A low-power cryogenic analog to digital converter in standard CMOS technology

This paper presents a cryogenic successive approximation register (SAR) based analog to digital converter (ADC) in standard 0.35 μm complementary metal oxide semiconductor (CMOS) technology that functions from 300 K (room temperature) down to 20 K. It has been designed to operate in low temperature mid- and far-infrared imaging systems. In order to ensure the circuit performance at the extreme temperatures, a dedicated integral-based comparator architecture is employed. SPICE models have been developed for circuit simulation at 20 K. At 20 K, the experimental results exhibit that the ADC achieves 1.6 LSB maximum differential nonlinearity (DNL), 1.7 LSB maximum integral nonlinearity (INL), and 10.4 effective number of bits (ENOB) at 100 kS/s sampling rate with a current consumption of 75 μA from a 3.3 V supply.     

Technique for stabilizing the phase of the reference signals in analog fiber-optic links

The effects of temperature and longitudinal stress on the phase delay of reference signals in a fiber-optic link are discussed. A feedback system that uses a fiber-optic phase modulator is used to compensate for the phase fluctuations of a reference signal in the link. The phase deviations of a 50-MHz reference frequency that are caused by temperature variations of the link is reduced by more than 95% on optimization of the correction system. The advantages of this technique are that the fiber-optic phase modulator has a greater stability compared with the electronic phase modulators, and signal conversions from electric to optic and optic to electric are avoided.     

Automatic calibration of analog and digital measuring instrumentsusing computer vision

This paper presents an automatic calibration system capable of calibrating measuring instruments that do not have a digital interface. Image analysis algorithms are used to automatically determine the instrument reading. It can be used with analog and with digital displays. The maximum uncertainty in the detection of the pointer's position in analog instruments is less than the human eye can discriminate     

Optical encryption of digital data

Smart-pixel architectures, which use the cells of field-programmable gate arrays to provide electronic functionality and intraplane communication, offer a general-purpose approach to exploiting new application areas that would benefit from this kind of structure. One such area, that of the encryption of digital data, is discussed here. Some of the characteristics exhibited by encryption algorithms and ways in which these are applicable to smart-pixel technology are described. The implementation of an algorithm in current use, the SAFER K-64, and its interfacing to an electronic host are then considered in detail. It is shown that this encryption algorithm maps well onto smart-pixel technology because it involves only parallel data transfers, simple regular operations, and interconnections plus a relatively low rate of transfer to the host.     

A survey of temporal data mining

Data mining is concerned with analysing large volumes of (often unstructured) data to automatically discover interesting regularities or relationships which in turn lead to better understanding of the underlying processes. The field of temporal data mining is concerned with such analysis in the case of ordered data streams with temporal interdependencies. Over the last decade many interesting techniques of temporal data mining were proposed and shown to be useful in many applications. Since temporal data mining brings together techniques from different fields such as statistics, machine learning and databases, the literature is scattered among many different sources. In this article, we present an overview of techniques of temporal data mining. We mainly concentrate on algorithms for pattern discovery in sequential data streams. We also describe some recent results regarding statistical analysis of pattern discovery methods.     

Real-time integration and differentiation of analog signals bymeans of digital filtering

A novel filter design method for broadband recursive digital integrators and differentiators is presented. The performance of the digital infinite-impulse response (IIR) filters designed with the method is compared with that of finite-impulse response (FIR) filters and that of classical numerical integration and differentiation. The common conviction that IIR filters with excellent amplitude characteristics always have poor phase behavior is refuted. It is shown that it is possible to design easily realizable IIR integrators and differentiators with an arbitrarily small amplitude and phase error. While there is no FIR alternative for IIR integrators, both FIR and IIR methods give competitive results for differentiators     

MPEG-2视频编码技术

本文介绍了动态图像专家组标准系列中MPEG 2视频标准的概念、组成以及特点 ,MPEG 2压缩编码的原理、技术 ,MPEG 2视频编码码流概念及其数据结构     

Improvement of digital geographic data quality

The article focuses on the study of characteristics of digital geographical data and the influence of these characteristics on the quality of the basis being ready for the decision-making processes. Characteristics of digital geographical data are mainly described from the point of view of their technical parameters and keeping the technological indicators while obtaining them. Our system brings a user's view into the assessment of characteristics. We define user's requirements on data and suggest the system of their evaluation. The assessment of data characteristics comes out of the standard ISO 19113 and the theory of value analysis. Both systems are joined into a complex system for data evaluation. Technical characteristics of data are evaluated mainly by the level of accomplishment of qualitative indicators, e.g. meeting all requirements of horizontal and vertical mean square error, or by completeness of filling of all expected information. Meeting all users’ requirements is usually expressed by the level of user's satisfaction with the particular product. This level is set based on the survey among users. Simultaneously, the weight of the individual evaluating criteria is set according to specific types of solved tasks. The system of data evaluation is supplemented with a system of calculation of costs that are needed for obtaining the data. It is possible, however, to work either with the complete database, or to count also the influences of particular groups of data (e.g. communications, residential buildings, etc.) on the complete quality of the final product. The system of costs calculation and evaluation of data quality then enables the optimisation of the use of funds or disposable time for obtaining quality data. The use of the complete system is presented in a pilot project in which a model of terrain passability by a military heavy vehicle is solved.     

Identification of melting snow using data from dual-frequency microwave links

Using data from a dual-frequency microwave link it is possible to identify periods of transmission affected by melting snow. This is because, in melting snow, the relation between attenuation and the amount of precipitation is nonlinear and depends on the frequency in a way that differs from the dependence in rain. This implies that the ratio of the single-frequency estimates of apparent rainfall rates will be different in melting snow from those obtained in rain. This forms the basis of an algorithm that is shown to work well for a 23-km dual-frequency (12.8 GHz/17.6 GHz) link near Bolton in north west England and for a 29-km dual-frequency (10.5 GHz/17.5 GHz) link near Essen in Germany. The effectiveness of the algorithm is judged by noting the recorded temperatures in those minutes identified by the algorithm as being affected by melting snow     

Bandwidth optimization of optical data links by use of error-control codes

A design approach to optimizing the bandwidth of optical data links while simultaneously decreasing the bit-error rate is proposed. Mathematical analysis indicates that bandwidth gains by factors of 10-60 with power gains of as much as 8.9 dB are possible. To achieve these performance levels requires several innovations. First, conventional forward error-correcting codes cannot be used because of their excessive hardware cost. A reasonably powerful multidimensional parity-based error-control code is proposed and analyzed. These codes offer excellent error detection and moderate error-correction capabilities. Most importantly, they can operate at the fast clock rates that are required. Second, a hybrid automatic-repeat-request protocol is exploited to correct complex error patterns. In thermal-noise-limited systems this unique combination allows the optical clock rate to be increased significantly, thereby resulting in large bandwidth increases. The proposed design approach can be used in optical data links in which propagation delays are moderate and is applicable to fibers that exploit wavelength-division multiplexing or time-division multiplexing, one-dimensional parallel-fiber ribbons, and two-dimensional optical data links that use free space or guided waves. Several design examples are illustrated.     

Characterization of dynamic microgyroscopes by use of temporal digital image correlation

The advanced mechanical testing of microelectromechanical systems (MEMS) is necessary to provide feedback of measurements that can help the designer optimize MEMS structures and improve the reliability and stability of MEMS. We describe a digital image correlation (DIC) method for dynamic characterization of MEMS using an optical microscope with a high-speed complementary metaloxide semiconductor-based camera. The mechanical performance of a series of microgyroscopes is tested. The DIC method is employed to measure the microgyroscope in-plane displacement with subpixel accuracy. Use of the DIC method is less restrictive on the surface quality of the specimen and simplifies the measurement system. On the basis of a series of temporal digital images grabbed by a high-speed camera, the stability characteristic of the microgyroscopes is analyzed. In addition, the quality factors of the microgyroscopes are determined and agree well with other experimental methods.     

Vibration measurement by temporal Fourier analyses of a digital hologram sequence

A method for whole-field noncontact measurement of displacement, velocity, and acceleration of a vibrating object based on image-plane digital holography is presented. A series of digital holograms of a vibrating object are captured by use of a high-speed CCD camera. The result of the reconstruction is a three-dimensional complex-valued matrix with noise. We apply Fourier analysis and windowed Fourier analysis in both the spatial and the temporal domains to extract the displacement, the velocity, and the acceleration. The instantaneous displacement is obtained by temporal unwrapping of the filtered phase map, whereas the velocity and acceleration are evaluated by Fourier analysis and by windowed Fourier analysis along the time axis. The combination of digital holography and temporal Fourier analyses allows for evaluation of the vibration, without a phase ambiguity problem, and smooth spatial distribution of instantaneous displacement, velocity, and acceleration of each instant are obtained. The comparison of Fourier analysis and windowed Fourier analysis in velocity and acceleration measurements is also presented.     

Impacts of impulse-based ultra-wideband data links on cooperative wireless ad hoc networks

The recently permitted unlicenced use of the regulated ultra-wideband (UWB) radio spectrum (regulated first by the US FCC in 2002 and subsequently by the standardisation bodies of EU and other major countries) provides wireless ad hoc networks a cheap and promising air-interface technology for their adopted wireless data links, thus offering the potential to greatly boost their applications. The impacts of such UWB data links, mainly the more likely adopted impulse-based UWB data links for low data rate applications, on the extensively developed cooperative wireless ad hoc networks are investigated. First, the authors investigate the diversity order of data transfer of each impulse-based UWB data link working in a corresponding fading channel, and give an approximate relationship between the diversity order and the channel model parameters (here the Saleh?Valenzuela model parameters); Secondly, the authors develop efficient cooperative and decentralised diversity schemes that can utilise the widely spread and independently distributed multiple paths of the fading UWB channels. Performance analysis and simulation studies show that proposed decentralised cooperative beamforming schemes can achieve full diversity and are more efficient than their decentralised cooperative routing counterparts.     

压缩机性能数据的相对标准不确定度分析

通过多年对压缩机性能的研究,发现影响压缩机性能数据的主要参数为压力、温度、电流、电压、功率、转速等独立物理量,对这些独立物理量测量不确定度进行分析,推导出压缩机主要性能指标——容积流量、轴功率、比功率的合成相对标准不确定度,并给出容积流量的测量相对标准不确定度值的实例.