基于SIMULINK的16QAM基带调制系统性能仿真

移动通信的物理层采用的调制方式主要有BPSK、QPSK、16PSK、16QAM等自适应数字调制解调技术。本文通过对信源产生的数字信号,经过16QAM调制解调方式对信号进行调制。通过对误码率的测试比较,来分析16QAM调制解调方式的性能。     

基于粒子滤波和Viterbi序列检测的数字信号盲解调算法

针对非协作通信下数字信号解调的问题,提出一种基于粒子滤波和Viterbi序列检测的盲解调算法。粒子滤波使用一组具有相应权值的粒子来表示未知参数的后验分布,再利用Viterbi算法对信号符号作进一步估计,最终实现对数字信号的盲解调。经仿真实验验证,该方法可以有效完成对BPSK、QPSK、UQPSK、OQPSK、8 PSK等常用PSK数字信号类型的盲解调,且较传统方法实现起来更为方便。     

一种高速多模式载波同步方法

针对载波同步的两个关键问题———提高速度和适应多模式,研究了锁相环的鉴频辅助方法,构建了基于Costas鉴相和点积、差积鉴频算法的环路。仿真结果表明,所研究的载波同步方法适应BPSK、QPSK和8PSK等调制方式,同步速度约为传统方法的2倍。     

多模多制式调制信号发生技术

随着通信行业以及数字技术的不断发展，市场上经常需要多模通信信号或多制式数字调制信号发生器，本文介绍了采用软件无线电思想，基于“DDR2+FPGA+DAC+DDS+宽带调制器”的硬件结构的信号发生装置，实现了TD-SCDMA、WCDMA、TD-LTE、FDD-LTE等多模信号以及BPSK、QPSK、OQPSK、DQPSK、8PSK、16QAM、32QAM、64QAM、2FSK、4FSK、GMSK等数字调制信号的发生，能很好满足现代信号模拟的实际需求。本文网络版地址：http：//www.eepw.com.cn/article/271645.htm     

突发自适应调制信号的调制识别算法研究

针对突发自适应调制信号中的PSK和QAM调制方式识别问题,本文提出了一种能够识别BPSK、QPSK、8PSK以及16QAM、32QAM、64QAM、128QAM、256QAM八种信号类型的盲识别算法。该算法首先对信号的循环平稳性进行了分析和讨论,给出了利用循环高阶累积量的特征实现信号识别分类的理论依据。然后,提出了三种基于循环累积量的特征分别实现了QAM和PSK类间识别、MPSK类内识别以及方形QAM与十字形QAM的识别。最后通过对MQAM信号的瞬时幅度分布特性的深入研究和分析,提出了一种基于瞬时包络平方的方差的特征实现了QAM的类内识别。该算法选择了二叉树支持向量机作为识别分类器,并设计了一种新的识别流程完成了对上述信号调制方式的识别。该算法无需精确同步,对载波相位具有较好的鲁棒性,并能够对中频信号进行识别。仿真实验表明,该算法能够实现在较低信噪比条件下突发信号的识别。      

基于软件无线电的调制器的模拟

主要讨论HSP50215内部各种功能模拟，分析其结构，用MATLAB对其进行功能仿真，实现BPSK、QPSK、OQPSK、MSK、GMSK、π/4-QPSK、QAM、AM、FM等调制，绘出波形和频谱。     

基带信号数字调制的设计与验证

数字信号的载波调制是数字通信中的关键技术,常用的载波调制技术有2ASK、2FSK、2PSK、QPSK、8PSK、4FSK等.这些电路的设计与验证用常规的方法来实现既费时又费力,借助于MultiSim10这一电子设计自动化工具,可以用VHDL建模的方法,实现基带信号数字调制的设计.使用在MultiSim10中创建的VHDL元件模型,设计出了基带信号常用的几种载波调制电路.通过观察分析电路输入输出波形,验证了载波调制和解调的实验结果.     

比特谱相关改进循环谱的单通道混合信号参数估计快速算法

为了应对复杂环境下非合作通信、电磁频谱监管等宽带接收中存在的先验信息缺失,针对单通道混合信号的参数盲估计问题,提出了一种基于比特谱相关算法改进循环谱估计的快速算法。针对信号集{BPSK、QPSK、OQPSK、8PSK、8QAM、16QAM、16APSK、32APSK、CPM},系统给出整套参数估计算法流程,通过高阶累积量以及功率中心方法确定信号个数以及载波频率,然后利用改进循环谱提取符号速率谱线,完成单通道混合信号参数估计。论文对改进算法的统计特性进行了理论推导。理论和实验表明:算法不需要同步码等先验信息,适用于高斯噪声信道和多径平坦衰落信道,同时降低了计算复杂度、存储空间、估计方差以及数据量的需求,当混合信号等功率混合时,且信噪比分别为-4 dB和-1 dB时,算法对载波频率和符号速率的估计正确率可以达到90%,验证了算法的有效性和可行性。      

Costas环法BPSK信号解调的研究与实现

载波同步与解调是通信系统中的关键技术之一。二相相移键控(BPSK)、四相相移键控(QPSK)调制是最基础、最常见的2种相移键控调制方式,应用比较广泛,因此其信号的正确、快速解调的研究变得非常重要。这里主要研究了科斯塔斯(Costas)环法BPSK信号的解调方法,QPSK信号可以看成2路BPSK信号,不难以文中所述为基础实现QPSK信号的解调。在Simulink平台对BPSK信号的解调进行了仿真,介绍了BPSK信号的产生、载波同步解调过程的仿真模型,给出了比较详细的实现过程,对仿真结果进行分析。仿真结果表明,文中搭建的仿真模型能够实现BPSK信号的解调。     

非平衡相移键控信号的调制识别算法研究

通信系统中具有非平衡相位键控特征的UQPSK信号与其他PSK调制方式的调制识别算法近些年受到了广泛关注。提出了一种基于二次方谱的非数据辅助自动调制识别算法,有效地利用离散谱线特征,将I/Q两路功率比2∶1～8∶1的UQPSK信号从常用的BPSK、QPSK、8PSK、OQPSK和π/4-DQPSK信号集中区分出来。算法特征参数门限划分不需依靠信噪比估计、非平衡因子估计等先决条件,并对不同载波频偏、码元速率和成型滤波系数的信号有良好的适应性。计算机仿真证明,算法对包含UQPSK的PSK类信号在信噪比5 dB以上有良好的识别效果(识别率≥90%)。     

卫星测控侦察中相位编码信号的调制识别

针对卫星测控链路中常用的数字调相信号BPSK、QPSK、OQPSK（偏移QPSK）和UQPSK（非平衡QPSK）的调制识别问题，提出了基于二阶矩和相位差统计特性的分类算法。该方法首先以二倍码速率对复基带信号进行采样，然后利用能量归一化的二阶矩的模和相邻样点相位差绝对值的统计特性，分两个等级实现对这四种信号的分类。分析了载频偏移、相位误差以及成形脉冲对分类算法性能的影响，并通过计算机仿真验证了算法的有效性。     

Study of behavior of digital modulations for beam steerable reflectarray antennas

This paper investigates the bit error rate (BER) performance of digital modulations in a system with a scanning reflectarray antenna. A reflectarray causes intersymbol interference (ISI) in a digitally modulated signal, its phase shifters' phase errors cause signal distortion, and its phase shifters' phase transient causes beam pattern degradation during direction switching. In this paper, composite signal models of the reflectarray are established for both static and transient states. Due to different feed-to-element distances and the element-to-observation distances, different delays exist in signal components. These delays cause ISI whose effect is analyzed and evaluated. Effects of phase shifters' phase errors and phase transient during beam switching are also analyzed and evaluated. Numerical calculations and simulations are performed. The analytical and simulation results for an example reflectarray at f/sub c/=26.5 GHz and bit rate of 1.325 Gbps show that the BER degradation due to ISI is proportional to the symbol rate and the loss ranges from about 1 dB to around 2 dB in E/sub b//N/sub o/, depending on original E/sub b//N/sub o/, for BPSK, QPSK, 8PSK, and 16QAM. The phase error effect is negligible for lower order modulations and is unacceptable for higher order modulations such as 64QAM and 256QAM. The degradation due to phase transient effect is about 2 dB for BPSK and QPSK.     

BPSK、QPSK、OQPSK、UQPSK信号识别研究

采用提取信号相位并用直方图统计的方法对BPSK、QPSK、OQPSK、UQPSK信号进行识别,并分析不同噪声背景下对这四种信号识别的影响。仿真结果表明在满足一定信噪比的条件下,能够完成对这四种调相信号的识别。     

Cramer-Rao lower bounds for QAM phase and frequency estimation

In this paper, we present the true Cramer-Rao lower bounds (CRLBs) for the estimation of phase offset for common quadrature amplitude modulation (QAM), PSK, and PAM signals in AWGN channels. It is shown that the same analysis also applies to the QAM, FSK, and PAM CRLBs for frequency offset estimation. The ratio of the modulated to the unmodulated CRLBs is derived for all QAM, PSK, and PAM signals and calculated for specific cases of interest. This is useful to determine the limiting performance of synchronization circuits for coherent receivers without the need to simulate particular algorithms. The hounds are compared to the existing true CRLBs for an unmodulated carrier wave (CW), BPSK, and QPSK. We investigated new and existing QAM phase estimation algorithms in order to verify the new phase CRLB. This showed that new minimum distance estimator performs close to the QAM bound and provides a large improvement over the power law estimator at moderate to high signal-to-noise ratios     

基于最大似然比准则的MPSK信号分类方法

本文提出了AWGN环境下一种基于最大似然比的MPSK信号识别方法,推导出了用于区分MPSK信号的特征参数通用表达式,提出了载频估计误差、信号功率对该参数影响的修正方法,本方法对实际BPSK,QPSK,8PSK,16PSK信号的正确识别率达到80%以上.     

On feasibility of a multiplier-less phase-shifting scheme for digital phase modulation and its VLSI implementation

In this paper, a multiplier-less phase-shifting scheme for digital phase modulation is proposed and its implemantation for very large-scale integration (VLSI) is examined. The abrupt phase shift of carrier waveform, required after each data transition in digital phase-modulation scheme, is realized by incrementing the frequency of a voltage-controlled oscillator (VCO) for a short duration, immediately following the data transition. The momentary increase in VCO frequency is realized by feeding the VCO with narrow control pulses, derived from the baseband data stream using a simple supporting circuit. This work currently deals with the VLSI design for binary phase-shift keying (BPSK). However, the underlying concept is generic and hence capable of implementing other digital phase-modulation schemes, such as, quadrature PSK (QPSK), quadrature amplitude modulation (QAM) etc, with a programmable control circuit for the VCO. Thus, the proposed multiplier-less phase-shifting scheme can find useful application in broadband wireless networks employing adaptive modulation schemes.