M. Sabbadini

A truncated Floquet wave diffraction method for the full-wave analysis of large phased arrays .II. Generalization to 3-D cases

For pt.I see ibid., vol.48, no.3, p.594-600 (2000). This paper deals with the generalization to three-dimensional (3-D) arrays of the truncated Floquet wave (TFW) diffraction method for the full-wave analysis of large arrays. This generalization potentially includes arrays consisting of microstrip excited slots, cavity-backed apertures, and patches. The formulation is carried out first by deriving an appropriate fringe integral equation (IE) and next by defining entire domain basis functions in terms of global-array functions shaped as TFW diffracted rays whose analytical expression is derived on the basis of prototype canonical problems. The efficiency and the accuracy of this method is demonstrated by comparison with the results of an element-by-element full wave approach for a rectangular slot array.

Practical Application of the Equivalent Source Method as an Antenna Diagnostics Tool [AMTA Corner]

Recently, significant efforts from different research groups have been aimed at the problem of reconstructing the extreme near field radiated by an antenna from measured field data. Among the different proposed solutions, the inverse-source or Equivalent-Current/Source Method (EQC), based on discretization of integral equations, has attracted considerable attention, due to a host of promising applications in antenna design and diagnostics. The integral-equation approach constitutes a complement to more-established tools, such as plane-wave or spherical-wave expansion. At the expense of a heavier computational burden, this method offers a greater generality and flexibility, since it allows reconstructing sources on arbitrary three-dimensional surfaces enclosing the antenna under test (AUT).

Astigmatic beam tracing for gtd/utd methods in 3-D complex environments

Asymptotic techniques are usually employed for electromagnetic analysis of large and complex scenarios. Determination of ray paths from source to observation region is the first stage of a computation. Beam tracing methods, formerly developed for computer graphics, ensure continuous scenario coverage overcoming drawbacks of usual ray tracing. In this paper these are extended for application to electromagnetic analysis and improved to solve for multiple order interactions with scatterers by resorting to the astigmatic beam scheme. Wedge diffraction is solved recursively by minimising an aberration error. A numerical analysis has been performed for comparisons with a backward ray tracer showing a good agreement of results.

Equivalent current approach as an advanced field interpolation technique

This paper presents an investigation of a new technique for the accurate determination of the full sphere pattern of an antenna from truncated spherical near field measurements. The approach was first described and is based on determining a set of equivalent currents that radiate the same pattern in the known area and thus extrapolate the unknown fields in the truncated area. The study is performed on actual measured near-field data to investigate the effectiveness of the technique in realistic spherical near field antenna measurement scenarios.

High frequency numerical modelling using measured sources

SatSIM has proved an efficient extension to the fast measurement capabilities of the SATIMO family of antenna measurements systems. The SatSIM code provides a user-friendly and economical way to accurately evaluate the behaviour of an antenna in its final operational environment based on near field measurements of the isolated real antenna and numerical modelling of the environment. In this paper, the SatSIM algorithm has been tested and validated using small source antennas in different positions on a scaled model of a complete satellite including solar panels and reflectors. Although the development and validation of the algorithm has been performed under an ESA contract specifically for accommodation analyses of spacecraft antennas, the powerful combination of antenna testing and simulation in a single environment also has strong potentials in other related fields

Infinite ground plane antenna characterization from limited groundplane measurements

The accurate measurement of the infinite ground plane antenna patterns are needed in different applications as discussed in [1–11]. The infinite ground plane condition is difficult to measure on a general antenna due to the finite dimensions of the measurement systems. In spherical near field measurement systems the measured antenna field is described completely by the spherical wave spectrum determined by a near field to farfield transformation [12, 13]. To recover the spherical wave spectrum of the finite ground plane source as if it was placed on an infinite ground plane the field scattered by the finite ground plane edges has to be removed.

FDTD improvement by dielectric subgrid resolution

Material inhomogeneities are taken into account in the standard finite-difference time domain method by staircase modeling of medium boundaries. Resolution is, therefore, limited by Yees cell sizes. In this paper, a new scheme is proposed, which improves material resolution without increasing the demand of computer resources.

Preconditioned astigmatic beam tracing for urban propagation

In wireless communication network planning, deterministic and statistical propagation tools have been developed. Astigmatic Beam Tracing, a deterministic method based on ray tracing (GO/UTD), can be applied to urban propagation modeling. A numerical code has been applied to a model of urban scenario with increasing complexity. The results of a numerical analysis are discussed to evaluate the relevance of the test case size on the computational charge.

Field interpolation across discontinuities in FDTD

Primary field quantities and their derivatives, like power flux density or surface equivalent currents, are usually required in practical applications of finite-difference time domain (FDTD). The data obtained from the FDTD algorithm are therefore interpolated to provide the whole set of the electrical and magnetic field components at each grid node to evaluate them. In the presence of a material discontinuity, however, the linear interpolation, having the accuracy of the FDTD algorithm at points where the field is continuous, will fail for the components which are orthogonal to the interface. A dielectric interpolator is presented for these cases which retains accuracy by preserving the correct field discontinuities.

Edge fringe approach for the full-wave solution of large finite arrays

The electromagnetic modeling of large finite arrays has been the object of a number of investigations. A method of moment (MoM) formulation is suggested, for predicting the distributions of the radiating currents (including those belonging to the edge elements of the array) but retaining a number of unknowns which is comparable with those occurring in the infinite array approach. This formulation is based on an integral equation in which the unknown function is the difference between the exact current distribution on the truncated array and the current distribution pertinent to an infinite array. This unknown function can be associated to the field diffracted at the edge of the array by the Floquet modes of the infinite array. Following this physical interpretation the unknown of the integral equation are efficiently represented by a few entire domain basis functions which are properly shaped.