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交叉相位调制对密集波分复用系统性能的影响 总被引:1,自引:0,他引:1
研究了交叉相位调制对密集波分复用系统性能的影响 ,分析了干扰信道为正弦调制时交叉相位调制效应对考察信道相位的影响 ,在此基础上 ,建立任意信号通过具有交叉相位调制效应的信道时的系统模型 ,并将该模型应用于基带不归零码数字信号传输的情形 ,计算了由交叉相位调制引起的系统光功率代价。结果表明 ,交叉相位调制效应对高速率调制系统的性能具有一定的影响 ,应该在系统设计时的功率预算中予以考虑。 相似文献
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多信道IM—DD密集波分复用光纤传输系统中的交叉相位调制效应 总被引:1,自引:0,他引:1
本文研究了交叉相位调制(XPM)对DWDM数字基带主干传输网性的影响,建立了表征XPM效应对任意调制信号在色散信道中传输的指标损伤的等效系统函数模型,并据此推导出了不同系统参数条件下(基带信号速率,波长信道间隔,复用信道数)计算XPM导致和系统光功率代价的计算公式,通过数值模拟计算证明了在基带信号速率高(>2.5Gbit/s),波长信道间隔窄(-1nm),复用信道数多(>8)的条件下XPM效应将成为限制系统性能的主要非线性因素。 相似文献
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高速移动Rayleigh信道下的相位调制OFDM系统 总被引:1,自引:0,他引:1
高速移动的Rayleigh信道会使得传输信号的频谱发生Doppler扩展。本文对存在Doppler扩展的OFDM系统进行子载波干扰的理论分析,并针对高速Rayleigh信道对误码率造成的影响进行了基带仿真。仿真结果证实,相位调制OFDM系统在存在Doppler扩展的Rayleigh信道条件下的性能可以用单载波相位调制系统在慢衰落条件下的误码率理论值来近似;即使在移动台高速移动的情况下,实际中的Doppler扩展并不会使相位调制OFDM系统的误码率出现地板效应,所以相位调制OFDM系统比较适合高速移动的Ravleigh信道条件下的高速数据传输。 相似文献
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在考虑光纤损耗的情况下,以两载频以及混频过程中产生的边带频率成分为研究对象,给出了研究群速度色散(GVD)、自相位调制(SPM)、交叉相位调制(XPM)综合作用下混频过程中调制不稳定性(MI)的耦合模分析法。导出了当某一相位匹配较好、其他相位失配严重时,两载频自相位调制或交叉相位调制引起的调制不稳定性增益的解析表达式。分析发现,当调制不稳定性主要由自相位调制或交叉相位调制引起时,增益的最大值与色散无关,交叉相位调制在各边带引起的调制不稳定性最大增益相等,同时,考虑损耗后,幅度增益减小的大小受功率、非线性系数、色散情况、损耗系数和传输距离等因素共同影响,调制小稳定性产生的增益只有当频率偏移量足够大时才会出现,载频自相位调制引起的最大增益对应的频率偏移量减小。 相似文献
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调制不稳定性对波分复用系统的影响 总被引:3,自引:2,他引:1
给出了调制不稳定性(MI)的小信号分析方法,推导的结果适用任何频率和相位调制的情况。此方法也可用来分析光纡中的高阶色散现象。运用小信号分析的结果,可以详细讨论了MI对波分复用(WDM)系统的影响。结果表明,MI使信号的强度下降;而且对噪声有放大作用,它将降低了WDM系统的信噪比(SNR);MI对WDM系统中各信道的影响不同的,它对短波段的作用强于长波段,也会使各信道的SNR产生偏差,将使长波段较短波段有大的SNR,△SNR将随着长度而累积。 相似文献
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在非合作通信中,很多情况下由于信道恶化,使得接收信号的信噪比偏低,导致无法对符号速率这一重要参数进行准确估计.随机共振能够在一定程度上利用噪声能量,使其转移并增强微弱信号,小波变换则可以有效检测相位和幅度的瞬变,利用二者各自优势,提出了一种将随机共振与小波变换联合进行MPSK(Multiple Phase Shift Keying,多进制数字相位调制)和MQAM(Multiple Quadrature Amplitude Modulation,多进制正交幅度调制)信号符号速率的估计方法.先利用自适应参数调节随机共振为带噪信号匹配最佳系统参数,之后利用Haar小波变换进一步提取突变信息,不仅弥补了单独使用随机共振效果不佳及其作为非线性系统易发散的缺点,还降低了小波最佳尺度难以确定的影响.仿真实验表明,该方法能够在一定程度上提高输出峰值,降低信噪比门限,适合于低信噪比下的符号速率估计. 相似文献
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This paper reports a complete characterization of hot carrier-induced degradation in the CHannel Initiated Secondary ELectron (CHISEL) regime covering a large set of different stress bias conditions. Using several physical and electrical parameters, our results demonstrate that in the CHISEL regime, differently from the channel hot electrons case, the device degradation is univocally related to the gate current independently of the drain, source, substrate bias, and of the oxide electric field. The gate current is thus identified as the electrical monitor for device degradation in the CHISEL stress conditions. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(5):2269-2278
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Ono M. Saito M. Yoshitomi T. Fiegna C. Ohguro T. Momose H.S. Iwai H. 《Electron Devices, IEEE Transactions on》1995,42(8):1510-1521
A systematic investigation of the influences of high substrate doping on the hot carrier characteristics of small geometry n-MOSFETs down to 0.1 /spl mu/m has been carried out. Results indicate that the dependence of substrate current and impact ionization rate on substrate impurity concentration is reversed in long channel and short channel devices. In the long channel case, both increase with rising substrate impurity concentration, while they decrease in the case of short channel devices. An explanation for this phenomenon based on the lucky electron model has been developed. The dependence of other characteristics on impurity concentration has also been studied. The dependence of off-leakage current has been found to fall as the gate oxide is reduced in thickness. Regarding the dependence of hot carrier degradations, the degradation of drain currents becomes smaller as the substrate impurity concentration increases in the case of short channel devices. Further, in the extremely high impurity doping region, a new hot carrier degradation mode was found, in which the maximum transconductance values of n-MOSFETs increase after hot carrier stress. This new degradation mode can be explained in terms of effective channel length shortening caused by electron trapping.<> 相似文献
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Wooncheol Hwang Hongku Kang Kiseon Kim 《Communications Letters, IEEE》2003,7(12):581-583
We derive an approximate expression for signal-to-noise ratio (SNR) degradation of orthogonal frequency division multiplexing due to carrier frequency offset over a shadowed multipath channel, to explicitly show the effects of system and channel parameters on the degradation of the received SNR. The results show that, for small frequency offset, the SNR degradation is proportional to the square of the frequency offset and the square of the number of subcarriers. It is also shown that, if E/sub s//N/sub 0/ is reasonably large, the SNR degradation becomes insensitive to E/sub s//N/sub 0/, which is contrary to the case of the additive white Gaussian noise channel. 相似文献
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Xiaoyi Tang Alouini M.-S. Goldsmith A.J. 《Communications, IEEE Transactions on》1999,47(12):1856-1864
We determine the bit-error rate (BER) of multilevel quadrature amplitude modulation (M-QAM) in flat Rayleigh fading with imperfect channel estimates, Despite its high spectral efficiency, M-QAM is not commonly used over fading channels because of the channel amplitude and phase variation. Since the decision regions of the demodulator depend on the channel fading, estimation error of the channel variation can severely degrade the demodulator performance. Among the various fading estimation techniques, pilot symbol assisted modulation (PSAM) proves to be an effective choice. We first characterize the distribution of the amplitude and phase estimates using PSAM. We then use this distribution to obtain the BER of M-QAM as a function of the PSAM and channel parameters. By using a change of variables, our exact BER expression has a particularly simple form that involves just a few finite-range integrals. This approach can be used to compute the BER for any value of M. We compute the BER for 16-QAM and 64-QAM numerically and verify our analytical results by computer simulation. We show that for these modulations, amplitude estimation error leads to a 1-dB degradation in average signal-to-noise ratio and combined amplitude-phase estimation error leads to 2.5-dB degradation for the parameters we consider 相似文献
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The performance of TSI-OQPSK (two-symbol-interval-offset QPSK) modems in nonlinearly amplified (saturated or hard-limited), adjacent channel interference (ACI) satellite earth station environment is studied. In closely spaced mobile satellite channels and higher frequency (≥ 14 GHz) earth stations, the effect of ACI on theP_{e} = f(E_{b}/N_{0}) performance of faded systems may become very significant. Simulation results indicate that for the frequently used close channel spacing case (≤ 77 percent of the bit rate) and a practical fade depth (≥ 12 dB), our new TSI-OQPSK signal(n = 2) has 1 dB less degradation than IJF-OQPSK and 3 dB less than OQPSK, and that conventional QPSK could not operate in such an environment. 相似文献
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The performance of multicarrier systems depends on the propagation channel behavior. The latter is subject to time and/or frequency selectivity. The designer has to select properly the guard interval and the number of carriers for a given system bandwidth to combat the channel dispersiveness. In this paper, we investigate the sensitivity of downlink multicarrier code-division multiple-access (MC-CDMA) performance to these parameters in different environments. We derive closed-form expressions of the useful and the different interference powers after maximum ratio combining and despreading. The optimum parameters correspond to the minimum of the signal-to-noise-ratio degradation. It turns out that the derivations in the paper of Steendam and Moeneclaey ( IEEE Trans. Commun., 1999) that are restricted to the orthogonal frequency-division multiplexing (OFDM) system are a particular case of our results. Numerical evaluation of the analytical expressions reveals that the optimum parameters of the MC-CDMA and its corresponding OFDM system are similar and depend in the same way on the channel characteristics. We show in this paper that the load of the MC-CDMA system only has small influence on the optimization of the parameters. Therefore, from the point of view of parameter optimization, single-user transmission is sufficient to find the optimum parameters. Furthermore, as the optimum parameters mainly depend on the channel characteristics, similar conclusions can be drawn for the uplink transmission 相似文献
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The impact of intrinsic series resistance on MOSFET scaling 总被引:1,自引:0,他引:1
《Electron Devices, IEEE Transactions on》1987,34(3):503-511
The intrinsic parasitic series resistance associated with the practical structure of a MOSFET is examined. The components considered include contact resistance, diffusion sheet resistance, spreading (injection) resistance, and accumulation layer resistance. The impact of the total resistance on MOSFET scaling is assessed, down to a channel length of 0.15 µm. The results show that, contrary to what has been claimed before, the transconductance and current of a MOSFET continue to increase as the channel length is miniaturized, although the degradation percentage-wise compared to an ideal device without series resistance continues to increase. Based on the degraded I-V characteristics and their effects on an inverter, it is shown here that for NMOS or PMOS digital circuits, the maximum degradation in speed due to series resistance is 20-35 percent compared to ideal scaling for the shortest channel considered. For CMOS circuits, the maximum degradation is reduced to 7-15 percent. In absolute terms, a loss of speed in either case due to miniaturization of channel length is not expected even down to 0.15 µm. 相似文献
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In this paper, we derive a simple expression for the degradation in signal-to-noise ratio caused by intersymbol and adjacent channel interference in MSK systems for which the total response is nonnegative and the response is such that only two intersymbol and one adjacent channel terms are dominant. An MSK system with Gaussian filters in transmitter and receiver satisfy this condition. The resulting expression is simple because we simultaneously maximize the signal value from the main channel (by selecting the sampling time) and the degradation caused by the signals in the interfering channels. For such systems we derive the relation between the optimal filter bandwidth and channel frequency separation. Numerical results are presented for the case of Gaussian filters in both transmitter and receiver or receiver only and either one or two adjacent interfering channels. 相似文献
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An expression is derived for the probability of error of an N th-order selection diversity system for the case where the receiver is forced to swell on one channel for several symbols before being allowed to make a decision regarding the best channel. It is found that the time-varying nature of a fading channel causes significant degradation of the probability of error when the dwell time becomes longer than about 10% of the inverse of the fading bandwidth of the channel. The onset of degradation is a function of the signal-to-noise ratio and of the order of diversity. Specific probabilities of error are calculated for differential phase-shift keyed modulation (DPSK). However, the calculations can be done for any other modulation technique 相似文献