IEEE Antennas and Propagation Society International Symposium 1997. Digest最新文献_第7页

Measurement of the noise improvement of a 34-meter Cassegrain antenna retrofitted with a low-backscattering strut 采用低后向散射支柱改造的34米卡塞格伦天线的噪声改善测量

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631494

A. Prata, F. Moreira, M. Thorburn, T. D. King, C. Stelzried, S. Keihm

{"title":"Measurement of the noise improvement of a 34-meter Cassegrain antenna retrofitted with a low-backscattering strut","authors":"A. Prata, F. Moreira, M. Thorburn, T. D. King, C. Stelzried, S. Keihm","doi":"10.1109/APS.1997.631494","DOIUrl":"https://doi.org/10.1109/APS.1997.631494","url":null,"abstract":"Large axially-symmetric ground-based dual-reflector antennas are used in a variety of applications simultaneously requiring very high gain and very low noise (e.g., satellite communications, radio astronomy, deep-space communications, and radar). In these systems, reducing the noise by 10% is equivalent to increasing the antenna gain by roughly 0.5 dB. Since the early days of radio astronomy this fact has continuously driven efforts to reduce the noise of front-end low-noise amplifiers-a major noise contributor. As the performance of the front-end amplifiers improved, the relative importance of the noise generated by the surrounding warm ground increased, causing the antenna noise to become a major factor in the overall system sensitivity. The results of Moreira, Prata and Thorburn (see IEEE Trans. Antennas Propagat., vol.44, no.4, p.492-9, 1996) are used to implement a low back-scattering cross section on a single strut of the Jet Propulsion Laboratory Deep Space Station 13 (DSS-13) antenna-a research and development 34-meter diameter deep-space communication beam-waveguide shaped Cassegrain antenna, located in Goldstone, California. The antenna and associated noise measurements are discussed, and the improvement on the system noise temperature is presented.","PeriodicalId":283897,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1997. Digest","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117235595","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

A fast nonlinear method for the harmonic effects analysis of a HTS stripline structure 一种用于高温超导带状线结构谐波效应分析的快速非线性方法

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.630155

S. Safavi-Naeini, H. Tang, Y. Chow

{"title":"A fast nonlinear method for the harmonic effects analysis of a HTS stripline structure","authors":"S. Safavi-Naeini, H. Tang, Y. Chow","doi":"10.1109/APS.1997.630155","DOIUrl":"https://doi.org/10.1109/APS.1997.630155","url":null,"abstract":"Nonlinear resistivity of the high temperature superconducting (HTS) thin films generates harmonic effects at medium and high power levels. These effects in general and the intermodulation products in particular limit the power handling capability of the HTS microwave circuits and antennas in many communication systems where the co-channel and adjacent channel distortion and interference are of major concern. An experimental study has shown that the dominant low order harmonics can be modeled by the following nonlinear relation between the surface resistance, R/sub s/, and the RF magnetic field intensity, H/sub RF/, at the temperature T and the frequency: R/sub s/(f,T,H/sub RF/)=a(f,T)+b(f,T)H/sup 2//sub RF/. This is also consistent with the Ginzburg-Landau (G-L) theory. For the theoretical study of the harmonic effects it is possible to apply directly the (G-L) theory to the fields inside the HTS medium. This makes the computation very intense both in time and memory. By considering each segment in the thin film circuit as a dipole, a lumped circuit model under harmonic voltage excitation has been constructed for a microwave HTS planar circuit. We have applied the harmonic balance method to this circuit model of a distributed field structure and thus avoided the time consuming direct solution of the G-L theory.","PeriodicalId":283897,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1997. Digest","volume":"28 44","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120823454","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

The near field behavior of nonsymmetric potentials in a multilayer medium 多层介质中非对称势的近场特性

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.625441

N. Hojjat, R. Faraji-Dana, S. Safavi-Naeini, Y. Chow

引用次数: 0

Application of genetic algorithms in the design and optimization of array patterns 遗传算法在阵列模式设计与优化中的应用

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631500

F. Ares, E. Villanueva, J. Rodríguez, S. Rengarajan

引用次数: 6

A spiral antenna on a cylinder 圆柱体上的螺旋形天线

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631478

K. Nakayama, H. Nakano

引用次数: 1

Synthesis of unequally spaced linear arrays by Legendre series expansion 用勒让德级数展开合成不等间距线性阵列

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.625414

B. Preetham Kumar, G. Branner

引用次数: 10

Computations of SAR distributions for two anatomically-based models of the human head using CAD files of commercial telephones and the parallelized FDTD code 利用商用电话的CAD文件和并行FDTD代码计算两种人体头部解剖模型的SAR分布

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/8.686769

A. Tinniswood, C. Furse, O. Gandhi

{"title":"Computations of SAR distributions for two anatomically-based models of the human head using CAD files of commercial telephones and the parallelized FDTD code","authors":"A. Tinniswood, C. Furse, O. Gandhi","doi":"10.1109/8.686769","DOIUrl":"https://doi.org/10.1109/8.686769","url":null,"abstract":"The finite difference time domain (FDTD) method is well suited for the computation of bio-electromagnetic effects and has become the method of choice for most researchers in this area. There does however remain some limitations on its use. Firstly the FDTD method requires large amounts of memory and computational power. The size of the model is dependent upon both the physical size of the model and its resolution. Higher frequencies of operation require higher resolutions. This can place the solution of some problems outside the capabilities of the technique. Secondly the representation of the problem (i.e. the head and the telephone) can cause some difficulties. Often the telephone has to be represented by a series of boxes which approximate the shape of the actual device. The paper addresses these two problems. The problem size is accommodated by the use of a parallelized version of the FDTD method, which is run on large parallel processing machines such as the IBM SP-2. Additionally a method of inputting data from the computer aided design (CAD) files of the telephone has been developed. These two techniques are used in combination with two head models which have been developed from MRI images of two human subjects. The usefulness of the techniques developed and comparisons of the specific absorption rates (SARs) in the two models is discussed.","PeriodicalId":283897,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1997. Digest","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124502893","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: 112

Genetic algorithm: the last word for solving all of your design problems? 遗传算法:解决你所有设计问题的最后一句话?

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631497

Raj Mittra

引用次数: 5

Rectangular microstrip antenna with a finite pyramidal horn-shaped ground plane 有限锥体角状接地面的矩形微带天线

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631676

N. Fayyaz, S. Safavi-Naeini

引用次数: 4

Edge fringe approach for the full-wave solution of large finite arrays 大型有限阵列全波解的边缘条纹法

IEEE Antennas and Propagation Society International Symposium 1997. Digest Pub Date : 1997-07-13 DOI: 10.1109/APS.1997.631743

A. Neto, S. Maci, M. Sabbadini, G. Vecchi

引用次数: 5