1998 Symposium on Antenna Technology and Applied Electromagnetics最新文献

{"title":"Microstrip antenna arrays for airborne high-performance, polarimetric SAR systems","authors":"J. Granholm, K. Woelders","doi":"10.1109/ANTEM.1998.7861708","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861708","url":null,"abstract":"Many dual-linear polarization antenna arrays, e.g. for polarimetric synthetic aperture radar (SAR) systems, are required to have very low cross-polarization levels. In order to improve the cross-polarization performance of the entire array over that of the basic dual-polarization element from which the array is constructed, a well-known element mirroring technique has often been employed. This technique improves the cross-polarization performance of the array, but it may also cause generation of grating lobes. A new principle is described for obtaining very low cross-polarization levels in dual-linear polarization antenna arrays and simultaneously avoiding the generation of grating lobes. This paper reviews the new principle and presents its implementation in a wideband, dual-linear polarization microstrip antenna array used in the Danish airborne L-band polarimetric SAR system “EMISAR”. The antenna array, comprising 8 × 2 probe-fed stacked patch elements, exhibits a 10 % bandwidth, a peak directivity of 18 dBi and a cross-polarization level of 40 dB below the co-polar. Suggestions for further enhancements to the novel principle are given.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116705965","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}

{"title":"On the use of multi-p hierarchical bases for the solution of electromagnetic integral equations","authors":"W. Quan, I. Ciric","doi":"10.1109/ANTEM.1998.7861755","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861755","url":null,"abstract":"Considerable efforts have been made in recent years to improve the computation efficiency of the method of moments (MoM) for the solution of electromagnetic integral equations. A class of algorithms that show a certain potential in reducing the computation cost are based on employing hierarchical basis functions. The classical hierarchical basis functions constructed with rectangular and triangular pulse functions were utilized recently in a multilevel formulation of the MoM [1]. Wavelets are orthogonal hierarchical basis functions which have also been used recently for the solution of integral equations [2]. The multi-p hierarchical basis functions [3] are constructed with Legendre polynomials, and have been widely used in the p-version of the finite element method. Their use was further extended to treat singularities in the integral equations for problems in mechanical engineering relative to polygonal domains [4].","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132840534","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}

{"title":"Dispersion characteristics of suspended microstrip line on segmented dielectric substrate","authors":"W. Chamma, N. Gupta, L. Shafai","doi":"10.1109/ANTEM.1998.7861682","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861682","url":null,"abstract":"This paper presents the dispersion characteristics of suspended microstrip line on the segmented dielectric substrate where the dielectric permittivity of the lower substrate is changing along the transverse direction. It is seen that the propagation characteristics of such type of transmission lines can be varied widely with the change in the dielectric constant of the lower substrate. Both open and closed microstrip configurations are analyzed using the two methods namely, the Finite Difference Time Domain (FDTD) and the Method of Lines (MOL). The characteristics thus obtained are compared and found to be in good agreement.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133365552","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}

{"title":"Millimeter-wave mobile access system with smart antenna and radio on fiber","authors":"K. Hettak, G. Delisle","doi":"10.1109/ANTEM.1998.7861716","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861716","url":null,"abstract":"For any wireless network based on mm-wave radio systems to be viable, the cost of the infrastructure must be much lower than is currently the case. One approach that promises this cost reduction is the radio over fiber, where radio signals at the carrier frequency are delivered over an optical network to the radio access point. Benefits of this centralized approach are that expensive and delicate pieces of equipment can be located in a begining environment and costs can be shared between a number of radio access point. However, the integration of such systems is conditioned by the development of low cost radio components, antennas, the packaging as well as the optic/radio transductors. However, due to large propagation losses in this MMW/radio-on-fiber system, large transmission power is required to cover the wide area of cell zones. In addition, the effect of the multipath becomes serious when the signal bandwidth is wide. To cope with these problems, intelligent antennas are expected to solve the problems of large propagation losses and multipath fading in MMW. Therefore, an intelligent antenna that enables beam control is one of the key components in this millimeter wave fiber wireless systems with the options such as range extension, improved immunity to flat fading, interference suppression, and Spatial Division Multiple Access. The paper explores therefore the areas of strategic importance in integration of new antenna array topologies which are appropriated for use as a building block for the millimeter wave fiber wireless system which employs an intelligent multibeam antenna where the direction of each sharp beam can be adaptively controlled. Thereby, the objective of truly monolithic array with integrated planar antennas and phase shifters was the driving force behind the development of the aperture coupled patch element which is especially relevant for these systems. Challenges arising from the development of this EHF-band antenna array include the minimization of the array's feed network loss, coupling between antennas and between feedlines and antennas, and the overall architecture that the system requires. The effectiveness of this antenna array has been theoretically confirmed. Finally, it worthy noting that the small wavelengths allow miniaturize of the size of components such as antennas which are very important for portable sets as well as base station (BS) facilities, which need to be readily installed.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125644026","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}

{"title":"The addition of a field strength contour capability to NEC-2 and its application to the field emitted by an AM radio broadcast array","authors":"J. E. Roy","doi":"10.1109/ANTEM.1998.7861762","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861762","url":null,"abstract":"This paper presents the development and the use of a FORTRAN program that was added to a NEC-81 version of the well known NEC-2 program for the purpose of computing field strength contours. Whereas a field radiation pattern identifies the field variation for a constant observation distance about the antenna, a field strength contour identifies the distance variation for a constant field strength (|Ez| here). Because field strength contours are meaningful in the near-field as well as the far-field zones, they are useful in providing a picture of the emission process everywhere about the antenna.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130448651","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}

{"title":"New types of TLM nodes for the analysis of axially symmetric structures","authors":"S. Le Maguer, M. Ney","doi":"10.1109/ANTEM.1998.7861732","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861732","url":null,"abstract":"The Transmission Line Matrix (TLM) method is a well-known numerical time-domain technique which has been widely used for solving electromagnetic field problems. Axially symmetric structures are frequently encountered in microwave engineering. For this purpose, a first memory-saving TLM algorithm was developed in the particular case of uniform guiding structures [1]. Based on the classical Symmetrical Condensed Node (SCN) [2], this approach leads to a 1D mesh array using 18 complex voltages. Low memory requirement and simple algorithm make this method a very versatile tool. Extension of this model to general axially symmetric structure (2D mesh array) is not memory competitive compared to other time domain methods as BoR-FDTD [3,4].","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117060309","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}

{"title":"Electromagnetic imaging of conducting cylinders by applying a genetic algorithm","authors":"W. Quan, I. Ciric","doi":"10.1109/ANTEM.1998.7861756","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861756","url":null,"abstract":"Detection of the shape of perfect conducting objects from information contained in their scattering data is formulated as an inverse problem in terms of nonlinear integral equations. The difficulties in obtaining acceptable reconstructed images lie in the nonlinear nature and in the ill-posedness of the associated inverse problem. Various algorithms have been proposed based on the physical optics approximation, as well as on the exact electromagnetic field equations. To overcome the ill-posedness of this inverse problem, an optimization procedure is usually implemented, where the shape of the conducting object is reconstructed by minimizing the root-mean-square error of the difference between the predicted and the measured data, subject to certain constraints or a priori information. Newton-Kantorovitch method, Levenberg-Marquardt algorithm, and conjugate gradient techniques axe typical deterministic optimization schemes which are used for inverse problems. These are local optimization methods and their efficiency strongly depends on the initial guess.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124351319","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}

{"title":"Characteristics of conical horns loaded with internal metallic discs","authors":"M. Clénet, L. Shafai","doi":"10.1109/ANTEM.1998.7861690","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861690","url":null,"abstract":"Horn antennas, pyramidal and conical, are extremely popular antennas at microwave and millimeterwave frequencies. Their widespread application stems from the simplicity of their construction, ease of excitation and large gain. However, they suffer from a number of deficiencies due to phenomena like spillover, phase error in the aperture field distribution or cross-polarization, resulting in reduced aperture efficiency of about 50% to 60% for optimum gain horn.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"58 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123303167","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}

{"title":"Modeling with the FDTD of cellphone — Hearing aid interaction","authors":"M. Okoniewski, M. Stuchly","doi":"10.1109/ANTEM.1998.7861748","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861748","url":null,"abstract":"The new cellular telephones and other personal communication services (PCS), as well as global system for mobile communication (GSM), pose new problems and challenges in interactions with the human body and medical devices. One type of device affected are hearing aids. Electromagnetic interference (EMI) with hearing aids is associated with the frame rate in the time division multiple access (TDMA) systems resulting in the pulse modulation of the RF signal in the audible range. The frequency of the pulses depends on the communication system, and typically is 50 Hz, or 217 Hz. While the EMI, in this case, does not generally pose a health risk, it constitutes a considerable annoyance, that may prevent the hearing aid bearers from using some of the new devices. Also, the proximity to cellular telephones used by others or the base station may result in sufficiently strong signals to interfere with proper perception of sounds. Evaluation of EMI has been done experimentally and protocols for testing are being developed, e.g. in the USA in the Center for Devices and Radiological Health, FDA [1], [2]. The experimental test procedures can be greatly simplified, if the levels of the electric and magnetic fields around and in the ear at various location where hearing aids are typically located are known for actual complex exposure situations. The complexity results from the perturbation by the human head of the electric and magnetic fields from cellular telephones or their equivalent representation. To evaluate the actual potential for EMI, the assessment of the fields has to be made for actual locations of the hearing aid, which is typically in the ear canal. Simplified testing of actual hearing aids performed in free space using a resonant dipole representing a cellular telephone [1], [2] can then be related to the practical complex fields.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123387094","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}

{"title":"Antenna research and development for broadband communications at the communications research centre","authors":"A. Petosa, A. Ittipiboon, J. Shaker, M. Cuhaci","doi":"10.1109/ANTEM.1998.7861753","DOIUrl":"https://doi.org/10.1109/ANTEM.1998.7861753","url":null,"abstract":"This paper presents several prototype antenna elements and arrays developed at the Communications Research Centre for potential use in broadband communication applications. Various configurations of dielectric resonator antennas and dielectric lens antennas are examined as well as reflectarray technology and advanced architectures for low-profile phased arrays.","PeriodicalId":334204,"journal":{"name":"1998 Symposium on Antenna Technology and Applied Electromagnetics","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117275979","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}