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Antennas and Propagation, IEEE Transactions on

Issue 7 • Date July 1988

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  • Experimental studies of magnetically scannable leaky-wave antennas having a corrugated ferrite slab/dielectric layer structure

    Publication Year: 1988 , Page(s): 911 - 917
    Cited by:  Papers (30)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The radiation characteristics of a magnetically scannable leaky-wave antenna using a corrugated ferrite slab supported by a Teflon waveguide have been demonstrated experimentally. A corrugated polycrystalline yttrium iron garnet (YIG) slab having the dimensions 150.0 mm*15.0 mm*10 mm has been fabricated. The corrugation depth, corrugation spacing, and number of corrugations are 150.0 mu m, 2.0 mm, and 55.0, respectively. Experiments have been carried out in the millimeter-wave frequency range from 40.0 to 50.0 GHz. The main beam direction of the leaky wave shifts continuously about 41.0 degrees at the operating frequency 46.8 GHz by altering the DC magnetic field up to 1.4 T. It is found that the corresponding half-power beamwidth varies from 3.2 degrees to 3.6 degrees and a maximum scanning rate is 1.0 degrees /0.02 T. Experimental results are compared with theory based on the dispersion relation of the ferrite slab/dielectric layer structure.<> View full abstract»

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  • Consideration on the measurement of current distribution on bent wire antennas

    Publication Year: 1988 , Page(s): 918 - 926
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (645 KB)  

    As part of the measurement of the current distribution on a bent wire antenna with a shielded loop, the electromotive force (EMF) induced on the loop is theoretically formulated, and the relation between the current distribution and the measured values is investigated. The EMF is expressed as a summation of terms involving the current and the derivative of the current with coefficients depending on the measurement point. The calculated EMF agrees well with the measured value. At points away from the antenna ends and bend, the EMF is proportional to the current, but near the ends and bend the difference between EMF and current increases. It is shown that the current distribution is easily estimated from the measured data. The authors also present the measurement of charge distribution using a small dipole. The expression for the open-circuit voltage of the dipole is formulated and compared with measured values.<> View full abstract»

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  • Analysis of skew antenna around a square tower for UHF TV broadcasting

    Publication Year: 1988 , Page(s): 927 - 935
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    The authors discuss the installation and characteristics of a UHF skew antenna mounted on a tower that already supports seven other VHF arrays used for TV broadcasting. The skew antenna consists of four antenna arrays arranged in a circle with a radius of about 3 m and radiating tangentially. The phase difference between the antenna arrays is 90 degrees . The skew antenna system produces a good omnidirectional pattern, but when located on the tower the reflections from the flat face and the wedge diffractions modify the pattern. The calculation of the horizontal radiation pattern using the geometrical theory of diffraction is compared with the measured pattern. Both the UHF antenna's radiation pattern and its mutual interference are compared with the existing VHF antennas.<> View full abstract»

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  • Design of profiled corrugated horns

    Publication Year: 1988 , Page(s): 936 - 940
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The design principles used to realize smoothly profiled corrugated horns are described. The smooth profiling causes power to be converted to higher order HE/sub 12/ modes which radiate to produce high sidelobes in the copolarization patterns. A computer-aided spherical modal-matching technique is used to study the higher-order mode conversion. The results show good agreement with measurements. A profiled horn using a series of discrete conical sections is proposed to eliminate most of the mode conversion. A horn designed in this way is presented and shown to possess improved performance characteristics in comparison to a smoothly profiled design.<> View full abstract»

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  • The truncation error in the application of sampling series to electromagnetic problems

    Publication Year: 1988 , Page(s): 941 - 949
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB)  

    Truncation error interpolation methods used in the evaluation and representation of scattered fields are discussed. Three main points are considered: the choice of the sampling point lattice: the choice of the type of sampling expansion: and the determination of the number of terms of the sampling series that must be retained to insure a negligible truncation error. The aim is to provide a clear reference frame for the applications which allow the optimal choice for the reconstruction algorithm. The cases of bounded and square integrable band-limited functions are separately dealt with in order to exploit the properties of each method. A general analysis of the multidimensional truncation error is carried out. No particular assumption on the sampling expansion is made, except for that concerning the use of a rectangular sampling lattice. Simple and effective expressions relating the multidimensional error to the corresponding one-dimensional bounds are derived. The one-dimensional error is then analyzed in detail with reference to the most relevant case of central interpolation. By very simple methods, error bounds for all the sampling expansions explicitly considered in the literature are derived in a systematic way. Expressions providing the values of the sampling rate and number of retained samples which minimize the overall computer time and memory requirement are derived. Some numerical examples are presented and briefly discussed.<> View full abstract»

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  • Matrix interpretation of the spectral iteration technique (electromagnetic scattering)

    Publication Year: 1988 , Page(s): 950 - 955
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A matrix interpretation of the spectral iteration technique is presented to illustrate improvements in accuracy and convergence for both transverse magnetic and transverse electric waves incident on two-dimensional homogeneous scatterers producing solutions identical to a method of moments scheme. In this scheme, it is possible to improve the convergence rate of the technique by the use of nonphysical Green's function terms in the extended matrix. These terms result in the generation of a nonphysical field outside the scatterer, while still maintaining the correct solution of the current. Although the problem of nonconvergence has not been entirely overcome, a particular taper method used in the examples provided shows an improvement over their nontapered counterparts.<> View full abstract»

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  • Electromagnetic scattering by pyramidal and wedge absorber

    Publication Year: 1988 , Page(s): 971 - 984
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (798 KB)  

    Electromagnetic scattering from pyramidal and wedge absorbers used to line the walls of modern anechoic chambers is measured and compared with theoretically predicted values. The theoretical performance for various angles of incidence is studied. It is shown that a pyramidal absorber scatters electromagnetic energy more as a random rough surface does. The apparent reflection coefficient from an absorber wall illuminated by a plane wave can be much less than the normal absorber specifications quoted by the manufacturer. For angles near grazing incidence, pyramidal absorbers give a large backscattered field from the pyramid side-faces or edges. The wedge absorber was found to give small backscattered fields for nuclear-grazing incidence. Based on this study, some new guidelines for the design of anechoic chambers are advocated because the specular scattering models used at present do not appear valid for pyramids that are large compared to the wavelength.<> View full abstract»

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  • Scattering from an open spherical shell having a circular aperture and enclosing a concentric dielectric sphere

    Publication Year: 1988 , Page(s): 985 - 999
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (923 KB)  

    The generalized dual series solution is presented for the scattering of an arbitrary plane wave from an open spherical shell having a circular aperture and enclosing a concentric homogeneous dielectric sphere. This solution explicitly exhibits the correct edge behavior, and it can handle spheres that are electrically small or large without special considerations. A variety of cross-section results is presented for the normally incident case. It is shown that effects corresponding to the presence of the interior cavity dominate all of the scattering data. In particular, the cross sections exhibit new resonance features that are due to the cavity-backed nature of the aperture and depend on the characteristics of the interior sphere. The results demonstrate that interior information is contained in the exterior scattering data.<> View full abstract»

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  • Canonical sources and duality in chiral media (antenna arrays)

    Publication Year: 1988 , Page(s): 1007 - 1013
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (614 KB)  

    The authors examine the characteristics of antenna arrays embedded in unbounded chiral media using the Green's dyadic for electric sources and the Green's vector for magnetic sources. The purpose is to bring to light the new characteristics of sources, both point and extended, which interact with this medium and to examine general characteristics of sources located in a medium with handedness. Very simple quality relations are presented that are characteristic of chiral media when the results are written in terms of the circular eigenmodes. Appropriate measures of chirality such as the chirality admittance and impedance and a dimensionless chirality factor are introduced as needed. It is shown that, in the far field, both point and extended sources, whether electric or magnetic, radiate two electromagnetic eigenmodes which are of opposing handedness. Sources that access only one of the eigenmodes of the medium are demonstrated. Several applications of the results and array performance in chiral media are noted.<> View full abstract»

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  • Numerical evaluation of radiation integrals for reflector antenna analysis including a new measure of accuracy

    Publication Year: 1988 , Page(s): 1018 - 1023
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (637 KB)  

    Results are presented for an investigation of popular numerical integration methods applied to the reflector antenna problem. The comparison of methods is facilitated by the introduction of a new figure-of-merit (the p-factor), which is a measure of how far out in pattern-space the results are accurate. The p-factor can also be used to determine how dense a sampling grid is required for a given pattern accuracy. Results of the comparison show that Gauss-Zirnike polynomial integration on the diameter and the trapezoidal rule on the circumference was the most accurate method tested. Somewhat less accurate but still good methods were the Gauss-Legendre/trapezoidal and Gauss-Legendre/Gauss-Legendre methods.<> View full abstract»

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  • Comments on "On the use of metallized cavities in printed slot arrays with dielectric substrates" [with reply]

    Publication Year: 1988 , Page(s): 1036 - 1041
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    Statements concerning a method used in a cited reference in the above named work (ibid., vol.AP-35, no.5, pp.477-87, 1987) are refuted and the method of analysis discussed is clarified. The original author acknowledges the clarification and agrees with the resulting interpretation of the method.<> View full abstract»

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  • Analysis of TE scattering from dielectric cylinders using a multifilament magnetic current model

    Publication Year: 1988 , Page(s): 1026 - 1031
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A moment solution is presented for the problem of transverse electric (TE) scattering from homogeneous dielectric cylinders. The moment solution uses fictitious filamentary magnetic currents to simulate both the field scattered by the cylinder and the field inside the cylinder and in turn point-matches the continuity conditions for the tangential components of the electric and magnetic fields across the cylinder surface. The procedure is simple to execute and is general in that cylinders of arbitrary shape and complex permittivity can be handled effectively. Metallic cylinders are treated as reduced cases of the general procedure. Results are given and compared with available analytic solutions, which demonstrate the very good performance of the procedure View full abstract»

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  • Comparison of lossy wedge diffraction coefficients with application to mixed path propagation loss prediction

    Publication Year: 1988 , Page(s): 1031 - 1034
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    A heuristic lossy wedge diffraction coefficient is compared to the exact Maliuzhinets diffraction coefficient for a 180° wedge neglecting surface waves. The comparison shows good agreement even for high incidence angles and greatly dissimilar wedge-face materials. This agreement provides justification for using the heuristic coefficient for the calculation of mixed path propagation loss, since wedge angles are typically near 180° for this application. The heuristic coefficient has the advantages of being continuous at the reflection boundary and of being relatively simple to evaluate, especially at angles other than 180° View full abstract»

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  • Remarks on `Comments on field equivalence principles' [and reply]

    Publication Year: 1988 , Page(s): 1034 - 1036
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    The commenter asserts that a statement quoted in the above named work (ibid., vol.AP-35, no.2, pp.242-4, 1987) that is said to be incorrect was actually quoted out of context and therefore misunderstood. The statement's validity is demonstrated. In replying, the original author maintains the correctness of his interpretation of the quoted statement View full abstract»

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  • Specular points and critical gimbal angles of ogival radomes

    Publication Year: 1988 , Page(s): 1023 - 1026
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Results on critical gimbal angles of ogival radomes have been presented as a function of fineness ratios and source point locations. It is shown that, for a given source point and reflected ray direction, no more than two specular points generally exist on the radome inner surface. The critical gimbal angle, beyond which reflected rays contribute to geometrical optics fields, is obtained in terms of a turning-point effect. Critical gimbal angles computed are significantly different from previously published results which overlooked the turning-point effect. Special techniques to determine the contribution of specular points near the turning point are briefly discussed. The techniques proposed can be applied to rotationally symmetric geometries other than ogives View full abstract»

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  • Improving numerical accuracy by iteration; application to computing spherical wave coefficients

    Publication Year: 1988 , Page(s): 1041 - 1043
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    It is known that numerical errors can be dramatically reduced by simply iterating the original solution. It is shown that this technique can be applied to reduce quadrature errors when evaluating orthogonality integrals. This technique can be applied to any numerical problem where a residual error can be computed. The author demonstrates its use in an algorithm for computing spherical wave coefficients from orthogonality integrals View full abstract»

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  • Beam deviations of large linear arrays due to wavy phase errors

    Publication Year: 1988 , Page(s): 1014 - 1018
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Beam deviations occurring when wavy phase errors are introduced into the aperture of an antenna are treated. As the antenna becomes large, the probability of introduction of such types of phase error increases and beam deviations become a problem. A basic formula that permits the evaluation of beam deviations due to small phase errors is presented and applied to derive, in a general form, expressions for beam deviations which would occur when sinusoidal or rn type phase error arises along a line source where r is a normalized distance and n is zero or a positive integer. Numerical examples show that sinusoidal phase errors often cause comparatively large beam deviations (relative to linear phase gradients), even for tapered illuminations View full abstract»

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  • Microwave reflection properties of a rotating corrugated metallic plate used as a reflection modulator

    Publication Year: 1988 , Page(s): 1000 - 1006
    Cited by:  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The performance of a simple microwave modulating retro-reflector based on a rotating corrugated metallic plate is analyzed theoretically and compared with laboratory measurements. Fields within the corrugations are described by waveguide modes and free-space fields by Floquet modes. The periodicity of the grooves is represented through the reciprocal lattice corresponding to the periodic structure. The accuracy of the calculation is analyzed as a function of the number of modes used to describe the electromagnetic field. Graphs are given for the design of a modulator for any wavelength View full abstract»

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  • A leaky-wave analysis of the high-gain printed antenna configuration

    Publication Year: 1988 , Page(s): 905 - 910
    Cited by:  Papers (107)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A leaky-wave analysis is used to explain the narrow-beam resonance-gain phenomenon in which narrow beams may be produced from a printed antenna element in a substrate-superstrate geometry. It is demonstrated that the phenomenon is attributable to the presence of both transverse electric and transverse magnetic-mode leaky waves, that are excited on the structure. Asymptotic formulas for the leaky wave are compared with the exact patterns to demonstrate the dominant role of the leaky waves in determining the pattern. Results are presented as a function of frequency, the scan angle, and the permittivity of the superstrate View full abstract»

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  • Electromagnetic diffraction of an obliquely incident plane wave field by a wedge with impedance faces

    Publication Year: 1988 , Page(s): 956 - 970
    Cited by:  Papers (39)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    A uniform asymptotic solution is presented for the electromagnetic diffraction by a wedge with impedance faces and with included angles equal to 0 (half-plane), π/2 (right-angled wedge), π (two-part plane) and 3π/2 (right-angled wedge). The incident field is a plane wave of arbitrary polarization, obliquely incident to the axis of the wedge. The formal solution, which is expressed in terms of an integral, was obtained by the generalized reflection method. A careful study of the singularities of the integrand is made before the asymptotic evaluation of the integral is carried out. The asymptotic evaluation of the integral is performed taking into account the presence of the surface wave poles in addition to the geometrical optics poles near the saddle points. This results in a uniform solution which is continuous acros the shadow boundaries of the geometrical optics fields as well as the surface wave fields View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung