IEE Proceedings H - Microwaves, Antennas and Propagation

The condition for circularly polarised radiation fields from waveguide apertures is discussed. It is shown that ideal circular polarisation cannot be achieved in practice for elliptical hybrid-mode waveguides, neither for corrugated nor for partly filled dielectric (dielcore) waveguides. The crosspolar performance of the elliptical dielcore waveguide supporting the fundamental hybrid-mode is calcu... View full abstract»

A simple and broadband orthomode transducer (OMT) is presented. It can be machined or moulded in two almost identical parts which implies a potentially cheap design. Both the mechanical construction and the principle of operation are described. The paper also presents results both from some pre-experimentations and for the complete OMT. These results show that the isolation between the ports for t... View full abstract»

This paper presents a moment method analysis of a rectangular slot coupled transition between two dissimilar rectangular waveguides. The effect of the finite thickness of the metallic wall, in which the slot is milled, is taken into account by considering the coupling slot as a small section of a rectangular waveguide. The reflection coefficient and VSWR are evaluated for a transition between WR-9... View full abstract»

Although six-port ANA theory requires that the input impedances of power detectors remain constant with incident power, this is not generally the case if diode detectors are used. Consequently, uncertainties in the measurement of the unknown load reflection coefficient appear. Measurements of the variations of diode impedances are used in a computer simulation to estimate these uncertainties. View full abstract»

The analysis of radiowave propagation through, and radar scattering from, the melting layer requires a model of the melting ice particles with appropriate statistics of shape, size, and orientation distributions. Previous studies have indicated that the melting layer can be modelled by a collection of wet snow spheroids in air, of which the effective permittivity and the volume fraction are the mo... View full abstract»

An extension of the multiport network modelling technique applied to rectangular microstrip patches on thin substrates covered with a dielectric layer is reported. The edge admittance networks for the radiating edges and the mutual coupling network for the external interaction between the two radiating edges are obtained from the spectral domain solution for fields of a magnetic current element pl... View full abstract»

A matching slot pair which radiates all the incident power in a circularly-polarised wave is proposed and analysed for use as a terminal in a leaky-wave slotted waveguide array. The position and size of the slots are numerically optimised to suppress reflection and to realise a desired polarisation in the tilted beam direction, which contributes to improving the antenna efficiency. It is verified ... View full abstract»

A new synthesis method based on the intersection approach is presented: the synthesis is viewed as the problem of finding the intersection of sets. This is a more natural, flexible and effective formulation of the problem but despite this it has not previously received much attention. The search for a point belonging to the intersection of two sets allows a very effective solution procedure, based... View full abstract»

By using the theoretical relationship between attenuation and depolarisation, a cumulative distribution of depolarisation can be predicted from a distribution of attenuation at the same frequency. In the case of Earth-space paths, however, it was found that there is poor correlation between measured attenuation and XPD because of so-called ice depolarisation. This implies that the predicted XPD va... View full abstract»

A simple moment solution is presented for the problem of electromagnetic transmission through a small radome of arbitrary shape. The radome is excited by either a plane wave (receive mode) or an elementary dipole inside the radome (transmit mode). The equivalence principle is used to replace the radome by a set of equivalent electric and magnetic surface currents radiating into an unbounded medium... View full abstract»

The rigorous spectral domain method is applied to analyse the resonant frequency characteristics of rectangular resonators in three broadside-coupled suspended stripline configurations. These are (a) broadside-coupled suspended stripline with a single dielectric (b) broadside-coupled suspended stripline with double dielectrics and (c) broadside-coupled suspended stripline with double inverted diel... View full abstract»

The Lorentz gauge is the preferred gauge when problems in electromagnetic scattering and diffraction are solved by a classical Maxwell equation potential function approach. The free space magnetic vector and scalar potentials subject to the Coulomb gauge are obtained in the paper. It is shown that the Coulomb gauge vector potential dyadic Green's function can be extracted from the well known Loren... View full abstract»

Based on the one-dimensional finite element method a general formulation is presented for the calculation of the conductor Q-factor, Qc, associated with metallic losses of cylindrical cavity resonators loaded axisymmetrically with dielectrics. The formulation is employed to accurately determine Qc relating to the first few modes of the cylindrical cavity resonator loaded with... View full abstract»

Infinite arrays of two-dimensional printed elements are analysed using the finite difference method. Grid models accounting for dielectric discontinuities and current continuity at rectangular junctions are developed. The procedure is used to study the behaviour of three configurations of planar strips over dielectric substrates in an infinite array environment. These configurations include the 'd... View full abstract»

The impedance properties of a dual concentric annular ring microstrip patch antenna are described. This patch operates at two frequency bands which may be closely spaced. The TM12 mode is primarily investigated but other modes are also treated. An equivalent circuit model for the input impedance is presented together with experimental verification. Surface waves are found to be importan... View full abstract»

The admittance characteristics of a system consisting of two centre-fed antennas of arbitrary orientation are investigated. Each antenna is modelled by a very thin prolate spheroid which is centrally fed by a gap voltage. By using the equivalence principle, each spheroidal dipole is replaced by a solid spheroidal conductor of the same size without a gap, encircled by a corresponding filamentary ri... View full abstract»

The problem of a centred-inclined radiating slot cut in a broad wall of a rectangular waveguide and excited by a TE10 mode wave is considered. Pertinent integral equations for the slot aperture electric field are solved using the method of moments. Scattering characteristics of the slot are then analysed including resonant length and the equivalent series impedance. Numerical results on... View full abstract»