共查询到19条相似文献,搜索用时 125 毫秒
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超宽带(UWB)技术的特点是传输持续时间极窄的脉冲,纳秒级窄脉冲(称为monocycle)的选择将直接影响到UWB通信系统的性能。本文研究了一种新的基于小波函数的超宽带窄脉冲,并比较其和传统的超宽带窄脉冲在AWGN信道中采用直接序列扩频(DS)的UWB系统性能。仿真结果表明了基于小波函数脉冲波形的UWB系统性能优于基于传统超宽带窄脉冲的UWB系统。 相似文献
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首次研究分析脉冲重复频率(PRF)对密集多径衰减信道下采用 THSS 和 PPM 的 UWB 系统 BER 性能的影响。通过使用混合选择/最大比率结合分集接收机(H-S/MRC)并利用虚拟分支技术,首次推导出基于 PRF、选择并结合的多径成分数量 L 以及信道的多径扩频的 UWB 系统准确 BER 表达式,并对 BER 性能进行分析和仿真评估。结果表明:在密集多径衰减环境下,不仅仅脉冲波形和 L,而且 PRF 对 UWB 系统 BER 性能影响极大。当固定 L 和脉冲波形时,增大 PRF 将大大降低 UWB 系统 BER 性能。 相似文献
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椭圆球面波函数(Prolate Spheroidal Wave Function,PSWF)脉冲具有最佳时域能量聚集性和频谱灵活可控性的特点,被认为是符合超宽带(ultra-wideband,UWB)系统要求的一种性能优良的脉冲。首先给出了满足FCC频谱掩膜要求的UWB脉冲波形设计方法,并将该方法应用于多进制TH-PPM超宽带系统中。分析了多进制TH-PPM超宽带系统原理,理论上推导了基于PSWF脉冲的多进制PPM-UWB系统的符号差错率公式,并与高斯脉冲进行比较。仿真结果表明,基于PSWF脉冲的UWB系统符号差错率性能要明显优于Gauss脉冲。 相似文献
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针对使用窄脉冲传输数据的超宽带系统,依据修正Hermite函数的正交、无直流分量等特性,提出了一种基于正交UWB脉冲的PSM超宽带系统.仿真结果表明该设计能改善系统性能,降低误码率. 相似文献
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《现代电子技术》2016,(3):131-134
在UWB脉冲信号发生器的研制中,通过分析UWB脉冲波形的特征,以一阶高斯脉冲为设计目标,提出了一种以振荡源、储能元件和高速开关为主体的UWB脉冲产生电路系统模型,并且在实际电路中设计了不同的实现方式。利用复杂可编程器件(CPLD)为UWB脉冲发生模块设计了脉冲时序触发电路。针对脉冲的产生方案,设计了一种利用雪崩晶体管产生UWB脉冲的电路,实际测试得到了1 ns以内的窄脉冲;与此同时设计了一种基于阶跃恢复二极管的UWB脉冲发生电路,在PSpice中仿真得到了宽度约400 ps的UWB脉冲信号。仿真结果表明,PSpice建立的SRD模型符合理论分析,设计的UWB脉冲信号发生电路也完全满足在超宽带引信上使用的需求。 相似文献
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超宽带(UWB)无线通信的关键技术之一是UWB窄脉冲产生技术.为简化光子超宽带脉冲源的设计,提出采用基于光纤可饱和吸收体效应的环形腔被动锁模光纤激光器来设计光子UWB脉冲源.为了获得满足UWB室内无线通信频谱范围的脉冲,利用色散和啁啾效应展宽脉宽的原理,在激光器环形腔内使用较长的增益光纤引入大量色散效应,将光脉冲展宽以符合美国通信委员会(FCC)规定的室内UWB通信频谱范围(3.1~10.6 GHz).并根据光纤激光器谐波锁模的原理,通过控制偏振态调制输出脉冲的周期以提高脉冲重复频率.实验中,展宽的光脉冲经光电转换器转换成UWB电脉冲序列后,由宽带数字示波器进行波形观测和测量.通过调节偏振控制器,获得了可输出8种不同脉冲重复频率的光子超宽带脉冲源. 相似文献
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This letter investigates all-optical frequency conversion of ultra-wideband (UWB) signals for UWB-over-fiber up-link and down-link systems. An electrooptical Mach-Zehnder modulator is used in nonlinear regime to realize frequency up and down conversion of UWB rectangular pulse and monocycle. All-optical frequency up-conversion of rectangular pulse at 18 GHz generates undesired local oscillator centered in the up-converted UWB spectrum, whereas up-conversion of monocycle waveform exhibits a power spectrum density optimally fitting the UWB emission mask. Up and down conversions of UWB monocycle, using the same UWB-over-fiber system, have shown low distortion induced by the optical mixing process on the UWB monocycle. 相似文献
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首先分析了在超宽带系统中高斯脉冲成形因子和微分阶数对其能量谱密度的影响,并在此基础上,为了提高高斯脉冲波形的频谱利用率,采用高斯导函数线性组合来产生脉冲波形,提出并分析了一种基于粒子群(PSO)优化算法的超宽带无线脉冲波形优化设计方法,仿真表明该方法产生的高斯导函数线性组合脉冲能够很好地满足FCC的频谱掩模限制。 相似文献
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Ang W.T. Jie Chen Tiejun Lv 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(8):1657-1665
Ultra-wide-band (UWB) technology can provide data throughput rate at gigabit per second. UWB also shows promising potentials for use in short-range indoor wireless communications and outdoor ad hoc networking. Adopting ultra-short impulses in UWB transmission, however, make systems vulnerable to timing jitter. To overcome this challenge, we propose a time-hopping high- order waveform modulation scheme in this paper. Central to our design is the adaptation of a high-order monocycle (HOM), which provides timing-jitter robust UWB communications. We present a CMOS pulse generator circuit to produce the HOM monocycle. We also use 0.18-mum CMOS technology with 1.8-V power supply to simulate the monocycle generator design using the Cadence software. The simulation results show that our generated waveform meets the UWB communication and the FCC requirements. Our modulation scheme outperforms other systems using traditional monocycles in terms of timing-jitter robustness. 相似文献
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We propose a direct‐sequence pulse‐amplitude modulation (DS‐PAM) ultra‐wideband (UWB) system which employs a non‐linear chirp waveform instead of the conventional Gaussian monocycle in this paper. In the approved frequency for UWB, there exist myriad narrowband interferers. Specifically, we focus on the mutual interference between UWB systems and 802.11a WLAN. This paper offers a method to suppress this inband narrowband interference by introducing a kind of non‐linear chirp waveform. Using the proposed non‐linear chirp waveform, the effects of one or more narrowband interference sources with different frequencies can be suppressed. System performance of UWB systems in the narrowband interference environment can be improved. Computer simulations with additive white Gaussian noise successfully demonstrate an increase in performance with the proposed system as compared to traditional linear chirp systems. 相似文献
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提出了一种基于色散位移光纤(DSF)的交叉相位调制(XPM)效应的超宽带(UWB)光学生成方法。该方法首先利用DSF的XPM效应实现高功率的高斯泵浦光对低功率的直流探测光的交叉相位调制,然后利用光纤布拉格光栅(FBG)对探测光进行鉴频,实现相位调制到强度调制的转换,从而获得单周期UWB信号。利用光子仿真软件对方案进行了仿真实验,得到了中心频率分别为7GHz和6.95GHz、相对带宽分别为143%和145%的UWB信号,验证了所提方法的可行性。同时,研究了输入信号脉冲宽度、FBG的反射率、鉴频器的类型对产生的单周期UWB脉冲信号波形和频谱的影响。仿真实验的结果表明,该方案对输入信号脉冲宽度不是过宽的情况下具有良好的容忍度,光学高斯带通滤波器、波分复用器和FBG等光滤波器均可作为鉴频器,采用FBG优点是可通过改变反射率灵活地调整产生的UWB脉冲信号的波形。 相似文献
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《Microwave Theory and Techniques》2006,54(10):3681-3687
A novel low-cost low-power fully integrated tunable transmit module composed of a tunable CMOS monocycle pulse generator and compact uniplanar antenna was designed, built, and tested for ultra-wideband (UWB) impulse systems. The CMOS tunable pulse generator integrates a tuning delay circuit, square-wave generator, impulse-forming circuit, and pulse-shaping circuit in a single chip using a standard low-cost 0.25-$muhbox m$ CMOS process. It can generate a monocycle pulse and Gaussian-type impulse (without the pulse-shaping circuitry) signals with tunable pulse duration. A compact uniplanar UWB antenna was also developed and integrated directly with the CMOS pulse generator chip to form the complete integrated tunable UWB transmit module. Measured results show that the CMOS tunable pulse generator can produce a 0.3–0.6-V peak-to-peak monocycle pulse with 140–350-ps tunable pulse duration and a 0.5–1.3-V peak-to-peak impulse signal with 100–300-ps tunable pulse-duration, and the uniplanar antenna has less than a 18-dB return loss and is suitable for transmitting/receiving UWB time-domain impulse signals covering the entire UWB bandwidth of 3.1–10.6 GHz. Good agreement between measured and calculated performance is also achieved. The UWB transmit module was experimentally characterized and its performance is verified. This UWB module finds applications in various time-domain UWB systems including wireless communications and radar. 相似文献
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Songnian Fu Wen-De Zhong Yang Jing Wen Shum P. 《Photonics Technology Letters, IEEE》2008,20(12):1006-1008
We demonstrate a photonic monocycle pulse frequency up-conversion scheme for ultrawideband (UWB)-over-fiber applications using nonlinear polarization rotation arising in a semiconductor optical amplifier. For the first time, we have successfully realized the photonic up-conversion of UWB monocycle pulses with an optical local oscillator signal at 24 GHz in the whole -band. The up-converted UWB monocycle pulse at 24 GHz exhibits a power spectrum density fitting the UWB emission mask. After electrical down-conversion, the UWB monocycle pulse has shown low distortion induced by the optical mixing process. 相似文献
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Abtahi M. Mirshafiei M. Magne J. Rusch L.A. LaRochelle S. 《Photonics Technology Letters, IEEE》2008,20(2):135-137
We propose and demonstrate experimentally a prototype for ultra-wideband (UWB) waveform generator based on optical pulse shaping. The time-domain pulse shape is written in the frequency domain, and a single-mode fiber performs frequency-to-time conversion. A U.S. Federal Communications Commission (FCC)-compliant power efficient pulse shape is inscribed in the frequency domain by a fiber Bragg grating (FBG) with an excellent match between optimized and measured pulses. Two other popular UWB pulse shapes (Gaussian monocycle and doublet pulses) are achieved by proper tuning of two FBG-based variable optical filters. A balanced photodetector removes an unwanted rectangular pulse superimposed on the desired waveform, assuring compliance at low frequency. 相似文献