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Microwave Conference, 1980. 10th European

Date 8-12 Sept. 1980

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Displaying Results 1 - 25 of 137
  • Contents

    Page(s): nil1 - nil28
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    Freely Available from IEEE
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  • Gigabit Electronics - Present State and Trends

    Page(s): 9 - 18
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    Application fields for Gb/s electronics, with high-throughput signal processing as the prime motive, are indicated. Recent implementations of Gb/s ICs are mentioned. After describing and commenting on the multitude of silicon and GaAs approaches, a projection on their ultimate functional throughput rate (FTR) is attempted, based on present experimental data. In a similar way, the possibilities of Josephson technology are analyzed. View full abstract»

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  • MIC Wave-Guiding Structures Filled with Anisotropic Media

    Page(s): 25 - 36
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    There are considered generalized multiconductor lines with many anisotropic layers which cover a broad range of practically importent microwave guides suitable for present and future applications in MIC technology. After a short review and evaluation of existing analyses enabling to study such lines a new and efficient analysis method is developed and implemented. As an example a thorough and detailed discussion of the properties of a composite slot line is cited. The discussion is based on the conclusion derived from studying numerically the dispersion diagrams of such a line. Some new properties and possible applications in MIC technology of the line are indicated. View full abstract»

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  • Low Noise mm-Wave Receivers

    Page(s): 38 - 47
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    In this review paper coherent low noise receivers for frequencies from about 20 GHz up to a few hundred GHz are discussed. Mixers using Schottky barrier diodes, the working horses in mm-wave receivers, are described in some detail. The noise sources are identified and methods to minimize the noise of room temperature and cooled single ended mixers, as well as subharmonically pumped mixers, are related. Liquid helium-cooled ~ 4 K superconducting mixers i.e. Josephson effect mixers and superinsulator-superconductor (SIS) mixers are described. It is pointed out that SIS mixers are quite promising for future ultra low noise receivers for frequencies up to a few hundred GHz. For long mm-waves (¿ ¿ 5 mm) the liquid helium cooled maser still offers the lowest noise and some recent results are mentioned. View full abstract»

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  • Microwave Aquametry

    Page(s): 48 - 58
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    Same problems connected with application of microwave techniques for moisture content measurement in solid and liquid materials have been presented. It has been shown that in many cases microwaves are superior to other methods because of the specific microwave properties of materials and the possibility of contactless, remote probing. Present state of the art in microwave instrumentation as well as in fundamental research is discussed and trends of further development are mentioned. View full abstract»

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  • Fast Calculation of Far-Field Patterns of Reflector Antennas with Fast Fourier Transform

    Page(s): 61 - 66
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    The development of a numerical technique for the fast calculation of farfield radiation patterns of reflector antennas is reported. The technique applies to antennas subjected to a small angle approximation, with no restrictions as to the reflector shape and as to the feed location. Considerable acceleration of calculations is achieved through the utilization of a two-dimensional FFT algorithm associated to the numerical integration procedure. Numerical examples, processed with FORTRAN programs, are presented, showing actual computational time reductions varying from 20 to 250. Results are compared to those obtained with classical Gauss-like numerical integration, with quite good agreement. Some extensions of the technique are also suggested. View full abstract»

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  • Numerical Evaluation of Antennas Field using a New Aperture-Like Expansion

    Page(s): 67 - 71
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    This paper deals with a new aperture-like expansion of the field scattered by a reflector antenna, which allows to reconstruct the field radiated by such an antenna starting from a limited number of computed values, essentially one per lobe. This values, in turn, are exact Fourier transforms evaluated at the Nyquist rate, which allows an optimal use of the Fast Fourier Transform algorithm. An extensive numerical analysis has been performed, whose results are presented and briefly discussed in this note. These results show the excellent performance of the proposed method, a very appealing one from the point of view of both flexibility and computer time reduction. View full abstract»

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  • A Complete GTD Analysis of RIM Loaded Cassegrain Antennas

    Page(s): 72 - 77
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    A complete numerical analysis of the radiation pattern of centered symmretric Casse grain antennas is carried out. The peripherical rims of both the reflector and the subreflector are assumed to be loaded by material media described in terms of surface impedances. The Geometrical Theory of Diffraction (GTD), properly generalized to handle surface impedance boundary conditions, is used to compute the far-out sidelobes caused by various diffraction processes, while the Physical Optics (PO) approach is used in the main beam region. Some examples are also referred; the patterns of copolar and crosspolar components are exploited. View full abstract»

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  • Calculation of the Radiation Patterns of Axially Symmetric Reflectors

    Page(s): 78 - 83
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    Scattered fields from axially symmetric reflectors (paraboloid, ellipsoid, hyperboloid, spheroid and plane) are calculated by high-frequency asymptotic techniques. For this purpose, the scattered fields from an axially symmetric reflector are expressed in terms of the reflector eccentricity. By using appropriate eccentricity values, the scattered fields from a reflector of any eccentricity can be obtained in a unified form. With the help of this approach, the effect of eccentricity on the focusing property of reflectors is studied. View full abstract»

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  • The Application of Single Reflector Multi-Feed Antennas to Direct T.V. Satellites

    Page(s): 90 - 94
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    The antenna technique associating a single offset-fed reflector cut out from a revolution paraboloid to a multi-element feed source is being widely used for telecommunication satellites. This paper shows over the example of the French coverage area that the antenna technique is also an excellent solution for direct T.V. Broadcast satellites because of these decisive features : - large flexibility of design, enabling an optimization of the power distribution across the aperture of the feed source. - very low cross-polarization levels, owing to the array geometry, the good performance of each element and the cancellation of the polarizer errors. - competitive gain performance provided by the use of a high efficiency feed element. - straightforward implementation of R.F. sensing to eliminate the beam pointing error caused by the residual variations of the satellite attitude. - rugged waveguide technology providing broadbandwidth performance. The single reflector multifeed antenna technique can be accurately modelled by a computer program, and it is exempt of technical uncertainty. Measurements performed on an engineering model have confirmed the exactitude of the computer prediction. View full abstract»

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  • A European Contoured Beam Reflector Antenna Development

    Page(s): 95 - 99
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    This communication provides the present results of an ongoing development, sponsored by the European Space Agency, of design software and of a feasibility model for a contoured beam reflector antenna (COBRA), to cover Europe from a geostationary satellite. The design software, feed array elements and feed network components are described. Present computed and experimental results are given. New results include the use of original power synthesis algorithms, the combination of GTD and of Whittaker's pattern reconstruction technique for fast analysis of contoured beam reflector antenna performances, data on circularly polarised hexagonal array feed elements and design techniques for high phase and amplitude accuracy feed distribution networks. View full abstract»

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  • Corrugated Horn of HE11 and HE21 Mode

    Page(s): 100 - 103
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    A corrugated conical horn for monopulse feed, which uses the HE11 mode as sum. one and the HE21 as difference one, is described in this paper. When the ratio for the radius of the hor aperture and the free space wavelength is very large, the balanced hybrid condition can be met for both HE11 and RE21 modes. Therefore, the horn has rotational symmetry beams and low side-lobe levels for both sum. and difference modes. The method of design on selecting modes by utilizing special point on trace charts and that of using ringloaded corrugated taper section as the transformation section from the smooth wall waveguide to corrugated horn will be discussed. The input VSWR measured in the sum. channel is less than 1.05 in 20% bandwidth. View full abstract»

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  • Experimental Analysis of Corrugated Conical Horns with very Wide Flare Angles

    Page(s): 104 - 108
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    It is well known the difficulty of predicting theoretically the radiation properties of a corrugated conical horn with very wide flare angle (2¿ ¿ 180°). So a detailed experimental analysis on these antenna feeders has been carried out as function of the geometrical parameters and of the frequency. The results are summarized in graphics and analytical expressions in order to predict the radiative properties and to obtain easy design methods. A logical prosecution of the formerly obtained relations for concave corrugated structures has been derived and then the characterization of the whole family of the corrugated conical horns has been accomplished. View full abstract»

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  • Ring-Shaped Dielectric Antenna

    Page(s): 109 - 113
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    This paper describes some results of an extensive theoretical and experimental work on a novel type of antenna design-a ring-shaped dielectric antenna. It consists of two basic elements:a dielectric ring and a primary feed. One possible construction of a such antenna has a ring with rectangular cross-section and a waveguide-dielectric radiator serves as a primary source. The optimum dielectric ring for a maximum antenna gain gets into the second Fresnel zone. A radiation theory and experimental results for an X-band antenna model are given in the paper. It is concluded that a ring shaped dielectric antenna is an efficient directional radiator with simple and cheap construction. View full abstract»

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  • Current Distribution in Microstrip Planar Antennas

    Page(s): 117 - 121
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    The accurate determination of surface currents in microstrip planar antennas requires the solution of a two-dimensional singular integral equation. The first problem encountered when solving this equation numerically, is the obtention of a fast and accurate algorithm for evaluating its kernel, which cannot be calculated by standard computer integration methods. A second problem is the implementation of an efficient moment method. This task is very delicate because the kernel is singular. In particular, the diagonal or self terms in the moment matrix must be carefully evaluated. This paper discusses both problems and presents some new techniques for their resolution. View full abstract»

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  • Design Considerations in Microstrip Antenna Fabrication

    Page(s): 122 - 126
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    Deviations in effective electrical dimensions caused by slight variations in finished microstrip antenna length, variations in the relative permittivity of the substrate material or nonuniformity in the substrate thickness lead to discrepancies between the designed and actual resonant frequencies. This sort of discrepancy is especially significant because of the narrow bandwidth of such antennas. It is found that for low dielectric substrate microstrip antennas, the critical parameter affecting the change in resonant frequency is the error in antenna length while for high permittivity substrates, the tolerance in dielectric constant is the critical parameter. View full abstract»

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  • Approximate Coupling Formulas for the Coupling Between Microstrip Resonator Antennas

    Page(s): 127 - 131
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    Generally the best-known methods for computing mutual impedances are based on a direct integration of the ¿ and H¿ fields, as given in Jordan [1]. Other methods involve approximations valid for large, in theory infinite arrays, reducing any integration in the spectral domain to mere summations [2]. Some derivations have been made by array specialists coming to the solution for identical slots in both the electric and magnetic wall formalism [3]. This theory will be extended here, and applied for the case of rectangular microstrip antennas. So simple formulas that can be used both for analysis and synthesis will be found by asymptotic approximations of the integrals found. View full abstract»

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  • Radiation from a Gap Cut Across the Conducting Strip of a Double Shorted Microstrip Resonator

    Page(s): 132 - 136
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    A double shorted linear microstrip resonator symmetrically loaded with a gap is used to investigate the radiation from the gap. Gap will only radiate in odd modes and its radiation can be predicted using far field approach. Measured properties of the gap using pdd and even modes of resonances gave results which are very close to the theoretical values up to 18 GHz. Resonator construction, ways of reducing short circuit radiation use of the resonator as a) a measurement set up and b) a micros trip antenna are given. View full abstract»

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  • Phased Array Matching with Grating Lobe Reduction

    Page(s): 139 - 143
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    An analysis is given of a method of phased array grating lobe suppression and matching in the inifinite array approximation. The method is suited to limited scan operation but not restricted to it. The theoretical approach is also applicable almost unchanged, to the design of strip polarizers and a class of waveguide directional couplers. View full abstract»

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  • Analysis and Tolerance Study of an Array Antenna for a New Generation of Secondary Radars

    Page(s): 144 - 148
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    An open array antenna is analyzed considering performance and tolerances with respect to the specifications given by Eurocontrol and F.A.A. Computed results and parametric charts are presented. The analytical methods used briefly described. Some considerations on the choice of the radiating element (slot or dipole) are given with respect to the wished performance. View full abstract»

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  • The Prismatic Array Antenna a non Dispersive Travelling Wave Array Antenna

    Page(s): 149 - 152
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    The prismatic array antenna is a new array antenna, the maximum gain direction of which is almost stationnary in the frequency band. A first scattering array acts as a feed for a second array tilted relative to the first one at some specific angle. Between the two arrays, propagation may be either a guided-space one (between parallel plates for example) or a free-space one (in case of two-dimensional arrays). This structure defines a non dispersive antenna, the "prismatic array antenna" in a frequency band of about 10%. View full abstract»

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  • Array Antenna on a Dielectric Layer

    Page(s): 153 - 158
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    Antennas of this type constitute a significant progress in the construction of complex linear antenna arrays used in micro-wave range because of their specific production technology. However, no theoretical characteristics of those antennas on a dielectric layer exist. The paper presents results of an analysis of radiation characteristics for an antenna array on a dielectric without a screen. We deal with a three-layer medium: air - dielectric - air. Radiation characteristics of the array antenna working on a dielectric layer have been calculated. Results of the calculations show that if the dielectric constant of the ground increases the width of the main lobe also increases. In order to check the correctness of the analysis a model array antenna working on a dielectric layer has been tested. A number of radiation characteristics of the antenna have also been presented. View full abstract»

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