一种新的正交多载波调制技术——滤波多音调制（FMT）

在无线通信中 ,以正交频分复用 (OFDM)为代表的正交多载波调制 (OMCM )技术正在获得深入研究和广泛应用。本文介绍了一种新的正交多载波调制技术———滤波多音调制(FMT) ,并对它与OFDM在无线通信中的特点和性能作了详细比较 ,就其在下一代宽带移动通信的应用前景作了初步探讨。     

基于滤波多音改进的F-OFDM方案

针对滤波OFDM（F-OFDM）系统对子带内定时同步要求严格的问题,提出了一种基于滤波器组的滤波多音（FMT）调制技术来实现F-OFDM的改进方案。通过滤波器组结构实现子载波级的滤波处理,采用载波频谱不重叠的FMT调制,改进方案降低了子带内严格的定时同步要求。仿真结果表明,所提方案可进一步将带外发射（OOBE）抑制到-65 dB深度,且在加性高斯白噪声（AWGN）信道和瑞利衰落信道下,具有较好的抗载波频率偏移（CFO）性能。相比于F-OFDM的直接实现,改进方案具有更低的运算复杂度。     

CMFB-DWMT多载波系统与DMT多载波系统的比较

本文首先讨论了基于余弦调制滤波器组（cosine modulation filter-banks-CMFB)的多载波调制解调结构的快速实现。然后在性能和抗噪方面对CMFB多载波结构与DMT（discretemulti-tone)作了分析和比较。计算机仿真结果显示，CMFB－DWMT(discrete wavelet multi-tone）在左频域特性、抑制噪声和抑制突发错误方面比DMT有较大的优势。     

滤波多音调制系统频偏分析与仿真

滤波多音调制技术通过采用频谱不重叠的多载波调制技术,有效地克服了传统的多载波调制技术正交频分复用的频偏敏感性问题,同时通过不太复杂的均衡技术消除系统的码间干扰。理论分析与仿真证明,滤波多音调制系统有着比正交频分复用系统更好的抗载波频偏的能力。     

数字滤波器组在多载波调制中的应用

介绍了用数字滤波器组实现多载波调制的原理、性能以及可能的研究方向,重点比较了用数字滤波器组实现多载波调制与用DFT实现多载波调制的性能,并给出了仿真结果。     

基于DFT滤波器组的多载波调制系统设计

采用DFT滤波器组来代替OFDM系统中的IDFT/DFT模块,形成基于滤波器组的收发器。设计适于多经衰落信道的DFT滤波器组收发器。其均衡与OFDM系统一样,是在接收端采用单抽头的均衡器。实验采用随机多径信道,仿真结果表明所提出的滤波器组收发器可以获得较好的频谱特性,以及较满意的SIR（信号与干扰比值）。     

离散多频音调制系统中符号间干扰的消除

介绍了用于高速率数字用户线中性能较优的数字调制技术－离散多频音调制，分析了调制原理及其实现方法，提出了加循环前缀与时域均衡器相结合的方法解决符号间干扰问题。     

非均匀多载波信道分路技术的FPGA设计方法

针对非均匀多载波整体解调中的信道分路实现问题,基于完全重构调制滤波器组的优化结构,提出一种非均匀多载波信道分路技术的FPGA设计方法。相对于均匀多载波信道分路的局限性,使得非均匀分路技术能够更加灵活地适应系统需求且易于实现。对非均匀多载波信道分路技术中涉及到的分析和综合两部分模块的FPGA实现方法进行了详细阐述,给出了硬件占用资源情况和误码测试结果,实现了多载波速率混合信号的重构。     

ADSL中离散多音调制（DMT）技术分析

本文首先介绍了离散多音(DMT)调制的实现和工作过程,其次分析了DMT系统的性能,最后对我国应用DMT-ADSL技术的前景提出了合理的建议。     

Hartley变换离散多音调制在可见光通信中的应用

针对传统调制方式难以满足人们对高速通信的要求,结合Hartley变换与离散多音调制(DMT)提出一种用于可见光通信的多载波调制方式.为了实现DMT,采用Harltey变换来代替傅里叶变换,然后对调制信号进行非对称式限幅来降低LED的发射功率.仿真结果表明,相比于直流偏置调制模式,非对称限幅调制模式更为节能.     

Performance limits for filtered multitone modulation in fading channels

In this paper, we investigate the best attainable performance for filtered multitone modulation (FMT) in time-variant frequency-selective fading channels when optimal maximum-likelihood (ML) detection is deployed. FMT generalizes the popular orthogonal frequency division multiplexing (OFDM) scheme through the deployment of subchannel shaping filters. The performance limits are derived by extending to this multichannel context the matched filter bounding technique. We first conduct an exact calculation for the average and the distribution of the matched filter error rate bound. Then, we follow a numerical procedure that overcomes the problems of accuracy and ill conditioning in the implementation of the exact method. This study allows for an analytical treatment of the diversity effect on performance as a function of the time/frequency selectivity of the channel. It is found that FMT is a diversity transform that is capable of yielding coding gains and time/frequency diversity gains as a function of the subcarrier spacing and the subchannel filter shape.     

Hybrid TDMA/CDMA based on filtered multitone modulation for uplink transmission in HFC networks

We present a hybrid TDMA/CDMA system for uplink transmission in multiple access networks that is based on filtered multitone modulation. We consider an application to uplink transmission in hybrid fiber/coax networks. After discussing the characteristics of the proposed system, we address the problem of initial ranging and power adjustment of unregistered stations. Finally, we introduce a new collision resolution algorithm in conjunction with FMT modulation that uses iterative identification of the competing stations to achieve high throughput on the collision channel. System performance is investigated by simulations.     

重叠滤波多音系统的频偏性能分析及优化

重叠滤波多音(O-FMT)是针对滤波多音(FMT)系统频谱利用率低的缺点而根据超奈奎斯特(FTN)概念引入子载波重叠得到的方案。鉴于O-FMT系统在频偏环境下的性能缺陷,理论分析了频偏对系统信号各部分的影响,比较了O-FMT与正交频分复用（OFDM）系统的抗频偏性能。针对频偏性能优化问题,提出了基于最佳线性无偏估计（BLUE）的改进盲估计算法,设计了基于频域滤波器系数的内嵌结构进行频偏补偿。仿真实验表明,O-FMT相比OFDM具有更好的抗频偏能力,改进的盲估计算法估计值精度更高,抗干扰、抗衰落能力更强,设计的频偏补偿结构可以使系统获得更好的性能。     

Spectral structure of multitone pulse width modulation

The multiple sidetone structure recently reported in pulse width modulation arising from multitone inputs can now be accurately predicted by a newly derived modulation formula. Excellent agreement is demonstrated between measurements and theoretical calculations.<>     

Comparison of single-carrier and multitone digital modulation forADSL applications

Single-carrier modulation such as quadrature amplitude modulation (QAM) or carrierless amplitude modulation-phase modulation (CAP), and DMT are alternative techniques for providing digital communication in a variety of applications, in particular ADSL for communication over the telephone company subscriber lines. Although theory predicts comparable performance under ideal implementations, a definitive comparison of performance over a wide range of conditions will require more experience from field trials. Similarly, accurate comparison of implementation costs must await the greater availability of commercial-grade devices. However, enough is now known about these modulation schemes to compare their inherent similarities and differences in performance and cost. Overall, a present view of single-carrier and multitone modulation indicates comparable performance with some differences depending on the type of degradation. Costs should also be approximately equal, with multitone having some advantage in digital processing, but requiring greater cost in analog circuitry     

Characterization of the modulation transfer function of discrete filtered backprojection

A mathematical expression for the modulation transfer function (MTF) of image reconstruction by discrete filtered backprojection (DFBP) is derived. A simulation study is used to investigate the dependence of the MTF of DFBP on: (1) the number of projection views; (2) the type of ramp filter used; (3) the interpolation method used during backprojection; and (4) the position of the object. These results were compared to MTFs calculated from point-source single-photon-emission computed tomographic (SPECT) acquisitions in air. The experimentally obtained MTFs contained much of the same structure as the MTFs of DFBP obtained through simulation. It is shown that the discretization of the filtered backprojection process can cause the tomographic transfer function to be anisotropic and nonstationary. However, through proper selection of the methods used in reconstruction, a nearly isotropic and stationary MTF can be obtained.     

RS理论在自组织调制识别技术中的应用研究

通信信号处理中最主要的问题是调制样式自动识别,其实质就是通过对输入信号的判别和归类进而理解该信号的结构和属性.本文研究了将粗糙集理论应用于自组织调制识别中的技术.它利用粗糙集理论进行信号的属性约简,求出约简和核;神经网络利用最简决策表构建分类器和提取主要特征参数.二者结合实现了信号自动调制识别,这不仅简化了网络结构和缩...     

Notes on the theory of modulation

The transmission system of "frequency modulation" (transmission by variation of the frequency of the radiated wave) is mathematically analyzed, and the width of the band of frequencies occupied by this method of transmission at a given speed is compared with the width of the corresponding band for transmission by amplitude variation. It is proved that the frequency modulation system using a spacing or compensating wave is inferior to the amplitude variation system both as to the width of the frequency band occupied and as to distortion of signal waveform.     

扩散光谱的原理和应用

详细介绍了扩散光谱(DWS)技术的基本原理及其常见的实验方法.对近年来发展起来的微流变学、时间分辨扩散光谱等技术进行了简要介绍,总结了DWS在粒度分析、微流变学、医学检测、电磁流变体研究中的应用情况.