Model based phase unwrapping of 2-D signals

A parametric model and a corresponding parameter estimation algorithm for unwrapping 2-D phase functions are presented. The proposed algorithm performs global analysis of the observed signal. Since this analysis is based on parametric model fitting, the proposed phase unwrapping algorithm has low sensitivity to phase aliasing due to low sampling rates and noise, as well as to local errors. In its first step, the algorithm fits a 2-D polynomial model to the observed phase. The estimated phase is then. Used as a reference information that directs the actual phase unwrapping process. The phase of each sample of the observed field is unwrapped by increasing (decreasing) it by the multiple of 2π, which is the nearest to the difference between the principle value of the phase and the estimated phase value at this coordinate. In practical applications, the entire phase function cannot be approximated by a single 2-D polynomial model. Hence, the observed field is segmented, and each segment is fit with its own model. Once the phase model of the observed field has been estimated, we can repeat the model-based unwrapping procedure described earlier for the case of a single segment and a single model field     

Phase-Locked Loops with Limiter Phase Detectors in the Presence of Noise

A nonlinear mathematical model of phase-locked loops with limiter phase detectors in the presence of noise is presented. The model, which is an extension of the well-known baseband model of loops with sinusoidal phase detectors without limiters, incorporates a modified nonlinear phase detector characteristic, the form of which is changed if the input carrier-to-noise ratio alters, as well as a modified phase noise as an input to the model. Both the modified phase detector characteristic and the spectral density of the modified noise term are calculated specifically for sinusoidal, triangular, and sawtooth types of limiter phase detectors, allowing the application of various methods to determine the loop noise performance. As an example, the phase error variance of a first-order phase-locked loop is calculated, thereby showing a strong dependence on the specific phase detector realization.     

Phase Noise Model of Single Loop Frequency Synthesizer

The phase noise spectrum of a single loop frequency synthesizer for S-band, which can be utilized in broadcasting terminals, was predicted based on the analyses for phase noise contributions of noise sources. The proposed phase noise model in this paper more accurately predicts the phase noise spectrum of a frequency synthesizer. To accurately model the phase noise contributions of noise sources in the frequency synthesizer, the phase noise sources were analyzed via modeling of the frequency divider and phase noise components using Leeson model for the reference signal source and VCO. The phase noise transfer functions to VCO from noise sources were analyzed by superposition theory and linear operation of the phase-locked loop. The frequency synthesizers were fabricated and the phase noise prediction model was evaluated by measured data and prediction data.     

缓冲器输出端相位噪声模型分析

相位噪声是振荡器的重要性能指标。近年来,研究人员在振荡器相位噪声表征方面已经做了大量的工作,在这些过程中开发出了很多不同类型的振荡器相位噪声模型。但是在这些模型中,都没有分析缓冲器噪声对振荡器相位噪声的影响。而在研究课题中,首先要对缓冲器噪声的功率谱密度函数进行数学建模,并易于将这个模型嵌入到相位噪声的非线性扰动分析模型,这样就得到了含有缓冲器噪声的振荡器相位噪声模型。     

Experimental Study of Pattern-Independent Phase Noise Accumulation in an All-Optical Clock Recovery Chain Based on Two-Section Gain-Coupled DFB Lasers

The pattern-independent phase noise accumulation in a chain of all-optical clock recovery devices (CRDs) based on two-section gain-coupled distributed feedback (TS-DFB) laser operating in the coherent mode is studied experimentally and theoretically. A simple theoretical model, where the CRD output phase noise is equal to the sum of the phase noise introduced by the CRD and the CRD input phase noise filtered by the phase noise transfer function, has been proposed for the CRD equivalent phase noise model. The accumulation of pattern-independent phase noise is investigated experimentally and theoretically for different cut-off frequencies of the phase noise transfer function of the TS-DFB laser and two different optical signal to noise ratios. It is shown that, due to the phase noise added by the CRD, phase noise accumulates in the passband of the phase noise transfer function, with the phase noise transfer function well approximated by a first-order lowpass filter. Excellent qualitative agreement between the experimental results and the theoretical model is observed. Also, it is concluded that the phase noise accumulation model for CRD, where the recovered clock is locked to the optical power of the incoming clock signal, presented by other authors holds in a qualitative point of view for the TS-DFB laser operating in the coherent mode. Since the root-mean-square (rms) of the timing jitter is proportional to the square root of the integrated power spectral density of the phase noise, the results show that a smaller cut-off frequency of the phase noise transfer function does not lead to a smaller rms value of the pattern-independent timing jitter along the chain of all-optical CRDs based on TS-DFB laser. It is shown that the minimum rms of the pattern-independent timing jitter along the CRD chain results from a compromise between the cut-off frequency of the phase noise transfer function and the phase noise introduced by the TS-DFB laser.     

码头校相值动态修正

通过对船载卫通天线跟踪接收机校相值修正模型的分析,阐述了其只能修正由极化角变化产生的相移和不能修正增益值变化的缺点。提出了校相值动态修正模型,该模型利用天线在不同地域对准固定信号源进行校相得到的校相值之差修正天线码头校相值。此算法不仅可以修正极化角变化产生的相移,而且可以修正环境变化引起的相移以及增益值的变化。采用后桅杆安装信号源的设计,以实现相位值动态修正模型。     

基于集成学习的风云四号遥感图像云相态分类算法

云相态分类在气象预报和气候研究中具有重要的地位。我国新一代气象卫星风云四号的成像仪在光谱通道数量和空间分辨率较上一代风云二号有较大提升,这为云相态的研究提供了新的遥感数据。本文首先对风云四号相隔15 min的遥感图像进行分析,然后提出亮温云相态指数,该指数可以进行初步云相态分类,最后在此基础上提出基于集成学习的云相态分类算法。实验结果与风云四号官方云相态分类结果进行比较,水云的一致率达到91.69%,冰云的一致率达到76.10%。     

数字锁相环相位噪声影响因素分析

数字锁相环作为广泛应用的一种频率合成技术,相位噪声是其关键的技术指标。介绍数字锁相环的关键组成部分,从数字锁相环的相位噪声分析模型出发,阐述各组成部分对相位噪声产生的影响,并分析各部分关键指标的选型依据,然后利用仿真软件搭建仿真模型验证分析结果。为数字锁相环的设计,提高相位噪声性能提供了参考依据。     

交叉眼干扰的波前相位畸变特性研究

交叉眼干扰是目前对抗单脉冲雷达的有效方式,为深入研究交叉眼干扰机理,对其形成的波前相位畸变特性进行了分析。根据相干叠加原理提出了一种基于相位畸变理论的模型,对干扰信号带来的指示角误差进行了计算;通过将波前相位畸变模型得到的结果与传统的几何分析模型进行对比验证,将干扰单元接收信号的幅度比作为研究重点,对波前相位畸变的模型进行了修正。结果表明:修正后的波前相位畸变的分析模型与传统几何分析结果一致,验证了波前相位畸变模型的准确性,为交叉眼干扰天线的参数优化建立了基础。     

OPTIMAL MODEL OF COMBINED PHASE CENTER FOR HORN FEEDS AND ITS COMPUTATIONAL METHOD

A definition of combined phase center for horn feeds is given.Formulas of E-planeand H-plane combined phase center for conical horns and the corresponding Optimal model arepresented,and a fast optimization method for solving this model is described.By using thismethod,the phase center of corrugated horn is discussed and calculated,and the variation of thephase center with distance and operating frequency is given.     

Maximum likelihood estimation of the parameters of nonminimum phaseand noncausal ARMA models

The well-known prediction-error-based maximum likelihood (PEML) method can only handle minimum phase ARMA models. This paper presents a new method known as the back-filtering-based maximum likelihood (BFML) method, which can handle nonminimum phase and noncausal ARMA models. The BFML method is identical to the PEML method in the case of a minimum phase ARMA model, and it turns out that the BFML method incorporates a noncausal ARMA filter with poles outside the unit circle for estimation of the parameters of a causal, nonminimum phase ARMA model     

A microscopic model for the static and dynamic lineshape of semiconductor lasers

Direct frequency modulation characteristics in semiconductor lasers are described theoretically in a physics-based multidimensional framework. A microscopic formulation of a phase equation without the need of linewidth enhancement factors is derived directly from Maxwell's equations. This novel model uses a local material phase coefficient instead of the linewidth enhancement factor. Hence, the impact of local phase changes on the optical mode can be described via a spatial integration in analogy to mode gain. The model is applied to the modulation-induced fine structure of the laser power spectrum. It is found that the asymmetry in the modulation-induced fine structure observed in measurements can be explained by the proposed model taking temperature, carrier, and photon effects on the material phase coefficient into account. Furthermore, the implementation of the photon phase into a multidimensional device simulator is described.     

锁相式频率合成器相位噪声分析与仿真

相位噪声是影响频率合成器性能的重要指标,首先分析了锁相式频率合成器各个组成部分的相位噪声,然后根据相位噪声传输函数,建立了频率合成器相位噪声的精确仿真预测模型.为了验证仿真方法的可靠性,设计了一个输出频率为2GHz的频率源,实验测得的相位噪声曲线和仿真结果非常吻合.     

Analytical Equations for Nonlinear Phase Errors and Jitter in Ring Oscillators

In this paper, we present a simple analytical equation for capturing phase errors in 3-stage ring oscillators. The model, based on a simple but useful idealization of the ring oscillator, is provably exact for small noise perturbations. Despite its simplicity and purely analytical form, our model correctly captures the time- dependent sensitivity of oscillator phase to external perturbations. It is thus well suited for estimating both qualitative and quantitative features of ring oscillator phase response to internal noises, as well as to power, ground and substrate interference. The nonlinear nature of the model makes it suitable for predicting injection locking as well. Comparisons of the new model with existing phase models are provided, and its application for correct prediction of thermal jitter demonstrated. Requiring knowledge only of the amplitude and frequency of the oscillator, the model is ideally suited for early design exploration at the system and circuit levels.     

基于幅-频曲线的系统时域响应特性评价方法

在电磁兼容测量中,通常采用频率响应来描述一个系统的特性。而系统的频响特性一般仅提供了响应幅度的频域分布,很少给出相位信息。在连续波测量时这种幅－频信息是足够的,但在利用频域测量结果评价一个系统的脉冲响应特性时,还必须知道系统的相位信息。本文假设系统为最小相位系统,采用Ｈｉｌｂｅｒｔ变换根据系统响应的频谱幅度估计相位信息,进而将系统的频域信息转换到时域,用于评价系统的时域响应特性。根据一组磁场探头的     

基于武器装备系统研制阶段的软件增量模型

提出并推荐一种基于系统研制阶段的软件增量模型作为武器装备软件的过程模型，该增量模型具有软件瀑布模型和演化模型的优点，并能较好地实现软件开发话动与系统研制阶段的协调统一。     

基于快速极限学习机和差分进化的机场噪声预测模型

该文针对传统机场噪声预测模型存在的建模成本高、实用性差的不足,引入时间序列相空间重构理论,提出一种新的基于快速极限学习机和差分进化算法的机场噪声一体化预测模型。该模型利用相空间重构理论对机场噪声时间序列进行重构,并使用快速极限学习机对重构的相空间矢量进行学习建模,同时采用改进的差分进化算法实现对重构参数和模型参数的同步优化选择,整个建模过程简洁高效,无需人工干预。实验结果表明,该一体化预测模型能较好地跟踪机场噪声的变化趋势,且具有较同类模型更小的预测误差。     

Image Reconstruction Scheme Based on Phase Correction and Singularity Function Analysis Model

The singularity function analysis (SFA) model is a mathematical tool that allows representing an image with much less coefficients than the conventional Fourier transform (FT) model while maintaining a better image quality. The performance of the SFA method for reconstructing medical images may however degrade if unwanted phase drifts are present in the acquired image. This paper proposes a new SFA-based reconstruction scheme by taking into account phase drifts. To this end, phase drifts are first mathematically formulated and corrected. The singularity function model is then applied to represent the phase-corrected image. The performance of this phase-corrected SFA reconstruction scheme is evaluated using both simulated and real brain images, and compared with the conventional FT model and SFA method without phase correction. The results demonstrate that the proposed reconstruction method achieves significant improvement in image quality.     

GH4037镍基高温合金激光打孔相变过程数值模拟

为了更准确地研究激光打孔相变过程,基于流体传热和流体力学理论,建立了GH4037镍基高温合金激光打孔相变模型。模型中考虑了重力、粘滞力、反冲压力的作用,以及材料的固-液相变和液-气相变过程,通过数值计算得到了激光打孔相变过程的温度场和速度场。结果表明,气化材料的反冲压力可以加快熔池的流动,在激光功率为2000W、脉宽为1.70ms时,材料最大气化蒸发速率可以达到250m/s。该模型为进一步开展激光打孔研究提供了理论基础。     

Phase-modulated resonances modeled as self-similar processes with application to turbulent sounds

In this paper, we propose a nonlinear stochastic model for time-varying resonances where the instantaneous phase (and frequency) of a sinusoidal oscillation is allowed to vary proportionally to an /spl alpha/-stable self-similar stochastic processes. The main motivation of our work stems from previous experimental and theoretical evidence that speech resonances in fricative sounds can be modeled phenomenologically as AM-FM signals with randomly varying instantaneous frequencies and that several signal classes related to turbulent phenomena are self-similar 1/f processes. Our general approach is to model the instantaneous phase of an AM-FM resonance as a self-similar /spl alpha/-stable process. As a special case, this random phase model includes the class of random fractal signals known as fractional Brownian motion. We theoretically explore this random modulation model and analytically derive its autocorrelation and power spectrum. We also propose an algorithm to fit this model to arbitrary resonances with random phase modulation. Further, we apply the above ideas to real speech data and demonstrate that this model is suitable for resonances of fricative sounds.