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Antennas and Propagation, IEEE Transactions on

Issue 2 • Date March 1975

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Displaying Results 1 - 25 of 38
  • [Front cover and table of contents]

    Publication Year: 1975 , Page(s): 0
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    Freely Available from IEEE
  • Correction to "Integral equation solution and RCS computation of a thin rectangular plate"

    Publication Year: 1975 , Page(s): 302
    Cited by:  Papers (2)
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    First Page of the Article
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  • [Back cover]

    Publication Year: 1975 , Page(s): c4
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    Freely Available from IEEE
  • A separation of the logarithmic singularity in the exact kernel of the cylindrical antenna integral equation

    Publication Year: 1975 , Page(s): 256 - 258
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The well-known logarithmic behavior of the singular "exact" kernel of cylindrical antenna integral equations is explicitly separated. The elliptic integral partitioning of the kernel by Schelkunoff is the point of departure in the development. The result is an expression for the kernel comprising the logarithmic term and a well-behaved economically computable residual term. This result is readily amenable to numerical solutions of integral equations of cylindrical geometries. Numerical results obtained from method-of-moments solutions to cylindrical antennas are given to verify the result. View full abstract»

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  • A new technique for feeding a cylindrical array

    Publication Year: 1975 , Page(s): 253 - 256
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    A new technique for exciting a cylindrical array is described. It uses a Butler matrix and a simple switching matrix for exciting only that sector of the array that contributes to formation of a desired radiation pattern. It accomplishes full circumferential coverage with fewer active components, reduced complexity, and better performance than other matrix methods for exciting cylindrical arrays. An array of N elements is configured so that N/M (M = 1, 2, 3, ...) contiguous elements spanning an active angular sector of 2\pi/M are excited simultaneously to form a radiation pattern. This paper considers the case M = 4 in which a quadrant array is excited by an N/4 -way power divider and an N/4 \times N/4 Buffer matrix. Pattern selection or rotation is accomplished by N/4 phasers and N/4 1P4T switches. Continuous full circle rotation of the radiation pattern requires N switching operations in addition to linear control of the phasers. View full abstract»

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  • On the design of a circularly polarized waveguide narrow wall linear array

    Publication Year: 1975 , Page(s): 244 - 250
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The design characteristics of a circularly polarized linear array are presented. The array elements are crossed slot radiators on the narrow wall of a T-septated waveguide that supports Odd and even symmetry modes. These modes have the same phase velocities, if the dual mode waveguide is properly dimensioned, and they excite independently the shunt and series portions of the crossed slot element. Based on theoretical and empirical design criteria, a linear array of such elements was constructed and tested and the results proved very satisfactory. View full abstract»

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  • Cross polarization losses in periodic arrays of loaded slots

    Publication Year: 1975 , Page(s): 159 - 164
    Cited by:  Papers (8)  |  Patents (1)
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    A periodic array of apertures in a conducting plane can act as a bandpass filter. With proper design the structure will be transparent at its resonant frequency but will have a transmission coefficient below unity at all other frequencies. These periodic surfaces are useful as radomes and in dual frequency antenna feeds. The resonant frequency of such an array may vary with incidence angle. This variation is undesirable for most applications, and can be greatly reduced by reactively loading the slots with the Babinet equivalent of a short circuited two-wire transmission line. It has been found, however, that singly loaded slot arrays have transmission loss due to cross polarized radiation when scanned in the H -plane (perpendicular polarization). It is shown that this cross polarized radiation may be eliminated by using symmetrical loaded slots, which have the further advantage of transmitting waves of arbitrary polarization. In conjunction with this investigation, the modal matching method, previously applied to arrays of rectangular and circular slots, has been extended to the more complicated loaded slot shapes. Both the single loaded and 4-legged symmetrically loaded slots are treated, and good agreement with measured data is obtained. View full abstract»

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  • The transient electric field response of an array of parallel wires on the Earth's surface

    Publication Year: 1975 , Page(s): 261 - 264
    Cited by:  Papers (2)
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    The transient electric field response of a step-function current excited cable lying on the surface of a homogeneous and isotropic earth is considered. Attention is focused upon that portion of the response at the earth's surface where the field is either constant or decaying with time. This information appears to have application in the measurement of the earth's conductivity using a single cable with finite length and grounded at both ends. Then, by superposition, the response of an array of equally spaced parallel cables is also studied. View full abstract»

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  • Sidelobe levels of a large radio telescope employing a combination of physical and resistive tapering

    Publication Year: 1975 , Page(s): 278 - 283
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    The main beam, sidelobe levels, and effective collecting area of a proposed radio telescope array, operating at 12 MHz, are considered. The telescope consists of two large rectangular arrays containing several thousand half-wave dipoles arranged horizontally in a tee shape above a ground plane. A narrow beam is formed by cross-correlating the outputs of the individual arms of the tee. The possibility of sidelobe reduction using a form of physical tapering consisting of reducing the width of each rectangular arm at appropriate intervals along the array is assessed, by comparing the performance achieved with this type of taper to that obtainable with the more common resistive taper. It is concluded that when the effects of random errors in element excitation are considered the performance of the physically tapered and resistively tapered arrays compares favorably. View full abstract»

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  • A circular active reflector antenna (CARA), energy distribution calculations, and an experimental test

    Publication Year: 1975 , Page(s): 228 - 236
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    Conventional high-frequency (HF) circular phased arrays, such as the Wullenweber circular array, have a cost factor that increases at a greater-than-square law rate as its radius is increased to produce larger apertures. A new method of forming simultaneous beams in an HF circular array has been proposed in which beams are formed in the space within the array from pickup element energy that has been amplified and reradiated. Such a device is called a circular active reflector antenna (CARA), and its cost increases at a substantially linear rate as its radius is increased to form larger apertures. This paper describes calculations of the distribution of reradiated energy within such an array in order to study the effect of changes in array configuration. A cost analysis is presented to establish the dependence of array cost on array size for both the conventional and CARA types of arrays. In addition, the performance of an experimental CARA array is reported. An experimental CARA array consisting of a 120\deg partially filled sector of 1500 m radius, forming six beams over a 2\deg field of view was constructed at a site in Utah to demonstrate the feasibility of the concept. Measurements made on the experimental array showed that at 14-MHz, it formed beams 0.7\deg wide at the 3-dB points, which agrees closely to the calculated value. The sidelobe response also compared closely to the level and angular position calculated for the sidelobes of the partially filled sector array tested. No evidence of instabilities or intermodulation distortion was noted. View full abstract»

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  • Slope diffraction and its application to horns

    Publication Year: 1975 , Page(s): 153 - 159
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The first order geometrical theory of diffraction (GTD) predicts vanishing fields along the surface of a conducting wedge for the incident electric field polarized parallel to the diffracting edge. The slope diffraction coefficient is a valid correction term for incidence angles removed from the shadow boundary. A new slope diffraction function for the half plane is presented along with applications. This new form of slope diffraction coefficient for the half plane is valid through the shadow region. Reciprocity is invoked to find the far-fields for a source on the surface of the conducting wedge. In addition to applying the two-dimensional slope diffraction analysis to practical problems, the equivalent current concepts have been extended to include equivalent slope currents for the analysis of either finite or curved edges. This new form of the slope diffraction function has been successfully used to provide an H -plane horn pattern analysis that is considerably less tedious than previously possible with GTD. Both pure GTD solutions and hybrid solutions using conventional aperture integration for the main beam region and GTD for the far-out side and back lobes are compared with experimental results. View full abstract»

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  • Characteristics of body-mounted antennas for personal radio sets

    Publication Year: 1975 , Page(s): 242 - 244
    Cited by:  Papers (2)  |  Patents (6)
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    The development of a multiturn loop antenna for a police officer's personal radio set is described. The antenna is small, low profile, lightweight, with dimensions of 2.7 \times 2.7 \times 0.7 in high ( 1.06 \times 1.06 \times 0.28 cm), and is tunable over the 150- to 170-MHz band. VSWR and radiation patterns are presented with the antenna mounted on a man's shoulder. The shoulder-mounted antenna characteristics are described with conditions where the man is in standing, stooping, and prone positions, with various head and arm movements, and with light and heavy clothing. Radiation patterns are referenced to a 6-in helical whip commonly used by police officers. Radiation patterns also indicate body absorption loss for loop and whip antennas mounted at waist level as compared with shoulder levels. The instantaneous bandwidth is 1.4 MHz for a VSWR \leq 3:1 . A dual-frequency model for use in a two-frequency push-to-talk mode, is also shown to be practical. View full abstract»

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  • Transient reflection from a plasma half space when losses are considered

    Publication Year: 1975 , Page(s): 298 - 300
    Cited by:  Papers (4)
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    An impulsive plane wave (TE mode) is incident on a cold uniform plasma half space. The known Laplace transform of the reflected wave is expanded in such a fashion that an inversion of the terms allows one to obtain the impulse response as an infinite series of modified Bessel functions of the first kind. For the special case of small losses it is shown this response simplifies to a previous result. View full abstract»

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  • On approximating Fourier integral transforms by their discrete counterparts in certain geophysical applications

    Publication Year: 1975 , Page(s): 264 - 266
    Cited by:  Papers (5)
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    In the past, fast Fourier transforms (FFT's) have been used in geophysical data analysis and, with some success, in theoretical analysis. However, in the general situation when neither the function nor its transform image is of compact support, the digital transforms inevitably introduce aliasing errors in both the domain and range space. A technique to assess and minimize this error is given for a restricted set of functions. View full abstract»

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  • Short range active transmitting antenna with very large height reduction

    Publication Year: 1975 , Page(s): 286 - 287
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A resistive input impedance transmitting antenna system with a total dipole height of \lambda /2000 instead of the conventional \lambda /2 has been built and compared with a passive dipole of equal height. The active network-antenna combination is extremely broadband and is capable of working at frequencies well below those where inductively loaded passive antennas can readily be made. View full abstract»

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  • Analysis of two coupled coplanar loops

    Publication Year: 1975 , Page(s): 250 - 253
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Two identical coplanar rectangular loops have been analyzed. For various shapes of the loops, as well as various spacings between loops, circuit properties have been investigated. The center-line-driven loop antenna has also been investigated as two coplanar loops with infinitesimal spacing. It is shown that the centerline-driven loop antenna may be characterized by a relatively high impedance property, and if the shape of the loop is appropriate, its impedance can have a broadband property. View full abstract»

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  • Attenuation and space diversity statistics calculated from radar reflectivity data of rain

    Publication Year: 1975 , Page(s): 221 - 227
    Cited by:  Papers (11)
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    During the summer of 1973 the rain reflectivity environment in three-dimensional space was routinely recorded on digital tape at Wallops Island, Va. A mode of operation consisted of sampling periodically 60\deg azimuth intervals over regions in which the rain activities were most intense and widespread. A series of plan-position indicator (PPI) sweeps over these intervals were implemented at a sequence of elevation angles starting from 0.5\deg up io an angle above which the reflectivity values were below a designated threshold level. Approximately 500 such raster scans were acquired in which each scan was obtained in less than 4 min and covered a range interval of 10 to 140 km. Using the above data base, reflectivity profiles along representative earth-satellite paths were determined from which attenuation and space diversity statistics were calculated at the frequencies of 13 and 18 GHz. Specifically, the form k = aZ^{b} was used to deduce the total path attenuation, where k is the attenuation coefficient (dB/km), and Z is the reflectivity factor (mm6/m3). The constants a and b were calculated using the raindrop distribution for thunderstorm activity as proposed by Joss. Probabilities that the attenuations exceed given fade depths, diversity gain as a function of fade depths, and diversity gain as a function of site separation distances are characterized and compared at the various frequencies. For the space diversity mode, a site spacing of 15 km is shown to give rise to a near optimum condition for the diversity gain. Furthermore, the diversity gain has been demonstrated to be minimally influenced by the transmitter frequency. View full abstract»

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  • Minimum directivity of multiple-beam antennas

    Publication Year: 1975 , Page(s): 283 - 284
    Cited by:  Papers (1)
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    The minimum directivity of a multiple-beam antenna is an important design parameter of the related communications system. This parameter is a function of the spacing between the feeds of a focusing device. In this communication it is shown that the minimum directivity can be optimized by the proper choice of feed spacing. View full abstract»

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  • Rain cancellation deterioration due to surface reflections in ground-mapping radars using circular polarization

    Publication Year: 1975 , Page(s): 269 - 271
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Ground mapping radars such as those encountered in airport surface traffic control use circular polarization to reduce the effects of rain clutter. The effectiveness of circular polarization is reduced significantly by ground reflections. Calculations are presented for representative cases. View full abstract»

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  • The effect of different testing functions in the moment method solution of thin-wire antenna problems

    Publication Year: 1975 , Page(s): 258 - 261
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    The use of piecewise sinusoids for expansion functions and rectangular pulses for testing functions is described in the application of the method of moments to thin-wire antennas and scatterers. This choice of expansion and testing functions allows efficient calculation of matrix elements and yields accurate results for certain widths of the testing function. However, for other widths, although the standard criteria for the selection of these functions are satisfied, erroneous results are obtained. The validity of the moment method solution can be checked by examining the near-field. View full abstract»

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  • Rain attenuation of millimeter waves at λ = 5.77, 3.3, and 2 mm

    Publication Year: 1975 , Page(s): 213 - 220
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Measurements of rainfall attenuation of millimeter waves at \lambda = 5.77 , 3.3, and 2 mm were conducted during the years 1969-1070. Simultaneously recorded meteorological quantities were the rainfall rate and a part of the drop-size spectrum. Attenuation coefficients as a function of rainfall rate were thus determined. These attenuation coefficients were related to parameters that, under certain assumptions, describe the drop-size distribution in rain. View full abstract»

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  • Evaluation of potential integral at singularity of exact kernel in thin-wire calculations

    Publication Year: 1975 , Page(s): 293 - 295
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    A technique is presented for calculating the potential integral of thin-wire theory at the singularity of the exact kernel in cases where the current is representable as piecewise constant and/or piecewise linear over an interval containing the singularity. The integral of the rapidly varying portion of the kernel is converted to a highly convergent power series. Examples of how one employs the results in computations are given. View full abstract»

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  • Dispersion measurements of one-element short backfire (SBF) antennas

    Publication Year: 1975 , Page(s): 289 - 293
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Three one-element short backfire (SBF) antennas at 40 MHz, 140 MHz, and 350 MHz were built in the institute for the use with the ATS-6 radio beacon experiment (RBE). Ehrenspeck's data experimentally measured in the GHz range were transformed into the VHF range. Since there were no relevant data available concerning the dipoles and feeder systems, various types were tested in combination with differently shaped SBF reflectors. The antennas were optimized with respect to gain, sidelobe suppression (ss), and forward-backward ratio (fbr). For all antennas ss was better than 20 dB and fbr better than 30 dB. The data, measured with the two identical antenna methods, are presented and compared with Ehrenspeck's data obtained with the pattern integration method. Ehrenspeck's gain seems to be about 0.8 dB higher than that measured at the antenna test range at Lindau, very likely due to the different measuring methods. In all other aspects the agreement of the data seems to be fairly good. The ATS-6 RBE yields the opportunity to measure the differential group delay of the RF signals. For this purpose the relative dispersion-phase shift \Delta _{D} -between the 40-MHz, 140-MHz, and 360-MHz carriers and their \pm1 -MHz sidebands has to be known fairly accurately. The following data were obtained: |\Delta _{D40/41}| \leq 4\deg /MHz; |\Delta _{140/141}| \leq 1.03\deg /MHz; |\Delta _{D360/361}| \leq 0.4\deg /MHz. Furthermore the total delay with respect to vacuum of the 360-MHz, 140-MHz, and 40-MHz SBF antennas was coarsely measured by using the two identical antennas method. We got the following figures 52.5 \times 10^{-9} s at 40 MHz, 15 \times 10^{-9} s at 140 MHz, and 5.8 \times 10^{-9} s at 360 MHz. These data are practically independent from azimuth and elevation angles of the antennas and from the conductivity of the ground as long as the elevation angle is larger than 15\deg . Similar measurements with Yagi antennas showed a strong variation of the aforementioned parameters when installing them at different locations. Thus the SBF antennas seem to be the best possible compromise of any antenna type for the specific purpose of the differential group delay measurements. View full abstract»

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  • Angular jitter in an amplitude comparison monopulse radar due to turbulence

    Publication Year: 1975 , Page(s): 274 - 278
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    Calculations are presented of the bias and spread of the angle estimator of an amplitude comparison monopulse radar caused by propagation through a layer that contains random index of refraction fluctuations. These fluctuations, caused by irregularities between a target and a receiver, bias the angle estimator towards boresight and cause a spread in the measurements of both on- and off-boresight angles. To illustrate the general results simplified expressions are given for Gaussian antenna patterns, targets near boresight, and a simple power-law irregularity spectrum. Comparisons with other models of angular jitter show that the mean square angular fluctuation observed with an amplitude comparison monopulse radar is closely related to the angular fluctuation, which is predicted when the averaging effect of a radar aperture is considered. View full abstract»

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  • Inadequacies of collocation solutions to Pocklington-type models of thin-wire structures

    Publication Year: 1975 , Page(s): 295 - 298
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Two shortcomings of the use of collocation method of moments procedures to solve Pocklington-type integral equations for thin-wire structures are discussed. One of the shortcomings, innate in the collocation procedure, is that match-points cannot be spaced sufficiently densely in the feed region of a wire antenna to accurately sample the highly local driving field when the feed diameter is very small The other shortcoming occurs when the current, expressed as a linear combination of the elements of the basis set, exhibits slope discontinuities. The behavior of the scattered field computed from such currents is discussed in terms of its influence on solution convergence. The results of numerical experiments embodying these two phenomena 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