van Mc Martijn Beurden

Analytical models for low-power rectenna design

The design of a low-cost rectenna for low-power applications is presented. The rectenna is designed with the use of analytical models and closed-form analytical expressions. This allows for a fast design of the rectenna system. To acquire a small-area rectenna, a layered design is proposed. Measurements indicate the validity range of the analytical models.

Fast convergence with spectral volume integral equation for crossed block-shaped gratings with improved material interface conditions

For block-shaped dielectric gratings with two-dimensional periodicity, a spectral-domain volume integral equation is derived in which explicit Fourier factorization rules are employed. The Fourier factorization rules are derived from a projection-operator framework and enhance the numerical accuracy of the method, while maintaining a low computational complexity of O(Nlog⁡N) or better and a low memory demand of O(N).

Efficient, Compact, Wireless Battery Design

Wireless batteries or rectennas- rectifying antennas - are conceived for converting wireless RF power into DC power. Although power conversion efficiencies exceeding 80% have been reported for high (20 dBm) rectenna input power levels, wireless batteries will be most beneficial at large distances from sources that will radiate at power levels limited by national and international regulations. Therefore, the challenge is in maximizing the power conversion efficiency of wireless batteries for low input power levels, say 0 dBm and below. By directly conjugate matching a rectifying circuit to a microstrip patch antenna, the need for a matching network between the two no longer exists. Thus the efficiency of the wireless battery will improve. Moreover, this matching technique automatically suppresses the reradiation of harmonics by the microstrip patch antenna since the harmonics will be mismatched. Thus, the impedance matching and filtering network encountered in traditional wireless battery designs has become obsolete. With the aid of analytical models developed for antenna and rectifier, single-layer, internally matched and filtered PCB rectennas have been designed for low input power levels. An efficiency of 52% for OdBm input power has been realized at 2.45 GHz for a wireless battery realized on FR4, showing an improvement - next to the size and complexity reduction - of more than 10% over a traditional rectenna design. A series connection of these wireless batteries is shown to be able to power a standard household wall clock.

Balanced-Fed Planar Antenna for Millimeter-Wave Transceivers

A balanced antenna design is presented that is tailored to broadband communication in the 60-GHz frequency band. The antenna can be realized in printed circuit-board technology, has a high radiation efficiency and can be used in array configurations. It is modeled with a method-of-moments implementation. The radiation efficiency is analyzed in detail, and design guidelines are given. Moreover, an optimization method is outlined that optimizes both antenna bandwidth and radiation efficiency. The antenna element and a circular antenna array have been realized. Measurements of these antennas are in good agreement with simulated results.

Analysis and Regularization of the Thin-Wire Integral Equation With Reduced Kernel

For the straight wire, modeled as a hollow tube, we establish a conditional equivalence relation between the integral equations with exact and reduced kernel. This relation allows us to examine the existence and uniqueness conditions for the integral equation with reduced kernel, based on a local argument. Further, we characterize the ill-posedness of integral equation with reduced kernel and we propose a regularization and filtering procedure to extend the range of this integral equation

A spectral volume integral equation method for arbitrary bi-periodic gratings with explicit fourier factorization

For dielectric periodic gratings, we propose the combina- tion of a spectral-domain volume integral equation and Fourier fac- torization rules to address the Gibbs phenomenon caused by jumps in both the flelds and the permittivity. From a theoretical point of view we discuss two ways to overcome the computational complexity caused by the inverse rule by changing the fundamental unknowns of the un- derlying electromagnetic problem. The resulting numerical system is solved iteratively and the corresponding matrix-vector product has an O(NM logM) complexity, where M is the number of Fourier modes and N is the number of sample points in the longitudinal direction.

Accurate and Efficient Computation of the Modal Green's Function Arising in the Electric-Field Integral Equation for a Body of Revolution

We present a computationally efficient way to compute the modal Greens function arising in the electric-field integral equation for a body of revolution. The computation of this function is time consuming due to its singular and oscillating nature, especially for high Fourier-mode indices. Efficient and accurate computation of this function is important to arrive at a fast numerical method for analyzing the scattering problem of a body of revolution. We compute the modal Greens function up to machine precision in a well-controlled way with limited effort, even for large bodies.

SIE approach to scattered field computation for 2D periodic diffraction gratings in 3D space consisting of high permittivity dielectric materials and plasmonic scatterers

We describe a surface integral-equation (SIE) method suitable for reliable computation of electromagnetic fields scattered by 2D periodic gratings in homogeneous 3D space in which the gratings may consist of high permittivity dielectric materials and metals. More in particular we brie y describe the formulation, the discretization and efficient evaluation of the Quasi Periodic Green Function (QPGF) and its gradient using Ewalds method. We present a case study to illustrate the methods capability of handling high permittivity dielectric materials and a second case study to demonstrate the effectiveness and indispensability of interpolating the QPGF and its gradient using tables with precomputed values.

A statistical characterization of resonant electromagnetic interactions with thin wires : variance and kurtosis analysis

A statistical characterization of random electromagnetic interactions affected by resonances is presented. It hinges on the analysis of the variance and the kurtosis to assess the intensity of the resonances. The method is illustrated by the study of a randomly varying thin wire modeled by a Pocklington integral equation.

Experimental validation of the stochastic model of a randomly fluctuating transmission-line

A modeling method is proposed to quantify uncertainties affecting electromagnetic interactions. This method considers the uncertainties as random and measures them thanks to probability theory. A practical application is considered through the case of a transmission-line of varying geometry, illuminated by a fixed electromagnetic field. The results of the stochastic numerical model are compared to the measurements performed on the transmission-line setup.