共查询到19条相似文献,搜索用时 140 毫秒
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连续相位的QPSK信号具有恒定包络,解决了传统QPSK信号由于相位跳变所带来的包络起伏问题,但其频带利用率没有8PSK高,为提高频带利用率,提出了连续相位8PSK(CP8PSK)调制。本文首先利用差分编码规则来表征8PSK信号一个符号周期的相位变化,进而将其表示为连续相位调制(CPM)的形式,再使用频率脉冲对其相位进行脉冲整形,最终得到具有连续相位的CP8PSK表达式。为了降低系统的整体复杂度,本文还对CP8PSK进行了Laurent分解。根据理论分析CP8PSK信号应当具有恒定包络,而且比连续相位的QPSK调制要有更高的带宽效率和更平滑的频谱,通过MATLAB进行仿真之后,得到的CP8PSK具有恒定包络,且带宽效率在同等情况下要高于整形的交错QPSK(SOQPSK)和8PSK,频谱也更加平滑,抗误码性能与理想8PSK相比损失也不大。 相似文献
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基于椭圆球面波信号的连续相位调制(Continuous Phase Modulation Based on Prolate Spheroi-dal Wave Function,CPM-PSWF)方法是一种新颖的数字调制方式,调制参数的优化与其调制信号性能有着直接联系.分析不同调制参数对CPM-PSWF信号性能的影响,优化选择调制参数,对获得能量聚集性和功率效率都较高的CPM信号具有重要意义.首先,对基于椭圆球面波信号的CPM信号进行描述;其次,采用韦尔奇(Welch)谱密度估计法,对时间带宽积、调制指数、关联长度等不同参数对CPM-PSWF调制信号的功率谱密度和带宽特性的影响进行了仿真分析.实验结果表明,选用0阶椭圆球面波信号,小时间带宽积、调制指数和符号进制数越小,关联长度越大时,CPM-PSWF信号具有频谱带外高频滚降快、占用带宽小的特点. 相似文献
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连续相位调制信号的功率谱及带宽特性研究 总被引:1,自引:0,他引:1
连续相位调制(CPM)的调制参数对信号的功率谱特性具有直接的影响。研究两者之间的关系,对优选调制参数,改善CPM的调制性能具有重要的指导意义。给出基于经典谱估计的CPM信号功率谱密度估计方法,该方法适用于任意形式的CPM信号,可利用FFT快速实现。利用该方法,仿真并分析了各种调制参数对CPM信号功率谱及带宽的影响,为实际应用中调制参数的选择提供了参考。 相似文献
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连续相位调制(Continuous Phase Modulation)是一类包络恒定且相位连续的调制方式,具有很高的带宽和功率利用率,优良的包络和相位特性使其适用于空间通信。在分析CPM信号的模型基础上,研究了基于微积分的代数运算方法来完成对CPM信号的解调,该方法几乎不需要任何的先验信息和参数信息就能实现信号的盲解调,目的能够降低接收机的复杂度,是一种优秀的CPM信号解调方式。 相似文献
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连续相位调制(CPM)技术是一类恒包络的数字调制技术,CPM信号的恒包络这一特性使它们对于非线性信道和衰落信道具有很强的抵抗性.特别适用于卫星通信和移动无线通信信道。与PSK调制方式相比,CPM调制系统不仅能够提供较高的频谱效率,而且具有一定的编码增益,这是因为接收器可以利用相位成型滤波器引入的记忆特性。CPM调制系统可以分解为一个连续相位编码器(CPE)和一个无记忆调制器(MM)的级联,因此出现了多种卷积码与CPM结合的调制方案,例如串行级联连续相位调制、基于环的串行级联连续相位调制、实用的连续相位调制、卷积编码器与扩展信道编码器的串行级联,等等。其中,基于环的串行级联连续相位调制具有很好的性能,在交织增益、自由距离、误码平层和收敛门限可能成为未来连续相位编码调制系统的发展方向。 相似文献
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Kuh S.S. Strozier T.A. Ryan C.R. 《Selected Areas in Communications, IEEE Journal on》1989,7(9):1462-1469
A continuous phase quadrature phase shift keyed (CPQPSK) modulation technique is presented. This method utilizes a conventional QPSK modulator and a phase trajectory converter to approximate M =4, h =1/4 continuous phase signal and allows low cost, low complexity, and high rate (>1 Gbit/s) CPM modem implementation for bandwidth efficient transmission through nonlinear satellite channels. Using a communications analysis computer program it has been found that CPQPSK has 99 percent out-of-band power of 0.8R (MSK has 99 percent out-of-band power of 1.2 R where R is defined as bit rate), continuous phase trajectories, and nearly constant envelope amplitude. Simulation of realistic hardware designs indicate that the CPQPSK will require an Eb /No of 14 dB to achieve a bit error rate (BER) of 10-6. Forward error correcting techniques using block codes with an overhead of 10 percent indicate that the Eb /No requirements can be reduced to 11.2 dB for 10-6 BER 相似文献
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基于分数阶Fourier变换减小OFDM系统PAPR的研究 总被引:1,自引:0,他引:1
介绍了基于分数阶Fourier变换的OFDM系统,给出了这种系统中经过变换后的信号的表达形式,探讨了该系统在不同的调制方式下(QAM调制和QPSK调制)使用Clipping算法降低系统PAPR的情况,并使用Matlab对不同阶数的CCDF进行了仿真。仿真结果表明,QAM调制下基于分数阶Fourier变换的Clipping算法性能不如基于傅立叶变换的Clipping算法好,而在QPSK调制方式下基于分数阶Fourier变换的OFDM系统PAPR性能比基于傅立叶变换的OFDM系统性能有了显著的提高。 相似文献
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椭圆球面波信号(PSWF)是时频域最佳能量聚集性信号,探索性地将PSWF信号应用于连续相位调制(CPM)技术,对基于椭圆球面波信号的CPM调制信号产生过程进行了描述;给出了采用自相关函数法对基于PSWF的CPM调制信号功率谱密度计算方法;结合数值计算、分析对比了最小频移键控、正弦频移键控、高斯最小频移键控以及基于高斯函数的CPM调制信号功率谱密度及其信号占用带宽等特性。数值计算结果表明椭圆球面波信号相比矩形脉冲、升余弦脉冲、高斯脉冲及(类)高斯脉冲作为CPM的基带调频信号,可以获得频谱性能、能量聚集性较好的CPM信号。 相似文献
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提出了一种基于顺序统计量特征的二进制相移键控/正交相移键控(BPSK/QPSK)信号调制识别算法.对观测信号进行平方并做离散傅里叶变换运算,将变换结果取模后去除最大值得到修正频谱,并取修正频谱的最大值作为识别特征量,利用恒虚警准则确定判决门限,将识别特征量与门限比较来完成对BPSK和QPSK两种调制信号的识别.计算机仿真表明,当信噪比适度时,所提算法可对BPSK及QPSK两类信号进行有效识别.当信噪比大于1 dB时,算法的平均识别正确率达到90%以上. 相似文献
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Yu‐Lun Chiu Jeng‐Kuang Hwang Juinn‐Horng Deng 《Wireless Communications and Mobile Computing》2013,13(17):1520-1531
This paper proposes two bandwidth and power efficient multicode multicarrier spread spectrum (MCSS) system modes based on a new cyclic shift orthogonal keying (CSOK) scheme that leads to low peak‐to‐average power ratio (PAPR) signals. Both system modes can improve the bandwidth efficiency by loading more data bits per symbol block. The first system mode is the hybrid CSOK (HCSOK) mode, which combines phase shift keying (PSK) or quadrature amplitude modulation (QAM) modulation symbol with the CSOK symbol, for example, the important hybrid quadrature PSK (QPSK)–CSOK case. The second is the quadrature CSOK (QCSOK) mode that transmits two parallel binary phase shift keying (BPSK)–CSOK branches at the same time. For both modes, maximum likelihood receivers are derived and simplified, leading to efficient fast Fourier transform‐based structures for maximum ratio combining and cyclic‐code correlation. Theoretical bit error rate (BER) analysis is conducted for the hybrid QPSK–CSOK case. Simulation results demonstrate that both the two system modes considerably outperforms the traditional Walsh‐coded MCSS system in terms of bandwidth efficiency, PAPR, BER, and antijamming capability. Furthermore, in indoor channel, QCSOK performs slightly worse than QPSK–CSOK, but it has almost twice the data rate when the code length is large. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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不同相位噪声谱对QPSK的性能影响分析 总被引:3,自引:3,他引:0
研究了相位噪声对QPSK系统的性能影响,利用高斯信道下带有相位噪声的条件误码率公式,分析了不同相位噪声谱所带来的解调损失。相位调制是一种恒包络调制方式,它对调制信号的相位偏移非常敏感,在单频相位噪声模型基础上,把相位噪声功率谱密度与相干解调的误码率公式相联系起来,计算了高斯信道条件下不同相位噪声谱对不同速率QPSK信号的解调损失。 相似文献
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Phase modulation with an analytic signal, which is a Gaussian random process, is examined in order to determine the amount of spectrum conservation that may be achieved by using single-sideband phase modulation (SSB-PM) rather than conventional phase modulation (PM). The autocorrelation function is derived and found to be an analytic signal in terms of the autocorrelation function of the actual modulating signal and its Hilbert transform. When the modulating signal strength is very low, the sideband spectral distribution is the same as that of the actual modulating signal or single-sideband amplitude modulation. As the modulating signal mean-square value is increased, the sideband spectrum broadens and approaches a Gaussian shape. The average power output of an SSB-PM system increases exponentially with input modulating signal strength, while the carrier power remains constant. For the same modulating signal mean-square value, a greater fraction of power is in the one sideband of an SSB-PM system than in the two sidebands of conventional PM. Single-sideband phase or frequency modulation always effectuates spectrum conservation in the continuum when it is compared with conventional phase or frequency modulation on the basis of equal relative sideband power. A Fourier transform computer program is used to generate SSB-PM spectral distributions with varying modulating signal mean-square values, when the modulating signal spectrum is a low-pass rectangular spectrum, a narrowband pass spectrum, and the shape of an average voice spectrum. These examples illustrate the power series formulation of the output spectrum as well as the theoretical analysis of bandwidth. 相似文献
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为研制北斗卫星导航模拟信号源,设计实现了北斗QPSK信号调制器。文中在分析了北斗卫星导航系统B1频段信号的正交相移键控调制信号的基础上,基于软件无线电的思想,在FPGA 硬件平台上实现了QPSK信号调制器,通过功率谱测试,QPSK解调和简单串口信息传输,验证了调制解调硬件单元的正确性。 相似文献