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Antennas and Propagation, IEEE Transactions on

Issue 6 • Date Jun 1990

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Displaying Results 1 - 25 of 28
  • Reflector spillover loss of an open-ended rectangular and circular waveguide feed

    Publication Year: 1990 , Page(s): 940 - 942
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    An important and frequently used parameter in the design of a feed for a reflector antenna is the spillover loss. A set of spillover curves is presented for several common feeds, namely circular waveguides with TE11 or TE21 excitations, rectangular guides for the monopulse application, etc. The difference between two common methods of normalizing the feed input power is also discussed View full abstract»

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  • Impedance characteristics of circular microstrip patches

    Publication Year: 1990 , Page(s): 942 - 946
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Effects of the feed probe an the size of the ground plane on the resonant frequency as well as the input impedance of a microstrip patch antenna are investigated. Measured data are provided for the first few modes. A method for cancellation of the unwanted modes is proposed and examined View full abstract»

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  • A method to design blended rolled edges for compact range reflectors

    Publication Year: 1990 , Page(s): 853 - 861
    Cited by:  Papers (15)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    A method to design blended rolled edges for compact range reflectors with arbitrary rim shape is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled parameters is also presented. The procedure leads to blended rolled edges that minimize the diffracted field emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system View full abstract»

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  • Pattern measurements of reflector antennas in the compact range and validation with computer code simulation

    Publication Year: 1990 , Page(s): 889 - 895
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described View full abstract»

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  • A simple dual-band corrugated horn with low cross polarization

    Publication Year: 1990 , Page(s): 946 - 951
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    A simplified design for dual-band corrugated conical horns with low cross-polarization characteristics is discussed. Measured results of the breadboard horn show that cross-polar levels of better than -34 dB and return loss of better than 28 dB have been realized over the designed frequency bands. It is shown that the performance of the single-depth corrugated horn can be optimized to give low cross-polarization fields over a 40% frequency bandwidth. Cross-polar levels on the order of -34 dB and return loss of better than 28 dB have been realized for the breadboard horn. The designed horn has potential application in direct-broadcast satellite antennas operating in the 12 and 17.5 GHz frequencies View full abstract»

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  • Calibration of the CCRS airborne scatterometers

    Publication Year: 1990 , Page(s): 903 - 918
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1336 KB)  

    A series of experiments and associated analyses which were designed to lead to an end-to-end calibration of the Canada Centre for Remote Sensing (CCRS) fanbeam scatterometers are described. The method followed was originally introduced in 1984 by A. Yizhar et al. for the Ku-band scatterometer at one incidence angle. This work was extended to yield a full calibration for the Ku-band and C -band scatterometers over the complete range of incidence angles accessible to the instruments. An array of 12 trihedral corner reflectors was deployed in a grassy field near Ottawa. The CCRS CV-580, equipped with two scatterometers, repeatedly overflew the array collecting radar replicas of the targets proportional to the unknown two-dimensional antenna pattern. Data from inertial navigation systems and aerial photographs from a Wild RC-10 mapping camera were used to determine the exact track of the aircraft during the acquisition. This data, with a field survey, alloyed the reduction of the scatterometer data from the reflector array to yield the unknown antenna pattern of the instruments. The cross-polarized antenna patterns were then deduced from the like-polarized results. The results show consistency within 0.5 dB and overall calibration accuracy is estimated to be better than 1 dB View full abstract»

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  • Integrating the dyadic Green's function near sources

    Publication Year: 1990 , Page(s): 919 - 921
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Formulas are derived which allow the dyadic Green's function to be integrated for well-behaved currents in the source region. The result is that the electric field due to a current distribution local to an observer can be expressed as a function of the current and its spatial derivatives at the point of observation plus a nonsingular integral over a surface containing the local currents. Although a spherical principal volume is used to derive the theory, the field due to this principal volume is exactly canceled by other terms. The exact form for pulse currents is derived. The theory is extended to nonpulse currents in an appendix View full abstract»

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  • Iterative radar target imaging based on modified extended physical optics method

    Publication Year: 1990 , Page(s): 847 - 852
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The modified extended physical optics method, which assumes the physical optics current property over the entire surface of conducting scatterers, is applied to the inverse problem of target profile imaging. The usefulness of the modified extended physical optics method for the direct backscattering problem is first demonstrated. Then this method is applied to the inverse problem, by introducing the phase factor determined iteratively for the shadowed portion of the target and by performing the Fourier transformation of the backscattered field in the frequency domain. As an example, the inverse profiling of nose-on spheroids, including a sphere, is tested and discussed View full abstract»

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  • An interference nulling algorithm for a single receiver phased array

    Publication Year: 1990 , Page(s): 951 - 953
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    An adaptive technique utilizing phase-only in interference suppression for a planar phased array is presented. No a priori knowledge of the interference direction is assumed, and the observed data are at the array output only: a single-receiver system. The sequential orthogonal search directions in the phase space are predetermined, and the algorithm is very simple computationally. Using the criterion of minimizing the interference power and a soft constraint in the look direction, for a 1369 element planar array and three interference sources, the required phase distribution is reached after approximately 220 time samples, or 11 ms (sampling rate 200 kHz) The convergence time varies approximately as a linear function of the number of interference sources, and is essentially independent of the array size. Some computed results are given View full abstract»

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  • On spatial filtering for angle-of-arrival estimation in a scattering environment by eigendecomposition-based methods

    Publication Year: 1990 , Page(s): 931 - 934
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    A method of spatial filtering is proposed as a preprocessor to restore the high resolution performance of eigendecomposition-based methods when used with a linear array for angle-of-arrival (AOA) estimation in the presence of spatially distributed coherent interference (SDCI). Applying the conventional bandpass filters used in the spatial frequency domain, the spatial filtering method effectively suppresses the unwanted coherence interference outside a specified frequency region. Therefore, the success of the method hinges on the assumption that direct arrival and its coherent interference are well separated in spatial frequency (in angle). Under this assumption, the eigendecomposition methods with a spatial filtering preprocessor can give accurate AOA estimates of direct arrivals in spite of the presence of SDCI. Simulation results are shown for the case of scattering from an infinite circular cylinder, using discrete prolate spheroidal sequences as the optimum band-pass preprocessing filters, and a uniformly spaced linear array in a conjunction with the MUSIC algorithm View full abstract»

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  • Analysis of the annular-ring-loaded circular-disk microstrip antenna

    Publication Year: 1990 , Page(s): 806 - 813
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A rigorous analysis of the natural resonance frequencies and input impedance characteristics of an annular-ring-loaded (ARL) circular-disk microstrip antenna is presented. Using vector Hankel transforms, the problem is formulated in terms of vector dual-integral equations. Galerkin's method is then used to solve the equations to obtain the resonance frequencies and the current distribution on the conductive patches arising from a probe excitation. Due to the singular nature of the current distribution, the singularity subtraction method has been used to accelerate the convergence of basis function expansions. Experiments for determining resonance frequencies and input impedance characteristics of an ARL circular-disk microstrip antenna with various substrate thicknesses have been made. The theoretical results are in good agreement with the experimental data even when the thickness of the substrate is 0.1 substrate wavelength. It is shown that this theory can be used to analyze some microstrip antennas with an electrically thick substrate, including the analysis of mutual coupling between conductive patches or between the path and the feed of a microstrip antenna View full abstract»

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  • Analysis and calculation of radiation patterns of Cassegrain antennas

    Publication Year: 1990 , Page(s): 823 - 830
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    The analysis and calculation of patterns of Cassegrain antennas are presented in detail. Usually in the calculation it is unavoidable to complete the integrals across the main reflector of the antenna, leading to a very long computation time for a large reflector. Here, by means of a series of mathematical evaluations the integration across the main reflector of the antenna is transferred to the aperture of the feeder and therefore the computation is drastically reduced. A number of simplified formulas of patterns suitable for numerical calculation by ordinary microcomputers are given View full abstract»

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  • Feed gap aperture field and input admittance of an infinitely long insulated antenna

    Publication Year: 1990 , Page(s): 922 - 928
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    Expressions are derived for the input admittance and aperture electromagnetic fields in the feed gap of a solid insulated antenna of infinite extent. This is done by solving the boundary value problem where the fields are represented by Fourier series built up by superposition of basic sets of φ-independent cylindrical waves. Such waves are obtained from the solution of the Helmholtz equation governing the z-directed electric Hertzian potential. The axial aperture electric field in the gap is in the form of a Fourier-Bessel series and is used to find the input admittance. Results are plotted for the aperture fields and tabulated for the input admittances at different radii, insulating shell dielectric constants, and gap widths View full abstract»

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  • Statistical assessment of evaporation duct propagation

    Publication Year: 1990 , Page(s): 794 - 799
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Over-the-horizon propagation from 0.6 to 18 GHz is presented in the form of accumulated frequency distributions of path loss, showing the comparisons between theory and two measurement programs. The path-loss theory is based on waveguide solutions for a family of refractivity/height profiles characterized by evaporation duct height in the range of 1 to 40 m. Annual frequency distributions of evaporation duct height have been prepared based on 15 years of marine surface meteorological observations and are combined with the waveguide path loss/duct height results to give accumulated frequency distributions from experiments performed in the Aegean Sea and the North Sea. Excellent agreement of theory and observation is noted in most cases View full abstract»

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  • Convergence in the spectral domain formulation of waveguide and scattering problems

    Publication Year: 1990 , Page(s): 869 - 877
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Many problems in numerical electromagnetics are formulated in the spectral domain, for example, microstrip and frequency-selective surfaces. In the formulation of a linear set of equations, infinite inner product integrals or summations need to be evaluated. The concepts of absolute and relative convergence using common basis functions are discussed using specific numerical examples. No evidence was found for the existence of a relative convergence phenomenon. It is shown that one should rely on absolute convergence where a sufficiently large number of satisfactory basis functions are used together with a large (approaching infinite) inner product truncation point View full abstract»

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  • Space wave radiation efficiency of a wraparound antenna and the effect of surface wave radiation due to the dielectric substrate truncation

    Publication Year: 1990 , Page(s): 934 - 938
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    A theoretical study of the problem of excitation of surface waves in wraparound microstrip antennas is presented. The surface waves are obtained by using a contour integral in the complex plane. The surface-wave energy loss in the antenna truncation region is partially radiated and interfaces with the space wave. The radiation efficiency and the effect of the dielectric substrate truncation of the antenna radiation pattern are shown as functions of antenna dimensions and for two values of substrate dielectric constants View full abstract»

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  • A new method for obtaining antenna gain from backscatter measurements

    Publication Year: 1990 , Page(s): 896 - 902
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    A method is presented for determining the gain of an antenna from analysis of backscatter data of the antenna. This approach is different from those which have been presented in the past because it accounts for the presence of resonances which can occur in the antenna during a backscatter measurement. In particular, this type of resonance appears in the backscatter measurement of symmetric reflector antennas. This technique is applied to determine the gain of a Ka-band Cassegrain antenna and an X-band prime focus-fed antenna View full abstract»

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  • SIRIO-OTS 12 GHz orbital diversity experiment at Fucino

    Publication Year: 1990 , Page(s): 777 - 782
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    When rain occurs at a site, orbital diversity (OD) may be an alternative diversity scheme for future satellite communications above 10 GHz. The SIRIO-OTS OD attenuation measurements at 12 GHz with an aperture angle of 27.8° at Fucino show that the statistical gain obtainable is 20-25% of the OTS attenuation in decibels (if OTS is assumed as the satellite of the normal mode and SIRIO as OD resource, or spare link), or 30-40% of the SIRIO attenuation (if SIRIO is assumed as the satellite of normal mode, and OTS as OD resource). At 12 GHz these percentages represent a gain of a few decibels but at higher frequencies, such as 20/30 GHz, the gain may be multiplied by 2.5 to 5, giving noticeable power reductions. The instantaneous gain is also analyzed. The fundamental aspects of balancing an unbalanced diversity configuration are shown by applying the theory to the unbalanced SIRIO-OTS OD. Fade durations of the joint link show the same characteristics as the single-path ones: few long fades and many short fades. More important, the intervals of time in which the resource is used are long; this fact is favorable to the diversity configuration since switchover inefficiency is lowered View full abstract»

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  • Dual parabolic cylindrical reflectors employed as a compact range

    Publication Year: 1990 , Page(s): 814 - 822
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Compact ranges using dual parabolic cylindrical reflectors are investigated, and the dependence of the aperture field on the feed pattern and system geometrical parameters is studied. A uniformity factor is defined to indicate the aperture field uniformity and the significance of the diffracted fields is explored. Offset configurations are also considered and studied. It is shown that their feed location and orientation can be optimized to minimize the geometrical-optics cross polarization. The effects of offset angle on the edge diffraction and aperture shape are also studied View full abstract»

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  • Analysis of soft and hard strip-loaded horns using a circular cylindrical model

    Publication Year: 1990 , Page(s): 783 - 793
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    Strip-loaded horns with transverse (soft) and longitudinal (hard) strips are analyzed theoretically. The method is based on a circular cylindrical and uniform waveguide model with a periodic strip structure. The field is represented by an infinite series of space harmonics (Floquet modes) in the air-filled central region and in the dielectrically filled wall region. The tangential field is forced to be continuous across the air-dielectric boundary. The propagation constant and the total field (including the hybrid factor) can be determined by solving the resulting matrix equations. The convergence of the solution has been accelerated by calculating the higher-order terms analytically. It is shown that the soft-strip-loaded horn in principle exhibits the same electrical behavior as a corrugated horn. The horn represents an interesting alternative to the corrugated horn in wide-band or dual-band applications, in particular for millimeter waves and for lightweight applications onboard satellites. The hard-strip-loaded horn has potentially high gain and low cross polarization over a certain frequency range, dependent on the horn dimensions, thickness of the dielectric wall and on how strongly the stripline modes are being excited View full abstract»

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  • Diffraction by a discontinuity in curvature including the effect of the creeping wave

    Publication Year: 1990 , Page(s): 929 - 931
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The existing geometrical theory of diffraction (GTD) solution for the diffraction by a discontinuity in curvature on a perfectly conducting cylindrical surface is uniformly extended in the region where the surface diffraction of the creeping wave launched by the discontinuity is involved View full abstract»

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  • Broad-band elliptical beamshape horns with low cross polarization

    Publication Year: 1990 , Page(s): 800 - 805
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    Horn antennas with an elliptical beam and low cross polarization are discussed. A new class of elliptical-beamshape horns has been investigated. The horns are based on the dielectric core approach, using a dielectric core inside a smooth-walled horn. Horns with rectangular as well as elliptical cross sections have been studied. Experiments show that they have considerably larger cross-polar bandwidth than that obtained from corrugated horns with an elliptical beam. They are also potentially much cheaper to manufacture View full abstract»

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  • The measurement of a large antenna using a spacecraft as a receiver

    Publication Year: 1990 , Page(s): 883 - 888
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Two computational methods for obtaining the gain pattern of a large antenna using power levels recorded by a spacecraft are developed from the transmission equation. Nominally, the large antenna is linearly polarized while the spacecraft's receiving antennas are circularly polarized. Since the spacecraft has no attitude control system, the orientation of the receiving antennas is not known a priori nor its orientation the same from orbit to orbit. The first method relies on an independent spacecraft attitude determination system to furnish the orientation of the receiving antennas. It combines this information with receiving-antenna gain measurements to give the power level of the incident radiation. Losses due to polarization mismatch are taken into account, but polarization loss factors are not actually computed. The second method relates simultaneous measurements made by separate channels with separate receiving antennas. By solving a system of equations numerically, one can determine the direction of the incident radiation as well as its power level. This alleviates the need for an attitude determination system. These methods originated in the operations of the spacecraft NUSAT1 (northern Utah Satellite) View full abstract»

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  • New sensors for measuring very short electromagnetic pulses

    Publication Year: 1990 , Page(s): 838 - 846
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    In order to detect very short electromagnetic pulses under 100 ps in width, a wide-band receiving antenna with a bandwidth from 0 to 14 GHz is needed. The usual short dipoles or monopoles do not provide both the required fidelity (bandwidth) and sensitivity. A novel type of electromagnetic pulse (EMP) sensor has been designed, analyzed, and tested. It is simple, inexpensive, and can detect the electromagnetic pulse with both high fidelity and high sensitivity. An approximate analysis is given for better understanding and optimum design of the proposed EMP antenna View full abstract»

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  • On the EMC dipole feed-line parasitic radiation

    Publication Year: 1990 , Page(s): 878 - 882
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    A rigorous analysis of the electromagnetically coupled microstrip dipole based on potential integral equations, Green's functions, and the moment method is presented. The computations of the antenna's radiated field using the steepest descent technique is then detailed, and the theoretical results are compared with experimental measurements in the X-band. By considering the feed as an antenna part, the excitation line parasitic radiation is shown clearly. Two possibilities to reduce this parasitic phenomenon are proposed. Also, it is shown that in any microstrip structure (one or two layers) excited by a microstripline, the feed parasitic radiation is nonnegligible 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