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.     

数字蜂窝移动通信系统的调制技术

本文主要讨论数字蜂窝移动通信中的调制解调问题。在指出其特点后,阐明线性调制及恒包络连续相位调制两类方案,着重介绍恒包络连续相位调制中的GMSK 调制。     

符号内连续相位差分相移键控调制方法

提出了一种幅度准恒包络、相位连续的差分相移键控调制与解调方法.该方法设计了一组基带信号集合,根据输入的信息值和状态值选择基带信号来实现信号调制.在信号解调中,通过计算接收信号在一个符号持续时间内的相位变化累积量来判决发送信息.仿真结果表明,该调制方法具有良好的频谱特性和准恒包络特性,并且避免了本振偏离、多普勒频移等引起的符号间相位变化对信号解调的影响.     

MC-BOC:应用于导航通信一体化系统的新型调制技术

针对导航通信一体化系统面临的在有限带宽内实现高速率信号传输和高精度测量的难题,结合正交频分调制与恒包络调制思想,提出了多载波二进制偏移载波（multi-carrier binary offset carrier,MC-BOC）调制,其能够有效利用频谱资源,提升信号的接收性能,并具备恒包络特性.分析北斗无线电测向卫星业务（radio determination satellite service,RDSS）采用该调制后的性能,结果表明:该调制方式具备优良的通信性能、抗干扰能力、测距性能以及抗多径能力.本文提出的MC-BOC调制技术为导航通信一体化系统信号体制设计和优化提供了一种可行的参考方案,可以用于北斗RDSS和站间时间同步/数据传输网络的信号设计.     

非线性功放对数字调制信号的影响研究

功放的非线性会带来调制信号的性能恶化,基于simulink建模,对比仿真了恒包络调制MSK和非恒包络调制BPSK,在功放线性和非线性区域时的误码性能,以及在带宽受限条件下,相邻信道干扰对信号误码性能影响.仿真结果表明,功放饱和对非恒包络调制信号影响更大,尤其是信道间隔较小的情况下,非恒包络调制信号的误码性能恶化严重.该研究为数字通信系统的工程设计提供了一种可借鉴分析方法.     

掺钕离子固体激光器的被动式Q调制及其锁模输出

用四种饱和吸收体 醋酸盐塑胶状染料 ,L i F:F2 -,Cr4 :YAG,离子性色滤片玻璃 colourfilter glass 做被动式调制元件 ,对 Nd:YAG激光器等做纯 Q值调制及 Q值调制包络的锁模调制 .分析了 Cr4 :YAG晶体材料的参数值、能级跃迁及其原子速率方程式 Rate equation 对产生 Q值调制及锁模调制的物理机制 ;并优化了 Cr4 :YAG晶体及激光共振腔和操作工作点 ,使其达到最低阈值、最高效益及 10 0 %锁模调制的激光输出 .     

CPM编码调制发展前景

连续相位调制（CPM）技术是一类恒包络的数字调制技术,CPM信号的恒包络这一特性使它们对于非线性信道和衰落信道具有很强的抵抗性．特别适用于卫星通信和移动无线通信信道。与PSK调制方式相比,CPM调制系统不仅能够提供较高的频谱效率,而且具有一定的编码增益,这是因为接收器可以利用相位成型滤波器引入的记忆特性。CPM调制系统可以分解为一个连续相位编码器（CPE）和一个无记忆调制器（MM）的级联,因此出现了多种卷积码与CPM结合的调制方案,例如串行级联连续相位调制、基于环的串行级联连续相位调制、实用的连续相位调制、卷积编码器与扩展信道编码器的串行级联,等等。其中,基于环的串行级联连续相位调制具有很好的性能,在交织增益、自由距离、误码平层和收敛门限可能成为未来连续相位编码调制系统的发展方向。     

连续相位调制(CPM)在战术无线通信中的应用研究

战术无线通信环境通常具有复杂多变及非视距的特征。连续相位调制由于其恒包络和带外能能量衰减快的特征,极大的提升了功放效率及频带利用率,在战术无线通信中获得了广泛的应用。本文分析了连续相位调制的技术特点,给出了在战术通信的典型应用,并展望了未来的应用前景。     

基于倾斜相位的CPM信号调制解调设计

连续相位调制(CPM)信号是一种具有高频谱效率和功率效率的恒包络调制技术,但基于传统相位网格的CPM信号调制解调算法复杂度高、计算量大。提出了一种基于倾斜相位网格的CPM调制解调算法,通过分析CPM相位网络图和分解模型,给出了CPM信号倾斜相位网格设计、状态存储、初始化及译码的实现方法,相比传统相位,该算法更加简洁、计算量更小,并通过仿真验证了设计方案的正确性。     

自适应调制的最优调制模式转换

根据信道条件采用自适应调制技术是解决衰落问题的有效手段,同时也可以有效提高误比特率性能或平均吞吐量.本文在无线衰落信道条件下采用方形正交振幅调制方式,以一般的恒功率自适应调制模型为基础,推导出了平均误比特率和平均吞吐量的一种近似的表述形式,并在平均误比特率的约束条件下,为了获得最大可能的吞吐量,利用Lagrangian最优化方法得出了调制模式的最佳转换等级,且通过仿真表明,采用了这种最佳转换等级模式的自适应调制方式,在保持恒定的平均误比特率的条件下表现出了优越的性能.     

SPWM单相逆变电路的谐波分析

在比较单相逆变电路几种PWM调制方法的基础上,对SPWM调制的谐波问题进行了分析,并在Matlab中进行了仿真,从仿真结果可以看出PWM逆变器的谐波特性与调制深度、载波频率有着密切关系,在实际中为得到较好的输出正弦波,既要考虑增加调制深度,又要增加载波频率。     

分布式反馈激光器调制特性研究

为了深入了解分布式反馈激光器（DFB）的发光机理与调制特性,通过理论分析和实验对DFB的调谐特性进行了研究。得到FITEL和JDS Uniphase两款激光器调制电流与输出中心波长的对应关系和两种确定系数不同的拟合方程,证明了这两款DFB激光器在实际应用中存在非线性关系。结果表明,FITELFRL15DCWD-A82激光器的3dB带宽与驱动电流幅值关系为3.715pm/mA;该调制结果优化了该激光器的可用相干长度,并验证了驱动信号频率变化不影响3dB光谱宽度。对DFB激光器低频调制特性的定量分析结果可为相干检测系统驱动电路设计提供实验依据。     

Novel matrix representation for OFDM/OQAM systems

In orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) systems, the relationship between the input of the synthesis filter bank (SFB) and the output of the analysis filter bank (AFB) is much more complicated than OFDM due to its special prototype filter. By analyzing the trans-multiplexer response characteristics, an equivalent trans-multiplexer matrix is proposed to describe the relationship between the input and the output. With the equivalent matrix, the output can be easily computed using matrix multiplication with the input. Moreover, with the inverse of the equivalent trans-multiplexer matrix, imaginary interference can be eliminated using the precoding method. The simulation results show the correctness of the equivalent trans-multiplexer matrix.     

10 Gbit/s四波混频型全光波长转换器的实验研究

利用自行研制的半导体光放大器(SOA)对四波混频(FWM)型波长转换器进行了实验研究。在10Gbit / s调制速率下,频率失谐达500GHz时仍现察到理想效果的四波混频型波长转换现象。研究了输出端各波形调制格式的关系,结果验证了基于半导体光放大器四波混频型波长转换中,泵浦光与信号光功率之间的关系对转换结果有直接影响。     

丙丁烷TDLAS测量系统的吸收峰自动检测

基于丙丁烷在3.37μm处的基频吸收峰,使用相应中心波长的连续带间级联激光器和长光程吸收池,研制了基于波长调制技术的丙丁烷气体检测系统。为自动确定波长调制过程中的锯齿波中心值参数,基于电流与输出光频率的线性关系,通过均匀增加激光器驱动电流获得直接吸收光谱。使用基于洛伦兹线型的拟合算法确定吸收峰值对应电流,使锯齿波输出光以其为中心覆盖吸收峰。实验证明,以拟合结果31.94mA为中心值的锯齿波,在叠加频率为20 000Hz、幅值为0.03V的高频正弦调制波后,系统二次谐波峰值超过100mV。算法全过程不依赖标气和F-P标准具等精密光学器件,可适应实际生产条件下的系统自动定参。     

Nonlinear dynamics of a laser diode with optical feedback systemssubject to modulation

The nonlinear dynamic behavior of a direct frequency-modulated diode laser with strong optical feedback is examined and compared to a laser diode subject to electro-optically modulated, strong optical feedback. Direct modulation is achieved by sinusoidal modulation of the diode laser injection current. Electro-optic modulation is achieved by applying a sinusoidal voltage to an intracavity phase modulating element. The output state (characterized by the output power versus time, the intensity noise spectrum and the optical frequency spectrum) for both types of modulation is dependent on the ratio of the modulation frequency to the external cavity resonant frequency, and the modulation power. A number of distinct states are observed: conventional amplitude modulation (with FM spectra); multimode, low-noise amplitude modulation; multimode, high-noise amplitude modulation; periodic limit-cycle operation; quasi-periodicity; chaos; low-frequency fluctuations; and mode-locking. There are significant differences between the direct and electro-optic frequency-modulation cases. The onset of the dynamic instability is characterized as a noisy period-one oscillation for direct modulation and a low-frequency fluctuation for intracavity electro-optic modulation. Phase portraits produced experimentally with the use of a digital phosphor oscilloscope are shown to agree well with those constructed from output power versus time data. This represents an experimental method for examining the dynamics phase portraits in real-time     

Research of the equivalent relationship between the space vector and the triangular carrier-based PWM modulation strategies in the flying capacitor multilevel inverters

ABSTRACT

The equivalent relationship between the carrier-based modulation (CBPWM) and the space vector modulation (SVPWM) based on the flying capacitor multilevel inverters has not been analysed systematically. Due to the redundancies of the flying capacitor multilevel inverters, this paper firstly focuses on the switching sequence and the working ratio of each switching state and then proposes a novel method of decomposing modulation wave. This method can distribute the ratio of redundancies arbitrarily to satisfy the requirements of the output. Taking three- and five-level inverters as examples, by injecting a zero-sequence voltage into the CBPWM modulation wave and then decomposing the new modulation wave, we can get the same sequence of SVPWM modulation. This method takes the advantages of using simple CBPWM to realise the complex output of SVPWM, such as double- and quadruple-frequency output. At last, we deduce the equivalent relationship between the SVPWM and CBPWM in n-level with an arbitrary number of segments. Experimental results verify the correctness of the equivalent relationship.     

Spectra of delta-sigma modulated inverters: an analytical treatment

Analytic expressions for the output voltage spectrum of an asynchronous delta (or delta-sigma) modulated inverter are reported and supported by experimental data. The analysis yields three functions that give the frequency, phase, and amplitude of each component of the spectrum. These functions are in terms of the sinusoidal reference waveform and the properties of the modulator. The method provides greater accuracy and computational efficiency than the numerical methods reported to date. The spectral components form pairs of sidebands around multiples of the average switching frequency. The functions detail the relationship between the number of significant sideband components and the depth of modulation and illustrate the spread-spectrum nature of delta modulation. Extensions to nonsinusoidal reference waveforms and to hysteresis current controllers are considered     

集成光收发芯片中激光器调制特性研究

文章从理论上研究了一种应用于光纤到户(FTTH)网络中的基于单片集成的双端口光收发芯片,结合器件的结构和参数分析了该产品的直接调制特性,计算了其驰豫振荡、增益抑制和频率啁啾,得到了该器件的直接调制频率限制和频率啁啾效应下的输出光场表达式,并通过仿真分析得出了高频直接调制频率啁啾下的输出光频谱.     

谐振式微光学陀螺中非连续频率调制特性研究

谐振式微光学陀螺（RMOG）中,方波频率调制的三角波实现形式消除了双频率锯齿波中复位时间与复位误差引起的输出光强波动。理论分析了三角波实现方波频率调制的过程中波形转折点引起非连续频率调制对输出光强的影响。仿真分析了不同调制频率偏置下调制波形转折点以及不同激光频率与谐振频率偏差对输出的影响。利用时域梳状滤波器对输出信号进...