基于Coiflets正交小波的超宽带脉冲波形设计

脉冲波形设计是超宽带(UWB)系统的关键技术。基于Coiflets正交小波提出一种产生UWB信号正交成形脉冲的新方法。仿真结果表明,基于Coiflets正交小波产生的新UWB脉冲的功率谱密度比高斯导函数脉冲能更好地满足FCC的频谱模板要求,有较高的频谱利用率。利用正交小波的正交性,设计的UWB脉冲波形可用于多用户通信。利用小波基函数产生的一系列脉冲进行组合叠加,可以达到更高的频谱利用率。     

基于认知无线电的超宽带系统中窄带干扰抑制技术

基于认知无线电的思想,在满足联邦通信委员会(FCC)频谱限制的基础上,提出一种能避开多个无线电台工作频段的UWB脉冲波形设计算法,从而达到抑制窄带干扰的目的.仿真结果表明,提出的脉冲比通常使用的Scholtz脉冲的性能更优,抗干扰能力更强.且此方法不需要在整个频段内降低UWB脉冲的功率谱密度,为提高UWB脉冲发射功率,增大UWB系统的通信距离,提供了一种灵活易行的方案.     

满足FCC频谱限制的UWB脉冲设计算法研究

在超宽带通信系统中,满足FCC频谱限制的UWB脉冲波形设计是一个研究的热点.首先对高斯脉冲及其导函数的频谱形式进行理论推导及仿真实现,在此基础上提出了两种满足FCC频谱限制的UWB脉冲波形算法,并比较了各自的优缺点.     

基于遗传算法的超宽带波形设计

采用遗传算法(GA)进行了一种新颖的超宽带(UWB)脉冲波形的设计。从多带Chirp信号出发,将波形设计问题转化成有约束条件的逼近问题求解,然后通过遗传算法解决逼近问题。得到的波形不仅满足联邦通讯委员会(FCC)的频谱模板,而且具有88%的频谱利用率。仿真结果验证了采用遗传算法的波形设计具有低时间复杂度;提出的UWB脉冲波形具有较高的频谱利用率,优于其他的UWB脉冲例如B样条脉冲。     

满足UWB室内辐射掩蔽的脉冲信号功率谱分析

通过分析高斯脉冲的求导阶数与功率谱密度(PSD)中心频率的关系,提出了一种利用高斯脉冲及其高阶导数组合波形作为发射信号,这种信号可以满足美国联邦电信委员会(FCC)对UWB信号的频谱规定.该方法通过选择适当的脉冲形成因子a和求导阶数n,对各段辐射掩蔽特性进行逼近.仿真验证了该方法的有效性,能够获得较好的逼近掩蔽特性的组合脉冲串.     

UWB脉冲的特征分析

介绍了超宽带脉冲无线电对脉冲波形的要求及FCC对UWB的频谱规划。详细分析了影响UWB脉冲波形及其谱形状的因素,分别给出了Rayleigh脉冲在不同脉冲形状参数α与不同求导阶数n时的时域波形及其频谱密度PSD,并研究了α与n对峰值频率及带宽的影响。分析结果表明,可通过仔细选择α与n来设计满足FCC频谱规划的脉冲,这对超宽带脉冲无线电中波形的选择具有指导性意义。     

基于认知的UWB系统软频谱自适应设计方法

认知无线电技术与UWB技术结合解决干扰问题已成为近几年研究的热点。基于认知的思想,在满足联邦通信委员会（FCC）频谱限制的基础上,设计出最佳脉冲波形,使其与周围电磁环境中的干扰设备的功率谱相互正交,从而有效地避开干扰。通过对电磁环境的周期性重复采样,UWB可以成为自适应抑制干扰的通信系统,实现了认知超宽带无线电的概念。此方法不需要在整个频段内降低UWB脉冲的功率谱密度,为提高UWB脉冲发射功率和增大UWB系统的通信距离,提供了一种灵活易行的解决方案。     

基于高斯脉冲导数的正交UWB波形最优化设计

超宽带无线通信由于其在短距离高速率无线通信中的潜在应用已经引起了广泛的关注.超宽带信号要符合FCC发布的辐射掩蔽,并且要充分利用分配的频谱,这就要求合理的脉冲波形设计.本文分别采用4阶和5阶高斯脉冲导数,进行组合来合成用于UWB通信的脉冲波形,设计中采用归一化有效信号功率作为频谱利用的衡量标准,将波形设计问题转化成为线性规划问题,线性规划问题可以高效地求解,得到的波形具有很高的频谱利用率,并且4阶和5阶高斯脉冲导数合成的脉冲是相互正交的,可以进一步扩大通信的容量.     

一种新的超宽带脉冲波形设计方法

首先介绍了UWB成形脉冲的算法,然后基于Hermite矩阵和Chirp信号得到了UWB的成形脉冲。在对Chirp脉冲的带宽、中心频率等性能参数比较分析的基础上,将若干个Chirp脉冲信号进行线性叠加,通过仿真结果表明,随之产生的脉冲信号不仅满足FCC对UWB脉冲信号辐射功率要求,而且其脉冲信号的频谱利用率也很高,同时还能有效抑制对其他窄带系统的干扰。     

窄带干扰抑制的一种新型频率编码正交UWB脉冲设计

文中提出一种基于正交载波和伪随机序列的新型频谱编码正交UWB脉冲设计方法，该方法是在频域中利用PN序列对经过频移的子脉冲进行编码来产生正交脉冲．在IR-UWB（脉冲无线电超宽带）中引入了正交载波和PN序列，使其不仅具有传统IR—UWB和多频带CB-UWB（基于载波的超宽带）优点，而且提高了UWB信号发射的瞬时频谱和瞬时能量的效率．脉冲的自相关和互相关特性皆优于传统的脉冲。另外，借助于认知无线电技术，可保证发送信号满足FCC的UWB频谱规划，避免与其他传统窄带系统干扰。仿真结果表明该脉冲设计方法能够有效的抑制窄带干扰，并降低复杂度。     

Generation of Power-Efficient FCC-Compliant UWB Waveforms Using FBGs: Analysis and Experiment

In this paper, we design, analyze, and demonstrate experimentally U.S. Federal Communications Commission (FCC)- compliant power-efficient ultrawideband (UWB) waveforms generated by optical pulse shaping. The time-domain pulse shape is written in the frequency domain, and a single-mode fiber performs the frequency-to-time conversion. The waveform is inscribed in the frequency domain by the fiber Bragg grating (FBG). A significant challenge for this approach is elimination of an unwanted, positive rectangular pulse superimposed on the desired waveform. Our innovative use of balanced photodetection eliminates this pedestal, assuring compliance with the FCC mask at low frequency. Three UWB pulses with duration of 0.3,0.6, and 1.2 ns are designed and tested experimentally. Whereas an excellent match between the optimized and measured pulses is achieved for the simpler, shorter duration waveforms, the noise in the fabrication process of FBGs limits the generation of the more complex, longer duration waveforms.     

一种基于多频带PSWFs组合的CUWB自适应脉冲波形设计

本文简述了认知超宽带(CUWB)系统的工作原理,并从自适应频谱环境和兼容FCC频谱模板的角度出发,建立了基于频谱感知来动态构建CUWB系统自适应辐射掩蔽的机制。然后,利用PSWFs函数的特性,提出了一种基于多频带的回转椭球波函数(PSWFs)基的加权线性组合来设计CUWB自适应脉冲波形的算法。仿真结果表明,该算法所产生的脉冲波形不仅能满足CUWB系统频谱模板的要求,而且能自适应模板的动态变化。     

Performance Evaluation of UWB Systems Exploiting Orthonormal Pulses

The novel pulses, which not only meet the power spectral mask of the Federal Communications Commission (FCC) but also preserve orthonormality at the correlation receiver, have been proposed by Kim for high data rate communications in indoor ultra-wideband (UWB) systems. The proposed multiple orthonormal pulses comply with the FCC spectral mask without additional frequency shifting or bandpass filters, and furthermore, provide enhanced bit-error rate (BER) performance, compared with a well-known Gaussian monocycle and modified Hermite pulses. This paper analyzes the impact of the proposed pulses' properties, such as their auto- and cross-correlations, on the correlation receiver of the UWB system based on the pulse position modulation. The performance of the proposed pulses are compared with different waveforms under various conditions, such as multipath fading, timing mismatch, and multiuser interference. We also discuss a modulation scheme using the multiple orthogonal pulses to achieve the enhancement of data rate and the impact of the correlation characteristics of the proposed waveforms on the BER performance. Simulation results demonstrate the effectiveness of the proposed orthonormal pulses in various conditions, comparing with different waveforms     

基于粒子群算法的UWB脉冲优化设计

从提高脉冲的频谱利用率和数据传输距离的角度出发,分析了高斯脉冲性能参数(脉冲形成因子和微分阶数)对其频谱产生的影响,提出了一种基于粒子群优化(PSO)算法的高斯导函数线性组合的超宽带(UWB)脉冲波形设计。仿真结果表明,基于粒子群优化算法组合的脉冲能够很好地满足FCC制定的室内辐射掩蔽标准,同时改善了系统链路性能。     

Comparisons of various pulse shapes for DS-UWB signals over the UWB channel

In this paper, we first investigate the power spectral densities (PSD) of bipolar modulated Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes under the FCC UWB emission mask. Considered pulse shapes are the first five derivatives of the Gauss pulse (p₁, p₂, p₃, p₄ and p₅), the first four orthogonal modified Hermite waveforms, and Daubechies wavelets (db-q). It is observed in the PSD results that p₄ and p₅ Gauss pulses, the Daubechies (db-q) for q>4 comply with the FCC UWB rule by selecting proper values for the pulse duration. Then, we derive the pulse shape dependent probability of error expression for bipolar DS-UWB signals over the standard UWB channel. The five pulse shapes (p₄, p₅, db-5, db-6 and db-7) complying with the FCC emission mask are numerically compared by using the derived probability of error expression over the CM1 model of the Standard UWB channel. Results reveal that the Daubechies have better performance than those of the two Gauss pulses.     

Pulse shape optimization for physical layer UWB communication and performance evaluation in Saleh–Valenzuela channel IEEE 802.15.3a

Ultra-Wideband communication faces constraints on radiated power from regulatory bodies to minimize the co-existing interference with the narrowband communication. These limitations cause sacrifices in terms of data rate. In this paper, a new methodology of pulse shaping is proposed to meet the spectrum mask given by Federal Communication Commission (FCC). This methodology acutely reduces the undesired ringing effect in the time domain which in turn reduces the required power per unit bandwidth of the signal. We select 7th order derivative of Gaussian monocycle as a base pulse and modulate this pulse with Gaussian window in the time domain to achieve the proposed pulse shape. The power spectral density (PSD) of the proposed pulse is perfectly fitted for spectral mask provided by FCC, in comparison of PSD of the base pulse, which in turn simultaneously provides better antenna power resolution due to the reduced ringing effect in the time domain for the proposed pulse. We also analyse the behaviour of the pulse in multi-user Time Hopped (TH) UWB environment for Saleh Valenzuela IEEE 802.15.3a multipath fading channel to find the suitability of the pulse for UWB communication.     

基于多频带PSWF脉冲组的多进制PPM-UWB系统研究

从PSWF脉冲的高能量聚集性和频谱灵活可控性入手,提出了一种满足FCC掩膜要求且具有高频谱利用率的多频带正交PSWF脉冲组设计方法,并将其应用于多用户、多进制的PPM-UWB系统中。理论计算了该系统的符号差错率公式,与使用单一PSWF脉冲UWB系统进行了性能比较。仿真结果表明,基于多频带正交PSWF脉冲组的UWB系统能够有效克服多用户干扰,从而使系统的误码性能得到显著提高。     

一种新颖的UWB成形脉冲算法

超宽带（UWB）通信系统利用优化成形脉冲方法，可以产生符合美国联邦通信委员会（FCC）制订的辐射限值的发射信号。此方法在数学表达上简单、清晰。仿真结果表明，该方法可以使UWB成形脉冲的功率谱在高、低频带都能逼近FCC的标准辐射值，得到的组合系数表达简单。在硬件实现时能够减少寄存器数量和提高运算速度。