IEEE Transactions on Antennas and Propagation

The objective of partially adaptive array design is to reduce the number of adaptive weights without significantly degrading the performance of the adaptive array. Previous work includes numerical techniques for approximately minimizing the average generalized sidelobe canceller (GSC) output power for a desired number of adaptive weights, where the average is over a range of jammer parameters. Our... View full abstract»

A new approach, based on global response surface (GRS) modeling techniques, is used to design two-layer electromagnetically coupled rectangular patch antennas. Data from a grid of design points is used to construct a model of the input impedance of the antenna. The model is then optimized to provide the best design geometries for the frequency band of interest. Three examples are presented to vali... View full abstract»

The effects of the spherical wave blockage in reflector antennas is investigated. This problem is likely to occur in axially symmetrical feed antennas of single- and dual-reflector type in both single- and dual-reflector configurations, owing to the presence of primary feeds and their supports including struts that are normally placed between the primary source and the main reflector. The main ref... View full abstract»

We describe an optically modulated scatterer as an electric-field probe for measuring radio-frequency and microwave fields. It has a high spatial resolution and the ability to operate very close to conducting and dielectric objects without appreciable distortion of the field to be measured. Thus, it can scan close to antennas and diffracting metal structures. We describe how the electric field is ... View full abstract»

The knowledge of directions of arrival (DOA) of waves is fundamental in understanding the physics of the mobile communications wide-band propagation channel. We first present a measurement setup that is able to accurately measure these DOA. It is based on the evaluation of the channel complex impulse response at regularly spaced locations on a circle. We theoretically investigate a new approach fo... View full abstract»

TM scattering from a hollow, slotted, circular cylinder with thickness is investigated. The mode-matching technique (MMT) is used to express the scattered and guided fields in the angular spectral domain in terms of the radial waveguide mode. The boundary conditions are enforced on the conducting surface and the slot to obtain simultaneous equations. The simultaneous equations are solved to repres... View full abstract»

A time-domain boundary integral equation (BIE) solution of the magnetic field integral equation (MFIE) for large electromagnetic scattering problems is presented. It employs isoparametric curvilinear quadratic elements to model fields, geometry, and time dependence, eliminating staircasing problems. The approach is implicit, which seems to provide both stability and permits arbitrary local mesh re... View full abstract»

A numerical approach to the electromagnetic scattering of a plane wave impinging at skew incidence on the edge of a wedge with two different anisotropic face impedances is presented. The diffracted field is obtained by applying the finite-difference (FD) method to solve two coupled parabolic equations. The solution obtained is valid in the high-frequency region View full abstract»

A multipath fading model has been used to examine the characteristics of a point-to-point microwave radio channel. The new attributes of this model that differ from other multipath models enable the incorporation of the ideas of fading severity and time variability. This is achieved by the use of a biased Rayleigh-distributed second (interfering) ray. The biasing constant determines the fading sev... View full abstract»

An analytical method to predict and optimize the performance of Berenger's (see J. Computat. Phys., vol.114, p.185-200, 1994) perfectly matched layer (PML) absorbing boundary condition (ABC) for finite-difference time-domain (FDTD) simulations is described. The shape of the conductivity in the PML layers has to be chosen carefully to obtain the best performance for a given number of layers. The re... View full abstract»

Kirchhoff's surface integral representation (KSIR) is used to calculate the near and far fields from the finite difference time domain (FDTD) simulation. The KSIR is very simple to implement and its distinct advantage is that the calculation of any of the six field components depends on the value of the same field component over a closed surface. This avoids interpolation errors when using the pop... View full abstract»

A capacitively loaded planar inverted-F antenna (PIFA) is proposed and studied. It is found that the capacitive load reduces the resonance length of the PIFA from λ/4 to less than λ/S. A design with a bandwidth of 178 MHz centered at 1.8 GHz is provided to demonstrate that compact antennas for mobile telephone handsets can be constructed using this approach. The finite-difference tim... View full abstract»

The general rule for reflection of a vector 2'-pole field on a plane interface between two media of different dielectric properties is established starting from the expansion of the spherical multipole field as a linear combination of inhomogeneous vector plane waves. In fact, by considering vector multipole fields that satisfy the radiation condition at infinity we are able to define a matrix tha... View full abstract»

The method of parabolic equation (PE) has been successfully applied to the numerical determination of diffraction, slope-diffraction, and multiple-diffraction coefficients of scalar impedance wedges illuminated by a line source. As a continuation, this paper studies-for the first time to the authors' knowledge-another important canonical problem for the uniform geometrical theory of diffraction (U... View full abstract»

An analysis of thin-wire antennas and scatterers using orthogonal wavelets on interval [0,1] is presented. The thin-wire version of the electric-field integral equation (EFLE) is solved by the hybrid wavelet expansion and boundary element method (HWBM). Maps between the curved solution domains and the interval [0,1] are established by using the geometrical representation of the boundary element me... View full abstract»

The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection lo... View full abstract»

The propagation of electromagnetic waves in a grounded dielectric slab has numerous applications in printed antenna technology and in the analysis of microwave- and millimeter-wave integrated circuits. For the accurate analysis of microstrip dipoles and circuits based on the moment of method (MoM), a crucial step is the precise evaluation of the impedance matrix elements which contain the integrat... View full abstract»

A novel broad-band microstrip antenna is presented. The printed configuration consists of a shorted circular patch and a concentric parasitic annular ring. Compared to a conventional microstrip patch, this ensemble is smaller in size with enhanced impedance bandwidth. Both experimental and theoretical impedance behavior and radiation characteristics of the modified patch are considered. Very good ... View full abstract»

This paper deals with the derivation of the edge-based shape functions for the distorted triangular prism and their applications for the analysis of doubly curved conformal antennas in the context of the finite element method (FEM). Although the tetrahedron is often the element of choice for volume tessellation, mesh generation using tetrahedra is cumbersome and the central processing unit (CPU) i... View full abstract»

A new numerical method for determining effective permittivity of dense random media in two dimensions is presented. The core of the method is to compare the average scattered field of a random collection of scatterers confined within an imaginary boundary with the scattered field from a homogeneous dielectric of the same shape as the imaginary boundary. The two-dimensional (2-D) problem is aggress... View full abstract»

A new phi flip unit matrix is introduced into the body of revolution (BOR) system matrix theory which aides in the development of negative mode expressions for the impedance, admittance, voltage, current, and row matrices. A demonstration of the phi hip matrix provides a succinct proof of existing results for scattered fields using positive modes. The BOR-PATCH system matrix equation and its solut... View full abstract»

From the asymptotic behavior of the plane wave spectrum, a simple method is derived for determining the minimum convex closed surface in which the sources of a given acoustic or electromagnetic far-field pattern can be located View full abstract»

A closed-form analytical solution is developed for predicting the early-time transient electromagnetic fields which are generated by a perfectly conducting parabolic reflector antenna when it is illuminated by a transient step spherical wave due to an elemental Huygen's source located at the focus. This closed-form time-domain solution, which is valid both near and far from the reflector (and anyw... View full abstract»