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Baseband digital synthesis and analysis for high-frequency software radio applications 基带数字合成和分析的高频软件无线电应用
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1146865
G. van Rooyen, J. G. Lourens
{"title":"Baseband digital synthesis and analysis for high-frequency software radio applications","authors":"G. van Rooyen, J. G. Lourens","doi":"10.1109/AFRCON.2002.1146865","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146865","url":null,"abstract":"Software-defined radio (SDR) employs digital modulation and demodulation techniques to solve traditionally analogue communications problems. To achieve this, the SDR must be capable of synthesising and analysing high-frequency analogue signals. However, sampling frequencies are limited by the capabilities of digital-to- analogue and analogue-to-digital converter technology. This paper presents quadrature synthesis and analysis techniques that cause the sampling rate, filtering frequencies and processing requirements to become functions of the signal bandwidth rather than the highest signal frequency component. A new investigation of the inaccuracies inherent to quadrature mixing is presented, and new techniques for digital compensation are suggested. It is shown that these proposed techniques allow all mixing artefacts to be suppressed to the level of the system's quantisation noise.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114389326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Qualitative and quantitative characteristics of deghosting in advanced radar systems 先进雷达系统中去鬼影的定性和定量特性
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1146799
L. Paradowski
{"title":"Qualitative and quantitative characteristics of deghosting in advanced radar systems","authors":"L. Paradowski","doi":"10.1109/AFRCON.2002.1146799","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146799","url":null,"abstract":"Deghosting, i.e. elimination of false targets during data processing in multi-sensor tracking of jamming targets, is a crucial process for effective use of air defence systems. It is particularly important for radar systems operating in passive mode because of their excellent properties against present-day electronic warfare techniques and tactics (especially jamming equipment and anti-radiation missiles). A deghosting algorithm based on bearing association/compounding strategy is outlined. A method of deghosting effectiveness evaluation using the ghost eliminator operating characteristic (reference to the receiver operating characteristic from statistical theory of signal detection) is presented. Such an approach enables to compare performances of various deghosting procedures in different operational conditions or scenarios.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115023820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 6
Induced currents on optical fibre cables installed in high voltage transmission line environments 高压输电线环境中光纤电缆的感应电流
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1159982
M.F. Khan, D. Hoch
{"title":"Induced currents on optical fibre cables installed in high voltage transmission line environments","authors":"M.F. Khan, D. Hoch","doi":"10.1109/AFRCON.2002.1159982","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159982","url":null,"abstract":"Specialized fibre optic cables may be installed by suspending the cables from transmission line towers such that they are situated under the high voltage conductors in an outdoor environment. Long term accumulation of wind-borne pollutants followed by periods of wetting may result in leakage currents flowing axially along the optical fibre cables. Under certain severe conditions, small arcs may form on the surface of the cable. The objective of this paper is to present two simulation processes that may be used to determine these leakage currents and compare the predicted values with experimentally determined values. The effects of system voltage, attachment point of the cable at the tower and span length on the magnitude of the leakage currents have all been investigated. The feasibility of using these models to predict dry-band arcing on these cables was also determined.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116456731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 3
Connecting EIB to Linux and Java 将EIB连接到Linux和Java
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1146847
W. Kastner, B. Thallner
{"title":"Connecting EIB to Linux and Java","authors":"W. Kastner, B. Thallner","doi":"10.1109/AFRCON.2002.1146847","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146847","url":null,"abstract":"This article deals with a Linux low-level hardware driver for the RS-232 data interface of the European Installation Bus (EIB). The RS-232 data interface is based on the widely used bus coupling unit 1 (BCU1), which requires a complex hard- and software protocol (physical external interface type 16) for communication. After a discussion about Linux and the module device driver programming, we explain the concepts for communication between a PC and the well-known BCU1. The article also shows the design and implementation of the Linux device driver and a Java-based middleware built on top of it.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123991901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Identification of types of distortion sources in power systems by applying neural networks 应用神经网络识别电力系统畸变源类型
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1160021
C. van Niekerk, A. Rens, A. Hoffman
{"title":"Identification of types of distortion sources in power systems by applying neural networks","authors":"C. van Niekerk, A. Rens, A. Hoffman","doi":"10.1109/AFRCON.2002.1160021","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1160021","url":null,"abstract":"To aid in the task of locating the geographical origin of distortions in power systems, the population of devices that causes distorted or non-sinusoidal conditions was divided into 3 main categories: Power electronic, arcing and ferromagnetic devices. An artificial neural network was developed that categorises randomly picked devices accordingly. The magnitude of the current harmonics was identified as the best distinguishing features. Typical relative current harmonic values for each device were found. Each category of distortions was investigated in terms of its harmonic content. It was found that significant correlations exist between the individual current harmonics of the same device. Matlab simulations indicated that a three layer neural network with five hidden units optimised by the Bayesian regularisation algorithm, provided the best results in terms of speed and accuracy.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124830906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 18
Concept for an architecture of a wireless building automation 无线楼宇自动化架构的概念
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1146822
G. Stein, K. Kabitzsch
{"title":"Concept for an architecture of a wireless building automation","authors":"G. Stein, K. Kabitzsch","doi":"10.1109/AFRCON.2002.1146822","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146822","url":null,"abstract":"In several applications for automation, radio transmission could be a good alternative to wired field buses (see Rauchhaupt, L. and Hahniche, J., Proc. Fieldbus Conf. FeT'99, p.48-54,1999). The advantages are an easy, fast and low cost installation scenario in common with the possibility of flexible device placing. However, the specifics of radio require a very specialized protocol stack which affects the whole system architecture. Starting from the requirements of building automation, the paper shows a concept of an architecture for the integration of wireless devices into wired field buses. It is shown that radio transmission is well suited for open loop sensors and user terminals. But for actuators and backbones, it is a better choice to keep them on wires.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129491043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Accurate digital current control of the reluctance synchronous machine with constant current angle 恒流角磁阻同步电机的精确数字电流控制
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1159995
P. D. Fick, M. Kamper
{"title":"Accurate digital current control of the reluctance synchronous machine with constant current angle","authors":"P. D. Fick, M. Kamper","doi":"10.1109/AFRCON.2002.1159995","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159995","url":null,"abstract":"Constant current angle controlled reluctance synchronous machine drives can be considered as near optimum efficiency controlled drives. This paper describes an accurate constant current-angle current-control technique for a digital controlled reluctance synchronous machine (RSM) drive. Using finite element calculated results accurate decoupled dq current regulators are designed and used in a digital controlled system using the TMS320F240-DSP. In the design of the controller the effect of dynamic inductances, due to saturation and cross magnetisation, on the performance of the PI-controllers is taken into account. Complete analysis, digital simulation and measured results are presented.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128306327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 7
On placing the reflection plane in numeric inductance calculations of thin-film superconducting structures using the method of images 利用图像法在薄膜超导结构数值电感计算中放置反射面
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1159958
C. Fourie, W. Perold
{"title":"On placing the reflection plane in numeric inductance calculations of thin-film superconducting structures using the method of images","authors":"C. Fourie, W. Perold","doi":"10.1109/AFRCON.2002.1159958","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159958","url":null,"abstract":"Determining the inductance of thin film superconducting structures accurately is extremely important in sub-Terahertz superconducting logic circuits. For numeric analysis, both the structure and ground plane need to be sufficiently segmented. The method of images significantly reduces the number of segments, but the selection of the position of the reflection plane is critical. The influence of the position of the reflection plane on inductance is investigated, and results presented. A study of segmentation and filamentation is also made, and these results used to calculate the inductance of a complex three-dimensional structure.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127111311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Performance improvement of spread spectrum spatial-domain watermarking scheme through diversity and attack characterisation 利用分集和攻击特征改进扩频空域水印方案的性能
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1146851
R. Bangaleea, H. Rughooputh
{"title":"Performance improvement of spread spectrum spatial-domain watermarking scheme through diversity and attack characterisation","authors":"R. Bangaleea, H. Rughooputh","doi":"10.1109/AFRCON.2002.1146851","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1146851","url":null,"abstract":"We present a spatial-domain-watermarking scheme for data hiding and copyright protection of still images using the attack characterisation approach. A small number of bits are embedded onto an image in the spatial domain using a method similar to the direct sequence spread spectrum. Perceptual analysis is used to guarantee the imperceptibility of the watermark and proper scaling of the raw mask values maximises the robustness of the watermark, while keeping it imperceptible to the human senses. We add two types of watermarks: reference and robust. The reference watermark is used to assess the way, in which the marked signal has been modified, so that the robust watermark can be optimally extracted. The watermarking system requires two keys; one for generating the pseudo-noise sequence for spread spectrum modulation and another for embedding the two watermarks in a checkerboard arrangement, where the use of the key introduces spatial uncertainty about the location of the watermark bits. This approach has been implemented for a spatial diversity of 64 and 256. Simulation results reveal the effectiveness of the new approach.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129924652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 25
Studies of DC conductor corona in a small corona cage 小型电晕笼中直流导体电晕的研究
IEEE AFRICON. 6th Africon Conference in Africa, Pub Date : 2002-10-02 DOI: 10.1109/AFRCON.2002.1159990
G. Sibilant, N. Ijumba, A. Britten
{"title":"Studies of DC conductor corona in a small corona cage","authors":"G. Sibilant, N. Ijumba, A. Britten","doi":"10.1109/AFRCON.2002.1159990","DOIUrl":"https://doi.org/10.1109/AFRCON.2002.1159990","url":null,"abstract":"The complex nature of corona phenomena, combined with the number of factors influencing these effects, make experimental studies indispensable for evaluating the corona performance of transmission lines. Different methods, ranging from tests in laboratory cages to measurements on operational transmission lines, may be used for obtaining the necessary data. This paper gives a brief introduction to the design of a small corona cage as well as presenting test results obtained from the cage at the HVDC center of the University of Durban-Westville. These tests involved changing the surface conditions of conductors in order to determine their corona performance.","PeriodicalId":185871,"journal":{"name":"IEEE AFRICON. 6th Africon Conference in Africa,","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132080715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
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