The near-field communication (NFC) technique finds wide applications in many aspects of modern life, e.g., contactless payment systems or authentication. Regardless of the application, typically, the requirements on the antenna structure are manifold. Frequently, limitations in the available space make the antenna design quite challenging. Beside geometrical limitations, also the matching of the antenna structure to the analog front end of the NFC transponder IC has to be taken into account. Furthermore, the NFC antenna together with the connected IC has to fulfill specific standardized values. In this paper, the optimization of an NFC antenna structure including the needed matching circuit in the multi-objective sense is proposed. Due to its simplicity and the consequently reduced computational effort, the partial-element electric circuit (PEEC) method is applied to carry out the needed field computation in the so-called NFC operating volume. Furthermore, the PEEC method offers the possibility of simply connecting lumped components to the antenna structure within the numerical analyses, which enables the optimization of the matching circuit parallel to the optimization of the antenna structure. The optimization relies on a stochastic optimization strategy, namely, the firefly algorithm (FFA). In this paper, an extended version of the general FFA is applied.

The field regions around antennas are distinguished through the properties of the electromagnetic field. The knowledge of the boundaries between these regions is very important for e.g. measurement engineers or in the numerical simulation to ensure a proper behavior of their results. In the present work the validity of the boundaries suggested from the literature has been analyzed using error estimations for different properties of the electromagnetic field. Analyses are conducted on dipole antennas, loop antennas as well as on Yagi-Uda arrays with various dimensions. In addition, different concepts are introduced allowing the definition of a more convenient boundary between the field regions. The proposed rules satisfy the IEEE standard definitions in a better way. For the numerical computations a one dimensional Method of Moments is applied.

Linear antenna arrays consisting of dipole antennas find wide applications in wireless communication systems. Typically, arrangements with uniform spacing between the array elements are applied to gain highly directive radiation patterns while controlling the radiation intensity in the side lobes. To describe such arrangements the so called Pattern Multiplication (PM) technique is frequently applied which inherently neglects the inter-element coupling. In the present paper an antenna array arrangement with non-uniformly spacing between the array elements is synthesized in the multi-objective sense. Therefore the PM technique is deficient. Hence, numerical techniques have to be applied to compute the electromagnetic field during the optimization process. Due to its simplicity and the consequently reduced computational costs the Partial Element Equivalent Circuit (PEEC) method is applied within the field computation process. The optimization relies on a stochastic particle swarm optimization strategy, namely the firefly algorithm. In the present paper an extended version of the general algorithm with additional hierarchical clustering is applied. Special attention is drawn to the development of a suitable objective function.

Estimating the coupling properties between a radiating structure and other conductive elements, the field behavior of the radiating source is essential to know. One well-known classification of the field behavior are the field-regions around antennas, namely, the far-field, the radiating near-field, and the reactive near-field. The different kinds of near-fields are distinguished by the reactive and radiating parts of the electromagnetic field, whereas in the far-field region the field behaves as a plane wave in the direction of propagation. One way to describe these field characteristics is to use the complex Poynting vector, which defines the electromagnetic power flow. This work presents a Poynting-vector-based approach to classify and visualize the field behavior around simple radiators using numerical simulations. First, the approach is applied to simple antenna structures such as dipoles and loop antennas. Later, the introduced field regions are utilized to predict the coupling behavior of practical applications, the coupling between single elements of a linear antenna array, and the coupling behavior of an electrically large loop antenna. It could be shown that the introduced approach, defining a surface description of the boundary between the near-field regions, enables the possibility of predicting the coupling behavior between radiating structures. The introduced error estimator for the far-field also delivers knowledge about the far-field quality in different angular directions and distances. All simulations have been executed applying a one-dimensional partial element equivalent circuit method.

Purpose: The purpose of this paper is to show that the computation of time-periodic signals for coupled antenna-circuit problems can be substantially accelerated by means of the single shooting method. This allows an efficient analysis of nonlinearly loaded coupled loop antennas for near field communication (NFC) applications. Design/methodology/approach: For the modelling of electrically small coupled field-circuit problems, the partial element equivalent circuit (PEEC) method shows to be very efficient. For analysing the circuit-like description of the coupled problem, this paper developed a generalised modified nodal analysis (MNA) and applied it to specific NFC problems. Findings: It is shown that the periodic steady state (PSS) solution of the resulting differential-algebraic system can be computed very time efficiently by the single shooting method. A speedup of roughly 114 to conventional transient approaches can be achieved. Practical implications: The proposed approach appears to be an efficient alternative for the computation of time PSS solutions for nonlinear circuit problems coupled with discretised conductive structures, where the homogeneous solution is not of interest. Originality/value: The present paper explores the implementation and application of the shooting method for nonlinearly loaded coupled antenna-circuit problems based on the PEEC method and shows the efficiency of this approach.

To understand wave propagation phenomena, complex mathematical and physical theory is needed. Therefore, many undergraduate students find it very difficult to deal with this area of research. In this paper, an interactive toolbox is proposed which can help students to gain profounder knowledge and understanding of wave propagation effects. Great importance was attached to the design of a very simple user interface to help the students focus on the essential. The data interface was created to be very general and simple for an easy extension.