一种采用高重复频率激光进行水声通信的方法

为研究空中平台与水下目标之间的激光声通信技术,提出了一种热膨胀机制下采用高重复频率激光进行水声通信的方法(重复频率法)。理论推导了高重复频率激光产生窄带声信号的过程,并通过实验测量进行了验证。利用高重复频率激光产生了频移键控(n-FSK)和多频移键控(n-MFSK)两种频移键控信号,结合现有激光器的技术指标,针对不同调制信号的水下通信距离、占用带宽、传输速率进行了分析计算,并与现有的方法(长脉冲法)进行了比较。结果表明,n-MFSK调制的传输速率比n-FSK调制的更快,频带利用率更高,但水下通信距离不及n-FSK调制;同为n-FSK调制,重复频率法的水下通信距离为1000m,比长脉冲法高40%,通信性能优于长脉冲法。     

基于预测控制的三相双降压逆变器统一调制策略

针对三相双降压逆变器(Dual Buck Inverter,DBI)这种无需死区时间、开关频率较高、输出高功率因数的变换器调制策略较多的问题,将现有的3种不同的调制策略进行结合,引入预测控制方法,提出统一的调制策略。所提方法能够在同一种控制方法下切换正弦脉宽调制策略(SPWM),空间矢量脉宽调制策略(SVPWM)和不连续空间矢量脉宽调制策略(DSVPWM)3种不同的调制方法,实现控制方法的简化。通过仿真与实验验证了3种调制方法之间的切换,同时对比了3种不同调制方法下的逆变器传输效率。     

基于光纤光栅的超宽带信号产生与传输

针对现有方法功率利用率低与调制实现困难的问题,采用基于光纤光栅（FBG）的超宽带（UWB）调制信号产生方法,建立了UWB信号产生系统。不仅可以实现UWB信号的调制,而且提高了产生信号的信噪比。实现了二进制相位调制（BPM）、脉冲幅度调制（PAM）和脉冲位置调制（PPM）等UWB信号产生。分析了光纤传输对产生信号的影响,...     

剩余振幅调制对波长调制光谱信号线型的影响

在基于可调谐二极管激光吸收光谱技术的痕量气体检测中,波长直接调制时剩余振幅调制也会伴随发生,并对检测信号的线型和系统噪声产生严重影响。为了探讨剩余振幅调制对波长调制光谱二次谐波信号线型的影响,采用同时考虑振幅调制和波长调制两种影响因素的计算方法,理论分析出二次谐波信号的计算公式,与仅考虑波长调制的信号计算方式进行同条件线型计算比对,取得了二次谐波信号基线和正负峰值随剩余振幅调制的变化数据。结果表明,剩余振幅调制的大小对检测信号的线型和信号基线有直接影响,采用这种方法计算得出的二次谐波信号线型更贴近实际检测。     

Carrier-Based Modulation Technique for Matrix Converter

This paper presents a carrier-based modulation method for a matrix converter. By using the offset voltage and changing the slope of carrier, it is possible to synthesize the sinusoidal input currents with the unity power factor and desired output voltages. The proposed method is equivalent to the so called space vector pulsewidth modulation method. The proposed method uses a new point of view to understand the matrix converter modulation method such as the voltage source inverter (VSI) modulation method. Using the proposed method, this paper presents the two-phase/three-phase modulation method and dynamic/steady-state overmodulation method for the matrix converter. These methods are well developed in the study of a VSI. By the proposed steady-state overmodulation method, it is possible to synthesize the fundamental component of output voltage to be equal to that of input voltage at the cost of some distortion of input current. The feasibility of the proposed modulation method has been verified by a computer simulation and experimental results. These results show that the proposed carrier-based modulation method can be implemented easily without any tables. It can be used for the application where a higher voltage transfer ratio is essential     

Modulation characteristic of waveguide-type optical frequency combgenerator

We report the modulation characteristics of a waveguide-type optical frequency comb generator (WG-OFCG) with the advantages of compactness, high modulation index and low driving power. The characteristics of the optical frequency comb (OFC) generated when the modulation index exceeds 2π are discussed. The power of the modulation sidebands was measured by the optical heterodyne method with an external-cavity laser as a local oscillator. The dependence of the modulation index of the WG-OFCG on the modulation frequency up to 40 GHz was measured. The generation span of the OFC at the modulation frequency detuned from an integer multiple of the free spectral range (FSR) is discussed     

Modulation for terrestrial broadcasting of digital HDTV

The digital modulation methods used by the DigiCipher, DSC-HDTV, ADTV, and ATVA-P digital high-definition television (HDTV) systems are discussed. Three of the systems use a quadrature amplitude modulation method and the fourth uses a vestigial sideband modulation method. The channel equalization and spectrum sharing of the digital HDTV systems is discussed     

优化参数对CPM-PSWF信号性能的影响

基于椭圆球面波信号的连续相位调制(Continuous Phase Modulation Based on Prolate Spheroi-dal Wave Function,CPM-PSWF)方法是一种新颖的数字调制方式,调制参数的优化与其调制信号性能有着直接联系.分析不同调制参数对CPM-PSWF信号性能的影响,优...     

半导体激光器的微腔结构调制及其脉码在光纤中的传输

采用腔量子电动力学(QED)方法,定量讨论了平面结构微腔半导体激光器的自发发射特征物理量随腔结构的变化规律.在微腔半导体激光器自发发射因子调制、自发发射寿命调制以及一些实验依据的基础上,提出了微腔结构调制方法.数值模拟了其脉码在光纤中的传输图形.结果表明,微腔结构调制方法在提高脉码比特率方面优于同参数下的电流调制方法.     

基于优化多重索引的椭圆球面波函数多载波索引调制解调方法

围绕如何提高椭圆球面波(PSWFs)多载波调制系统频带利用率,该文在双模PSWFs多载波索引调制解调方法的基础上,引入由额外星座点组成的第3星座图,提出基于优化多重索引的PSWFs多载波索引调制解调方法BIM-MCM-PSWFs。该方法通过对分组后每个子块中子载波的多重排列组合,拓展了信号索引维度,增加了调制符号组合数,实现了双模PSWFs多载波索引调制解调方法中频谱资源的进一步利用,有效提高了系统频带利用率。理论和仿真分析表明,该文所提方法相较于双模PSWFs多载波索引调制解调方法,以适当牺牲误码性能为代价,具有更高的系统频带利用率,当n=9, k=1, m=4时,以误比特率(BER)牺牲了0.70 dB为代价,系统频带利用率(SE)提升了20.1%。     

基于延时相关频谱的调制识别方法

以简单脉冲、线性调频、二项编码和频率编码信号为例,通过提取信号的延时相关频谱特征,对雷达信号的脉内调制特征进行了分析。在分析和提取了信号的延时相关频谱结构特征后,提出了一种基于延时相关频谱进行调制方式识别方法。仿真和试验结果表明:在低信噪比情况下,是一种较好的雷达脉内调制方式识别方法。     

A simple simultaneous geometric and intensity correction method for echo-planar imaging by EPI-based phase modulation

A technique, based on Echo planar imaging (EPI)-based phase modulation factor maps, is described for correction of EPI distortions resulting from field inhomogeneity. In this paper, a phase modulation factor was employed to remove the distortions. The phase modulation factor was obtained experimentally by collecting EPI images with a spin-echo (TE) spacing, deltaTE, equal to the inter-echo time interval, T(i). Then, the distortions resulting from the field inhomogeneity were removed by modulating the kappa-space data with the phase modulation factor. One of the advantages of this method is that it requires only a few extra scans to collect the information on field inhomogeneity. The proposed method does not require a phase unwrapping procedure for field inhomogeneity correction and, hence, is easier to implement, compared to other techniques. In addition, it corrects geometric distortion as well as intensity distortions simultaneously, which is robust to external noise or estimation error in severely distorted images. In this work, we also compared the proposed technique with others including, a) interpolation method with EPI-based displacement maps, and b) modulation method with phase modulation factor maps generated from spin-echo images. The results suggest the proposed technique is superior in correcting severely distorted images.     

Voltage modulation factor of the magnetic flux control PWM methodfor inverter

The voltage modulation factor of the magnetic flux control pulse-width modulation (PWM) method is discussed. The modulation factor is derived from a theoretical study on the flux locus produced from the inverter output voltage. The derivation is based on the fact that the fundamental component of the inverter output voltage is proportional to the radius of the flux locus. It is shown theoretically that the voltage modulation factor is expressed by the content of a zero vector in one cycle of the selected PWM pattern of the space vector expression. The modulation factor of the magnetic flux control PWM method is calculated. The modulation factor can be varied from zero to 12/π². The output voltage of the magnetic flux control PWM method can be controlled by the modulation factor linearly from zero up to overmodulation. The simulation and experimental results are also shown     

差分空间调制中的非恒模调制方法

差分空间调制(DSM)由于不依靠信道状态信息(CSI)而备受关注.传统的DSM采用了恒模调制的方法,例如相移键控(PSK),但是在高速传输时PSK对星座图的空间自由度利用很低.针对该问题提出了一种DSM系统中的非恒模调制方法,通过对发射信号做相关预编码处理,使之消除非恒模调制在DSM系统中存在的幅度迭代问题.除此之外,为了使之可以体现分集增益,通过减小传输速率来达到满分集增益,并且加入一个功率均衡项来使该系统可以利用非恒模调制.仿真结果表明所提算法随着信噪比的提高,性能会逐渐优于PSK.     

一种新的酉空时调制

为了更有效地提高系统的频带利用率,该文提出一种多调制方式联合的设计思想,并推导出其实现的必要条件和几种可能途径。由理论结果导出一种新的调制方式差分相位酉空时调制(DPUSTM),并设计了相应的非相干解调算法。DPUSTM将酉空时调制(USTM)和差分相移键控(DPSK)调制有机地融合,在提高系统频带利用率方面比目前已有的USTM系统更简单易行。可以较低的复杂度分别解调出酉空时(UST)信号和DPSK信号,不仅保持了UST信号低误比特率的优点,并可适用于多种速率并行传输的无线数据通信。仿真结果证明理论分析和给出的设计是有效的,而且表明了DPUSTM的性能可比USTM和DSTM更优越。     

An optical modulation method to suppress stimulated Brillouin scattering and the phase noise in a remote interferometric fiber sensing system

A novel optical modulation method for stimulated Brillouin scattering (SBS) and the phase noise suppression in a remote interferometric fiber sensing system is proposed. Compared to the conventional phase modulation method to suppress SBS with only one phase modulation signal, another phase modulation signal with π shift is applied at the output end of the fiber, which converts the generated multi-frequency light to single-frequency light. Therefore the method can suppress not only SBS but also the phase noise induced by linewidth broadening owing to the first phase modulation. As a result, the method can keep the system a low phase noise level with a higher input power, which overcomes the conventional drawback of linewidth broadening. The results show a good reference to the design of remote interferometric fiber sensing systems.     

基于排序时频特性的雷达脉内调制信号识别

提出了一种基于排序时频特性的雷达脉内调制信号识别算法.该算法可分为三步:首先,通过检验信号时频曲线的互易回归特性,识别出线性调频信号;然后,通过检验信号时频RANKIT图的正态性,识别出常规信号;最后,检验信号平方后时频RANKIT图的正态性,用以区分二相编码与四相编码信号.仿真结果表明,该算法无需接收信号的任何先验知识,在较低信噪比条件下可实现对常用雷达脉内调制方式的有效识别.     

两种新型无源OLED显示列驱动电路的研究与设计

针对两种采用不同灰度调制方式和预充方法的新型无源OLED显示列驱动电路进行研究和设计。阐述了脉冲宽度调制和脉冲幅度调制两种灰度显示方式的一致性,提出相对应两种灰度调制方式的列驱动电路,从电路设计到版图实现上比较了这两种电路。阐述了电压和电流两种预充方式,设计出两种新型预充方法,并且应用到OLED显示驱动芯片中。Hspice仿真和版图实现后表明,两种列驱动电路中前者的版图面积约是后者的1/2,采用省电模式预充方法的后者的功耗约是前者的1/3。     

Wavelet analysis of modulated signals

The relationship between Haar wavelet decomposition coefficients and modulated signal parameters is discussed. A new modulation classification method is presented. The new method uses the amplitude, frequency and phase information derived from Haar wavelet decomposition as feature vectors to distinguish the modulation types of M-ary Frequency-Shift Keying （MFSK）, M-ary Phase-Shift Keying （MPSK） and Quadrature Amplitude Modulation （QAM） modulation types. A parallel combined classifier is designed based on these feature vectors. The overall successful recognition rate of 92.4% can be achieved even at a low Sig- nal-to-Noise Ratio （SNR） of 5dB.     

共路外差干涉测量液晶空间光调制器相位特性

为了对液晶空间光调制器进行高精度的校准, 使其满足线性相位调制的应用需求, 采用共路外差干涉法测量了液晶空间光调制器的相位调制特性, 分析了实验系统的测量原理, 取得了液晶空间光调制器相位调制量随输入灰度值变化的实验数据, 并进行了线性校准。结果表明, 实验中所用的液晶空间光调制器的最大相位调制量为2.55π, 利用反插值法对20~240灰度范围内的相位调制曲线进行线性校正后的理论相位调制曲线非常接近理想线性曲线, 相位调制曲线与理想线性调制曲线的相关系数可达0.9996;该测量方法可克服传统测量方法对图像处理的依赖性, 具有较高的测量精度, 相位调制量直接通过锁相放大器就可获得。该研究为基于液晶空间光调制器的高精度波前校正和精密测量提供了参考。