共查询到19条相似文献,搜索用时 78 毫秒
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基于相位调制器(PM)级联高斯带通滤波器,提出了一种超宽带(UWB)多功能调制方案,可以实现通断键控(OOK)、脉冲极性调制(PBM)和脉冲形状调制(PSM)。该方案结构简单,只需单个光源,利用率较高,仅改变比特序列发生器(BSG)的编码就可实现三种UWB调制格式间的灵活切换;产生的三种信号只包含一个波长,在光纤中传输时无需复杂的非线性控制和色散管理。使用光通信软件Optisystem进行模拟,研究了光源功率、调制速率以及两支路PM和滤波器系统误差的影响,对OOK、PBM和PSM信号的传输性能进行了分析。结果表明,光源功率和调制速率在一定范围内变化时,可以获得性能最佳的UWB调制信号。 相似文献
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伽利略系统采用二进制偏移载波(BOC)调制,这种调制方式极大改善了导航信号的抗干扰性能。介绍了BOC调制方式的原理与性质,阐述了BOC调制与传统的二相编码复合(BPSK)调制相比较的优缺点,分析了BOC调制的功率谱密度和自相关函数,并在现场可编辑门阵列(FPGA)平台上实现了BOC调制,最后给出仿真实验结果和实现频谱图,实验结果表明,该实现方式正确可行。 相似文献
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首先分析了超宽带(UWB)通信的传输载体及其具有的特征,并从传输载体的时间与幅度参数变更出发来表述几种常用的UWB多址调制与数据调制方式及其信号特征。最后从低功率谱的平坦性、密集多径环境下性能等方面对各种调制作了适当的评述。 相似文献
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提出了一种基于半导体光放大器(SOA)和电吸收调制器(EAM)实现超宽带(UWB)脉冲波形调制(PSM)的方案,利用SOA的交叉增益调制(XGM)和增益饱和效应产生高斯单边带(monocycle)信号,利用EAM的交叉吸收调制(XAM)效应控制泵浦光与monocycle信号的叠加,进而实现UWB PSM。与其它方案相比,本文方案具有结构简单、易于控制和色散管理相对简单的优势。利用OptiSystem7.0软件进行了仿真研究,分析了输入信号功率、调制速率和光源波长对UWB PSM信号的影响,研究了UWB PSM信号在光纤中的传输特性。结果表明,本文方案对输入信号波长不敏感。给出了输入信号功率和调制速率的优化范围。 相似文献
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本文提出一种二阶类BPSK方法,该方法兼顾了运算量和灵敏度,有效消除了BOC调制信号的模糊度,使得接收机能够准确捕获卫星导航新体制信号.经过验证,该方法可以提高信噪比,实现BOC调制信号的高灵敏度捕获. 相似文献
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首先分析了在超宽带系统中高斯脉冲成形因子和微分阶数对其能量谱密度的影响,并在此基础上,为了提高高斯脉冲波形的频谱利用率,采用高斯导函数线性组合来产生脉冲波形,提出并分析了一种基于粒子群(PSO)优化算法的超宽带无线脉冲波形优化设计方法,仿真表明该方法产生的高斯导函数线性组合脉冲能够很好地满足FCC的频谱掩模限制。 相似文献
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基于水声通信系统的需求,设计了基于FPGA的CDMA技术的调制/解调模块,选用m序列作扩频码,BPSK作为调制方式。该设计在EP3C10E144C8N芯片上,实现了各个功能模块,完成了CDMA调制/解调功能,仿真结果表明该设计功能正常并且工作稳定。CDMA调制/解调模块将应用于水声通信系统。 相似文献
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This paper presents a technique for optimizing the baseband pulse shapes in digital angle modulated signals to minimize the fraction of out-of-band power for a given channel bandwidth. As examples of practical interest, the optimization is carried out for channel bandwidths up to three times the bit rate and for the range of modulation indices usually encountered in digital transmission. Results for MSK-type signals appear as a special case. 相似文献
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Continuous phase modulation (CPM) schemes, using Nyquist 3 pulse shaping and correlative codes, are popular candidates for mobile radio applications. This paper presents a detailed study of the effects of Nyquist 3 pulse shaping on the spectral characteristics of CPM schemes with a modulation index of 1/2. The influence of pulse parameters such as its shape, bandwidth, coding polynomial, and truncation length on spectral characteristics such as main lobe, fractional power bandwidths, and out-of-band power levels is thoroughly investigated; error performance is also briefly analyzed. Among uncoded schemes, a new scheme using a pulse satisfying both Nyquist 3 and Nyquist 2 criteria is pointed out as a promising candidate and as a good compromise between spectral and power efficiencies. 相似文献
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近年来,超宽带(UWB)无线通信成为短距离、高速无线网络最热门的物理层技术之一。介绍了超宽带无线通信技术的概念及其信号传输过程中使用的关键技术,包括脉冲成形技术、调制技术以及接收技术,给出了超宽带无线传输系统的基本模型,最后分析了该技术在无线多媒体个域网中的应用。 相似文献
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针对无载频脉冲低频分量大、辐射效率低、频带可调性差等问题,设计了一种以阶跃恢复二极管、D触发器及超宽带调制器为主的宽频带、高重复频率、低振铃水平的有载频超宽带脉冲源。该脉冲源电路由驱动电路、高速开关电路、整形电路、超宽带调制器及振荡器电路组成。实测结果表明,脉冲源输出脉冲信号重复频率可达125 MHz,脉冲宽度600 ps(底宽),脉冲振铃水平低于10%,峰-峰值为5.4 V,-10 dB带宽可达4.2 GHz。脉冲信号中心频率与载频相同,可在6.6~8.5 GHz之间灵活设置。利用所设计的脉冲源进行时域测量,其结果与矢量网络分析仪频域测量结果相比幅频特性均方根误差小于0.21 dB。该脉冲源可应用于超宽带时域测量、短距离高速无线通信、高精度室内定位等应用。 相似文献
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遥控副载波与高斯白噪声发生器是测控系统检测设备的重要组成部分,主要实现BPSK信号调制和高斯白噪声生成功能。该发生器通过在信号传输过程中加入随机噪声来模拟实际信号传输过程,通过在信号调制过程引入比例因子实现有效信号与高斯白噪声信号输出功率的可调,从而实现信噪比控制的目的。并应用于工程实践,证明了设计的有效性。 相似文献
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The behavior of CPFSK systems with modulation pulse shaping and limiter-discriminator detection is tested in the prsence of multipath fading. With the aim of determining the eye-closure domain, a theoretical analysis is presented for a generic number of modulation levels. It is shown that, by suitably varying the maximum angular frequency deviation ωd , control of outage probability Pout is possible. Moreover, the choice of duty-cycle in the modulation pulsetau/T < 1 leads to a lower value of Pout with respect to the conventional casetau/T = 1 , if we fix, as happens in practice, an upper bound in the transmitted power. This promising characteristic deeply differentiates the CPFSK from the PSK, DCPSK, and QAM systems: CPFSK systems, with a fixed number of modulation levels, allow us to obtain decreasing values of Pout at the cost of increasing transmission power by suitably varying the set of signal parameters, even in the absence of diversity techniques and/or adaptive equalization. 相似文献
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《Microwave Theory and Techniques》1987,35(1):41-46
A method for determining the modal dispersion of gigahertz-bandwidth pulses on microstrip transmission lines is described. We have investigated the evolution of temporal waveforms propagating on microstrips, with very good agreement noted between experimental pulse shapes and numerical simulations. The resulting pulse distortion contributed to a pulse-shaping application where 100-ps rise times were stretched to the nanosecond durations necessary to control the shape of high-energy optical pulses used in fusion research. The tunability of the shape of the rising edge was investigated through variation of the stripline geometry and the substrate material. Additional effects due to high-frequency attenuation in several dipolar liquid dielectrics were substantiated experimentally, and the relevance of the results has been discussed. 相似文献