QPSK通信系统的设计与仿真.doc

evaluation of scientific development. Nature security type-nature security is to maintenance people of health value for target, through strengthening security based management, and risk management, and equipment management and technology supervision, ensure production in the people, and real, and system, and system, elements security reliable, and harmony unified, full control various against factors, achieved thought no slack, and management no empty document, and equipment no hidden, and system no blocked, and unit zero non-stopped. Quality and efficiency-quality benefit is to adhere to the enterprise survival, profit and development business truth, adhere to the all activity is economic activity, all costs can be controlled, money should not be wasted management philosophy, management analysis, to improve management quality, improve cost control capacity and market competitiveness. Innovation of science and technology-science and technology innovation is to play the role of science and technology as the primary productive force, active use of new technologies, new materials, new processes, new equipment, increase investment in science and technology, strengthening scientific and technological training, speeding up transforming scientific and technological achievements, forming a number of proprietary technology, enhancing core competitiveness. Resource-saving-the-resources saving enterprise was to reduce coal consumption, water consumption, electricity at the core, enhance the operation of lean management to realize low consumption, high efficiency, reduce production costs. Second is to strengthen the business, financial, material, information and the optimization of organization and management, saving the internal transaction costs. Harmonious development of harmonious development-is to construct a foreign environment for development. XING refers to the internal security firm and internal management of the internal management measures are effective, harmonious. Foreign currency means Enterprise coordinating development of homeopathy, well, get along with the neighbors better. (B) XX 2013 five enterprises building intrinsic safety power company goals are: unplanned outage 0 times. Class of disorders 0, 0 is equivalent forced outage rate. No personal injury accident, material and equipment accidents do not occur, no fire, no environmental pollution accident. Enterprise integrated to achieve zero cases of violation, zero accidents, zero. Quality goal is: when generating capacity 7.5 billion-kilowatt, sales of over 7.11 billion kWh, total profits of 306.6 million Yuan, . BFS+、PI、MIS、SCM Information systems infrastructure, fully integrated information system to realize information resources sharing; to expand the breadth and depth of the portal system, information system of Enterprise Management Assistant role to play; to improve the day-to-day operation and maintenance operation record of promoting causes and transfer system; to strengthen the training 摘要 介绍了数字通信中的QPSK调制解调的原理,通过用Matlab编写脚本程序对QPSK通信系统的发射和接收过程的具体实现进行模拟仿真,绘出信号在理想信道和加噪信道中模拟传输时的时域图,并对各模块进行了频谱分析,所得到的结果与理论基本相符,对于理解QPSK系统的性能并在系统的实际应用上作进一步的设计,提供了有效的参考依据。 通过利用MATLAB软件SUMLINK实现了QPSK通信系统的仿真，完成了QPSK通信系统的调制解调过程的仿真实现，使接收端能够准确地接收到来自发放的信息。QPSK调制方式在通信工程中的应用十分广泛，其误码率随信噪比的增加而减少并最终可能为零。在QPSK调制方式以后，还会出现进制更多的调制方式。而我们着重要解决的问题也从如何提高相位谱利用率转变为如何减少误差以及提高传送速率。阐述QPSK调制解调的实现过程，并运用软件实现手段对信号变换过程加以分析，希望有所收获。关键词：数字通信 四相相位键控(Quadrature Phase Shift Keying,QPSK) MATLABsupervision in large and medium goods vehicle. A is established large vehicles and small vehicles classification management of motor vehicle test mode, increased medium van car, and dangerous goods transport car, and school car test project; II is established motor vehicle test regulatory platform, achieved motor vehicle test full process video, and data remote regulatory; three is strictly motor vehicle identification management, equipped with unified of identification equipment and tool, using mobile identification Terminal, and law enforcement records instrument, technology identification means. As to 20XX years June 20 statewide motor vehicle keep volume for 567,408 car, and last year earlier than growth 75,814 car, growth 13.36%; this year January-June, vehicles management section and license archives management section total accepted the motor vehicle registration business 42,543 car times, which registered registration 6,905 car times, and transfer registration 3,592 car times, and change registration 1033 car times, and mortgage registration 696 car times, and cancellation registration 187 car times, and into business 980 car times, and Archives corrections 81 pieces times, and issued test qualified logo 25,429 car times, and other vehicles business 3,640 car times; supervision Survey Section relies on motor vehicle detection remote issued test qualified logo software platform supervision motor vehicle test, and identification situation 7418l liangci, investigation motor vehicle exception business 30 car times, his pards business warning 244 article, vehicles and driving people sound video regulatory screenshots 1852 Zhang, checks motor vehicle archives 716 pieces times, and medium bus, and medium above truck, and Of hazardous chemicals, vehicles and school buses and other key vehicle inspection record of 420. (C) based on their own, and strict adherence to defense, more cheating, false false fugitive suspects, robbery suspect vehicles and the Internet crackdown. DMV full play to the first line of Defense position control, investigating cheating, fake identification and robbery suspect vehicles through operational work, and carefully examine the documents and legal proof, check traffic violations, traffic accidents, the fugitive suspect suspected vehicles and theft than to work, further tight car, driving management business formalities review procedures. . Truck driver information management platform. Motor vehicles and traffic police departments, State transport authority to further clarify the Division of labour, implementation responsibility, strengthen our collaboration and management together, reinforcing the management of drivers on which strongly synthetic warfare and information warfare. 3 strictly implemented. From May 1 up, a is implemented complex road and bad weather driving exam, currently DMV is urged contractors party in treasures driving school increased simulation Highway, and continuous urgent detours, and snow days, and wet sliding road, and burst situation disposal, subjects II field to driving exam project, is expected目录前言1一、 QPSK简介22.1 QPSK调制原理32.2 QPSK解调原理5三、 MATLAB仿真结果63.1 QPSK的产生及加噪仿真63.2 QPSK解调前后信号仿真63.3 QPSK码元恢复73.4误码率分析9四、 程序清单10五、 总结17六、 参考文献18七、致谢19前言 随着数字技术的飞速发展与数字器件的广泛使用,数字信号处理在通信系统中的应用已经越来越重要。数字信号传输系统分为基带传输系统和频带传输系统,频带传输系统也叫数字调制系统,该系统对基带信号进行调制,使其频谱搬移到适合在信道(一般为带通信道)上传输的频带上。数字调制和模拟调制一样都是正弦波调制,即被调制信号都为高频正弦波。数字调制信号又称为键控信号,数字调制过程中处理的是数字信号,而载波有振幅、频率和相位3个变量,且二进制的信号只有高低电平两个逻辑量即1和0,所以调制的过程可用键控的方法由基带信号对载频信号的振幅、频率及相位进行调制,最基本的方法有3种:正交幅度调制(QAM) 、频移键控( FSK) 、相移键控( PSK) 。根据所处理的基带信号的进制不同分为二进制和多进制调制(M进制) 。多进制数字调制与二进制相比,其频谱利用率更高。在数字通信、数字视频广播、数字卫星广播等领域中,广泛采用M进制的调制方式 1 。理论分析指出,在恒参信道中利用PSK方式可以获得最佳接收性能,在接收机噪声的作用下, PSK误码率最低。本文用Matlab软件对M = 4的四相相位调制解调(QPSK)进行模拟,并对各模块进行了仿真分析。一、 QPSK简介 在多相调制中，可以用多种相位差来表示数字数据信息。把要传送的二进制信息序列每K比特编为一组，那么便构成了K比特码元，每一K比特码元都有2K种不同的状态，要用2K 种不同的相位或相位差来表示。由于K比特码元包括的信息量是二进制码元所含信息量的K倍，所以，多相调制系统与二相调制系统相比，在码元传输速率相同时，信息传输速率更高。例如，四相调制系统的信息传输速率是二相调制系统的两倍。另外，在系统信息传输速率的情况下，由于多相调制系统的码元速率比二相调制要低，因而多相调制时，信号码元持续时间比二相调制时长。码元时间长，则对应的带宽就窄，因此压缩了信号的频带，可以叫嚣由于新到特性引起的码间串扰的影响。由此可见，多相调制是提高数据通信有效性、可靠性的一种途径。 由于四相绝对移相信号可以看成两个正交2PSK信号只能采用相干检测法解调， 4PSK信号也只能采用两个正交的相干载波分别来检测这两个分量A和B。在四相绝对移相调制系统中，实现起来最困难的问题在于接收端如何产生一标准的相干载波。通常采用的方法是四倍频-四分频法，然后经过四次分频，便可以得到所有的相干载波输出。这种方法也会由于分频起始点不同而使提取的相干载波的相位出现四种不确定性。因此，在实际中，通常采用四相相对移相调制。 二、QPSK调制解调原理2.1 QPSK调制原理 四相相移键控信号简称“QPSK”。它分为绝对相移和相对相移两种。由于绝对相移方式存在相位模糊问题，所以在实际中主要采用相对移相方式QDPSK。它具有一系列独特的优点，目前已经广泛应用于无线通信中，成为现代通信中一种十分重要的调制解调方式。在数字信号的调制方式中QPSK四相移键控是目前最常用的一种卫星数字信号调制方式,它具有较高的频谱利用率、较强的抗干扰性、在电路上实现也较为简单。 QPSK四相绝对相移键控，用载波信号的4个初始相位对应4进制码元。因此，对于输入的二进制数字序列每2比特分为一组，称为双比特码元AB，然后用4种不同的载波相位分别表征这4种数字码元。按AB分组与载波相位的对应关系有/2体系(也称A方式)与/4体系(也称B方式)，具体定义如表所示：双比特码元AB载波相位AB/2体系（A方式）/4体系(B方式)000（）5/4（225）10/2（）7/4（315）11（）/4（45）013/2（）3/4（135） 图2-1 QPSK信号双比特码元与相位矢量关系图 图2-2 四相相移调制是利用载波的四种不同相位差来表征输入的数字信息，是四进制移相键控。QPSK是在M=4时的调相技术，它规定了四种载波相位，分别为45，135，225，315，调制器输入的数据是二进制数字序列，为了能和四进制的载波相位配合起来，则需要把二进制数据变换为四进制数据，这就是说需要把二进制数字序列中每两个比特分成一组，共有四种组合，即00，01，10，11，其中每一组称为双比特码元。每一个双比特码元是由两位二进制信息比特组成，它们分别代表四进制四个符号中的一个符号。QPSK中每次调制可传输2个信息比特，这些信息比特是通过载波的四种相位来传递的。解调器根据星座图及接收到的载波信号的相位来判断发送端发送的信息比特。数字调制用“星座图”来描述，星座图中定义了一种调制技术的两个基本参数：（1）信号分布；（2）与调制数字比特之间的映射关系。星座图中规定了星座点与传输比特间的对应关系，这种关系称为“映射”，一种调制技术的特性可由信号分布和映射完全定义，即可由星座图来完全定义。同时QPSK信号可以看作两个载波正交2PSK信号的合成，下图表示QPSK正交调制器。图2-3 QPSK调制系统原理图2.2 QPSK解调原理 数字调制用“星座图”来描述，星座图中定义了一种调制技术的两个基本参数：（1）信号分布；（2）与调制数字比特之间的映射关系。星座图中规定了星座点与传输比特间的对应关系，这种关系称为“映射”，一种调制技术的特性可由信号分布和映射完全定义，即可由星座图来完全定义。四相相移调制是利用载波的四种不同相位差来表征输入的数字信息，是四进制移相键控。QPSK是在M=4时的调相技术，它规定了四种载波相位，分别为45，135，225，315，调制器输入的数据是二进制数字序列，为了能和四进制的载波相位配合起来，则需要把二进制数据变换为四进制数据，这就是说需要把二进制数字序列中每两个比特分成一组，共有四种组合，即00，01，10，11，其中每一组称为双比特码元。每一个双比特码元是由两位二进制信息比特组成，它们分别代表四进制四个符号中的一个符号。QPSK中每次调制可传输2个信息比特，这些信息比特是通过载波的四种相位来传递的。解调器根据星座图及接收到的载波信号的相位来判断发送端发送的信息比特。由QPSK信号的调制可知，对它的解调可以采用与2PSK信号类似的解调方法进行解调。解调原理图如下所示，同相支路和正交支路分别采用相干解调方式解调，得到和，经过抽样判决和并/串交换器，将上下支路得到的并行数据恢复成串行数据。图2-4 QPSK解调系统原理图3、 MATLAB仿真结果3.1 QPSK的产生及加噪仿真 图3-1 通过matlab产生两路相互正交的2PSK信号，信号叠加后的到合成序列，对合成序列进行加噪处理。3.2 QPSK解调前后信号仿真图3-23.3 QPSK码元恢复然后相干解调中，正交路和同相路分别设置两个相关器(或匹配滤波器)，得到I(t)和Q(t)，经电平判决和并一串变换后即可恢复原始信息。当然，如果调制端是差分编码的，那么解调中并串变换后还需一个差分解码。假如已调信号分别为同相路和正交路，为载波频率，那么相干解调后，同相路相乘可得 正交路为： 经过低通滤波后，可得： 在完成通过滤波器之后，将码元再通过并串转换，就可以恢复出原始信号的码元序列。图3-33.4误码率分析图3-4有图示可知，QPSK调制解调有比较低的误码率，所以因其抗干扰性能强、误码性能好、频谱利用率高等优点,广泛应用于数字微波通信系统、数字卫星通信系统、宽带接入、移动通信及有线电视系统之中。4、 程序清单clear allclose all t=-1:0.01:7-0.01;tt=length(t);x1=ones(1,800);for i=1:tt if (t(i)=-1 & t(i)=5& t(i)=0 & t1(i)=4& t1(i)0 data_recover_a(i:i+19)=1; bit_recover=bit_recover 1; else data_recover_a(i:i+19)=-1; bit_recover=bit_recover -1; endend error=0;dd = -2*bit_in+1;ddd=dd;ddd1=repmat(ddd,20,1);for i=1:2e4 ddd2(i)=ddd1(i);endfor i=1:1e3 if bit_recover(i)=ddd(i) error=error+1; endend p=error/1000; figure(1)subplot(2,1,1);plot(t2,ddd2);axis(0 100 -2 2);title(原序列);subplot(2,1,2);plot(t2,data_recover_a);axis(0 100 -2 2);title(解调后序列);clear allclose all % 调制bit_in = randint(1e3, 1, 0 1);bit_I = bit_in(1:2:1e3);bit_Q = bit_in(2:2:1e3); data_I = -2*bit_I+1;data_Q = -2*bit_Q+1; data_I1=repmat(data_I,20,1);data_Q1=repmat(data_Q,20,1);for i=1:1e4 data_I2(i)=data_I1(i); data_Q2(i)=data_Q1(i);end;t=0:0.1:1e3-0.1;f=0:0.1:1;xrc=0.5+0.5*cos(pi*f); data_I2_rc=conv(data_I2,xrc)/5.5;data_Q2_rc=conv(data_Q2,xrc)/5.5;f1=1;t1=0:0.1:1e3+0.9; I_rc=data_I2_rc.*cos(2*pi*f1*t1);Q_rc=data_Q2_rc.*sin(2*pi*f1*t1);QPSK_rc=(sqrt(1/2).*I_rc+sqrt(1/2).*Q_rc); % 解调I_demo=QPSK_rc.*cos(2*pi*f1*t1);Q_demo=QPSK_rc.*sin(2*pi*f1*t1);I_recover=conv(I_demo