The VA Tech OLYMPUS propagation experiment, which includes 12, 20, and 30 GHz beacon receivers at an elevation angle of 14 degrees , provides valuable multifrequency scintillation data. The frequency scaling law, of the scintillation intensity derived from V.I. Tatarski's (1961) weak fluctuation theory is compared to experimental results. An analysis of a few scintillation events indicates that for large scintillations the scaling ratios of the scintillation intensity are well predicted by the theory. For small scintillations it is necessary to take the effects of the thermal noise into account.<>
VA Tech的OLYMPUS传播实验包括12 GHz、20 GHz和30 GHz信标接收器，仰角为14度，提供了有价值的多频闪烁数据。根据塔塔斯基(1961)的弱涨落理论推导了闪烁强度的频率标度规律，并与实验结果进行了比较。对几个闪烁事件的分析表明，对于较大的闪烁，该理论可以很好地预测闪烁强度的标度比。对于小的闪烁，有必要考虑热噪声的影响
{"title":"Preliminary results on scintillation intensity frequency scaling from the Virginia Tech OLYMPUS experiment","authors":"F. Haidara, C. Bostian","doi":"10.1109/APS.1992.221939","DOIUrl":"https://doi.org/10.1109/APS.1992.221939","url":null,"abstract":"The VA Tech OLYMPUS propagation experiment, which includes 12, 20, and 30 GHz beacon receivers at an elevation angle of 14 degrees , provides valuable multifrequency scintillation data. The frequency scaling law, of the scintillation intensity derived from V.I. Tatarski's (1961) weak fluctuation theory is compared to experimental results. An analysis of a few scintillation events indicates that for large scintillations the scaling ratios of the scintillation intensity are well predicted by the theory. For small scintillations it is necessary to take the effects of the thermal noise into account.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122133142","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}
Transverse magnetic (TM) plane-wave scattering from a rectangular channel engraved in a perfectly conducting plane is investigated. A Fourier-transform technique is employed to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. An approximate series solution for scattering is presented in a closed-form which is valid for the high-frequency scattering regime. Approximate solutions which are valid for the quasi-static and low-frequency scattering regimes are also obtained. Using the stationary phase approximation, the far-zone scattered field is obtained and its scattering behavior is studied in terms of the scattering angle, frequency, and channel size.<>
{"title":"TM-scattering from a rectangular channel in a conducting plane","authors":"H. J. Eom, T. J. Park, K. Yoshitomi, T. Choi","doi":"10.1109/APS.1992.221914","DOIUrl":"https://doi.org/10.1109/APS.1992.221914","url":null,"abstract":"Transverse magnetic (TM) plane-wave scattering from a rectangular channel engraved in a perfectly conducting plane is investigated. A Fourier-transform technique is employed to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. An approximate series solution for scattering is presented in a closed-form which is valid for the high-frequency scattering regime. Approximate solutions which are valid for the quasi-static and low-frequency scattering regimes are also obtained. Using the stationary phase approximation, the far-zone scattered field is obtained and its scattering behavior is studied in terms of the scattering angle, frequency, and channel size.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129940033","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}
Transient currents for a wire antenna with a nonlinear diode load are calculated directly using finite-difference time-domain (FDTD) methods. In the FDTD cell that contains the load, a nonlinear equation is solved at each time step. As a test case the transient current in a long dipole antenna with a nonlinear load excited by a pulsed plane wave is computed. The results agree well with both calculated and measured results previously published. The approach given allows the time step to be set at the Courant limit and can be applied to scattering from targets with nonlinear loads and materials, to nonlinear harmonic generation, and to propagation through nonlinear materials.<>
{"title":"FDTD calculations for nonlinear lumped loads","authors":"R. Luebbers, K. Kunz","doi":"10.1109/APS.1992.221485","DOIUrl":"https://doi.org/10.1109/APS.1992.221485","url":null,"abstract":"Transient currents for a wire antenna with a nonlinear diode load are calculated directly using finite-difference time-domain (FDTD) methods. In the FDTD cell that contains the load, a nonlinear equation is solved at each time step. As a test case the transient current in a long dipole antenna with a nonlinear load excited by a pulsed plane wave is computed. The results agree well with both calculated and measured results previously published. The approach given allows the time step to be set at the Courant limit and can be applied to scattering from targets with nonlinear loads and materials, to nonlinear harmonic generation, and to propagation through nonlinear materials.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128328089","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}
The bridge of a ship contains a large amount of sophisticated electronic equipment. The performance of this equipment must be ensured by hardening against external electromagnetic fields which may enter the bridge through windows, doors, and seams. For this reason it is essential to be able to predict the penetration of fields inside the bridge. In the present work the finite-difference time-domain (FDTD) method and the electric field integral equation (EFIE) implementation of the moment method are used to compute the electromagnetic fields inside the bridge. Effects of factors such as the shape of the incident pulse, the discretization of the structure, and the resonance of the structure on CPU time and accuracy of field computations are demonstrated.<>
{"title":"EM field penetration inside the bridge of a ship","authors":"S. Kashyap, M. Burton, A. Louie","doi":"10.1109/APS.1992.221531","DOIUrl":"https://doi.org/10.1109/APS.1992.221531","url":null,"abstract":"The bridge of a ship contains a large amount of sophisticated electronic equipment. The performance of this equipment must be ensured by hardening against external electromagnetic fields which may enter the bridge through windows, doors, and seams. For this reason it is essential to be able to predict the penetration of fields inside the bridge. In the present work the finite-difference time-domain (FDTD) method and the electric field integral equation (EFIE) implementation of the moment method are used to compute the electromagnetic fields inside the bridge. Effects of factors such as the shape of the incident pulse, the discretization of the structure, and the resonance of the structure on CPU time and accuracy of field computations are demonstrated.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125123472","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}
NASA's CRAF/Cassini (C/C) project requires the use of multiple RF frequencies at S, X, Ku, and Ka bands for science investigations and data communications links. A single high-gain antenna (HGA) will be used. It incorporates a frequency-selective subreflector (FSS) to allow a Cassegrain configuration at X (7.2 and 8.4 GHz) and Ka (32 and 34.5 GHz) bands, and a prime focus configuration at S (2.3 GHz) and Ku (13.8 GHz) bands. A four-based FSS design for the C/C application is reported. The selection of the concentric ring elements is based on the fact that the ring's geometry is particularly conformable to the present circular polarization requirement and ease of manufacture.<>
{"title":"Multi-ring element FSS for multi-band applications","authors":"T. Wu, K. Woo, S. Lee","doi":"10.1109/APS.1992.221506","DOIUrl":"https://doi.org/10.1109/APS.1992.221506","url":null,"abstract":"NASA's CRAF/Cassini (C/C) project requires the use of multiple RF frequencies at S, X, Ku, and Ka bands for science investigations and data communications links. A single high-gain antenna (HGA) will be used. It incorporates a frequency-selective subreflector (FSS) to allow a Cassegrain configuration at X (7.2 and 8.4 GHz) and Ka (32 and 34.5 GHz) bands, and a prime focus configuration at S (2.3 GHz) and Ku (13.8 GHz) bands. A four-based FSS design for the C/C application is reported. The selection of the concentric ring elements is based on the fact that the ring's geometry is particularly conformable to the present circular polarization requirement and ease of manufacture.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129117773","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}
Two possible ways of realizing wideband beamforming networks (BFNs) are presented. Initial physical values for backward-wave couplers can be maintained at fixed values irrespective of the coupling level. This significantly reduces alignment errors in the mask layout of a relatively large array. With codirectional couplers only a single 0 dB design is needed to obtain the rest of the coupling levels required for the BFN.<>
{"title":"Wide band beam forming networks for frequency scanned phased arrays","authors":"S. Uysal, J. Watkins","doi":"10.1109/APS.1992.221904","DOIUrl":"https://doi.org/10.1109/APS.1992.221904","url":null,"abstract":"Two possible ways of realizing wideband beamforming networks (BFNs) are presented. Initial physical values for backward-wave couplers can be maintained at fixed values irrespective of the coupling level. This significantly reduces alignment errors in the mask layout of a relatively large array. With codirectional couplers only a single 0 dB design is needed to obtain the rest of the coupling levels required for the BFN.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"458 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123210885","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}
A microwave signature model based on the vector radiative transfer equation has been developed for a forested canopy. The model is designed to operate over a wide frequency band and to account for the size and orientation distributions of each forest component, the layering effect, and multiple scattering. The average Muller matrix is formulated in terms of the iterative solution of the radiative transfer solution up to the second order in albedo and then used to determine the co-polarized and cross-polarized power returns. Numerical results show that a significant difference exists in the polarimetric signatures of a forested canopy when the crown region is treated as two layers versus one layer with the same leaf and branch distributions.<>
{"title":"Polarimetric signatures of a forested canopy","authors":"M. Karam, F. Amar, A. Fung","doi":"10.1109/APS.1992.221673","DOIUrl":"https://doi.org/10.1109/APS.1992.221673","url":null,"abstract":"A microwave signature model based on the vector radiative transfer equation has been developed for a forested canopy. The model is designed to operate over a wide frequency band and to account for the size and orientation distributions of each forest component, the layering effect, and multiple scattering. The average Muller matrix is formulated in terms of the iterative solution of the radiative transfer solution up to the second order in albedo and then used to determine the co-polarized and cross-polarized power returns. Numerical results show that a significant difference exists in the polarimetric signatures of a forested canopy when the crown region is treated as two layers versus one layer with the same leaf and branch distributions.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123480177","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}
UWB radar is of interest because of its highly successful application to ground probing radar and to the challenge of working in an area which requires technology different from more conventional narrowband (NB) radar. The status of UWB technology is examined, and differences between UWB and NB radar are discussed with reference to the transient nature of target scattering, dispersive propagation effects, antenna effects, transmitters, and signal processing.<>
{"title":"Status of ultrawideband (UWB) radar and its technology","authors":"M. Skolnik","doi":"10.1109/APS.1992.221669","DOIUrl":"https://doi.org/10.1109/APS.1992.221669","url":null,"abstract":"UWB radar is of interest because of its highly successful application to ground probing radar and to the challenge of working in an area which requires technology different from more conventional narrowband (NB) radar. The status of UWB technology is examined, and differences between UWB and NB radar are discussed with reference to the transient nature of target scattering, dispersive propagation effects, antenna effects, transmitters, and signal processing.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"101 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123520587","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}
The use of an adaptive artificial neural network (ANN) for direct-wave elimination in time-domain measurements of electromagnetic scattering is considered. Many artificial experiments have been performed with the AST286 computer. The results obtained show that the adaptive ANN network, which ensures both real-time and high reliability and decreases the operational quantity considerably, is an effective technique for the elimination of direct waves in time-domain measurements of electromagnetic scattering.<>
{"title":"Elimination of direct waves in time-domain measurements of electromagnetic scattering by adaptive artificial neural network","authors":"B. Song, Gong Long, J. Fu","doi":"10.1109/APS.1992.221398","DOIUrl":"https://doi.org/10.1109/APS.1992.221398","url":null,"abstract":"The use of an adaptive artificial neural network (ANN) for direct-wave elimination in time-domain measurements of electromagnetic scattering is considered. Many artificial experiments have been performed with the AST286 computer. The results obtained show that the adaptive ANN network, which ensures both real-time and high reliability and decreases the operational quantity considerably, is an effective technique for the elimination of direct waves in time-domain measurements of electromagnetic scattering.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123567876","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}
A self-consistent, quasi-classical, linear kinetic theory adopting a six-dimensional angular momentum/configuration phase space is used to develop the linear magnetization for a finite, anisotropic, magnetic medium biased with a large, uniform magnetostatic field. Only the classical dipole and quantum mechanical exchange interactions are incorporated into the theory. With suitable approximations, the equilibrium and linear magnetizations agree with existing theories. The ferrimagnetic medium is composed of two interpenetrating magnetic ion sublattices. Transverse wave oscillations result in the medium due to exchange interaction. With exchange interaction, Maxwell's equations are of differential/integral form.<>
{"title":"A quasi-classical, linear kinetic theory for a ferrimagnetic medium-linear magnetization","authors":"R. Schill, J. Tischer","doi":"10.1109/APS.1992.221402","DOIUrl":"https://doi.org/10.1109/APS.1992.221402","url":null,"abstract":"A self-consistent, quasi-classical, linear kinetic theory adopting a six-dimensional angular momentum/configuration phase space is used to develop the linear magnetization for a finite, anisotropic, magnetic medium biased with a large, uniform magnetostatic field. Only the classical dipole and quantum mechanical exchange interactions are incorporated into the theory. With suitable approximations, the equilibrium and linear magnetizations agree with existing theories. The ferrimagnetic medium is composed of two interpenetrating magnetic ion sublattices. Transverse wave oscillations result in the medium due to exchange interaction. With exchange interaction, Maxwell's equations are of differential/integral form.<<ETX>>","PeriodicalId":289865,"journal":{"name":"IEEE Antennas and Propagation Society International Symposium 1992 Digest","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123725363","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}
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