IEE Proceedings - Microwaves, Antennas and Propagation

A rigorous formulation of the spectral-domain dyadic Green's functions for surface current excitation in planar stratified bianisotropic media is presented. The media may consist of any number of layers bounded by optional perfect electric/magnetic conducting walls. The surface current can be impressed along any of the layer interfaces. Both electric and magnetic dyadic Green's functions are deriv... View full abstract»

Observation of phase delay from GPS satellites, followed by signal and data processing allows the quantity of water vapour in the atmosphere to be continuously monitored. At millimetre-wavelengths, water vapour has significant impact on radiowave propagation, along with rain, cloud and oxygen. Comparisons are presented of integrated precipitable water vapour measured by GPS with a co-sited radiome... View full abstract»

A broadband equivalent circuit of a dipole antenna valid from very low frequency to its second resonance, consisting of a series resonant circuit and two parallel resonant circuits, with frequency independent lumped elements is presented. Empirical formulas for the elements in the proposed equivalent circuit are given. Feed-point impedances calculated using the present equivalent circuit are compa... View full abstract»

An aperture antenna is constructed using a triplate transmission line. The top and bottom conducting plates of the triplate transmission line have circular apertures. The aperture in the bottom plate is backed by a circular cavity of depth Dcav. The radiation characteristics of this antenna are analysed using the finite-difference time-domain method. It is found that the cavity reduces ... View full abstract»

Sources of radiation and surface wave excitation from microstrip feeders are reviewed. And instances when the commonly used approximations break down are illustrated. The conditions for cancellation of radiation from novel symmetric feeder structures are shown. Radiation patterns from prototype antennas made for the 28 GHz band with gains of 18 and 27 dBi are compared. And a set of `good practice'... View full abstract»

A method-of-moments analysis is carried out so as to obtain, in closed form, the nonuniform current distributions, and their resulted radiation patterns in both near and far zones, of circular loop antennas with electrically larger circumferences. An oblique incident field in its general form is considered in the formulation of the nonuniform current distributions. In Galerkin's method-of-moments ... View full abstract»

A branch-line coupler with eight stubs is proposed for size reduction. A two-section stub consisting of high- and low-impedance transmission lines to make interconnection of low-impedance transmission lines easy is presented. According to the transmission-line theory. Almost the same frequency characteristics as those of a normal branch-line coupler can be obtained. Although there are slight diffe... View full abstract»

Analytical expressions for the Green's function of an annular elliptical ring microstrip antenna (AERMA) are developed and reported. The modal, radiation and input impedance characteristics of the TMnm modes are determined from these expressions. The resonant frequencies of odd modes are greater than that of the even modes for all TMnl modes (n=1, 2, 3,...) unlike elliptical ... View full abstract»

A gyromagnetic resonator of interest in the design of planar circulators is the irregular hexagonal geometry biased above the Kittel line. One purpose of the paper is to present some split mode charts on this resonator for three different values of magnetisation. Another is to investigate the effect of a triplet of magnetic walls on the gyromagnetic mode chart. The direct magnetic variables of the... View full abstract»

A moment method analysis procedure is described to determine the aperture field distribution in a finite-length straight longitudinal slot cut in the broad wall of a rectangular waveguide. The waveguide is fed from one end with the dominant waveguide mode, while the other end of the waveguide is shorted, exactly at the far end of the slot. From the aperture distribution the far-field radiation pat... View full abstract»

Thin cavity-backed Archimedean slot spirals are analysed through an efficient implementation of the finite element method. Through numerical analysis, fundamental differences between the free-space and cavity-backed configurations are identified. The bandwidth limitation imposed by the presence of the cavity is remedied by terminating the spiral slot with tapered resistive loading and employing la... View full abstract»

An element-by-element approach to the modelling of arrays of finite size enables the elements to be located on arbitrary lattices, including those curved in more than one plane. An analysis for dual-polarised ring-patch elements is given. Planar and parabolic surfaces are used as examples, with the rings on circular and triangular lattices. They are illuminated by plane waves. The currents induced... View full abstract»

A photogrammetric fading prediction method for mobile satellite scenarios is introduced. Using this photogrammetric satellite services prediction (PSSP) method, the first- and second-order statistics of satellite-earth propagation fading properties can be easily obtained. Also, the fading properties as a function of elevation angle can be effectively predicted without any new radio frequency measu... View full abstract»

The aperture-coupled cylindrical dielectric resonator antenna (DRA) on a thick ground plane is investigated using the finite-difference time-domain method and verified by measured results. Reasonable agreements are obtained. It is found that increasing the thickness of the ground plane would reduce the coupling from the feedline to the antenna. The H-shaped coupling slot is also studied numericall... View full abstract»

The paper presents a novel approach for microwave imaging of a perfectly conducting cylinder in free space using measured scattered data, with or without the effect of random noise. The contour of the cylinder is denoted by a shape function which is approximated by trigonometric series. The scattering problem is solved using point-matching method. The inverse problem is cast into a restrained opti... View full abstract»

A method of moments technique is described for the analysis of eccentric spiral antennas printed on grounded dielectric substrates which uses piecewise sinusoidal current expansion and testing functions over curved segments. This technique is shown to be significantly more computationally efficient than a linear segmentation strategy. Whilst accuracy is demonstrated through comparisons with publis... View full abstract»

A general characterisation procedure based on the extraction of a 2n-port admittance matrix corresponding to n uniform coupled lines using the finite difference time domain (FDTD) technique is presented. The frequency-dependent normal mode parameters are obtained from the 2n-port admittance matrix, which in turn provide the frequency-dependent distributed inductance and capacitance matrices. To il... View full abstract»