Krzysztof Nyka

Efficient Model Order Reduction for FEM Analysis of Waveguide Structures and Resonators

An e-cient model order reduction method for three- dimensional Finite Element Method (FEM) analysis of waveguide structures is proposed. The method is based on the E-cient Modal Order Reduction (ENOR) algorithm for creating macro-elements in cascaded subdomains. The resulting macro-elements are represented by very compact submatrices, leading to signiflcant reduction of the overall number of unknowns. The e-ciency of the model order reduction is enhanced by projecting flelds at the boundaries of macro- elements onto a subspace spanned by a few low-order waveguide modes. The combination of these two techniques results in considerable saving in overall computational time and memory requirement. An additional advantage of the presented method is that the reduced- order system matrix remains frequency-independent, which allows for very fast frequency sweeping and e-cient calculation of resonant frequencies. Several numerical examples for driven and eigenvalue problems demonstrate the performance of the proposed methodology in terms of accuracy, memory usage and simulation time.

A Review of Antennas for Indoor Positioning Systems

This paper provides a review of antennas applied for indoor positioning or localization systems. The desired requirements of those antennas when integrated in anchor nodes (reference nodes) are discussed, according to different localization techniques and their performance. The described antennas will be subdivided into the following sections according to the nature of measurements: received signal strength (RSS), time of flight (ToF), and direction of arrival (DoA). This paper intends to provide a useful guide for antenna designers who are interested in developing suitable antennas for indoor localization systems.

Enhancing performance of switched parasitic antenna for localization in Wireless Sensor Networks

This paper presents an Electronically Steerable Parasitic Array Radiator (ESPAR) antenna with enhanced performance of estimating the Incoming signal direction. Designed antenna is dedicated for 2.4 GHz ISM applications with emphasis on Wireless Sensor Networks (WSN). The limitations of the existing design approach are illustrated, as well as perspectives and challenges of the proposed solution in relation to the localization in Wireless Sensor Networks.

A New Type of Macro-Elements for Efficient Two-Dimensional FEM Analysis

This letter deals with a model order reduction technique applicable for driven and eigenvalue problems solved using the finite element method (FEM). It allows one to efficiently compute electromagnetic parameters of structures comprising small features that require strong local mesh refinement. The subdomains of very fine mesh are separated from the global domain as so called macro-elements that undergo model reduction. The macro-elements of reduced order are described by a significantly smaller number of unknowns, thus improving overall simulation speed. In addition, we present an algorithm of macro-elements multiple reuse, called cloning, which provides further decrease of the computation time and memory requirements. The results of the two numerical experiments, in which the local mesh refinement exceeds the factor of 400, illustrate the properties of the proposed methodology and prove that it increases the FEM efficiency significantly and is particularly suitable for multiscale problems with strong variations of desired mesh density.

Quasi-static finite-element analysis of a skewed microstrip crossover

In this work, we present a quasistatic analysis of a microstrip crossover on a dielectric substrate. The microstrips are located at different planes and may cross at an arbitrary angle. Capacitances and inductances are calculated from scalar potentials. For magnetostatic formulation, the boundary conditions for scalar potential are introduced by means of partitioning surfaces. The use of the adaptive finite element method provides the required flexibility with respect to the analyzed geometry, optimal discretization and good efficiency.

A 3D-FEM mesh technique for fast analysis of waveguide problems containing rotatable tuning elements

In this paper a meshing technique for 3D Finite Element Method is presented. It allows for fast analysis and optimization of the waveguide structures, which contain rotatable tuning elements. In the proposed procedure a thin layer of varying cylindrical mesh buffer is introduced in order to reuse unchanged mesh and FEM matrices in the rest of the domain.

Adaptive finite-element multigrid method in 3D magnetostatic analysis

We present a procedure of magnetostatic analysis of microwave circuits comprising conductors of arbitrary shapes. It is assumed that the magnetic field excitation is given as a total current flowing in signal conductors. The boundary conditions in structures of arbitrary geometries without symmetry are introduced by means of partitioning surfaces. This formulation leads however to several implementational issues that are addressed in this paper. The use of adaptive finite element method and multigrid method provides required flexibility with respect to analyzed geometry, optimal discretization and good efficiency.

Improved jamming resistance using electronically steerable parasitic antenna radiator

This paper presents an idea of using an Electronically Steerable Parasitic Antenna Radiator (ESPAR) for jamming suppression in IEEE 802.11b networks. Jamming (intentional interference) attacks are known to be effective and easy to perform, which may impose connectivity problems in applications concerning Internet of Things (IoT). In our paper, theoretical considerations are presented and the results of experiments performed in anechoic chamber are examined. During the test, IEEE 802.11b standard was used to provide communication between transmitter and receiver, and Software Defined Radio (SDR) device, which was used as a source of an intentional interference (jammer). The results showed that connectivity during jamming attack can be improved by using switched-beam antenna enhancing systems bandwidth.

Wideband Model Order reduction for macromodels in Finite Element Method

This paper presents a novel algorithm for accelerating 3D Finite Element Method simulations by introducing macromodels created in local model order reduction in the selected subdomains of the computational domain. It generates the projection basis for a compact system of equations associated with a separate subdomain. Due to non-linear frequency dependency in the Right Hand Side (RHS), the standard reduction methods do not perform properly. The proposed algorithm alleviates this problem being easy to implement and accurate in wide frequency band simulations of complex structures.

Dual polarization antennas for UHF RFID readers

This paper presents various concepts of switching polarization in patch antenna dedicated for UHF RFID readers. Proposed designs allow for switching between linear and circular polarization. The first design does not require electronic switching as the polarization can be changed by choosing one of two available feeding terminals. Two remaining designs use PIN diode or FET SPDT switch.