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Antennas and Propagation, IEEE Transactions on

Issue 2 • Date Feb. 1989

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Displaying Results 1 - 21 of 21
  • Analysis of the cylindrical-rectangular patch antenna

    Publication Year: 1989 , Page(s): 143 - 147
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB)  

    An analysis is presented of a thin cylindrical-rectangular microstrip patch antenna. After obtaining the electric field under the curved patch and the resonant frequencies using the cavity model, the far-field is found by considering the equivalent magnetic current radiating in the presence of a cylindrical surface. The input impedance and the total Q-factor are then calculated. Numerical and graphical results are presented to illustrate the effect of curvature on the characteristics of the TM/sub 10/ and TM/sub 01/ modes.<> View full abstract»

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  • Multiport network approach for modeling the mutual coupling effects in microstrip patch antennas and arrays

    Publication Year: 1989 , Page(s): 148 - 152
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A method is described for representing the mutual coupling between edges of a microstrip patch (or the edges of two different patches in an array) in form of a mutual admittance matrix. Coefficients of the mutual admittance matrix are evaluated by modelling the edge fields by equivalent magnetic current line sources. The formulation is an extension of the multiport network modeling of microstrip patches and the segmentation method of analysis. Results are found to be in good agreement with the measured data on mutual coupling available in the literature. Relative contributions of various edges of rectangular patches to the mutual coupling are discussed.<> View full abstract»

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  • A microstrip array feed for land mobile satellite reflector antennas

    Publication Year: 1989 , Page(s): 153 - 158
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (715 KB)  

    A circularly polarized feed array for a spacecraft reflector antenna is described that was constructed by using linearly polarized microstrip elements. The array has seven subarrays which form a single cluster as part of a large overlapping cluster reflector feed array. Each of the seven subarrays consists of four linearly polarized microstrip elements. The array achieved a better than 0.8-dB axial ratio at the array pattern peak and better then 3 dB antenna gain to 20 degrees from the peak, across a 7.5% frequency bandwidth. A teardrop-shaped feed probe was used to achieve wideband input impedance matching for the relatively thick microstrip substrate. The low impedance and axial ratio bandwidths were achieved using a relatively thick honeycomb substrate with the impedance-matching feed probes.<> View full abstract»

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  • Integral equation analysis of radiating structures of revolution

    Publication Year: 1989 , Page(s): 159 - 170
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (903 KB)  

    A methods for solving radiation problems involving structures of revolution is presented that is based on the direct solutions of one-dimensional integral equations for the currents. The kernels of these equations are derived explicitly and their singularities are studied. Efficient methods for their computation are presented. The numerical solution is obtained by a method of moments technique using sinusoidal basis functions. Applications include the determination of the current densities, reflection coefficient, and far-field patterns for several waveguide-fed structures. Numerical checks and comparisons with experiment demonstrate the accuracy of the method.<> View full abstract»

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  • Measurements of very low-sidelobe conical horn antennas

    Publication Year: 1989 , Page(s): 171 - 177
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB)  

    A description is given of conical corrugated-horn antennas that were designed for millimeter-wave radiometers with a 7 degrees field of view, namely the Differential Microwave Radiometers (DMRs) that will measure the large-angular-scale anisotropy of the cosmic background radiation that is generally thought to be the remnant of the primeval explosion, the Big Bang. The DMRs will be part of the Cosmic Background Explorer (COBE) satellite. Measured test results for three radiometers at 31.4, 53, and 90 GHz are reported along with those of a circular polarization orthomode transducer designed and characterized at 31.4 GHz. The measurement techniques and facilities are described, including an outdoor far-field facility where measurements down to levels 90 dB below the main beam maximum were achieved. The goal of achieving very low-sidelobe antennas with good symmetry has been demonstrated.<> View full abstract»

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  • A K-space method of moments solution for the aperture electromagnetic fields of a circular cylindrical waveguide radiating into an anisotropic dielectric half-space

    Publication Year: 1989 , Page(s): 187 - 193
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB)  

    A method of moments solution is presented for the problem of determining the electromagnetic aperture fields that occur when a circular cylindrical waveguide radiates into an anisotropic dielectric-covered ground plane. The method of moments solution is derived by using a reaction matching technique and by using K-space theory to develop the aperture matrix elements of the system. An example of radiation into an anisotropic dielectric is given. The anisotropic dielectric for this example is assumed to be formed by the presence of a static magnetic field placed within a plasma.<> View full abstract»

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  • Shooting and bouncing rays: calculating the RCS of an arbitrarily shaped cavity

    Publication Year: 1989 , Page(s): 194 - 205
    Cited by:  Papers (205)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (743 KB)  

    A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration: (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed.<> View full abstract»

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  • High-frequency scattering from a wedge with impedance faces illuminated by a line source. I. Diffraction

    Publication Year: 1989 , Page(s): 212 - 218
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (527 KB)  

    The canonical problem of evaluating the scattered field at a finite distance from the edge of an impedance wedge which is illuminated by a line source is considered. The presentation of the results is divided into two parts. In this first part, reciprocity and superposition of plane wave spectra are applied to the left far-field response of the wedge to a plane wave, to obtain exact expression for the diffracted field and the surface wave contributions. In addition, a high-frequency solution is given for the diffracted field contribution. Its expression, derived via a rigorous asymptotic procedure, has the same structure as that of the uniform geometrical theory of diffraction (UTD) solution for the field diffracted by a perfectly conducting wedge. This solution for the diffracted field explicitly exhibits reciprocity with respect to the direction of incidence and scattering.<> View full abstract»

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  • Scattering from composite materials: a first-order model

    Publication Year: 1989 , Page(s): 219 - 228
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB)  

    The nonspecular electromagnetic scattering from finite composite laminates is investigated. The composite material is modeled as planar lamina composed of undirectional collimated fibers with regular spacings between the elements. The fibers, perfectly or partially conductive, are assumed to be embedded in a resin matrix translucent to electromagnetic radiation. For the partially conductive case, the Schelkunoff Ansatz is used. The case of two-plied laminates with skewed fiber orientation is discussed. The mathematical formulation is based on the electric-field integral equation solved with an entire-domain Galerkin expansion. Results are obtained for laminates with both finite and infinite numbers of elements. For the latter, the Floquet-Galerkin solution for periodic structures is used. The effect of truncation of the panels is discussed for arbitrary angles of illumination. It is shown that in many cases implementation of the Floquet-Galerkin solution using diagonal system matrices yields accurate results for the nonspecular cross sections of the laminates. The theoretical results are confirmed by experimental data.<> View full abstract»

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  • Generalized pencil-of-function method for extracting poles of an EM system from its transient response

    Publication Year: 1989 , Page(s): 229 - 234
    Cited by:  Papers (263)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (430 KB)  

    A generalized pencil-of-function (GPOF) method is developed for extracting the poles of an electromagnetic system from its transient response. The GPOF method needs the solution of a generalized eigenvalue problem to find the poles. Subspace decomposition is also used to optimize the performance of the GPOF method. The GPOF method has advantages over the Prony method in both computation and noise sensitivity, and approaches the Cramer-Rao bound when the signal-to-noise ratio (SNR) is above threshold. An application of the GPOF method to a thin-wire target is presented.<> View full abstract»

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  • Impedance control of microstrip antennas using reactive loading

    Publication Year: 1989 , Page(s): 247 - 251
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (331 KB)  

    It is shown that it is possible to change the input impedance of a microstrip antenna over a wide range without affecting its resonant frequency by moving short circuits along prescribed loci. This theory has been verified by experiment; specifically, it is shown that the resonant frequency of the mode is left relatively unchanged by the appropriate placement of the short circuit loads. The experiment also shows that the agreement between the predicted and observed input impedance is quite reasonable in most cases. There was qualitative agreement between theoretical antenna patterns and measured antenna patterns although the measured cross-polarized components in the double-loaded element were higher than expected from the theory. A single load, varying in position, was seen to provide a reasonable range of impedance variation while retaining a very nearly constant resonant frequency, although the resulting asymmetries in the magnetic current distribution caused a high level of cross-polarized fields. The use of two loads, instead, produced an even greater range of possible impedances, with reduced cross-polarization levels as well.<> View full abstract»

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  • Improved numerical solution of Ott's integral equation for HF ground wave attenuation

    Publication Year: 1989 , Page(s): 260 - 262
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    An alternative solution is presented for Ott's (1970) integral equation for the attenuation of a high-frequency vertically polarized radio signal propagating over rough inhomogeneous terrain. The method circumvents the numerical stability occurring with an earlier method at steep slopes and/or high radar frequencies. The method is illustrated by application to a steep profile at 20.08 MHz. The obtained values for the attenuation function agree well with experimental measurements.<> View full abstract»

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  • Moist-air attenuation at 96 GHz over a 21-km line-of-sight path

    Publication Year: 1989 , Page(s): 262 - 266
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (282 KB)  

    A propagation experiment at 96 GHz over a line-of-sight (LOS) path provided data on attenuation characteristics of atmospheric water vapor. Two consecutive time periods (three days in May and 1.5 days in August 1986) with a total of about 100 h of data on signal level and meteorological conditions were analyzed with respect to absolute humidity (3-21 g/m/sup 3/) and temperature (4-32 degrees C) variations. Experimental details, the data analysis, and a comparison with model predictions are discussed. The validity of the millimeter-wave propagation model is considered and it is concluded that the field experiment tends to uphold the validity of this model at 96 GHz.<> View full abstract»

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  • A heuristic UTD slope diffraction coefficient for rough lossy wedges

    Publication Year: 1989 , Page(s): 206 - 211
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Heuristic wedge diffraction coefficients for computing propagation path loss over finitely conducting earth are extended to include slope diffraction, with the assumption that propagation of energy through the wedge is negligible. The slope diffraction terms for the lossy wedge are obtained in an analogous manner as for the perfectly conducting case, except that special care must be taken with the factor multiplying the incident field for grazing incidence. Results given show that the slope diffraction term produces continuous results that behave reasonably when compared with results for perfectly conducting wedges View full abstract»

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  • The mode features of an ideal-gap open-ring microstrip antenna

    Publication Year: 1989 , Page(s): 137 - 142
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A rigorous analysis of the features of the modes of an ideal-gap open-ring (closed ring with a cross cut) printed microstrip antenna is presented. General expressions for its radiation field are derived by using the cavity model, trigonometric identities, and the properties of the cylindrical functions. The solution and the computed results for the radiation patterns and the field distributions for the even and odd modes are presented. The solutions for the even modes are the same as those for the closed-ring printed microstrip antenna. The results for the radiation patterns and other antenna characteristics for the odd modes indicate the superiority in the radiation properties of the ideal-gap open ring when excited in the TM12 mode over those of a closed ring View full abstract»

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  • Radiation pattern of an offset hyperbolic reflector

    Publication Year: 1989 , Page(s): 251 - 253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    The radiation pattern of a focus-fed offset hyperbolic reflector is determined by using the uniform geometrical theory of diffraction (UTD) and the uniform asymptotic theory of diffraction (UAT). The patterns predicted by these two theories are observed to differ considerably around incident and reflection boundaries. The effects of the slope diffraction as well as those of additional terms in the improved UTD solution are ignored View full abstract»

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  • Scattering by finite, open cylinders using approximate boundary conditions

    Publication Year: 1989 , Page(s): 253 - 257
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Simplified integral equation formulations for electromagnetic scattering from finite, open, circular cylinders are developed by invoking approximate boundary conditions. The approximate calculations are compared to calculational results of formulations based on exact boundary conditions. It is shown that the approximations work quite well despite the curved edges of the cylinders View full abstract»

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  • Polarization effects in microwave diversity imaging of perfectly conducting cylinders

    Publication Year: 1989 , Page(s): 235 - 244
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A theoretical vector development is derived for the directly and mutually scattered wavefield of two cylinders in a bistatic measuring system. The approach is first to give an expression for the field scattered from a single cylinder illuminated by a right-hand circularly polarized plane wave. This expression is then extended to the case of the directly scattered (or first-order) field of two cylinders. The mutually scattered (or second-order) field of two cylinders is then formulated in terms of a coherent summation of the scattered field from each cylinder due to the incident wave scattered from the other cylinder. In order to simplify computational tasks, only the second-order scattered field is analytically derived; this is called the mutually scattered field. The total wavefield scattered by two cylinders becomes the coherent superposition of the directly scattered component and the mutually scattered component for each polarization. The use of an automated microwave imaging facility employing frequency, polarization and angular diversity to verify the results of theoretical analysis is described. The analytical and experimental results are shown to be in good agreement. The results show that the effects of polarization state transformation or change in the mutually scattered field component are more pronounced than in the directly scattered component View full abstract»

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  • Supergain antennas and the Yagi and circular arrays

    Publication Year: 1989 , Page(s): 178 - 186
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    The characteristics of endfire, Yagi, and circular arrays of dipoles are reviewed with special reference to their directional properties and the possibility of supergain. The quantum-mechanical analog that suggested the investigation is described. The critical newly emphasized feature is the high-Q property of a correctly designed closed loop of coplanar dipoles when only one element is driven and all dimensions (the length of the elements, their cross-sectional size and shape, the number of elements, and the circumference of the closed loop array) are correctly chosen so that the entire array is adjusted to resonance. An immediate application to beam scanning is described View full abstract»

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  • Radar cross-section effects relating to a horn antenna

    Publication Year: 1989 , Page(s): 257 - 260
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Practical vector network analyzer measurements were made to identify the antenna mode component of a wide-bandwidth horn antenna. It was found that the addition of a 24-in transmission line with various load terminations results in data in which the antenna mode and structural mode can be separated View full abstract»

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  • On the resonant frequencies of microstrip antennas

    Publication Year: 1989 , Page(s): 245 - 247
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    An appropriately corrected formula for the resonant frequencies of microstrip antenna elements is obtained that is based on the evaluation of the average value of the effective dielectric constant. The author describes the integration averaging technique and presents two examples of its use in more accurately calculating the resonant frequencies of the first five modes of an equilateral triangular microstrip antenna 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