一种新的FSK最佳相干解调器

本文讨论在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声(IGDF-ACGN)信道条件下,FSK信号的最佳相干解调问题。基于矢量表示系统模型的方法,导出了最佳解调器的结构。从理论分析和计算机模拟实验结果都证明了所导得的最佳解调器,不仅在IGDF-ACGN信道条件下是最佳的,而且在加性高斯白噪声(AWGN)信道条件下也是最佳的。文中还导出了相应的误码率公式,给出了误码率数值计算和计算机模拟曲线。     

新型MFSK最佳相干解调器

本文推广了作者在1999年提出的方法和结论[1],讨论了在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声(IGDF-ACGN)信道条件下,M进制FSK(MFSK)信号的最佳相干解调问题。导出了最佳解调器的结构,说明了该解调器中有关参数的估计方法,以及实现时遇到的矢量、矩阵运算的有关快速算法。从理论和计算机模拟实验两方面说明了所导得的最佳解调器,不仅在IGDF-ACGN信道条件下是最佳的,而且在加性高斯白噪声(AWGN)信道条件下也是最佳的。文中给出了误码率的计算机模拟曲线。     

基于MMSE准则的最佳相干FSK解调器

 本文提出用MMSE准则 设计最佳相干FSK解调器.在信道噪声分布未知条件下,导出了该解调器的结构.并给出了分析和计算机模拟实验结果,证明了该解调器在AWGN信道条件下与普通FSK解调器误码性能相同,在信号各个频率振幅受到的衰减不一致,并且为ACGN信道条件下误码性能优于普通FSK解调器,与文献[2]基于MAP准则的改进型FSK解调器的误码性能十分接近;在信道中的噪声为其它分布(如均匀分布)情况下,也有类似上述的结果.     

中微子通信：通信技术史上的一场新革命

本文概括性地介绍了中微子通信的基本原理、地位和作用、国际上的现状、应用价值、可行性及战略意义等，提出了发展我国中微子通信技术的计划和建议。     

基于旋转永磁体的低频通信技术研究

旋转永磁体天线作为一种新型低频磁天线,克服了传统低频线圈体积大、功耗高、效率低的缺点,主要应用于近场低频磁通信中。该文利用FEKO分析了天线近区磁场随方向的变化规律,探究了近场范围内无限大地面对天线近区磁场分布的影响,结果表明：天线在其径向辐射强度最大,在其轴向辐射强度最小。并且在较近的通信距离范围内,地面对磁场信号的影响较小。分析了转动惯量和磁矩之间的关系,对永磁体结构参数进行了优化,研制了两款样机,并对优化前后的旋转永磁体天线功耗进行测试,实验结果表明：在质量大30 g的情况下,优化后的永磁体天线比优化前的天线平均功耗低5.5 W左右。利用直接天线调制方式磁场的2FSK调制,通过非相干解调恢复码元信息,测试结果表明：复杂电磁环境下,优化后的永磁体天线可以在20 m范围内实现码元速率为3.5 bps的超低频通信。     

基于脉冲位置调制的无线光通信多级编码调制及其多阶段解调译码算法

针对无线光通信脉冲位置调制(PPM)与信道编码的结合应用,提出了一种多级编码调制方案,利用多级编码的多级标签结构,将PPM符号所对应的分组比特分拆到不同子码通道的码字中,同时结合PPM的信号集分割和极大似然检测解调方法,推导了方案的多阶段解调译码算法。在弱湍流大气条件下的仿真分析表明,PPM多级编码调制相对单级编码调制在误码率10-6下获得0.85 dB以上的增益,且可实现对不同重要程度信息段的不等差错保护。在分量码码型给定的条件下,按纠错能力逐级配置分量码并采用所推导的多阶段解调译码,可为系统提供更好差错性能,优于直接的并行译码方法。     

数字调制解调技术及其应用的研究进展

本文首先介绍数字调制解调技术的基本原理,然后介绍多进制的数字调制以及调制技术的新应用,最后提出了一些当今最新的调制解调技术和发展趋势。     

Bandwidth compressive 64-state sqam modems for non-linearly amplified satcom systems

A new class of spectral and power efficient offset modes of the M-ary QAM modulation technique, 64SQAM (superposed QAM), is analysed. The power spectrum of 64SQAM reveals a fast spectral roll-off and a low out-of-band energy. P(e) performance is analysed with different baseband wave shapes of 64SQAM in AWGN linear channels. For the operation of M-ary QAM at the highest power efficiency (i.e. at the saturation mode of HPA), a new bandwidth compressive NLA (non-linearly amplified) 64SQAM is investigated. Retaining a compact power spectrum and allowing a simple filtering strategy, NLA-64SQAM operates within 0–75 dB C/N degradation at P(e) = 10^?6.     

Low earth orbit satellite communications experiments using the digital signal processing payload on the PoSAT-1 microsatellite

There is a growing interest in using networks of small satellites in low Earth orbit (LEO) to provide a variety of communications services in conjunction with small ground terminals. The only ’little LEO’ microsatellite digital store-and-forward communications network (HealthNet) in commercial operation at the time of writing uses microsatellites, communications payloads, and protocols designed and built at the University of Surrey, U.K. In order to provide an in-orbit research test-bed for improving communications with microsatellites in LEO by optimizing modulation and demodulation techniques, an advanced DSP payload, the digital signal processing experiment (DSPE), was included on board the latest Surrey microsatellite (PoSAT-1). In-orbit experiments using the PoSAT-1 DSPE first optimized the existing non-coherent CPFSK communication systems and then investigated the use of coherent MSK to provide a potential 3dB advantage while remaining compatible with the spacecraft systems. A novel DSP implementation of the Hodgart-Massey coherent MSK demodulator/decoder was developed by the authors and its behaviour compared with the classical de Buda demodulator undertypical LEO conditions through a sequence of rigorous computer simulations and laboratory bench tests. The simulations and bench tests quantified a practical 2dB improvement in BER performance when compared with non-coherent CPFSK, while also exhibiting considerable tolerance to the frequency and amplitude variations which are encountered in an LEO environment. These characteristics were subsequently confirmed by in-orbit demonstrations using the PoSAT-1 DSPE. The microsatellite, payload, modems and experimental results are presented in this paper and discussed with a view towards implementing an adaptable DSP-based communications system capable of optimizing data throughput with LEO microsatellites.     

Adaptive modulation as a fade countermeasure. An olympus experiment

With the launch of the European Space Agency's Olympus-1 satellite, a whole new era of communication experiments in the 20/30 GHz bands will start. Of particular interest will be those experiments concerned with fade countermeasures for the very small aperture terminals (VSATs). Portsmouth Polytechnic's experiment will focus on adaptive modulation as a type of fade countermeasure, and this paper introduces and describes the whole concept. Based on the assumption that the performance of a VSAT operating at 20/30 GHz band will be affected to a major extent by amplitude scintillations and rain fading, the performance of a range of combinations of earth-station power amplifier and antenna characteristics is presented. An adaptive multi-phase shift keying technique is then compared with conventional systems in terms of availability and data throughput. It is shown that such a fade countermeasure contributes to increasing both the overall system availability and the total data throughput of a digital communication system, while the inevitable reductions in data rate occur smoothly.     

A new generation of modems for power efficient radio systems

A new class of generalized intersymbol-interference and jitter-free (GIJF) modulated signals is introduced. Computer simulation and hardware experimental research results demonstrate that our proposed new generation of signals and modulators leads to significant performance improvements in non-linearly amplified broadband radio systems. For increased power efficiency, non-linear amplification is required in most commercial satellite and terrestrial microwave systems. In particular, we demonstrate that the 3 dB envelope fluctuation of currently used offset raised-cosine overlapped QPSK systems is reduced to 0-5 dB, and that the BER performance is improved by approximately 1 dB. These significant technical performance advantages are expected to lead to more economical implementations of digital transmission systems.     

WCDMA系统的调制技术

介绍第三代移动通信ＷＣＤＭＡ 系统的调制技术,包括ＱＰＳＫ 调制和解调的基本原理,以及ＷＣＤＭＡ 系统的调制方式。分析了在实际应用中多普勒频偏和频率稳定度对调制性能的影响,并简要介绍了调制、解调的实现方法。     

高效频谱调制方式在蜂窝移动通信系统中的性能分析

本文研究高效频谱调制方式ＭＰＳＫ及ＭＱＡＭ在蜂窝移动通信中的应用及其性能。在综合考虑共道干扰，Ｒａｙｌｅｉｇｈ衰落以及高斯噪声等影响因素的基础上，结合分集接收技术，我们给出了ＭＰＳＫ及ＭＱＡＭ应用于蜂窝移动通信时误码率计算的通用近似公式。蒙特－卡洛仿真表明文中给出的误码率近似公式能很好地吻合实际系统的仿真结果。     

几种AM信号数字化解调算法比较

数字信号与模拟信号相比有很多优点,因此信号的数字化处理应用越来越普遍.作为常用信号,幅度(AM)调制信号的数字化处理也会得到更广泛的运用.通过研究3种AM信号数字化解调的算法,给出相应的解调原理、公式推导以及系统模块;采用Matlab对一段信号采用3种方法分别进行仿真解调,并对结果进行比较.在原理分析与仿真结果的基础上...     

基于FPGA的2FSK数字信号调制解调

基于FPGA的调制和解调的数字信号有多种,包括2ASK、2FSK、2PSK等,文中介绍了2FSK信号的调制与解调,以及该信号的功率谱。最后提供验证结果,证明仿真结果符合要求。     

软件无线电基带处理系统的DSP实现

给出了一种基于DSP技术实现的软件无线电基带处理系统,包括一个DSB模拟调制系统和一个FSK数字调制系统,并对软件无线电在移动通信领域的应用进行了探讨。     

数字电路倍增设备中的传真解调与再调制

对DCME (数字电路倍增设备 )中的传真解调、再调制技术进行了研究 ,对基于ITU TV 2 9建议的 960 0bit/s传真信号提出了一个全数字调制解调器模型 ,并给出了算法。在调制部分采用了符号成形法 ,较好地解决了频谱混叠的问题 ,该算法计算量小 ,具有较好的性能 ,易于DSP (数字信号处理器 )实现。     

基于软件无线电的LFM的设计与实现

软件无线电技术是近年来提出的一种实现无线通信的新的体系结构,它具有很强的灵活性与开放性。采用BOK调制的方法,基于软件无线电来研究线性调频信号的调制解调,在Simulink环境下对该线性调频系统进行建模和仿真,并利用FPGA进行软件仿真验证。     

AM信号数字化解调方法研究

数字信号相比模拟信号而言,具有许多优点,因此数字化信号处理得到了越来越普遍的运用,而幅度调制信号数字化处理也会得到更多的运用。对于幅度调制信号的数字化解调,目前最常用的是正交相干解调的方法。但是这种方法消耗资源较多,使用数字器件易引入误差。为此文中提出了一种包络解调算法,该算法简单实用,误差较小,具有较高的工程应用价值。     

On optimal threshold and structure in threshold system based detector

Threshold systems are widely used in nonlinear signal detection. The optimal threshold and the optimal structure are crucial to obtain good performance. In this paper, we propose an efficient method to estimate optimal threshold in a threshold system based detector (TD). In addition, we investigate the structural issue of TD and propose a technique to determine the optimal structure. An optimal threshold detector is then implemented based on the optimal structure with the optimal threshold(s). Experiments show that the proposed optimal TD can be fairly compared to the optimal detection with much easier implementation and much less computational complexity.