【正文】 for highfrequency modulation. In the same band, M 2 the MARY modulation with a greater rate of information transmission than M = 2 binary modulation. However, the MARY modulation are able 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 43 to raise the data ratetobandwidth ratio, they usually at the cost of reducing its power utilization. Because of with the value of M increasing in the signal vector diagram the minimum distance between signal points will be reduced accordingly. So when the signal was damaged by noise and interference, the error probability of received signal will increase. In the 1960s put forward a joint amplitude and phase modulation (APM) [also known as amplitude phase shift keying (APK)] and attracted people’s attention. This is because this kind of modulation pare with conventional Mary modulation it not only has a high data ratetobandwidth ratio but also has good power utilization which had developed rapidly. The socalled a joint phase and amplitude modulation is the amplitude and phase of carrier was changed with the two independent baseband signal’s changing.[1,2] principle of 16QAM modulation and demodulation In the orthogonal modulation circuit, the slip of the two orthogonal carrier was bilateral suppression carrier amplitude modulated by the amplitude discrete baseband signals, QAM signals can be received. MQAM signal can be expressed as: S(t) = Σxkg(t kTs) cos wct .∑ ykg(t kTs)sin wct .It is the sum of 2 branchs 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 44 modulated orthogonal carrier signal. In the circuit, the orthogonal carrier sin wct can be obtained by carrier coswct phaseshifted π / (t) stands for the system impulse response units, xk, yk respectively express the kvalue of the symbol of 2way multilevel signals transmitted, Ts is symbol duration, Wc is the carrier angular frequency. Ideally, the carrier states of 16QAM can modulate 4b signal. 16QAM provides 16 states,every 4b signal can express one state,each 16QAM symbols cycle transmits 4b signal. According to the constellation map and the receiving carrier signal amplitude and phase, demodulator can determine the information of the sending side. 16QAM adopt the orthogonal with the projection on I coordinate modulating carrier amplitude, the projection on Q coordinates modulating orthogonal carrier add 2 amplitude modulated signals is required phasemodulation signal. The input data sequences through Serial/Parallel conversion and transform into two road I and using rectangular constellation chart, the level code of 2 road orthogonal signal use 2 bits signal for representation, namely the L = 24 level conversion,the output value of I and Q two way for 0,1,2, constellation mapping pletes converting a digital sequence 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 45 consisting of 0,1,2,3 to a digital sequence consisting of 3,1,1, corresponding relations as follows: 00 —— +3， 01 —— +1， 10 —— 1,11 —— , I road value for 4 levels, namely x = 177。同時(shí)，通過此次畢業(yè)設(shè)計(jì)，充分調(diào)動(dòng)了自身對(duì)知識(shí)的運(yùn)用。需要進(jìn)行改進(jìn)模型，減小時(shí)延。 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 35 第 6 章 結(jié)論與總結(jié) 本文總結(jié) 本文研究的重點(diǎn)是對(duì)基于 MATLAB/SIMULINK 的 16QAM 調(diào)制解 調(diào)系統(tǒng)進(jìn)行設(shè)計(jì)與仿真，并與 2DPSK 系統(tǒng)進(jìn)行了比較，得到以下的結(jié)論 16QAM 調(diào)制解調(diào)系統(tǒng)基本原理進(jìn)行了較為深入地理解與分析，并且根據(jù)其原理構(gòu)建了 Simulink 的仿真模型。采用 64QAM 調(diào)制方式，可在傳統(tǒng)的 8 MHz 模擬頻道帶寬上傳輸約 40 Mbps數(shù)據(jù)流，可在一個(gè)標(biāo)準(zhǔn) PAL 通道上傳輸 4~8 套數(shù)字電視節(jié)目，它的末端用戶可以是計(jì)算機(jī)，也可以是帶數(shù)字機(jī)頂盒的電視機(jī)。 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 31 16QAM 與 2DPSK 系統(tǒng)性能比較 本節(jié)設(shè)計(jì)一個(gè) 2DPSK 調(diào)制和解調(diào)系統(tǒng)的仿真模型，以觀察其與 16QAM信號(hào)的抗噪聲性能，并對(duì)它們的誤碼率進(jìn)行比較。 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 29 誤碼率 對(duì)于 QAM，可以看成是由兩個(gè)相互正交且獨(dú)立的多電平 ASK 信號(hào)疊加而成。 16QAM 調(diào)制解調(diào)的眼圖如圖 4 42 所示： 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 25 圖 41 16QAM信號(hào)的發(fā)送端眼圖 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 26 圖 42 16QAM 信號(hào)的接收端眼圖 由圖 4 42 比較可知，加噪后的眼圖線跡變得模糊且線條變粗，但并不是很明顯。它的參數(shù)設(shè)置如下： Switch： Criteria for passing first input: u2=Threshold Threshold： 所以，當(dāng)輸入脈沖序列為 1 時(shí)，選擇器輸出第一路信號(hào)；當(dāng)輸入脈沖序列為 0 時(shí)，選擇器輸出第二路信號(hào)。 石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 19 16QAM 解調(diào)模塊的模型建立與仿真 相干解調(diào) 系統(tǒng)先前所得的 16QAM 調(diào)制信號(hào)通過高斯白噪聲信道以后便可 以解調(diào)了。石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 16 這里輸入信號(hào)為兩路二進(jìn)制信號(hào)，假設(shè)它們是 ab，則在 a=1 時(shí)讓它輸出一個(gè)幅度為 2 的信號(hào)，當(dāng) a=0 時(shí)輸出幅度為 2 的信號(hào)。系統(tǒng)首石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 14 先將輸 入的偽隨機(jī)序列分成兩路并將其中的一路直接按整數(shù)因子 2抽取，然后進(jìn)行一個(gè)單位的延時(shí)，這樣便得到了原隨機(jī)序列的奇數(shù)碼元；對(duì)于另外一路則先進(jìn)行延遲然后下采樣便可得到原序列的偶數(shù)碼元，至此串并轉(zhuǎn)換也是結(jié)束了。接受到的信號(hào)分兩路進(jìn)入兩個(gè)正交的載波的相干解調(diào)器，再分別進(jìn)入判決器形成 L 進(jìn)制信號(hào)并輸出二進(jìn)制信號(hào)，最后經(jīng)并 /串變換后得到基帶信號(hào)。星座圖中，兩個(gè)信號(hào)石家莊鐵道大學(xué)四方學(xué)院畢業(yè)設(shè)計(jì) 8 點(diǎn)距離越大，在噪聲干擾使信號(hào)圖模糊的情況下，要求分開兩個(gè)可能信號(hào) 點(diǎn)越容易辦到。在這種調(diào)制中，已調(diào)載波的振幅和相位都隨兩個(gè)獨(dú)立的基帶信號(hào)變化。 正交振幅調(diào)制的概述 在現(xiàn)代通信中，提高頻譜利用率一直是人們關(guān)注的焦點(diǎn)之一。上海 506 研究所和天津通廣集團(tuán)下屬的一個(gè)通信機(jī)部門現(xiàn)狀正在做這方面的研究，但至今都未形成產(chǎn)品，在實(shí)際的應(yīng)用中還有所欠缺。Matlab 語言的 Simulink 動(dòng)態(tài)系統(tǒng)仿真軟件包，是一個(gè)常用的電子設(shè)計(jì)自動(dòng)化 (EDA)軟件，它支持連續(xù)、離散兩種混合的線性和非線性系統(tǒng) ， 也支持具有多種采樣速率的多速率系統(tǒng)。摘 要 16 進(jìn)制正交振幅調(diào)制技術(shù) (16QAM)是一種功率和帶寬相對(duì)高效的信道調(diào)制技術(shù)，這種方式具有很高的頻譜利用率，在調(diào)制進(jìn)制數(shù)較高時(shí)，信號(hào)矢量集的分布也較合理，同時(shí)實(shí)現(xiàn)起來也較方便。 關(guān)鍵詞： 16QAM 仿真 2DPSK 誤碼率 Abstract Hexadecimal orthogonal amplitude modulation technology (16 QAM) is a kind of power and bandwidth relatively efficient channel modulation technology, this kind of means is of high frequency spectrum efficiency in the modulation system into several high, the distribution of the signal vector set more reasonable also realize rise more convenient has been used widely in field of largecapacity digital microwave munication systems highspeed data transmission cable television work and satellite ,16QAM application up easy to implement and have the advantages of the strong performance of the noise. This article briefly introduce how QAM modulation and demodulation system works. After a simulation of the 16QAM modulation system ,through the analysis of signal is added a noise of the constellation chart, before and after eye chart ,and signaltonoise ratio change conditions the system BER,so as to analyze 16QAM and system ,in order to prove that the 16QAM is a relatively superior demodulation system,make its and 2DPSK BER pare. Through the simulation test the system to satisfy the design requirements can perform its system simulation and through the eye chart const