Calculation of Fresnel diffraction patterns via the Kotel’nikov theorem

The efficiency of calculation of Fresnel diffraction patterns via the Kotel’nikov theorem is considered. A computer model based on an algorithm proposed earlier is built. It is shown that this algorithm provides satisfactory agreement with the results of calculations performed with the use of well-known, but more laborious, methods.     

Stable-phase microwave-signal transmission channels and simulation synthesis of wave beams performed on the basis of beam waveguides

The prominent contribution of Academician V.A. Kotel’nikov to creation of an underground testing ground formed from a periodic sequence of phase equalizers (lenses and reflectors) is reported. A series of experiments that were performed on this unique facility and that involved laser-beam transmission with low loss over a line of a highly stable electric length are described. It is shown that the experience in investigations dealing with beam waveguides initiated research aimed at formation of wave beams with unique properties.     

Shannon-Kotel?nikov Mappings in Joint Source-Channel Coding

This paper deals with lossy joint source-channel coding for transmitting memoryless sources over AWGN channels. The scheme is based on the geometrical interpretation of communication by Kotel?nikov and Shannon where amplitudecontinuous, time-discrete source samples are mapped directly onto the channel using curves or planes. The source and channel spaces can have different dimensions and thereby achieving either compression or error control, depending on whether the source bandwidth is smaller or larger than the channel bandwidth. We present a general theory for 1:N and M:1 dimension changing mappings, and provide two examples for a Gaussian source and channel where we optimize both a 2:1 bandwidth-reducing and a 1:2 bandwidth-expanding mapping. Both examples show high spectral efficiency and provide both graceful degradation and improvement for imperfect channel state information at the transmitter.     

Sampling theorem in signal theory and its originators

Formulation of the sampling theorem for deterministic signals with a limited energy is presented. Basic primary sources of the sampling theorem and the role of the authors of these sources in the development of signal theory are analyzed. A conclusion about the correctness of referring to the signal-theory sampling theorem as the Kotel’nikov-Shannon theorem is drawn.     

New constructions of 1D and 2D generalized Kravchenko-Kotel’nikov theorems on the basis of atomic function up(t)

New constructions of 1D and 2D generalized Kravchenko-Kotel’nikov sampling theorems based on atomic function up(t) are proposed and justified. The theorems are rigorously proved for both 2D and 1D cases. A simulation performed to analyze the construction and improvement of new series estimates shows their advantage over the classical Whittaker-Kotel’nikov-Shannon series.     

数字化发展环境下城市信息视觉传达导向系统设计

21世纪是人类的数字科技时代,科技的发展为人们的生活和社会带来了很大的变化,生活的各个方面都与数字化紧密结合,从而出现了学习数字化、工作数字化的模式.在这个生活数字化和数字媒体发展的环境下,艺术也逐渐与数字化联系,视觉传达设计就是其中之一.随着数字技术与视觉传达设计的结合,视觉传达导航系统的建设也逐渐随着城市化发展被人...     

A BiCMOS time interval digitizer based on fully-differential,current-steering circuits

A time interval digitizer cell with a 0-16 ns input range and a nominal LSB width of 1.0 ns has been integrated in a 2-μm BiCMOS technology, The circuit exhibits both integral and differential nonlinearity below 0.15 LSB and a timing error of 0.32 ns RMS. Logic gate propagation delays are used as time measurement units, and the nominal value of the delays is set by an on-chip phase-locked loop (PLL). Fully-differential, current-steering circuits with low voltage swings are used to implement the time interval digitizer so as to generate minimal switching noise. The cell is to be used in the monolithic, multi-channel realization of a high-sensitivity, mixed-signal data acquisition front-end. By virtue of the time digitization architecture used, the average power dissipation of the cell is only 19.8 mW, despite the use of circuits that dissipate static power, and the layout area is a compact 448 μm×634 μm     

Superconductor digital RF development for software radio

We review a new “direct digitization” approach for “digital RF” architectures for software radio. Although direct digitization usually implies the simultaneous digitization of all channels in a particular band at a downconverted IF, we use this term to refer exclusively to the direct digitization of all bands, from near DC to RF. Furthermore, we present results on band selection and digitization of RF signals directly at the carrier frequency with high resolution. These novel approaches are enabled by a superconductor analog-to-digital converter technology using an ultra-fast IC logic known as Rapid Single Flux Quantum (RSFQ) logic, with performance capable of enabling envisioned software radios     

Digital correlators for synthetic aperture interferometricradiometry

A numerical simulator is developed to assess various design implications of a digital correlator used by a synthetic aperture interferometric radiometer (SAIR). The simulator permits control of the type of digitization, the digitization thresholds with respect to noise power, and the degree of correlation between the two antenna signals which are being cross correlated. Digitization schemes are considered which use 2, 3, 4, and 8 levels. Estimates are made of the increase in inherent radiometer noise (ΔT) due to the digitization. The increase in ΔT is found to depend strongly on the degree of correlation, with higher correlations suffering less increase. In most cases, 3 level digitization is recommended based on this sensitivity consideration. Two levels perform significantly noisier and four levels only slightly cleaner. Several case studies are also considered regarding the need to control the signal level relative to the digitizer thresholds. Automatic gain control circuitry prior to digitization is found not to be necessary, provided the thresholds are preset within a fairly broad region of minimum sensitivity to variations in signal power, and provided the system noise temperature of the radiometer is monitored with reasonable accuracy. It is also found that, under conditions of very high correlation between the two signals, digital correlators have better SNR performance than analog. Reasons for this behavior are discussed     

基于DM6437的数字摄像机

为了适应现代采集系统的小型化以及数字化需要,设计了一种基于达芬奇技术DSP芯片的数字图像采集系统。这种设计方法不需要外接编解码芯片,直接连接数字摄像头,减少了D/A转换带来的图像干扰,同时利用了达芬奇系列DSP上集成的视频处理子系统组件(VPSS),其中的视频处理前端(VPFE)以硬件方式对数字视频图像进行视频采集、CFA插值、色彩空间变换等图像预处理操作,简化了软件设计。结果显示,该系统采集到的视频图像清晰、稳定、色彩均衡,满足普通摄像机对视频图像的要求。     

数字化背景下提升高校信息化管理能力的路径研究

随着信息化技术的发展，其在推动教育数字化的过程中发挥着越来越重要的作用。文中首先分析了高校数字化过程中面临的问题，包括线上教学低效、人员管理缺失、人员轨迹难查和线下数据量大4个方面。其次阐述了信息化技术的重要作用，通过线上线下混合式教学、校园智能门禁系统、大数据精准决策和线上一站式服务等管理实践，能有效解决高校数字化中遇到的问题。最后总结了信息技术在高校数字化中的应用优势，即其不仅能有效提升师生的数字化素养，还能通过信息技术与教育教学的深度融合，促进教育资源共享。     

有线数字电视的困惑与突破

有线电视数字化是近几年国家广电总局的重点工作之一。2007年以来，部分省市的有线电视数字化整体平移有了较大的突破，但就全国大部分省、市的情况看来，有线电视数字化工作依然不温不火，前景不容乐观。面对步履艰难、困难重重的有线电视数字化进程，业界人士不断地思考：是什么原因造成这种局面？是我们的政策和规划不符合国情还是我们的网络公司操作不力？从剖析有线电视数字化进程中出现的问题着手，提出了解决这些问题的思路和方法。     

数字化校园中即时通信技术的应用

近几年来,随着科学技术和信息化的不断发展,信息化和数字化技术已经得到了广泛的应用。在教育领域中,信息化的具体体现就是数字化在校园中的应用,以网络和数字化信息为基础的校园就是数字化校园。在数字化校园中,要加快数字化校园的建设进程,需要各种文字、视频、语音等各种能够即时沟通的方式,而这些即时沟通方式都需要即时通信技术提供。在此以即时通信技术为主要研究对象,对其在数字化校园当中的应用进行探究和分析。     

视频信号数字化传输关键技术解析

数字电视技术经过多年的发展已相当成熟,特别是目前各省台演播室数字化建设改造基本完成,更是加速了端到端数字化播出的进程。对福建省台8套节目数字化下传实例做一个简要的介绍,针对视频信号在数字化传输维护中所遇到的调制、适配、抖动3个技术问题进行分析。     

红外焦平面列级数字化技术北大核心CSCD

红外焦平面列级数字化技术是一种将模拟信号通过列级数字化技术最终实现读出电路数字信号输出的技术,不仅对外部的噪声具有很好的抗干扰能力,同时可以有效避免外部电子电路的非线性。由于不受像元面积限制及其优异的性能,列级数字化技术正在成为红外焦平面数字化技术一个重要的发展方向。本文主要介绍了主流的列级数字化技术。     

Digital speech networks

Digital techniques, already widely used for transmission of data, are now being introduced in the field of voice communications. By appreciating some of the long-range implications of this trend we can help point the way towards appropriate usage of this developing technology for improved customer service. This paper focuses on the voice problem and the possibilities offered by complete digitization of the voice signal immediately following the microphone. Included in the discussion are a summary of the properties of the speech signal and its potentialities for efficient transmission, a survey of the existing voice digitization algorithms, some examples of voice digitization implementations, and a brief treatment of voice packetization. There are some comments, near the end of the paper, on the possibility of digitized-voice inputting to, and outputting from, computers in an integrated telephone-computer network.     

雷达中频信号数字化研究及实现

文中结合雷达中频信号数字化课题的具体要求,在讨论数字中频的理论算法和工程实现方案的基础上,设计了基于软件无线电思想的雷达中频数字化硬件平台。针对软件无线电的中频数字化技术进行探讨,深入研究了有关信号采样和数字正交的理论,探讨了实现数字正交采样相干检波的高精度算法,设计了基于软件无线电思想的中频数字化硬件系统,主要包括信号采集电路设计、中频数字化电路设计、逻辑控制电路设计和系统自检电路设计四个部分。此外,本方案还可在无雷达回波数据的情况下进行系统自检,大大提高了系统的可调试性和可靠性。     

新疆有线电视数字化SWOT分析及对策研究

目前，新疆有线电视正处在数字化转换的关键时期。运用SWOT分析方法，对新疆有线电视数字化转换进行了优势、劣势、机会和威胁分析，通过建立SWOT分析模型，提出数字化转换对策，为推进新疆有线电视数字化发展提供决策依据。     

安全测试在工业信息安全领域的应用浅析

随着信息网络时代的到来,奏响了科技革命和产业变革的时代强音,但同时信息安全的控制也是我们尤其关注的一部分。作为第二大产业的工业,信息安全更显得尤为重要。之前,一些控制系统的专业的技术封闭系统,已经可以避免一些信息丢失和免受网络攻击,因此,在工业控制和信息领域被广泛应用。科技的进步给人们的生活更加快捷便利,带来了更加偏向自动化、数字化、网络化发展的系统,让人们生活的更加轻松快意,但信息安全对我们飞速发展的更加科学有效的工业化系统带来了挑战,这一新形势对工业信息安全控制提出了更高的要求。     

用于生物医学成像的多通道流水线数字化电路设计

针对生物医学成像中前端读出电路多通道以及要求高速数字化的特点,设计了一个16通道的流水线数字化电路.整个电路由模拟多路选择器、单端转差分电路、8-bit 25Ms/s 1.5bit/stage流水线ADC以及数据输出模块组成.模数转换和数据输出在两相邻时间窗口内采用流水线方式进行.电路采用TSMC 0.18μm mixed signalCMOS工艺实现.电路仿真结果表明,流水线ADC的DNL为-0.62/0.67LSB,INL为-0.39/0.72LSB,SNR为45.99dB,ENOB为6.03bit,该电路能够在两个相邻时间窗口内完成16通道的信号数字化并输出,满足系统设计要求.