Boundary Value Problem of an Infinite Array of Loaded Apertures

IEEE Transactions on Antennas and Propagation, 2002

IEEE Transactions on Antennas and Propagation, 1974

The final and most significant measure of antenna performance is 0ight testing under operationa.1 conditions. During November 1972 and March 1973, flight check personnel performed tests on the cylindrical array TACAY antenna. The antenna system was deployed a t a test site and operated with a transportable T-4CAX beacon. Data was recorded by strip chart recorders in t.he test a.ircraft. Orbital flights of 10 nm and 40 nm were flown at 3000 and 9000 ft, respectively. These flights were used to determine the bearing accuracy at a.11 angles around the ground &ation. In these cases, the error distribution did not. exceed &lo, which is well within accept.able TACAK perfornlance requirements. Radial flights were made at 15 500 feet to a dist,ance of 96 nm, 23 500 feet from 165 nm, 1000 ft. t,o 30 nm, and 500 ft to 25 nm. A landing approach was nade from 3500 ft a t 40 nm. Radial flights are used t.o ident,ify poor signal conditions caused by improper a.ntenna elevation pat.t,ern charact,eristics. The primary measurement made during these flights is bearing signa1 variation, which should be within f3.0". A secondary measurement,, R.F signal level, showed no unacceptable bearing signal variation and no loss of signal wit.hin t.he radio horizon. , 411 measurements were within standard syst.em t.olera.nces. The flight test results were as forecast. by calculat,ions based on t.ransmitter power a.nd receiver sensitivity. In a.ddit.ion, antenna system performance m-as satisfactorily demonstrated in a.n operational environment.

1998

Large, finite arrays are often studied in hypothesis of infinite structure, thus allowing the reduction of the numerical effort to that of a single periodic cell. Sometimes this approximation leads to reasonable results in predicting the input impedance of elements far out from the edges. However, for near edge elements it is visibly wrong. Furthermore, when wide beam angle scanning occurs, the effects of truncation can be relevant also for elements very far from the edges. A truncated Floquet waves (TFW) method has been presented, for predicting the distributions of the radiating currents, including those belonging to the edge elements of the array, while retaining a number of unknowns which is comparable with that occurring for the infinite array problem. This approach is based on the method of moments (MoM) solution of an integral equation in which the unknown function can be interpreted as due to the edge diffracted field excited by the Floquet waves of the infinite structure. In this paper, the formulation of the TFW method is applied to the 3D case of rectangular array of slots in an infinite ground-plane.

IEEE Transactions on Antennas and Propagation, 2013

The analysis of the scattering by a perfectly conducting rectangular plate by means of Galerkin's method in the spectral domain with products of Chebyshev polynomials of first and second kind multiplied by their orthogonal weights as basis functions is fast convergent even for scatterers size of some wavelengths but leads to the numerical evaluation of infinite double integrals of oscillating and slowly decaying functions. The aim of this paper is the introduction of a new analytical technique that allows to write such integrals as combinations of very quickly converging integrals.

2004

In the following we present a new variational direct boundary integral equation approach for solving the scattering and transmission problem for dielectric objects partially coated with a perfect conductive layer (PEC) layer. This development originated as a transmission through aperture in PEC casing problems and was extended to account for the situation of coated arbitrary dielectric bodies. This represents a new development in the range of aperture problems – covering an area eluded at present by most of the commercially available tools. The main idea is to use to use the electromagnetic Calderon projector along with transmission conditions for the electromagnetic fields. This leads to a symmetric variational formulation that lends itself to Galerkin discretization by means of divergence-conforming discrete surface currents. Whole ranges of numerical experiments were carried on – and results reported here, confirming the efficacy of the new method

Optics Express, 2004

We demonstrate that the resonantly enhanced transmission spectrum associated with a periodic array of subwavelength apertures is dependent upon the shape of the apertures. This is demonstrated using coherent terahertz radiation and aperture arrays fabricated in 75 µm thick stainless steel foils. We examine rectangular apertures with different aspect ratios as well as circular apertures. In the absence of periodicity in the arrays, no resonance features are present. For periodic arrays, we show that the ratio of the transmission coefficients for the two lowest order resonances can be directly related to the ratio of the appropriate aperture dimensions. From the time-domain waveforms, we find two independent, yet phasecoherent, transmission processes: non-resonant transmission related to the simple transmission through subwavelength apertures and a time-delayed resonant transmission related to the interaction of the THz pulse with the periodic aperture array. In these waveforms, we also observe a sign inversion for the primary bipolar pulse relative to the reference. This is shown to be a simple consequence of diffraction.

International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 1991

Calculation of the electromagnetic field diffracted by an aperture situated in a perfectly conducting ground plane can be made through the well-known theory of polarizabilities. However, simple expressions are only obtained under conditions which are not often fulfilled in electromagnetic compatibility problems since, for example, the disturbing field incident on the aperture must be considered as a uniform one. Furthermore, if the aperture is loaded by a low conducting material, available approximate formulas are only valid for a small circular hole. In this paper, we present a numerical approach based on the determination of the equivalent magnetic current distributed on the surface of the aperture. This distribution is the solution of an integral equation solved by the method of moments. This formulation allows us to take the surface impedance of a loading material and the contact resistance between this material and the rim into account. The validation of the computer code is shown by comparing computed and analytical results on some typical examples. Few applications are also described.

IEEE Transactions on Antennas and Propagation, 1969

Communications in Mathematical Sciences, 2009

Periodic arrays are structures consisting of geometrically identical subdomains, usually named periodic cells. In this paper, by taking the Helmholtz equation as a model, we consider the definition and evaluation of scattering operators for general semi-infinite periodic arrays. The well-posedness of the Helmholtz equation is established via the limiting absorption principle. A method based on the doubling procedure and extrapolation technique is first proposed to compute the scattering operators of Sommerfeld-to-Sommerfeld type. The advantages of this method are the robustness and simplicity of implementation. However, it suffers from the heavy computational cost and the resonance wavenumbers. To overcome these shortcomings, we propose another more efficient method based on a conjecture about the asymptotic behavior of limiting absorption principle solutions. Numerical evidences suggest that this method presents the same results as the first one.