情况下提升1/4码片偏差相关峰能量1 dB以上.针对跟踪部分,提出了一种调整闭环控制系统的零极点分布优化锁相环时域响应的锁相环设计方法,给出了基于控制理论优化锁相环闭环系统的零极点分布的四点原则,利用该方法设计的锁相环能大大降低信号跟踪的收敛时间.仿真结果表明,所提改进算法与传统同步方法相比能有效提高信号的捕获概率,加快信号跟踪的收敛速度,明显减少信号的同步时间.     

一种新型的单相数字锁相环

本文提出了一种新型的高精度数字锁相环（DPLL）技术,以一个改进的鉴相器（PD）环节代替常用的二阶通用积分器构成的PD环节,为了抑制该方法在同步信号频率上引入的二次谐波干扰,本文分析了引入谐波的原因,提出针对同步信号频率二次谐波的带阻滤波器,并研究了基于FPGA的数字锁相环实现方法。该方法锁相精度高,速度快,结构简单,计算量较小。仿真和实验结果表明该方法是有效可行的。     

全数字锁相环电路的研制

介绍了一种全数字锁相环电路工作原理,并讨论了在同步数据通信中,利用Intel8253可编程计数/定时器设计全数字锁相环电路,实现位同步的方法。     

Novel signals for optimized timing synchronization in direct‐sequence spread‐spectrum communication systems

The paper presents design techniques for novel signaling waveforms to optimize timing synchronization in direct‐sequence spread‐spectrum communication systems. Both coarse code timing acquisition and fine delay‐locked loop tracking systems are considered, and their performance metrics are analyzed in terms of initial acquisition detection probability and residual tracking jitter, showing a strong dependency on signal waveform spectral characteristics. Bit error performance under imperfect synchronization is also assessed. A design methodology is formulated with a low complexity parametric optimization approach based on prolate spheroidal waveform expansions for the generation of signals that minimize the probability of acquisition miss and tracking error jitter subject to additional constraints on signal energy and phase transitions. Novel optimized waveforms are synthesized with different levels of effective root mean square bandwidth occupancy and compared with conventional pulses to illustrate their advantages. Performance trade‐offs are demonstrated between the acquisition and tracking systems, whereby signals with low effective bandwidth are found to have better acquisition capability at the expense of poorer tracking jitter, while the converse holds for signals with higher effective bandwidth. It is found that an effective root mean square bandwidth occupancy in the range of 40% to 50% of the chip rate can achieve a good compromise between the requirements of the 2 code timing synchronization phases. Numerical results are presented to quantify the relative merits of representative waveforms with respect to the different performance measures in terms of acquisition capability, tracking jitter, and bit error probability.     

Fast Frequency Offset Acquisition and Accurate Tracking in OFDM Systems

1　IntroductionOrthogonalFrequencyDivisionMultiplexing(OFDM )isaneffectivetransmissionschemetocombatmultipathfading[1～ 2 ,1 7] .Byinsertingaguardintervalbetweensymbolblockscalledcyclicprefix,theInter SymbolInterference (ISI)canbemitigated .OFDMisadoptedasthemodulationschemeforaDigitalAudioBroadcasting (DAB)sys tem[3] andAsymmetryDigitalSubscriberLoop(ADSL) [4] andisalso proposedastheterrestrialHDTVtransportinEurope[5] .OFDMsystemisverysensitivetocarrierfre quencyoffset.Manymet…     

Application of Adaptive Filtering to Direct-Sequence Spread-Spectrum Code Acquisition

A novel hybrid scheme utilizing an adaptive FIR filter is proposed for acquisition of DS-SS signals. Timing information on the delay offset between the incoming DS-SS signal and the locally generated replica of the spreading code is extracted from the tap-weight vector of the acquisition adaptive filter. Expressions for the mean acquisition time, detection, and false alarm probabilities for a coherent, chip synchronous DS-SS system in AWGN are derived. The improvement in acquisition performance over serial search techniques is twice the length of the adaptive filter. This is similar to that gained by other hybrid schemes that search the same number of cells at a time. However, a significant reduction in hardware complexity is obtained. The proposed system is also compared to a system utilizing a partial matched filter structure. Moreover, the same hardware could be used for code tracking and, hence, eliminating the need for a separate tracking loop.     

Frequency acquisition and tracking for optical heterodyne communication systems

A frequency acquisition and tracking system for use in optical heterodyne communication systems employing semiconductor lasers is described. Analytical models for acquisition and tracking are used to predict performance; probability of incorrect acquisition is predicted for the acquisition system, and rms error is predicted for the tracker. Experimental data is presented and compared to the analytic results.     

A contribution to fast telecommunication system conception: Application to a DS-SS tracking stage improvement

This paper presents an improvement of the synchronization and tracking stages of a direct sequence spread spectrum (DS-SS) communication system to reduce the acquisition time. We propose a multi-branches solution, implanted in a virtual prototype for a home automation application. The virtual prototype is based on the VHDL-AMS high-level language and the most significant physical parameters will be transferred at a high level. Finally, acquisition time simulations are compared to other classic methods and synthesis results dedicated to a real FPGA prototype are also presented.     

Network Synchronization of an Orthogonal CDMA Satellite Communication System

This paper provides the network synchronization of an orthogonal CDMA geostationary satellite system for fixed service communications. It includes the synchronization procedures, the system architecture and the performance evaluation. The main objective is to provide network wide synchronization of all uplink orthogonal CDMA transmissions. This is achieved in steps; first by providing coarse synchronization using the uplink random access channel and then fine sync using innovative tracking control mechanisms. The uplink access channel receiver utilize a parallel/serial search method for rapid code acquisition, while the code tracking of the uplink orthogonal CDMA traffic channel is based on a delay feedback early-late gate in which the sych control resides in the receiver. The proposed system is designed to minimize the onboard complexity and satisfy the performance requirements. As shown in the performance section, the requirement that all uplink transmissions are synchronized to a reference time within 10% of the chip length can be achieved. In addition, the system analysis determines the design parameters values which optimize performance.     

高速运动环境TDMA卫星通信同步控制技术

分析了高速运动对TDMA卫星通信系统造成的影响,提出一种适用于高速运动环境的TDMA卫星通信同步控制技术。利用装载平台的导航信息辅助实现多普勒频偏的快速捕获,结合TDMA卫星通信特点完成多普勒频偏的跟踪补偿,同时使用多普勒频偏估计并修正运动引起的定时误差,可以在不改变TDMA卫星通信网现有其他设备技术状态的情况下,消除高速运动产生的影响,实现高速运动环境下TDMA卫星通信终端的快速入网和同步保持。     

CMMB地面转发系统时间同步信号解调方法

提出了一种用于CMMB地面转发系统的时间同步信号解调方法,并详细阐述了同步捕获、同步跟踪和载波频偏估计等关键算法.实验结果表明,该方法具有较高的可靠性和准确性,可以很好地满足系统需求.     

基于前导脉冲辅助的相位调制1090ES信号载频同步算法

基于相位调制扩容1090ES信号为ADS-B带来新的功能和应用,载波频率同步是扩容信号需解决的一项关键技术。针对扩容1090ES信号的突发载频同步问题,提出了一种基于频偏捕获和相位误差跟踪环的快速同步方法,频偏捕获采用前导辅助脉冲相关性判决进行二叉树频率搜索,捕获载频偏差并校正得到频偏较小的基带信号,相位误差跟踪环实现对小频偏信号进行频率估计和补偿。仿真结果表明:该方法适用于基于相位调制的扩容1090ES信号接收系统。     

一种扩频接收机的设计分析

基于直接序列(DSSS)扩频通信原理,阐述了直接序列扩频接收机的组成和工作原理,对解扩解调部分进行了详细设计,给出了关键模块的原理和实现方法;尤其对扩频信号的自动增益控制、伪码捕获、伪码跟踪、载波跟踪以及定时同步等电路进行了细致论述,并说明了注意事项;最后,给出了硬件实现方式和测试数据。设计采用低成本的现场可编程门阵列(FPGA)和数字信号处理器(DSP)实现,具有灵活性强、速度快等特点,而且通过工程应用证明了设计是正确可行的。