SNR improvement by intergranular exchange coupling in CGC perpendicular magnetic recording media

Effect of intergranular exchange coupling in coupled granular and continuous (CGC) perpendicular media was investigated in terms of improvement of signal-to-noise ratio (SNR). The exchange coupling improves SNR and byte error rate (BER); however, it tended to widen the magnetic track width (MWW) of a track. That degradation is of concern for the CGC media. This paper discusses intergranular exchange coupling in CGC media to optimize track density and linear density to achieve high areal density.     

Modeling of 2.5 Gbps-intersatellite link (ISL) in inter-satellite optical wireless communication (IsOWC) system

Free-space optics (FSO) has the combined features of most dominated telecommunication technologies: wireless and fiber optics. Many of the aspects of FSO are related to fiber optics with an important difference of transmission medium which is air/free space rather than the glass of the fiber-optic cable. Inter-satellite optical wireless communication systems (IsOWC), one of the important applications of FSO/WSO technology, will be deployed in space in the near future as such systems provide a high bandwidth, small size, light weight, low power and low cost alternative to present microwave satellite systems. In this paper, we have designed a model of IsOWC system using OPTI-SYSTEM™ simulator to establish an inter-satellite link (ISL) between two satellites estranged by a distance of 1000 km at data rate of 2.5 Gbps which is not reported in previous investigated works.     

A new regularized forward blind source separation algorithm for automatic speech quality enhancement

This paper addresses the problem of speech enhancement and acoustic noise reduction by adaptive filtering algorithms in a moving car through blind source separation (BSS) structures. In this paper we propose a new regularized forward blind source separation (RFBSS) algorithm that does not need voice activity detection (VAD) systems, and allows getting efficient speech enhancement performances with low complexity.     

Improvement of transmission performance of adaptively modulated optical OFDM signals

An adaptively modulated optical orthogonal frequency division multiplexing (OOFDM) based system has been simulated in present research. Performance analysis in terms of bit error rate (BER) and signal to noise ratio (SNR) has been carried over the system using fixed modulation for different M-array quadrature amplitude modulation (M-QAM). An adaptive modulation over OOFDM has been analyzed over three different algorithmic schemes. Impact of adaptive modulation on spectral efficiency has also been investigated for OOFDM. Simulation results show the enhancement in terms of spectral efficiency and capacity for adaptively modulated OOFDM system.     

全天时星敏感器光学系统参量选择与光学设计

以10km观测高度探测4.5等星为例,分析星点在600~1100nm谱段的辐射特性,使用Modtran软件计算同谱段的天空背景辐射亮度以及大气透过率,在信噪比阈值为5的情况下,选择一组典型的光学系统参量.采用一块平面反射镜和石英球面镜系统设计了轻、小型化的光学系统,该系统在600~1 100nm宽光谱范围内全视场光斑形状接近圆形、调制传递函数接近衍射极限,色差很小,具有良好的成像质量.计算了地面环境下星敏感器的昼夜探测信噪比,以信噪比阈值5对星敏感器的探测能力评估,结果表明在白昼地面环境下可以实现2.5等G型恒星的探测,在夜间地面环境下可以实现6等G型恒星的探测.     

Small Target Detection Algorithm Based on Average Absolute Difference Maximum and Background Forecast

Detecting small targets in clutter scene and low SNR (Signal Noise Ratio) is an important and challenging problem in infrared (IR) images. In order to solve this problem, we should do works from two sides: enhancing targets and suppressing background. Firstly, in this paper, the system utilizes the average absolute difference maximum (AADM) as the dissimilarity measurement between targets and background region to enhance targets. Secondly, it uses a predictor to suppress the background clutter. Finally, our approach extracts the interested small target with segment threshold. Experimental results show that the algorithm proposed has better performance with respect to probability of detection and less computation complexity. It is an effective small infrared target detection algorithm against complex background.     

Analytically exact correction scheme for signal extraction from noisy magnitude MR signals

An analytically exact method is proposed to extract the signal intensity and the noise variance simultaneously from noisy magnitude MR signals. This method relies on a fixed point formula of signal-to-noise ratio (SNR) and a correction factor. The correction factor, which is a function of SNR, establishes a fundamental link between the variance of the magnitude MR signal and the variance of the underlying Gaussian noise in the two quadrature channels. A more general but very similar method is developed for parallel signal acquisitions with multiple receiver coils. In the context of MR imaging, the proposed method can be carried out on a pixel-by-pixel basis if the mean and the standard deviation of the magnitude signal are available.     

掺铒光纤放大器在多路模拟光纤传输系统中应用

对应用掺铒光纤放大器的副载波频分复用模拟电视光纤传输系统的噪声和失真进行了实验研究，利用掺铒光纤放大器作为系统的功率提升和中继放大器，分别成功地进行了１８５ｋｍ和２１５ｋｍ的系统传输试验