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Microwaves, Antennas and Propagation, IEE Proceedings H

Issue 3 • Date June 1986

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Displaying Results 1 - 18 of 18
  • Accurate analysis of latching phase s.hifters

    Page(s): 165 - 168
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (475 KB)  

    Ferrite-latching phase shifters in a generalised waveguide geometry (grooved rectangular guide with lateral ridges) are analysed using a combination of mode-matching and perturbation techniques. By this method, the double transverse inhomogeneities of the waveguide configuration and of the toroid corner magnetisation are both considered exactly, leading to accurate predictions of differential phase shift and of cutoff frequencies of higher-order modes. View full abstract»

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  • Stopband optimised E-plane filters with multiple metal inserts of variable number per coupling element

    Page(s): 169 - 174
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (487 KB)  

    Improved stopband attenuation of E-plane filters is achieved by replacing merely a few of the conventional single insert coupling elements by triplets or quintuplets of metal inserts. The method of field expansion into suitable eigenmodes used considers the effects of finite insert thickness and the mutual higher order mode interaction of all inserts. Calculated stopband attenuations of more than 50 dB up to about 30 GHz, or 60 GHz respectively, have been attained, although the passbands of the corresponding filter examples are chosen to operate at the upper waveguide band limit of the mount (at 18 GHz for Ku-band and at 40 GHz for Ka-band respectively). The results demonstrate that high stopband conditions can be satisfied by designs with only a modified number of multiple inserts. This helps to maintain the low-loss and low-cost qualities of E-plane filters and also provides for improved stopband demands. The thickness of all inserts of t = 190 ¿¿m makes possible accurate metal-etching fabrication. View full abstract»

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  • Dynamic transfer properties of frequency multipliers

    Page(s): 175 - 182
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (893 KB)  

    Noise and transfer properties of frequency multipliers with step-recovery diodes and depletion-layer varactors are investigated both theoretically and experimentally. Parameters are the multiplication factor the number of diodes drive level and detuning of the input frequency, the bias conditions and the terminations at the harmonics. Distortions of angle-modulated signals mainly originate in AM-PM-conversion whereas the intrinsic noise plays only a subordinate role. Fixed bias and detuning either the input or the output circuit are remedy against this source of distortion. The bias modulation sensitivity is also investigated snowing that the bias supply voltage must be carefully stabilised in order to reduce the PM output noise. View full abstract»

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  • Phase comparator at 2.5 GHz

    Page(s): 183 - 186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Images of biological objects can be obtained by exploration with microwaves. Reconstitution of the image takes place by distribution in phase and in amplitude of the diffracted field on a portion of a spherical surface. Obtaining these parameters requires a precision phase comparator at a working frequency of 2.5 GHz. The comparator consists of an arrangement of four couplers of 3 dB, one phase shifter of 90¿¿ followed by filtering and detection circuits such that one obtains: (¿¿l¿¿¿¿2) = arctan V1/V2, where V1 and V2 are measured directly. The realised system permits a phase measurement with an error of less than 5¿¿ at the nominal frequency (2.5 GHz) for levels of power between ¿¿10 dBm and ¿¿30 dBm. View full abstract»

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  • Analysis of microstrip-slotline ring 3 dB directional couplers

    Page(s): 187 - 190
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    The paper deals with the analysis of a new class of microstrip slotline ring 3 dB directional couplers which possess topological symmetry with respect to two of the input ports. Slotline or slotline microstrip T-junctions are used to obtain the frequency independent 180¿¿ phase shift. This provides for a high frequency independent isolation between the input ports. In the analysis effects of microstrip T-junctions and impedance transformation in the microstrip slotline transitions have been taken into account. The numerical results obtained predict that couplers operating over 30¿¿50% bandwidth are feasible. Some additional design flexibility resulting from the coupler impedance transformation properties has also been demonstrated. View full abstract»

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  • Interdigital microstrip capacitor as a four-port network

    Page(s): 191 - 197
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (699 KB)  

    For versatile connections in an MIC circuit, an interdigital microstrip capacitor may be considered as a four-port network with some open ports instead of a straight two-port one. The impedance of the four-port network can be simple, up to its resonant frequency, based on some simple expressions for the even- and odd-mode capacitances for microstrip fingers. View full abstract»

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  • Simple analysis and design of annular ring microstrip antennas

    Page(s): 198 - 202
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    A simple analysis of thin annular-ring microstrip antennas (AR-MSA), along with a design technique that yields the optimum ring dimensions which maximises the radiation efficiency and the bandwidth, is presented in this paper. Using the cavity model, exact closed form solutions for the radiation fields are derived. The antenna fields distribution, resonance dimensions, radiation patterns, directivity, radiation conductance, quality factor and bandwidth are investigated for the different TMnm modes. AR-MSAs operated at the high order TMn2 modes are found to have better radiation properties and broader bandwidths than the corresponding disk-MSAs. A design table for the optimum ring dimensions for different types of the dielectric substrate material is also given in the paper. View full abstract»

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  • Scattering of an arbitrary wave by a thin strip grating reflector

    Page(s): 203 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    A simple approximation method to calculate scattering from a thin strip grating of a finite size is proposed for arbitrarily polarised incidence with an arbitrary plane of incidence. First, the grating is projected on the plane normal to the direction of incidence. The grating parameters are transformed at the same time according to a simple rule. Then, reflection and transmission coefficients for a plane wave are readily calculated for the fictitious problem of normal incidence on the projected grating. Equivalent electric and magnetic currents are derived using these coefficients at every point on the actual grating. Finally, integration of these equivalent currents over the actual grating gives the scattering of an arbitrary wave from a grating of arbitrary size and shape. The accuracy and validity of this method are also verified by experiments, where an arbitrarily-oriented grating is illuminated by either a plane or a spherical wave. View full abstract»

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  • Transformation of linearly constrained broadband processors to unconstrained partitioned form

    Page(s): 209 - 212
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    The paper presents a technique for transforming linearly constrained broadband time-domain processors to an unconstrained partitioned form via an orthogonal decomposition of the constraint matrix. It is shown that the partitioned structure drops out naturally from solving the mathematics of the transformed unconstrained, optimisation problem. This approach enables the relationship between the Frost-type processor and the unconstrained partitioned processor to be established in a direct way. View full abstract»

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  • Direct far-field GO synthesis of shaped beam reflector antennas

    Page(s): 213 - 220
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (871 KB)  

    The problem of synthesising a reflector surface to produce a prescribed far-field radiation pattern when illuminated by a point source feed is treated using the complex co-ordinate method of Westcott. The far-field boundary value problem is formulated on a Cartesian grid and the solution technique demonstrated for two example specifications typical of satellite communication systems. The potential of the design approach is examined through diffraction analysis of shaped antennas derived from the example solutions. View full abstract»

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  • Dual reflector antennas with amplitude phase or Abb¿¿ conditions

    Page(s): 221 - 226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    The design of dual reflector antennas has been simplified by a method of deriving the secondary reflector from any prescribed main reflector for quite general focusing conditions. Consequently, main reflectors which are constructed from a series of generic curves can be considered, and they and their associated subreflectors optimised to satisfy a given second condition by numerical methods. This is illustrated for antennas obeying the Abb¿¿ sine condition or giving a prescribed aperture distribution by optimising the coefficients and parameters of a quite arbitrary series of generic curves. View full abstract»

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  • Numerical solution of scattering from coated bodies of revolution using different integral equation formulations

    Page(s): 227 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    The electromagnetic scattering from coated conducting bodies of revolution is computed using the moment method. The equivalent principle is used to generate different formulations for the problem. These formulations are then used to compare the numerically determined solutions with the analytic ones, for coated spheres using the Mie series solution. It is shown that the solution accuracy generally depends on the formulation type. The method is then used to determine the solution for other rotationally symmetric geometries. The results indicate that the resonance effects are less severe for nonspherical geometries. View full abstract»

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  • Radiometric sky temperature measurements at 35 and 89 Ghz

    Page(s): 233 - 237
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (521 KB)  

    A set of radiometric sky temperature measurements at 35 and 89 GHz is presented in the paper. The system used to make the measurements is described as well as the method used for calibration. The temperatures were measured as a function of elevation twice a day over a period of about six months. Examples of the results obtained are presented together with a cumulative frequency graph of zenith temperature for the entire period. The results are converted to one-way attenuation through the atmosphere and correlation with meteorological conditions is discussed. View full abstract»

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  • Mutual admittance between slots on a cylinder using the extended Poynting vector method

    Page(s): 238 - 240
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (330 KB)  

    The extended Poynting vector method is used to derive formulas for the mutual admittance between two identical slots on a perfectly conducting circular cylinder. Formulas for this geometry have earlier been derived via the reaction theorem. A disadvantage with those expressions is the poor convergence of the integral for large axial slot separations. Through extensive manipulations one formula can be converted into the other but for large axial slot separations the Poynting vector method gives converging expressions directly. It is thus proved that the extended Poynting vector method provides an alternative way of obtaining the mutual admittance between apertures on a cylinder. View full abstract»

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  • Microwave propagation in dust storms: a review

    Page(s): 241 - 247
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1035 KB)  

    A review is given of the literature covering the effects of dust storms on microwave links. Most authors have calculated the effects of absorption of energy, revealing that it is not very significant unless very high suspended dust densities are assumed. A few papers indicate the possibility of more significant cross polarisation. Air refractive effects associated with dust storms have been relatively neglected but are strongly indicated by observations. View full abstract»

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  • Technical memorandum: Analysis of electromagnetic systems by means of fourier transform techniques

    Page(s): 248 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (411 KB)  

    We have developed a method for calculating eigenfrequencies and field distributions for the modes of waveguides and resonant cavities The core of the method is the application of Fourier transforms to a time-domain solution of Maxwell's equations. For quasi-one-dimensional systems we find a convergence criterion relating the spatial and time mesh widths which makes it extremely convenient. Finally, we have applied the method to two simple cases the homogeneous and the partially homogeneous parallel plane waveguides. View full abstract»

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