The application of the hybrid shaped reflector/array feed approach to the design of multiple contoured antennas is examined. The results show that a hybrid antenna can achieve coverage gain performance comparable to that of a conventional array-fed parabolic reflector design but with a significantly reduced number of feed elements. Increasing the number of feed elements results in a reduced amount of reflector shaping, which in turn leads to better control of the sidelobes and roll-off characteristics. For single and dual beam coverages, improvements can be achieved by imposing constraints on these parameters during the optimization process. For multiple coverages, however, the need to share the reflector shape between several beams restricts the freedom to control the spurious radiation. It appears that for such requirements the sidelobes can be improved only by increasing the number of feed elements to reduce the amount of reflector shaping. This design approach has been used to deal with different multicoverage scenarios including dual-beam AFSAT coverage (C-band), the seven-beam EUROPESAT coverage (Ka-band), and the modified five-beam EUROPESAT supercoverage.<>
{"title":"Multicoverage shaped reflector antenna designs","authors":"N. Adatia, P. Ramanujam, S. Tun","doi":"10.1109/APS.1989.134919","DOIUrl":"https://doi.org/10.1109/APS.1989.134919","url":null,"abstract":"The application of the hybrid shaped reflector/array feed approach to the design of multiple contoured antennas is examined. The results show that a hybrid antenna can achieve coverage gain performance comparable to that of a conventional array-fed parabolic reflector design but with a significantly reduced number of feed elements. Increasing the number of feed elements results in a reduced amount of reflector shaping, which in turn leads to better control of the sidelobes and roll-off characteristics. For single and dual beam coverages, improvements can be achieved by imposing constraints on these parameters during the optimization process. For multiple coverages, however, the need to share the reflector shape between several beams restricts the freedom to control the spurious radiation. It appears that for such requirements the sidelobes can be improved only by increasing the number of feed elements to reduce the amount of reflector shaping. This design approach has been used to deal with different multicoverage scenarios including dual-beam AFSAT coverage (C-band), the seven-beam EUROPESAT coverage (Ka-band), and the modified five-beam EUROPESAT supercoverage.<<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":"86652103","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}
Numerical results concerning the validity of the thin-wire approximation for conductors near a material half-space are presented. The propagation constants and associated current distributions for the discrete characteristic modes supported by cylindrical conductors located near a lossy planar interface are determined. An axially directed current is still assumed, but an arbitrary azimuthal distribution is taken into account in the formulation. The effect of the lossy interface is incorporated in the Green's function using a Sommerfeld-type integral. The thin-wire approximation is shown to be acceptable for calculating the fields even when Delta /a<1 as long as the observation point is not directly under the conductor.<>
{"title":"Validity of the thin-wire approximation for conductors near a material half-space","authors":"G. Bridges, L. Shafai","doi":"10.1109/APS.1989.134658","DOIUrl":"https://doi.org/10.1109/APS.1989.134658","url":null,"abstract":"Numerical results concerning the validity of the thin-wire approximation for conductors near a material half-space are presented. The propagation constants and associated current distributions for the discrete characteristic modes supported by cylindrical conductors located near a lossy planar interface are determined. An axially directed current is still assumed, but an arbitrary azimuthal distribution is taken into account in the formulation. The effect of the lossy interface is incorporated in the Green's function using a Sommerfeld-type integral. The thin-wire approximation is shown to be acceptable for calculating the fields even when Delta /a<1 as long as the observation point is not directly under the conductor.<<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":"86866061","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 application of diffraction theory to an impressed electric field on a linear cylindrical antenna is considered. It is shown that, physically, the impressed field on the antenna is the result of a diffraction of the driving field from the gap to the antenna surface and can be found by the methods of diffraction theory. The equation for the impressed field on a zero-gap antenna is reexamined. It is found that the impressed field on a zero-gap antenna is concentrated on a narrow strip on the order of the antenna radius. On the other hand, inside the strip the impressed field is inversely proportional to the antenna radius.<>
{"title":"An impressed field on a linear antenna: the diffraction theory","authors":"G. Nedlin","doi":"10.1109/APS.1989.134693","DOIUrl":"https://doi.org/10.1109/APS.1989.134693","url":null,"abstract":"The application of diffraction theory to an impressed electric field on a linear cylindrical antenna is considered. It is shown that, physically, the impressed field on the antenna is the result of a diffraction of the driving field from the gap to the antenna surface and can be found by the methods of diffraction theory. The equation for the impressed field on a zero-gap antenna is reexamined. It is found that the impressed field on a zero-gap antenna is concentrated on a narrow strip on the order of the antenna radius. On the other hand, inside the strip the impressed field is inversely proportional to the antenna radius.<<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":"85650466","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 localized temperature distribution inside a biological material (human muscle) is obtained through the use of a parabolic reflector to focus an electromagnetic pulse. With the point-matched time-domain finite-element method, the focused field and its penetration into the biological material are found, then the temperature profile in the material is calculated. The temperature is localized so that it can heat a specific spot without overburning the surrounding tissue. Attention is given to the factors which influence the localization characteristics, including the applied frequency, the associated electric parameters of the biological material, and the size of the parabolic reflector. The penetration depth and localization volume can be controlled by the adjustment of the applied frequency and the parameters of the reflector.<>
{"title":"Penetration of a focused electromagnetic pulse into a biological material and its application to hyperthermia","authors":"H. Chang, K. Mei","doi":"10.1109/APS.1989.134742","DOIUrl":"https://doi.org/10.1109/APS.1989.134742","url":null,"abstract":"A localized temperature distribution inside a biological material (human muscle) is obtained through the use of a parabolic reflector to focus an electromagnetic pulse. With the point-matched time-domain finite-element method, the focused field and its penetration into the biological material are found, then the temperature profile in the material is calculated. The temperature is localized so that it can heat a specific spot without overburning the surrounding tissue. Attention is given to the factors which influence the localization characteristics, including the applied frequency, the associated electric parameters of the biological material, and the size of the parabolic reflector. The penetration depth and localization volume can be controlled by the adjustment of the applied frequency and the parameters of the reflector.<<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":"85656299","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}
Vezzosi (Ann. des Telecommun., vol.37, p.425-39, Sept. 1982) proposed an eigenvector (EV) rotation method to resolve multiple signal arrivals to a sensor array and to estimate their angles-of arrival. In the present work it is shown that the model assumed by Vezzosi implies uncorrelated sources, and that the criterion by which the EV rotation is carried out is based on this implicit assumption. The authors present simulation results demonstrating the behavior of the method in a correlated two-source environment with various magnitudes of correlation coefficient, and they show the dependence of the quality of the estimates on the phase of the correlation coefficient. It is concluded that Vezzosi's method is very effective for resolving uncorrelated arrivals. However, it will encounter problems when the arrivals are partly correlated.<>
{"title":"On the limitation of Vezzosi's subspace rotation method for angle-of-arrival estimation","authors":"F. Haber, Q. Shi","doi":"10.1109/APS.1989.134865","DOIUrl":"https://doi.org/10.1109/APS.1989.134865","url":null,"abstract":"Vezzosi (Ann. des Telecommun., vol.37, p.425-39, Sept. 1982) proposed an eigenvector (EV) rotation method to resolve multiple signal arrivals to a sensor array and to estimate their angles-of arrival. In the present work it is shown that the model assumed by Vezzosi implies uncorrelated sources, and that the criterion by which the EV rotation is carried out is based on this implicit assumption. The authors present simulation results demonstrating the behavior of the method in a correlated two-source environment with various magnitudes of correlation coefficient, and they show the dependence of the quality of the estimates on the phase of the correlation coefficient. It is concluded that Vezzosi's method is very effective for resolving uncorrelated arrivals. However, it will encounter problems when the arrivals are partly correlated.<<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":"87435343","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 computed and measured influences of a radome on both the input impedance and radiation pattern of an electromagnetically coupled dipole are described. The analysis proceeds from the integral equation technique solved by the moment method and associated with the simple one-port model. Return losses S/sub 11/ of electromagnetically coupled dipoles covered and uncovered by a radome are presented. As expected, with a radome a shift in the resonance frequency and also a degradation of the matching take place. Theoretical and experimental data agree within 0.3% for the frequency and 1.4% for the amplitude. Results show that the resonant frequency is shifted, the matching is significantly degraded, and the radiation pattern is not deeply altered.<>
{"title":"Radome effects on an electromagnetically coupled dipole","authors":"M. Gaouyer, J. Floch, J. Citerne","doi":"10.1109/APS.1989.134761","DOIUrl":"https://doi.org/10.1109/APS.1989.134761","url":null,"abstract":"The computed and measured influences of a radome on both the input impedance and radiation pattern of an electromagnetically coupled dipole are described. The analysis proceeds from the integral equation technique solved by the moment method and associated with the simple one-port model. Return losses S/sub 11/ of electromagnetically coupled dipoles covered and uncovered by a radome are presented. As expected, with a radome a shift in the resonance frequency and also a degradation of the matching take place. Theoretical and experimental data agree within 0.3% for the frequency and 1.4% for the amplitude. Results show that the resonant frequency is shifted, the matching is significantly degraded, and the radiation pattern is not deeply altered.<<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":"82662798","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 method is presented which reduces the complex scattering problem of objects buried inside a lossy ground to a simpler one for the solution of the standard magnetic-field integral equation and for determining the field of elementary sources located inside a lossy half-space. The scattering problem is formulated using both the electric-field integral equation and the magnetic-field integral equation unbounded region. Solutions are generated and numerical results are examined for a few limiting cases to confirm their accuracies. The method is then used to generate numerical results for fields at the interface over a buried spheroid.<>
{"title":"Scattering by a buried imperfectly conducting spheroid at low frequencies","authors":"A. Helaly, A. Sebak, L. Shafai","doi":"10.1109/APS.1989.134979","DOIUrl":"https://doi.org/10.1109/APS.1989.134979","url":null,"abstract":"A method is presented which reduces the complex scattering problem of objects buried inside a lossy ground to a simpler one for the solution of the standard magnetic-field integral equation and for determining the field of elementary sources located inside a lossy half-space. The scattering problem is formulated using both the electric-field integral equation and the magnetic-field integral equation unbounded region. Solutions are generated and numerical results are examined for a few limiting cases to confirm their accuracies. The method is then used to generate numerical results for fields at the interface over a buried spheroid.<<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":"89946035","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 shaped reflector antenna, illuminated by a corrugated horn, has been designed, fabricated, and tested. The test results show that the feed blockage and the strut support blockage cause performance degradation. The deficiency can be corrected by using a shaped lens, illuminated by a corrugated horn. The lens antenna avoids both the feed and the strut blockage. The lens surface is shaped to provide a nearly uniform coverage over a +or-90 degrees cone. A good axial ratio at 44 GHz is achieved by designing the corrugated horn with nearly equal E- and H-plane patterns.<>
{"title":"An EHF omnidirectional lens antenna","authors":"E. Lee, Y. Hwang","doi":"10.1109/APS.1989.135034","DOIUrl":"https://doi.org/10.1109/APS.1989.135034","url":null,"abstract":"A shaped reflector antenna, illuminated by a corrugated horn, has been designed, fabricated, and tested. The test results show that the feed blockage and the strut support blockage cause performance degradation. The deficiency can be corrected by using a shaped lens, illuminated by a corrugated horn. The lens antenna avoids both the feed and the strut blockage. The lens surface is shaped to provide a nearly uniform coverage over a +or-90 degrees cone. A good axial ratio at 44 GHz is achieved by designing the corrugated horn with nearly equal E- and H-plane patterns.<<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":"90167816","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}
In order to overcome the limitations of previous methods (the spectral- and spatial-domain methods) for analyzing problems connected with the grounded double-layer (substrate-superstrate) configuration, the authors propose the use of an asymptotic closed-form representation of the spatial Green's function. This approach makes the mutual coupling computation extremely efficient and can be used even for relatively small lateral distances between source and observation points (usually down to a few tenths of the free-space wavelength). Numerical results are presented.<>
{"title":"An asymptotic closed-form representation for the substrate-superstrate Green's function (microstrip antennas)","authors":"M. Marin, P. Pathak","doi":"10.1109/APS.1989.135052","DOIUrl":"https://doi.org/10.1109/APS.1989.135052","url":null,"abstract":"In order to overcome the limitations of previous methods (the spectral- and spatial-domain methods) for analyzing problems connected with the grounded double-layer (substrate-superstrate) configuration, the authors propose the use of an asymptotic closed-form representation of the spatial Green's function. This approach makes the mutual coupling computation extremely efficient and can be used even for relatively small lateral distances between source and observation points (usually down to a few tenths of the free-space wavelength). Numerical results 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":"90362912","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 authors describe the variational and Fourier analyses for gain enhancement and input characteristics of infinite and finite dielectric loaded antennas with an infinite ground plane. They derive the variational expressions for the input characteristics in two cases of dielectric loaded antennas, a waveguide aperture, and a current element or patch excited by a coaxial line.<>
{"title":"Variational analysis for gain enhancement and input characteristics of dielectric loaded antennas","authors":"Y. Sugio, T. Makimoto, T. Tsugawa","doi":"10.1109/APS.1989.134967","DOIUrl":"https://doi.org/10.1109/APS.1989.134967","url":null,"abstract":"The authors describe the variational and Fourier analyses for gain enhancement and input characteristics of infinite and finite dielectric loaded antennas with an infinite ground plane. They derive the variational expressions for the input characteristics in two cases of dielectric loaded antennas, a waveguide aperture, and a current element or patch excited by a coaxial line.<<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":"77190066","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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