【導讀】要求MSK數(shù)據(jù)調制電路的工作頻率為455kHz，信息碼元速率最大為5hbit/s，輸入信號幅度100。設計完整電路，在EDA工具Multisim環(huán)境下對所設計電路進行仿真分析。，格式符合燕山大學畢業(yè)設計論文規(guī)范；調制在通信系統(tǒng)中具有重要作用。近年來，隨著科技的進步，數(shù)字調制技術得到了突飛猛進的發(fā)展，被廣泛應用于科技，軍事，居民生活等各個領域。而備受關注的無線數(shù)傳模塊也發(fā)展相當迅速。研究MSK數(shù)字調制電路也成為當今的一個重要課題。本文首先簡要介紹了數(shù)字調制，二進制移頻鍵控，接著重點研究MSK的信號特點和調制原理。通過研究，分析仿真所得的波形，結合教材所學知識得出MSK信號包絡恒定，并且在兩個碼元相接處，相位是連續(xù)的?！　∫苿油ㄐ沤洑v了近一百年的發(fā)展，特別是近十年來，其發(fā)展速度驚人。移動通信從最初的單電臺對講方式發(fā)展到現(xiàn)在的系統(tǒng)和網絡方式；從小容量到大容量；從模擬方

　　

【正文】 訂單 ,清楚地表明了性能的差異碼所得采用不同的代碼設計準則,我們 只考慮兩個值 ,是1和4 . 這里,而前者提供小額多樣性命令( 2號和3號=2和=3 ) ,后者提供了相當大的多樣性令( 8 =2和=3) . 根尖顯示的業(yè)績,為擬建的四國和八國碼時,將和或接收天線是指能量傳輸每比特信息. 為比較起見,其性能優(yōu)于經典MSK是吉奧似乎也增加ofstates提高丟幀 實驗結果的四國情況下,代碼,優(yōu)于代碼,時,兩名傳送和接收之一 天線在考慮之列. 這可能是因為第一部法典,其中較大行列式導致更好的錯誤 表現(xiàn)所期望 和 ,不過,碼大優(yōu)勢是某一國家的數(shù)目. 這些都是符合結果給出[2],從圖中,化學需氧量荷蘭取得優(yōu)勢 被越來越多的國家增加了多少個接收天線是增加了.比較性能的STMSK碼兩個和三個發(fā)射天線在1至4個接收天線所吸附是看到碼優(yōu)于自己的記憶同一順序 . 盡管四國STMSK代碼的行列式為零,它略優(yōu)于四國STMSK代碼的牙槽 八國情況圖表 , ,分別在相應的八個國家STMSK碼時,我們增加 從兩個增加到三個. 5．結論提交四國和八國時空MSK碼全率和全碼多樣,有兩名或三名傳遞 天線獲得小額和大額訂單多樣性和模擬了準靜態(tài)瑞利衰落當號碼 接收天線是一個四調制，結果表明,新的代碼提供可觀的利潤比常規(guī)MSK 對同一信息率和較好的表現(xiàn),由于一些國家和/或數(shù)量發(fā)送接收天線增加. 今后研究,設計STMSK碼超過三個發(fā)射天線可數(shù), 分解的STMSK編碼到信道編碼和MSK調制和決心的渠道編碼,政學院的格狀結構,在這個領域將是一個有趣的問題. Space–time trellis codes for MSKIbrahim Altunbas*Electrical and Electronics Faculty,Istanbul Technical University,34469 Maslak,Istanbul,TurkeyReceived 28 September 2004。received in revised form 15 April 2005。accepted 4 May 2005Abstract Minimum shift keying(MSK)is a power/bandwidth efficient continuous phase modulation technique with constant envelope and,hence,is attractive for use in wireless systems employing inexpensive nonlinear power –time coding provide high transmission rates,diversity and coding this paper,by bining these two techniques,fullrate fulldiversity space–time trellis codes for MSK employ ing two and three transmit antennas are proposed for quasistatic Rayleigh fading frame error rate performances are evaluated by puter simulations when one and four receive antennas are used and it is shown that the proposed codes have good error performance.Keywords:Rayleigh fading。Space–time coding。Continuous phase modulation。Minimum shift keyingOver the past several years,there has been a great deal of research to improve performance of wireless munications systems,where multipath fading usually has a severe impact on the error –time trellis codes have been introduced to improve the error performance as well as the information rate of wireless systems using multiple antennas[1].They provide diversity and coding gains without sacrificing the full transmission design criteria for space–time codes were given in[1,2]for small and large diversity orders, the literature,several space–time trellis codes that provide good diversity and coding advantage have been presented for linear modulations such as phase shift keying(PSK).Continuous phase modulation(CPM)is a signaling method that provides low spectral occupancy due to its phase continuity[8,9].It generates constant envelope waveforms and allows the lowcost nonlinear transmitter amplifier to operate at peak output has also memory and thus an inherent code structure which can be used to mitigate against advantages make CPM very attractive modulation scheme for wireless power efficiency of CPM can be further improved by bining it with space–time coding,while maintaining the full transmission ,space–time code design for CPM is more dicult than the linear modulation case due to the nonlinearity and more plex resulting performance and Fitz[10]recently presented space–time trellis coding for CPM systems and introduced the design criteria to enable linear deposition of CPM signals,they were able to identify some general code construction with CPM.A special type of CPM is minimum shift keying(MSK)which has rectangular frequency pulse shape and modulation index of is of practical importance in wireless munications,due to its simplicity besides the constant envelope,bandwidth and power efficiency advantages[11].In[12],space–time coding based on MSK has been considered,where the diversity gain is obtained by using an offset modulation MSK can be viewed as a quadrature linear modulation[9,11],the conventional criteria given for linear modulations can be directly used in the design of space–time codes for this approach,in this paper,we design space–time trellis codes for MSK employing two and three transmit antennas based on the criteria given in[1,2]for quasistatic Rayleigh fading then verify their good performance by puter simulations.The paper is organized as Section 2 we describe the system model under 3 presents the space–time MSK trellis codes and Section 4 presents simulation results of the proposed are given in Section 5. modelWe consider the‘‘tilted phase’’MSK whose signal s(t,b)for nth interval is given by[11,13]where Es is the symbol energy,Ts is the symbol duration and b={bn}is the‘‘modified’’information 2{0,1}denotes the modified nth information symbol which is defined as bn=(an+1)/2 where an 2{177。1}is the nth information symbol[11].The modified carrier frequency f1 is defined as fc 1/4Ts,where fc is the carrier excess phase hn corresponds to the memory term of the modulation process and it satisfies hn+1=hn+pbn(mod 2p) where hn and hn+1 2{0,p}.This leads to MSK timeinvariant twophase state trellis as depicted in (a).The states in the trellis are labeled by the phase values of hn as initial branches are labeled by the MSK symbols 0,1,2,3 whose normalized signal constellation is shown in (b).These symbols correspond to the unitenergy(Es=1)MSK waveforms,at time interval[0,Ts],as 。From (b),it is seen that tiltedphase has a biorthogonal signal constellation identical to ,needless to say that it provides lower spectral sidebands than QPSK in the power spectrum due to the phase uncoded MSK scheme presented above has an information rate of 1/Ts bits/s.Now,let us consider a munication system employing nT antennas at the transmitter and antennas at the receiver as in this system,data is encoded by a space–time MSK (STMSK)encoder,which generates nT parallel streams of MSK symbols preserving the phase continuity for each fact,the STMSK encoder consists of a ratek/nT channel encoder followed by nT MSK modulators for each output bits of the channel encoder where k is the number of input bits of the ,in this paper,we only consider the bined structure,.,the STMSK encoder and its trellis,and do not pursue investigation of the