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Antennas and Propagation, IEEE Transactions on

Issue 7 • Date Jul 1990

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Displaying Results 1 - 25 of 30
  • Resistively loaded loop as a pulse-receiving antenna

    Publication Year: 1990 , Page(s): 1123 - 1126
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    The impedance-loaded loop antenna is theoretically analyzed in steady state using the Fourier series expansion technique. An expression is derived for the receiving transfer function or sensitivity. An equivalent circuit for the receiving antenna is presented. Numerical results are provided to illustrate the dependence of sensitivity on frequency, loop radius, distributed resistance, and incident wave direction. The time-domain receiving response of a resistively loaded loop antenna is calculated for Gaussian and differentiated-Gaussian incident wave pulses, and the numerical results are discussed View full abstract»

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  • Efficient evaluation of spectral integrals in the moment method solution of microstrip antennas and circuits

    Publication Year: 1990 , Page(s): 1127 - 1130
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A numerical algorithm for the moment method solution of printed circuit antenna problems is developed. The formulation uses a spectral domain approach. However, the integration variables are in the Cartesian instead of the polar coordinate system. This numerical scheme separates the integration involving the longitudinal and the transverse dependence of the basis functions. This aspect may reduce the computation effort drastically. The approach is found to be very efficient and easy to use, and is suitable for a variety of basis functions including mixed-type basis function sets View full abstract»

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  • Electromagnetic complex source pulsed beam fields

    Publication Year: 1990 , Page(s): 957 - 963
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Vector electromagnetic pulsed beam fields are constructed by using current dipoles located at complex coordinate points. As in the scalar case, the direction, collimation, and directivity of the field are determined essentially by the imaginary displacement of the source coordinate. The vector fields also depend on the polarization of the dipole with respect to the beam axis. The properties of the field for two special cases in which the dipole is directed either along or transverse to the beam axis are examined analytically and numerically. The general polarization case is thereby considered as a superposition of these two special cases. As expected, the strongest radiation is achieved when the dipole is directed transverse to the beam axis View full abstract»

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  • Accurate computation of the radiation from simple antennas using the finite-difference time-domain method

    Publication Year: 1990 , Page(s): 1059 - 1068
    Cited by:  Papers (103)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    Two antennas are considered, a cylindrical monopole and a conical monopole. Both are driven through an image plane from a coaxial transmission line. Each of these antennas corresponds to a well-posed theoretical electromagnetic boundary value problem and a realizable experimental model. These antennas are analyzed by a straightforward application of the finite-difference-time-domain (FD-TD) method. The computed results for these antennas are shown to be in excellent agreement with accurate experimental measurements for both the time domain and the frequency domain. The graphical displays presented for the transient near-zone and far-zone radiation from these antennas provide physical insight into the radiation process View full abstract»

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  • Maximum likelihood localization of diversely polarized sources by simulated annealing

    Publication Year: 1990 , Page(s): 1111 - 1114
    Cited by:  Papers (40)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The maximum likelihood estimator of the angle-of-arrival of sources having diverse polarization is derived and computed via the simulated annealing optimization technique. The estimator is applicable equally well to the case of coherent signals appearing, for example, in multipath propagation problems and to the case of a single snapshot. Simulation results that demonstrate the performance of the algorithm are included View full abstract»

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  • Computation of monopole antenna currents using cylindrical harmonics

    Publication Year: 1990 , Page(s): 1130 - 1133
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A novel method for computing the input impedance and induced currents on cylindrical antenna structures is investigated. This technique considers the antenna when placed between two parallel ground planes, thus allowing the use of cylindrical harmonic Fourier expansions to represent the fields. Enforcement of boundary and continuity conditions on the tangential field components results in solutions for the discrete spectral coefficients of these expansions. Convergence is discussed and computational validations are presented for varied cases View full abstract»

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  • Polarization correction and extension of the Kennaugh-Cosgriff target-ramp response equation to the bistatic case and applications to electromagnetic inverse scattering

    Publication Year: 1990 , Page(s): 964 - 972
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    An analytical time-domain expression derived by Kennaugh (1967) for the early time impulse response for smooth, convex, perfectly conducting scatterers under the physical optics approximation for the bistatic case is reinterpreted. The physical optics bistatic early time impulse responses can be interpreted as cross-sectional areas of the scatterer. A crude polarization correction to the leading edge of the physical optics impulse response is obtained for the bistatic case, leading to a simple asymptotic relation between the specular principal curvature difference and certain co-polarized phase terms in the bistatic scattering matrix. Applications to direct scattering are discussed. Profile reconstruction from bistatic data with a priori knowledge of the validity range of physical optics in the time domain is proposed and tested with the sphere View full abstract»

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  • The magnetically coated conducting surface as a dual conductor and its application to antennas and microwaves

    Publication Year: 1990 , Page(s): 1069 - 1077
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    An electric conducting surface coated with a thin, lossy magnetic layer has been both theoretically and experimentally observed to be equivalent to a surface that is conducting to both electric and magnetic fields of plane waves at near-grazing incidence angles. This dual conductivity phenomenon has been utilized to design horn antennas for desired performance characteristics such as symmetric beams, low sidelobes, and low cross polarization. The effects of this surface are in many ways similar to those of the corrugated conducting surface. However, this coated surface appears to have a broader spectrum of applications in other antennas and microwave devices because of its apparent dual (electric and magnetic) conductivity View full abstract»

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  • Natural resonances of conducting bodies of revolution

    Publication Year: 1990 , Page(s): 1133 - 1136
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The complex plane natural resonances for several perfectly conducting bodies of revolution (sphere, right circular cylinder, prolate spheroid, and circular disk) are calculated using electric, magnetic, and combined field integral equation formulations (EFIE, HFIE, and CFIE, respectively). These results are compared with some recently published values, and numerical discrepancies are noted and discussed View full abstract»

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  • Guidelines for design of electromagnetically coupled microstrip patch antennas on two-layer substrates

    Publication Year: 1990 , Page(s): 1136 - 1140
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Graphical guidelines for design of electromagnetically coupled square and circular microstrip antennas are given. Substrates composed of two different dielectric layers are considered. The analysis is extended to electrically thick substrates. Given the required resonant frequency and the bandwidth, material parameters are selected. Patch dimension and the optimal position of the feed line are obtained from the provided graphs. The design data were computed by applying the method of moments in the spectral domain to solve the integral equation for the currents on the patch and portion of the microstrip feed line. The integral equation was formulated using the appropriate dyadic Green function for the grounded multilayered slab View full abstract»

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  • Fan beam generated by a linear-array fed parabolic reflector

    Publication Year: 1990 , Page(s): 1046 - 1053
    Cited by:  Papers (9)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The theoretical background and the results of computer simulations and experimental studies for a parabolic reflector fed by a linear array are detailed. The concept of using a parabolic reflector antenna fed by a small linear array to generate fan-beam patterns is validated. Large angle scan along the broad-beam direction of the fan beam can be achieved by offsetting the linear array laterally. It is both empirically and numerically demonstrated that the array feed must be displaced in the reflector's axial direction to an optimum location from the focal plane in order to achieve the best antenna gain performance. As a result, the linear-array fed parabolic reflector can be used in place of a long planar array in a multifunctional reflector antenna system View full abstract»

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  • Analysis of higher order regular polygonal loop antennas

    Publication Year: 1990 , Page(s): 1114 - 1117
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Higher order regular polygonal loop antennas are analyzed. The input impedance of higher order antennas varies gradually when the operating frequency or the order of polygon changes. This behavior of input impedance provides a wide range of input impedance and many resonant points to antenna designers. The higher order regular polygonal loop antenna generally possesses higher directivity but poorer broadband impedance property. As the operating frequency becomes higher its directivity increases remarkably and the broadband property becomes more prominent. To achieve the desired properties one may select one of the many design data sets with a trade-off between broadband property and directivity View full abstract»

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  • Dielectric-covered waveguide longitudinal slots with finite wall thickness

    Publication Year: 1990 , Page(s): 1039 - 1045
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    An accurate method for analyzing dielectric covered waveguide slot arrays with nonzero wall thickness is presented. The method is based on an integral equation formulation which results in the evaluation of the slot's parameters such as self-admittance and resonant frequency. This formulation is supplemented by a simple model to correct for the resonant frequency shift caused by the finite thickness of the walls. Results derived using the above method are compared to available experimental data and are in excellent agreement View full abstract»

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  • On the application of the Sommerfeld representation in a two-dimensional rotationally invariant anisotropic medium

    Publication Year: 1990 , Page(s): 1028 - 1034
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A.J.W. Sommerfeld's (1959) bundle of rays field representation is applied in a fictitious two-dimensional isotropic space that is mapped into a real rotationally invariant anisotropic region via a polarization-dependent coordinate transformation selected so as to obtain a field solution in the anisotropic region. Two elementary transformations are found, and the resulting representations (in the form of a modal angular spectrum or in terms of nonperiodic anisotropic ray bundles of complex trajectories) are analyzed. Field singularities are encountered and discussed in the context of their relation to the isotropic space rays. As an application, the solution to the canonical scattering problem of an anisotropically coated (ten material parameters, five for each polarization) circular cylinder is presented. Only H polarization is treated explicitly since the other (E) is obtainable via duality View full abstract»

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  • Analysis of near-field Cassegrain reflector: plane wave versus element-by-element approach

    Publication Year: 1990 , Page(s): 1010 - 1017
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    A near-field Cassegrain reflector (NFCR) is an effective way to magnify a small phased array into a much larger aperture antenna for limited scan applications. Traditionally the pattern wave approach, i.e. the field from the feed array incident on the subreflector is approximated by a truncated collimated beam with planar phase and tapered amplitude distribution. This approach simplifies the computation tremendously, but fails to provide design information about the most critical component of the whole antenna system, namely, the feed array. With the help of today's computers, it is now feasible to calculate the pattern of a NFCR by a more exact element-by-element approach. Each element in the feed array is considered individually and the diffraction pattern from the subreflector is calculated by the geometrical theory of diffraction (GTD). The field contributions from all elements are superimposed at the curved main reflector surface, and a physical optics integration is performed to obtain the secondary pattern View full abstract»

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  • Performance analysis of structured gradient algorithm [antenna array processing]

    Publication Year: 1990 , Page(s): 1078 - 1083
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The structured gradient algorithm uses a structured estimate of the array correlation matrix to estimate the gradient required for the constrained least mean square algorithm. This structure reflects the structure of the exact array correlation matrix for an equispaced linear array and is obtained by spatial averaging of the elements of the noisy correlation matrix. In its standard form the LMS algorithm does not exploit the structure of the array correlation matrix. The gradient is estimated by multiplying the array output with the receiver outputs. An analysis of the two algorithms is presented to show that the covariance of the gradient estimated by the structured method is less sensitive to the look direction signal than that estimated by the standard method. The effect of the number of elements on the signal sensitivity of the two algorithms is studied View full abstract»

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  • Scattering by a narrow gap

    Publication Year: 1990 , Page(s): 1102 - 1110
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    For a plane wave incident on a cavity-backed gap in a perfectly conducting plane, the coupled integral equations for the induced currents have been solved numerically and the far-field scattering computed. The results are compared with a quasi-analytic solution previously derived. For a narrow gap the agreement is excellent for all cavity geometries and for all material fillings that have been tested View full abstract»

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  • Characteristics of the cylindrical-circular patch antenna

    Publication Year: 1990 , Page(s): 1119 - 1123
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    An analysis of a thin cylindrical-circular microstrip patch antenna is presented. Using the cavity model as a base, formulas are obtained for the far-zone electric field and the input impedance of a coax-fed patch. Numerical and graphical results are given to illustrate the effects of curvature on the characteristics of the TM11 mode View full abstract»

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  • Analysis of reflector antenna systems with arbitrary feed arrays using primary field superposition

    Publication Year: 1990 , Page(s): 994 - 1000
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    In contrast to secondary pattern superposition, where the fields reflected from the main reflector arising from each element are superimposed in the far field of the reflector, the approach presented here sums the primary fields at the reflector surface before the physical optics radiation integral is performed. The method allows each feed array element to have arbitrary position, orientation, pattern, and excitation (magnitude and phase). In addition, it is inherently efficient because evaluation of only one time-consuming radiation integral is required, rather than one per feed element as in secondary superposition. The method allows for accurate calculation of the power radiated from the feed, permitting the reflector gain and spillover efficiency to be determined within the context of a single computer program. The accuracies and characteristics of this method are demonstrated with several examples View full abstract»

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  • Optical techniques for reconfiguring microwave phased arrays

    Publication Year: 1990 , Page(s): 1054 - 1058
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Very large phased array antennas, particularly in radar and adaptive receive applications as opposed to communications usages, require large amounts of digital data processing for beamsteering, null-formation, imaging, and signal correlation computations. Such processing requires a computational capability which is effectively proportional to the square of the antenna size, and can readily become one of the main design drivers. This processing bottleneck problem is addressed for large phased array antennas. An approach in terms of parallel processing in the optical domain is presented as a potential solution. The defining equations for a phased array antenna system are given, along with the transfer functions for an embedded optical spatial filter control element. Such a control element is shown to have the potential of rapidly reconfiguring a large phased array antenna without the speed penalties associated with conventional sequential addressing methods. A hypothetical phased array antenna, with optical spatial filter control elements, is simulated in a computer model and performance results are presented View full abstract»

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  • Using half-plane solutions in the context of MM for analyzing large flat structures with or without resistive loadings

    Publication Year: 1990 , Page(s): 1001 - 1009
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The size of the scatterers that can be analyzed using the conventional method of moments (MM) is limited to only a few wavelengths, due to large storage requirements in the computer. One way to circumvent this problem is to use techniques that temper the growth in the size of the impedance matrix to a reasonable level even as the scatterer becomes large in terms of the wavelength. It is shown that this can be done by choosing an appropriate set of entire or semi-entire domain basis functions that incorporate the actual physics of the scattering phenomenon. The functional forms of the basis functions are obtained either from an exact or an asymptotic solution to certain canonical problems. As an example, the problems of scattering from perfectly conducting or resistively loaded flat strips and plates are solved by utilizing the exact or asymptotic solutions to half-plane problems as basis functions View full abstract»

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  • Strong fluctuation theory equations for electric field second moments in anisotropic media

    Publication Year: 1990 , Page(s): 1099 - 1101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    Three different exact wave equations are derived for the second moment of the electric field in a random anisotropic medium using strong fluctuation theory. Approximate equations that may be used for practical computations are derived from the exact equations View full abstract»

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  • Resistive tapers that place nulls in the scattering patterns of strips

    Publication Year: 1990 , Page(s): 1117 - 1119
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Tapering the resistivity on the surface of an object modifies the scattering patterns of that object. For instance, gradually tapering the resistivity on a strip, half-plane, or an antenna ground plane reduces the edge effects of that surface. Greater control over the sidelobe response of the scattering pattern of a strip is possible by relating the resistive taper to a low sidelobe taper via physical optics. The idea of relating antenna aperture tapers to scattering patterns is extended to placing nulls in the sidelobes of scattering patterns of strips. A resistive taper for placing nulls is found by solving the scattering integral equations of a resistive strip for the resistivity, then substituting the desired nulling current density taper into the appropriate equation and solving for the resistive taper. This method is capable of placing multiple nulls in the bistatic scattering pattern or a single null in the backscattering pattern View full abstract»

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  • Satellite path diversity reception at 11.4 GHz: direct measurements, radar observations, and model predictions

    Publication Year: 1990 , Page(s): 1035 - 1038
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Two-site diversity gain measurements made with a pair of 11.4 GHz satellite beacon receivers are compared to predictions based on dual-polarized radar reflectivity data and to values calculated from the Hodge model. All three agree closely. Examinations of data for a third path synthesized from radar data alone indicate that baseline orientation has a negligible effect on diversity gain View full abstract»

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  • Long rectangular patch antenna with a single feed

    Publication Year: 1990 , Page(s): 987 - 993
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Radiation characteristics of a long rectangular patch antenna excited by a single feed are investigated. The equivalent circuit of the patch including the feed line section is developed. It is found theoretically that a single feed long rectangular patch supports a leaky traveling wave along the length of the patch. The complex propagation constant of the traveling wave is estimated by solving the wave equation with impedance boundary conditions. Radiation patterns of the antenna are obtained using the principle of equivalence. Various radiation characteristics of center-fed and end-fed long patch antennas are presented 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