It is demonstrated that metallic strip arrays can be used to load the slot arrays in a frequency selective surface to compensate for the variation in incident angles. Unlike previous structures which are made up of either strip or slot arrays only, the structure considered consists of both strip and slot arrays in the same frequency selective surface. Combining strip and slot arrays in a frequency selective surface provides additional parameters to control its performance. The transmission coefficients for two closely spaced slot arrays located in free space are obtained. The resonant frequency and bandwidth vary for different incident angles. To reduce this variation, a strip array is inserted between the slot arrays. Finally, results for arrays embedded in dielectric slabs are shown.<>
{"title":"Frequency selective surfaces combining slot and strip arrays in a stratified medium","authors":"K. Ng, S. Spitz","doi":"10.1109/APS.1989.134885","DOIUrl":"https://doi.org/10.1109/APS.1989.134885","url":null,"abstract":"It is demonstrated that metallic strip arrays can be used to load the slot arrays in a frequency selective surface to compensate for the variation in incident angles. Unlike previous structures which are made up of either strip or slot arrays only, the structure considered consists of both strip and slot arrays in the same frequency selective surface. Combining strip and slot arrays in a frequency selective surface provides additional parameters to control its performance. The transmission coefficients for two closely spaced slot arrays located in free space are obtained. The resonant frequency and bandwidth vary for different incident angles. To reduce this variation, a strip array is inserted between the slot arrays. Finally, results for arrays embedded in dielectric slabs are shown.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90814944","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 systematic approach has been developed to model the surfaces encountered in aerospace engineering for electromagnetic applications. The basis of this modeling is the quadric canonical shapes which are the coordinate surfaces of the Eisenhart coordinate systems. The building blocks are visualized as sections of quadric cylinders and surfaces of revolution. The surface modeling paradigm facilitates the treatment of hybrid nondevelopable QUASORs (quadric surfaces of revolution) such as a satellite launch vehicle modeled as a GPOR (general paraboloid of revolution)-cylinder combination. Some examples of hybrid QUASORs are presented.<>
{"title":"A surface modeling paradigm for electromagnetic applications in aerospace structures","authors":"R. Jha, S.A. Bodhari, V. Sudhakar, P. Mahapatra","doi":"10.1109/APS.1989.134656","DOIUrl":"https://doi.org/10.1109/APS.1989.134656","url":null,"abstract":"A systematic approach has been developed to model the surfaces encountered in aerospace engineering for electromagnetic applications. The basis of this modeling is the quadric canonical shapes which are the coordinate surfaces of the Eisenhart coordinate systems. The building blocks are visualized as sections of quadric cylinders and surfaces of revolution. The surface modeling paradigm facilitates the treatment of hybrid nondevelopable QUASORs (quadric surfaces of revolution) such as a satellite launch vehicle modeled as a GPOR (general paraboloid of revolution)-cylinder combination. Some examples of hybrid QUASORs are presented.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91201751","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}
H. Lai, R. Marth, D. Rucker, F. Freyne, D. Nyquist
Rectangular slots are cut in the broad or narrow side walls of rectangular waveguides. The slots are arranged in a random-tilt fashion on a planar surface. Waveguides are excited by an arbitrary amplitude and phase combination wave in the dominant waveguide mode and are terminated by an arbitrary reflection coefficient. Scattering due to slots and mutual couplings between waveguides is accounted for by means of both internal and external Green's functions. A coupling system of Hallen-type integral equations for the slot fields excited in each of the array elements is formulated on the basis of the boundary condition for tangential magnetic fields in the slot aperture. The system of equations is solved numerically by the method of moments to determine the slot voltage distribution in each array element. Slot fields of a single-waveguide array are compared with those of a multi-waveguide array with equal magnitude and phase excitation.<>
{"title":"Radiation characteristics and coupling effects of a planar slotted waveguide phased array","authors":"H. Lai, R. Marth, D. Rucker, F. Freyne, D. Nyquist","doi":"10.1109/APS.1989.134864","DOIUrl":"https://doi.org/10.1109/APS.1989.134864","url":null,"abstract":"Rectangular slots are cut in the broad or narrow side walls of rectangular waveguides. The slots are arranged in a random-tilt fashion on a planar surface. Waveguides are excited by an arbitrary amplitude and phase combination wave in the dominant waveguide mode and are terminated by an arbitrary reflection coefficient. Scattering due to slots and mutual couplings between waveguides is accounted for by means of both internal and external Green's functions. A coupling system of Hallen-type integral equations for the slot fields excited in each of the array elements is formulated on the basis of the boundary condition for tangential magnetic fields in the slot aperture. The system of equations is solved numerically by the method of moments to determine the slot voltage distribution in each array element. Slot fields of a single-waveguide array are compared with those of a multi-waveguide array with equal magnitude and phase excitation.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74952015","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}
To obtain deep and local hyperthermia in the microwave region, lens applicators for concentrating electromagnetic energy in a lossy medium such as human muscle are presented. The applicators are a direct-contact metal plate lens and a partially dielectric-filled waveguide lens. Electric field and heating simulation with phantom modeling of human tissue shows that the heating depth is over 50 mm using the lens applicator at microwave frequencies.<>
为了在微波区域获得深度和局部热疗，提出了用于在有损介质(如人体肌肉)中集中电磁能的透镜应用器。施加器是直接接触的金属板透镜和部分介质填充的波导透镜。模拟人体组织的电场和加热模型表明，在微波频率下，使用透镜施加器加热深度超过50 mm
{"title":"Lens applicators for microwave hyperthermia","authors":"Y. Nikawa","doi":"10.1109/APS.1989.134738","DOIUrl":"https://doi.org/10.1109/APS.1989.134738","url":null,"abstract":"To obtain deep and local hyperthermia in the microwave region, lens applicators for concentrating electromagnetic energy in a lossy medium such as human muscle are presented. The applicators are a direct-contact metal plate lens and a partially dielectric-filled waveguide lens. Electric field and heating simulation with phantom modeling of human tissue shows that the heating depth is over 50 mm using the lens applicator at microwave frequencies.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76306001","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 fast Fourier transform conjugate gradient method solves numerically the electric field integral equation, using the method of moments with pulse basis function and point matching, but substantial errors are found in this method for the 2-D TE case. In the present work, the authors analyze the source of errors in these approximations and show that the modified method empirically proposed by D.T. Borup, D.M. Sullivan, and O.P. Ghandi (IEEE Trans. Microwave Theory Tech., vol.MTT-35, p.383-95, Apr.1987) would not have been necessary if correct terms in the integral equation were used. With this aim, the authors propose a new integral formulation using generalized functions and compare it with two previous formulations, that of S.C. Hill, C.H. DAmey, and D.A. Christensen Radio Sci., vol.18, p.328-36, May-June 1983 and D.E. Livesay and K.M. Chen (IEEE Trans. Microwave Theory Tech., vol.MMT-22, p.1273-80, 1974). For all the numerical methods discussed, the conjugate gradient technique is used to solve the linear system, and the convolution products are computed by means of a Fourier transform. The results are of interest in connection with refining numerical methods to support biomedical applications (e.g. microwave imaging and hypothermia treatment).<>
{"title":"Comparison between three integral formulations for the 2D-TE scattering problem","authors":"N. Joachimowicz, C. Pichot","doi":"10.1109/APS.1989.134799","DOIUrl":"https://doi.org/10.1109/APS.1989.134799","url":null,"abstract":"The fast Fourier transform conjugate gradient method solves numerically the electric field integral equation, using the method of moments with pulse basis function and point matching, but substantial errors are found in this method for the 2-D TE case. In the present work, the authors analyze the source of errors in these approximations and show that the modified method empirically proposed by D.T. Borup, D.M. Sullivan, and O.P. Ghandi (IEEE Trans. Microwave Theory Tech., vol.MTT-35, p.383-95, Apr.1987) would not have been necessary if correct terms in the integral equation were used. With this aim, the authors propose a new integral formulation using generalized functions and compare it with two previous formulations, that of S.C. Hill, C.H. DAmey, and D.A. Christensen Radio Sci., vol.18, p.328-36, May-June 1983 and D.E. Livesay and K.M. Chen (IEEE Trans. Microwave Theory Tech., vol.MMT-22, p.1273-80, 1974). For all the numerical methods discussed, the conjugate gradient technique is used to solve the linear system, and the convolution products are computed by means of a Fourier transform. The results are of interest in connection with refining numerical methods to support biomedical applications (e.g. microwave imaging and hypothermia treatment).<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73593348","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 Stein efficiency is calculated for several cases of finite and infinite two-dimensional multibeam antenna array systems. The results show that the efficiency increases quadratically for small beam separations for large arrays.<>
{"title":"Stein's limit for finite and infinite multi-beam arrays","authors":"J. Johansson","doi":"10.1109/APS.1989.134788","DOIUrl":"https://doi.org/10.1109/APS.1989.134788","url":null,"abstract":"The Stein efficiency is calculated for several cases of finite and infinite two-dimensional multibeam antenna array systems. The results show that the efficiency increases quadratically for small beam separations for large arrays.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73952016","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 time-saving reflection point locating technique based on the geometrical optics approximation is proposed. The technique provides an efficient evaluation of a Cassegrain or Gregorian antenna system. For comparison, all the reflection points are calculated with the proposed technique and W.V. Rusch's approach (1979). Patterns calculated by these two techniques show very similar results. However, the computation time of the proposed technique is only one-fourteenth that of Rusch's approach. It is concluded that, for a slightly defocused feed system, the proposed approximation technique works well for a dual reflector antenna system. It can be extended to a monopulse tracking antenna system with multiple feeds.<>
{"title":"Efficient approach to analyze the dual-reflector antenna system with defocused feeds","authors":"D. Chang, C. Cheng, M.-R. Ho, S.-Y. Yang","doi":"10.1109/APS.1989.134918","DOIUrl":"https://doi.org/10.1109/APS.1989.134918","url":null,"abstract":"A time-saving reflection point locating technique based on the geometrical optics approximation is proposed. The technique provides an efficient evaluation of a Cassegrain or Gregorian antenna system. For comparison, all the reflection points are calculated with the proposed technique and W.V. Rusch's approach (1979). Patterns calculated by these two techniques show very similar results. However, the computation time of the proposed technique is only one-fourteenth that of Rusch's approach. It is concluded that, for a slightly defocused feed system, the proposed approximation technique works well for a dual reflector antenna system. It can be extended to a monopulse tracking antenna system with multiple feeds.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79074981","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 near fields and far fields of a corner reflector antenna were numerically predicted using the boundary-element method. Measured far-field patterns at 0.9 GHz are found to agree well with the numerical data over the whole range of radiation angles.<>
{"title":"Radiation pattern analysis of corner reflector antennas by boundary-element method","authors":"K. Miyata, I. Fukai","doi":"10.1109/APS.1989.134696","DOIUrl":"https://doi.org/10.1109/APS.1989.134696","url":null,"abstract":"The near fields and far fields of a corner reflector antenna were numerically predicted using the boundary-element method. Measured far-field patterns at 0.9 GHz are found to agree well with the numerical data over the whole range of radiation angles.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79298598","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}
To verify predictions and establish a baseline for comparing analytical results and scan performance, an engineering model with offset confocal paraboloids was designed and built. The model was thoroughly tested and compared with analytically calculated results. The agreement between the measurements and the calculations was remarkable, considering the complexity of the antenna system geometry. The scan peaks, main beams, and sidelobe structures were accurately predicted by the computer program; even for the severe scan cases, the agreement was acceptable.<>
{"title":"An array-fed, dual-reflector antenna system (of offset, confocal paraboloids) for satellite antenna applications","authors":"E. Ekelman, B.S. Lee","doi":"10.1109/APS.1989.135028","DOIUrl":"https://doi.org/10.1109/APS.1989.135028","url":null,"abstract":"To verify predictions and establish a baseline for comparing analytical results and scan performance, an engineering model with offset confocal paraboloids was designed and built. The model was thoroughly tested and compared with analytically calculated results. The agreement between the measurements and the calculations was remarkable, considering the complexity of the antenna system geometry. The scan peaks, main beams, and sidelobe structures were accurately predicted by the computer program; even for the severe scan cases, the agreement was acceptable.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84769624","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 author introduces an adaptive modeling scheme for characterizing radio propagation channels and shows its application to problems caused by adverse propagation conditions. The proposed scheme is based on a similar adaptive modeling scheme for an unknown system using an LMS (least-mean-square) adaptive filter. An identical and synchronized signal must be provided to drive the channel and the adaptive filter. For excellent performance, the adaptation of the adaptive filter must be faster than the variations of propagation characteristics. The adaptive modeling scheme can monitor channel characteristics while the data are being transmitted. The channel modeling scheme can automatically cope with adverse propagation effects without knowledge of propagation conditions.<>
{"title":"Adaptive modeling of radio propagation channels","authors":"C. P. Tou","doi":"10.1109/APS.1989.134812","DOIUrl":"https://doi.org/10.1109/APS.1989.134812","url":null,"abstract":"The author introduces an adaptive modeling scheme for characterizing radio propagation channels and shows its application to problems caused by adverse propagation conditions. The proposed scheme is based on a similar adaptive modeling scheme for an unknown system using an LMS (least-mean-square) adaptive filter. An identical and synchronized signal must be provided to drive the channel and the adaptive filter. For excellent performance, the adaptation of the adaptive filter must be faster than the variations of propagation characteristics. The adaptive modeling scheme can monitor channel characteristics while the data are being transmitted. The channel modeling scheme can automatically cope with adverse propagation effects without knowledge of propagation conditions.<<ETX>>","PeriodicalId":11330,"journal":{"name":"Digest on Antennas and Propagation Society International Symposium","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1989-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79682862","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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