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1、毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文The Modulation Technology of QAM and The Simulation in Matlab QAM调制技术应用及其MATLAB仿真学生姓名： 学 号： 专 业： 通信工程 所在学院： 信息技术学院 指导教师： 职 称： 说明：要求学生结合毕业设计（论文）课题参阅一篇以上的外文资料，并翻译至少一万印刷符（或译出3千汉字）以上的译文。译文原则上要求打印（如手写，一律用400字方格稿纸书写），连同学校提供的统一封面及英文原文装订，于毕业设计（论文）工作开始后2周内完成，作为成绩考核的一部分。The Modula
2、tion Technology of QAM and The Simulation in Matlab taken from Abstract: This paper first outlines the principles of QAM modulation techniques, then focuses on technology in the cable system QAM modulation in the role and significance, and on the QAM channel settings and output are described. The ar
3、ticle also using MATLAB QAM-based digital communication system simulation, good results have been received constellation after constellation and compensation, channel estimation diagram, the system BER analysis diagram. MATLAB simulation results show that the implementation of digital communications
4、 through the system can be realized with a strong, practical application and for the scientific and rational design of quadrature amplitude modulation system, providing an efficient simulation platform.Foreword Modulation in digital video broadcasting system DVB system has a very important role. In
5、the HFC network, the transmission channels of analog channels, the limited bandwidth in order to transmit more bits of information, need to adopt efficient modulation techniques, QAM modulation and the major function is to re-use after the digital television signal modulation, it has a high anti-jam
6、ming capability, ease of transmission in the cable television network. QAM constellation diagram can also accommodate more constellation points to achieve higher bandwidth efficiency, it is within the bandwidth of 6MHz baseband quadrature amplitude modulation of the X band (X = 2,4,8,16) two-dimensi
7、onal vector digital modulation techniques, the complete expression for the XQAM. (X = 2,4,8,16), inhibition of the carrier away from the channel at the low end of about 3MHz. As XQAM modulation, the signal flow to logX as a group was divided into two, each road has X level, each path of the signal l
8、evel that the amount is logX (Mbit / s), so the two orthogonal modulated signal, The maximum number of signals can pass the bit stream for the 2 logX5.4 = 10.8 logX (Mbit / s). QAM modulator first binary signal stream input string and re-divided into two I and Q, respectively, into the corresponding
9、 The D / A, into the X band of the analog signal, then low-pass filter, respectively, orthogonal and bilateral with suppressed carrier amplitude modulation, two AM signals add up to a QAM modulation wave, the power amplifier .After mixing the analog TV signal into the cable system.1QAM is a non-cons
10、tant envelope modulation technique.The nonlinear distortion performance of its anti-poor, but can be modulated by the variable rate program, to guarantee a certain transmission quality, the full use of its characteristics of high-frequency band utilization, which also requires the demodulation syste
11、m to adapt to change symbol rate. Using QAM modulation technique ,channel bandwidth is at least equal to the symbol rate, for timing recovery, but also require additional bandwidth, generally increased about 15%.Compared with other modulation techniques, QAM encoding with full use of bandwidth, nois
12、e immunity and so on. To achieve ideal performance characteristics, QAM receiver needs one and the same transmitter frequency spectrum and the corresponding characteristics of the input signal for decoding, QAM receivers using adaptive equalizer to compensate for transmission distortion in the signa
13、l .Order of selection for QAM, mainly on the transmission capacity and interference dilemma. QAM order of choice, depending on the quality of transmission channel, the better the quality of transmission channel, less interference, the greater the order of available. Level quadrature amplitude modula
14、tion according to the magnitude and phase, into 16/32/64/128/256-QAM.Now has reached the highest QAM 1024QAM (10240) sampling sites, the more the number of samples, the higher the efficiency of its transmission. Considering the DVB-C system, using anti-jamming capability is relatively modest, but hi
15、gh spectral efficiency modulation 64QAM is more appropriate. 64QAM is through the 2-6 binary signal level converter will be divided into a six-string group and converted to form a1a2a3 and b1b2b3, 3 bits can represent a total of eight states, so the two six-level quadrature amplitude keying signal i
16、s superimposed on a total of 8 8 = 64 species .Using 64QAM modulation in a traditional 8MHz channel bandwidth analog transmission of about 40Mbit / s data stream, the equivalent of four to eight sets of standard-definition digital TV programs.2 digital channels set Digital TV and analog TV spectrum
17、is completely different structure and energy distribution. QAM is the modulation amplitude balance, inhibit the carrier. Spectrum analyzer from the point of view, a digital channel as a modulated signal by raising the noise level, evenly spread on the limited bandwidth (8M), the audio signal in MPEG
18、-2 (Moving Picture Experts Group, from the motion picture Expert Group) has been with the image signal encoding in the form of re-used to package together. Therefore, a digital TV channels without the so-called image carrier and sound carrier. As digital television whole translation will take time,
19、so the existing HFC (Hybrid Fiber / Coaxial Cable, coax cable and hybrid networks) transmission network are often used in mixed-mode analog and digital signal transmission. To reduce the digital TV and analog TV interference between the channels should be set on all the digital TV channels adjacent
20、arrangements and arrangements for the digital television transmission in the high channel.2.1 QAM output level to determine QAM digital channels with the measured level is the average signal power to channel expression, known as the digital channel average power. Since the existence of digital chann
21、els, analog channels on non-linear product of the interference was severe than the digital channels. Therefore, in general, the digital signal level should be higher than the low level analog image carrier 10dB. Level measurement method is to scan the entire channel description, sampling, random sam
22、pling points for each power is randomly distributed, so the power of each sampling point value averaging, this analog level measurement function is not available in test equipment, it can not measure the level meter with analog digital channel level, the results were correct as a digital channel lev
23、el, but only digital channels with a digital meter to measure the average power level. Measurement frequency should be set at the center frequency of the channel, no digital level meter in the case of analog TV Signal Level Meter can also be used to estimate the level of digital television signals,
24、the digital signal level = simulated field intensity measured value + (5 10 dB). Digital signal level should not be adjusted too low, otherwise it would drop its anti-jamming capability, resulting in the image mosaic and discontinuity.2.2 QAM modulation principle Quadrature amplitude modulation QAM
25、With two independent baseband signal with two orthogonal frequency carrier double sideband suppressed carrier amplitude modulation, the use of this spectrum of the modulated signal bandwidth at the same orthogonality to achieve two parallel digital information of transmission. The modulation is usua
26、lly binary QAM (4QAM), quaternary QAM (l6QAM), octal QAM (64QAM), ., the corresponding spatial distribution of the signal vector endpoint called Constellation, respectively, 4,16,64, . a Vector endpoint. M and the signal level between the state M is. For 4QAM, when two equal amplitude signals, its g
27、eneration, demodulation, and phase performance are related to 4PSK the same vector. QAM signals in phase and quadrature components, respectively, can be independently transmitted digital signal to ASK. QAM modulation and amplitude modulation is actually a combination of phase modulation, phase + amp
28、litude state defines a number or numbers. The advantage is greater. QAM symbol rate, and thus obtain higher system efficiency .Usually determined by the symbol rate bandwidth .Therefore, the bits per symbol (basic units of information), the more the higher the efficiency. For a given system, the req
29、uired number of symbols 2n, where n is the number of bits per symbol. For 16QAM, n = 4, so there are 16 symbols, each symbol represents 4 bit: 0000, 0001, 0010 and so on. For 64QAM, n = 6, so there are 64 symbols, each symbol represents 6bit: 000000,000001,000010 and so on.3 System Simulation MATLAB
30、, Simulink is a visual simulation tool, the toolbox offers a rich communication module, based on MATLAB / Simulink simulation of communication systems simulation module of the design process from the library of Simulink model of a combination of the various modules. Design simulation model, you can
31、use the mouse from the Simulink Library Browser window onto the model editor window, each module will be connected correctly, hit a few in the two-module, the module parameters dialog box pops up, change the module to complete the various parameter values .System simulation model .MATLAB / Simulink-
32、communications toolbox Digital modulation in a variety of digital modulation / demodulation module .Of these, the passband (passband) module and baseband (baseband) of the points. Pass-band carrier signal included in the simulation model of the transmitter, the signal carrier frequency is usually mu
33、ch higher than the highest frequency. By the Nyquist sampling theorem, in order to recover the original signal at the receiving end, the simulation of the sampling frequency should be at least twice the maximum carrier frequency. If the signal frequency is high, then the simulation becomes very slow
34、 or no direct computer simulation. Simulation is generally referred to as baseband low-pass, etc. follow the example of the simulation, the bandpass equivalent baseband signal, making the modulation and demodulation performance analysis with the carrier frequency and channel band has nothing to do,
35、thereby reducing the system resources. System Simulation as follows:3.1 binary bit stream3.2 Analysis of the system BER MATLAB simulation of the communication has an important application, MATLAB / Simulink Communication system is a powerful tool for computer simulation, this paper provides a practi
36、cal simulation example. The actual channel is very complex, in the actual application should be selected according to different requirements of different modulation methods. In this paper, MATLAB / Simulink for M = 16 ary quadrature amplitude modulation systems for simulation, verification theory he
37、xadecimal. Quadrature amplitude modulation system works, and for the practical application of scientific and rational design of quadrature amplitude modulation system, providing a convenient, efficient and intuitive important ways.3.3 Based QAM signal space programTaking into account the complexitie
38、s of implementation and the actual performance improvement, the article choose to change the signal constellation of adaptive modulation scheme, and said that this modulation is variable rate QAM modulation, changes in the constellation known as modulation level change.3.31 Variable rate QAM signal
39、structure The traditional square QAM false lock problem because there is not suitable for fading channels, so we use star QAM, which is DAPSK modulation, it has not false lock error, but also because it uses differential coding modulation, so greatly reduces the receiver complexity.3.32. Variable ra
40、te QAM modulation frame structure Often used in multi-user multiplexing method with TDD and FDD, TDD is different users using different time slots, FDD different users use different frequencies.4 Conclusion QAM is a non-constant envelope modulation technique, the nonlinear distortion performance of
41、its anti-poor, but can be modulated by the variable rate program, to guarantee a certain transmission quality, the full use of its characteristics of high-frequency band utilization, which also requires the demodulation system to adapt to change symbol rate. Using QAM modulation techniques, channel
42、bandwidth is at least equal to the symbol rate, for timing recovery, but also require additional bandwidth, generally increased about 15% .Compared with other modulation techniques, QAM encoding with full use of bandwidth, noise immunity and so on. To achieve ideal performance characteristics, QAM r
43、eceiver needs one and the same transmitter frequency spectrum and the corresponding characteristics of the input signal for decoding, QAM receivers use adaptive equalizer to compensate for transmission distortion in the signal.QAM调制技术及其Matlab仿真 -摘自摘要: 文章首先概述了QAM调制技术的原理,然后重点介绍了QAM调制技术在有线电视系统中的作用和意义,并
44、且对QAM的频道设置和输出进行了说明。文章还利用MATLAB对基于QAM的数字通信系统进行仿真,得到了良好效果的接收星座图和补偿后的星座图、信道估计图、系统BER分析图。仿真结果表明这种通过MATLAB实现的数字通信系统具有较强的可实现性,为实际应用和科学合理地设计正交幅度调制系统,提供了高效的仿真平台。前言调制在DVB系统数字视频广播系统中具有十分重要的作用。在HFC网中,传输通道为模拟通道,为了在有限的带宽内传送更多的信息比特,需要采用高效的调制技术,而QAM调制的主要功能是对复用后的数字电视信号进行调制,使其具有较高的抗干扰能力,便于在有线电视网络中传输。同时QAM星座图中可以容纳更多的
45、星座点即可实现更高的频带利用率,它是一种在6MHz 基带带宽内正交调幅的X 进制(X=2,4,8,16)的二维矢量数字调制技术,完整的表达式为XQAM。(X =2,4,8,16), 抑制的载波在离频道低端大约3MHz处。由于XQAM调制方式中,信号流以logX为一组分为两路, 每一路具有X电平,每一路电平表示的信号量是logX(Mbit/s),所以两路信号正交调制后,能传的最大数字信号比特流为2logX5.4=10.8 logX (Mbit/s)。QAM 调制器首先将输入的二进制信号流进行串/并重组,分为I和Q两路, 并分别进入相应的D/A, 转化为X进制的模拟信号,再经低通滤波,分别对相互正
46、交的载波和进行双边带抑制调幅。两路调幅信号相加后成为QAM的调制波,经功率放大后与模拟电视信号混合送入有线电视系统。1.QAM 是一种非恒包络调制技术其抗非线性失真的性能较差,不过可通过变速率调制方案,在保证一定传输质量的前提下,充分利用其高频带利用率的特点, 这也就要求解调系统可适应变符号率。采用QAM 调制技术,信道带宽至少要等于码元速率,为了定时恢复,还需要另外的带宽,一般要增加15%左右。与其他调制技术相比,QAM 编码具有能充分利用带宽、抗噪声能力强等优点。要取得较为理想的工作特性,QAM 接收器需要一个和发送端具有相同的频谱和相应特性的输入信号用于解码,QAM 接收器利用自适应均衡
47、器来补偿传输过程中信号产生的失真。对QAM 阶次的选择, 主要是对传输容量和抗干扰取舍的问题。QAM 阶次的选择,取决于传输信道的质量,传输信道的质量越好,干扰就越小,可用的阶次就越大。正交幅度调制根据电平的幅度和相位,分为16/32/64/128/256-QAM。目前QAM 最高已达到1024QAM(10240)个样点,样点数目越多,其传输效率越高。综合考虑在DVB-C 系统中,采用抗干扰能力相对适中但频谱利用率很高的64QAM 调制方式较为适宜。64QAM 就是通过2-6 电平变换器将二进制信号每6个分为1 组进行串并转换,形成a1a2a3 和b1b2b3,3 个位共可表征8 种状态, 所
48、以两路正交的六电平幅度键控信号叠加共计88=64 种。采用64QAM 调制方式可在传统的8MHz 模拟频道带宽上传输约40Mbit/s 的数据流,相当于48 套标清数字电视节目。2 数字频道的设置数字电视和模拟电视的频谱结构及能量分布完全不同,QAM 中的调幅是平衡调幅,抑制了载波。从频谱分析仪上看,一个数字频道的已调信号象一个抬高了的噪声电平, 均匀地平铺于整个限定带宽(8M)内,伴音信号在MPEG-2(Moving Picture Experts Group,由运动图像专家组)编码时已经与图像信号以包的形式复用到了一起。因此一个数字电视频道没有所谓的图像载波和伴音载波。由于数字电视整体平移尚需时日,因而在现有的HFC(Hybrid Fiber/Coaxial Cable,光缆与同轴电缆混合网) 传输网中常采用模拟和数字信号混合方式传输。为了减少数字电视与模拟电视相互之间的干扰, 在频道设置上应尽量把所有的数字电视频道邻频安排,并把数
