Phase Modulations in a Speech Signal

Acoustical Physics - Mathematical models of the phase function and its parameters in speech-signal analysis problems have been investigated. The phase spectrum of a speech signal has been...     

Phase Transitions in q-States Signal Reconstruction

Compressed sensing is a new signal acquisition method that acquires signal in a compressed form and then recovers the signal by the use of computational tools and techniques. This means fewer measurements of signal are needed and thus it will save huge amount of time and storage space. We, in this paper, consider the compressed sensing of sparse integer-valued signal (referred as “q-states signal” throughout the paper). In order to accelerate the speed of reconstruction, we adopt the sparse rather than dense measurement matrices. Using methods and tools developed in statistical physics, we locate the reconstruction limit for L₀-reconstruction method and propose a belief propagation-based algorithm that can deal with instance with large size and its typical reconstruction performance are also analyzed.     

用于冷原子干涉仪的低相噪信号源设计

冷原子干涉实验中涉及复杂的激光调制技术,为调制器提供合适的射频驱动信号至关重要,驱动信号的相噪直接影响了冷原子干涉仪的灵敏度。设计了一种能够产生6.834GHz信号的低相噪信号源,该信号源采用二级锁相环频率合成技术,将恒温晶振输出的10MHz信号倍频到100 MHz,再将100 MHz信号倍频到7 GHz,最后与外部DDS芯片产生的166 MHz信号混频实现6.834 GHz微波信号源。经过测试,信号源的输出相位噪声为-61.9dBc/Hz@1Hz,满足冷原子干涉实验的需求。     

数字相位测距仪信号源的研究与设计

在相位激光测距仪中,信号初始相位的相对稳定性对测距仪的测量精度非常重要.对于如何得到全同步的主振信号、本振信号、差频参考信号以及填充脉冲,给出了采用单片机控制频率合成器(DDS)直接数字频率合成芯片,直接滤波以及FPGA软件模拟DDS原理三种不同的方案,最后对这三种方案进行了比较.直接滤波法实现起来简单且成本较低,适合测量精度不是很高的系统.另外两种方案可用于测量精度较高的系统,但是成本较高.     

弹光调制非等相位干涉信号的快速光谱反演算法

在弹光调制傅里叶变换光谱仪(PEM-FTS)中,由于调制光程差的非线性,不能直接采用快速傅里叶变换(FFT)进行反演光谱,且直接计算开销过大。首先在Matlab软件中用非均匀快速傅里叶变换算法(NUFFT)对PEM非等相位干涉信号进行了软件仿真,其次设计了以TMS320C6713高性能浮点数字信号处理器(DSP)芯片为核心的光谱信息处理系统,实现了硬件上的光谱实时处理。研究表明,算法对光谱反演具有速度快、精度高等优点,1024点光谱反演的速度较直接运算的速度提高20多倍,反演精度可达0.78%。     

码盘偏心对叠栅条纹信号相位的影响

根据两计量光栅产生叠栅条纹的几何光学基本理论,在改进计量光栅码盘理论模型的基础上,推导出码盘偏心情况下读头输出的叠栅条纹信号相位的理论公式,对码盘偏心给叠栅条纹信号相位带来的偏差进行了分析与讨论.     

Phase Control of Transient Optical Properties of Quantum-Dot Nanostructure via Terahertz Signal Radiation

We theoretically analyze the transient properties of a probe field absorption dispersion in a quantum-dot nanos- trueture driven by terahertz signal radiation. Here a four-level quantum-dot nanostructure is designed numerically by Schrodinger and Poisson＇s equations. We show that in the presence of the THz signal, the medium becomes phase dependent and the absorption dispersion can be dramatically influenced by the relative phase between applied fields.     

Methods for Measuring the Signal of the Phase Calibration of the VLBI Radio Telescopes

Radiophysics and Quantum Electronics - In the majority of modern radio telescopes, which are used for radio interferometry with very long baselines, a special signal is introduced into the signal...     

码盘偏心对叠栅条纹信号相位影响的理论分析

增量式光学编码器根据径向辐射光栅产生的叠栅条纹进行角度测量，两光栅码盘轴之间及其与系统转动轴之间的偏心和晃动，影响着编码器读头输出的叠栅条纹信号的相位，这给角度测量带来了一定的系统误差。根据光栅码盘产生叠栅条纹的基本理论，在改进计量光栅码盘理论模型的基础上，推导出码盘偏心情况下码盘读头输出的叠栅条纹信号相位的理论公式，对码盘偏心给叠栅条纹信号相位带来的偏差、增量式光学编码器光学设计原理及消除此由此带来的系统误差的技术原理进行了分析与讨论。     

利用相位步进脉冲消除探头13C NMR背景信号

由静态探头线圈外有机材料产生的¹³C NMR背景信号强度大，化学位移范围广（δ_C 20~250），此背景信号在交叉极化实验中还可被增强，并随着样品信号的累积而累积，严重影响谱图分析.将相位步进脉冲引入交叉极化实验（称为PIPCP）中可以有效去除经交叉极化增强的¹³C NMR背景信号，但样品信号不受影响.这是由于经过相位步进脉冲后，线圈外相位严重畸变，而且线圈外锁定场强度急剧降低，来自探头材料的¹³C NMR背景信号无法有效地进行交叉极化.而对于被测样品甘氨酸来说，由于I核和S核之间强烈的偶极耦合作用，所加相位步进脉冲对锁定场强度的影响只有1.4%.     

Optical Heterodyne Impulse-Response Measurement of Lithium Tantalate Phase Modulator Driven by Wideband Frequency Signal

In this paper, we describe a novel optical heterodyne interferometer for characterizing phase modulation systems including a lithium tantalate phase modulator. A wideband random signal is imposed on the modulator so that the resultant beat photocurrent is modulated in phase at random. The cross-power spectrum of the fluctuating phase with the wideband random signal driving the modulator is computed to give the transfer function and the impulse response of the phase modulation system. The frequency and time response of the phase modulation are measured up to 15 MHz in a practical experiment.     

基于超高分辨率光谱分析的周期光信号相对相位测量方法

提出了一种基于超高分辨率光谱分析实现周期性光信号频域中相位分布的测量方法.在已测得待测信号高分辨率光谱的情况下,利用马赫泽德调制器载波抑制效应调制激光器产生双泵浦,激发高非线性光纤中的受激布里渊散射效应形成有源双滤波器.用泵浦激光器在测量波长范围内进行连续扫描,得到包含待测信号相位信息的拍频信号,经数据采集和处理后得到待测信号频域上的相对相位信息.实验给出了速率为5Gb/s,字长为31bit的周期性光信号在频域上的相对相位分布信息,证明了这种有源双滤波器的频率响应特性可以满足相位测试的需要.     

Development of the Concept of High-Power Microwave Oscillators with Phase Locking by an External Signal

Radiophysics and Quantum Electronics - By simulations and experiments we develop a method for generation phase locking of a Ka-band subgigawatt nonstationary relativistic backward-wave oscillator...     

舰船尾流气泡层散射相位函数及其后向散射信号特性分析

根据实测舰船的尾流气泡分布模型,利用米氏理论计算得到尾流气泡层的散射相位函数,并将其应用于尾流气泡层后向散射光接收信号的Monte Carlo仿真分析中,以便为实际海况下的舰船尾流气泡层后向散射光探测的实验设置与信号预测、分析提供可靠的依据.通过对不同距离处尾流气泡层的散射相位函数及后向散射光接收信号特性的分析,可以得出:尾流中气泡层散射相位函数的变化小明显,且对接收信号的影响较小;气泡数密度的变化导致的多次散射效应和气泡层衰减系数的变化是引起后向散射光强度变化的主要原因,数密度越大,散射光信号中的多次散射光成分越大;当气泡层厚度达到一定倍数的衰减长度时,继续增加气泡层厚度对后向散射接收信号的影响较小.     

自启动的非归零/归零码和光电时钟信号发生器及码型转换

采用双波长注入一包含伪随机码发生器与相位调制器的光电振荡器可以同时得到非归零(NRZ)码,归零(RZ)码以及光,电时钟信号输出。该方案使用了光域耦合的双环路结构,在不增加有源器件的条件下实现边模抑制。相位调制器用于反馈调制并同时实现占空比可调的非归零码到归零码的转换。双波长的注入排除了编码信号在振荡器中引入的非时钟频率成分。实验给出了10 Gb/s工作速率下的结果,得到了抖动为637 fs的光信号输出。转换得到的归零码信号占空比约为33%。输出电时钟信号的相位噪声在频偏10 kHz处为-109 dBc/Hz,边模抑制比为58 dB。     

Characteristics of the Phase Noise Correlation of Injection Locked Lasers for RF Signal Generation and Transmission

Theoretical and experimental results on phase noise characteristics of an optical radio-frequency generation and transmission system using heterodyne photo-detection and side band injection locking is reported. Optical phase noise correlation of the lasers is achieved by noise transfer from a modulated master laser. Our investigation takes into account phase noise enhancement in optical comb generation, injection dynamic, path delay, and fiber dispersion. Theoretical expressions are derived from an adiabatic approximation and compared with experimental measures.     

基于相位调制器产生六倍频光毫米波的OFDM信号光传输系统研究

提出了两个并行相位调制器产生六倍频光毫米波并传输正交频分复用信号的全双工光纤无线通信系统.将2.5Gbt/s的正交频分复用信号调制到60GHz光毫米波上.从理论上分析了毫米波产生的原理,并分别模拟了毫米波信号承载OOK信号和正交频分复用信号在光纤中的传输性能.从而验证系统的可行性.仿真模拟结果表明,在光纤无线通信系统中,正交频分复用比非归零码更具有优势.     

Using the Maximum-Likelihood Method for the Angular Resolution of the Signal Sources in Multibase Phase Direction Finders

Radiophysics and Quantum Electronics - We show that the angular resolution of the signal sources in the phase direction finders with the antenna systems in the form of linear arrays of the weakly...