Diagonalized Macromodels in Finite Element Method for Fast Electromagnetic Analysis of Waveguide Components

K. Nyka Electronics – 2019
A new technique of local model-order reduction (MOR) in 3-D finite element method (FEM) for frequency-domain electromagnetic analysis of waveguide components is proposed in this paper. It resolves the problem of increasing solution time of the reduced-order system assembled from macromodels created in the subdomains, into which an analyzed structure is partitioned. This problem becomes particularly relevant for growing size and count of the macromodels, and when they are cloned in multiple locations of the structures or are used repeatedly in a tuning and optimization process. To significantly reduce the solution time, the diagonalized macromodels are created by means of the simultaneous diagonalization and subsequently assembled in the global system. For the resulting partially diagonal matrix, an efficient dedicated solver based on the Schur complement technique is proposed. The employed MOR method preserves frequency independence of the macromodels, which is essential for efficient diagonalization, as it can be performed once for the whole analysis bandwidth. The numerical validation of the proposed procedures with respect to accuracy and speed was carried out for varying size and count of macromodels. An exemplary finite periodical waveguide structure was chosen to investigate the influence of macromodel cloning on the resultant efficiency. The results show that the use of the diagonalized macromodels provided a significant solution speedup without any loss of accuracy

Improved RSS-Based DoA Estimation Accuracy in Low-Profile ESPAR Antenna Using SVM Approach

In this paper, we have shown how the overall performance of direction-of-arrival (DoA) estimation using lowprofile electronically steerable parasitic array radiator (ESPAR) antenna, which has been proposed for Internet of Things (IoT) applications, can significantly be improved when support vector machine (SVM) approach is applied. Because the SVM-based DoA estimation method used herein relies solely on received signal strength (RSS) values recorded at the antenna output port for different directional radiation patterns produced by the antenna steering circuit, the algorithm is wellsuited for IoT nodes based on inexpensive radio transceivers. Measurement results indicate that, although the antenna can provide 8 unique main beam directions, SVM-based DoA of unknown incoming signals can successfully be estimated with good accuracy in a fast way using limited number of radiation patterns. Consequently, such an approach can be used in efficient location-based security methods in Industrial Internet of Things (IIoT) applications.

A novel calibration method for RSS-based DoA estimation using ESPAR antennas

In this paper, we introduce a new calibration method that can successfully be used in direction of arrival (DoA) estimation using electronically steerable parasitic array radiator (ESPAR) antennas and employing power-pattern cross-correlation (PPCC) algorithm, which relies on received signal strength (RSS) values recorded at the antenna output port. Instead of the commonly used two-step approach, during which ESPAR antenna calibration is performed and then the overall DoA estimation accuracy is measured, a single setup, which allows simultaneous calibration and verification, has been proposed. Measurement results indicate that the new calibration method reduces the total time required for calibration and verification in RSS-based DoA estimation using ESPAR antennas, which makes this approach easily applicable in practical wireless sensor network (WSN) deployments saving the time and associated costs required for system implementations, where the number of WSN nodes can easily reach hundreds.

Automatic Reduction-Order Selection for Finite-Element Macromodels

An automatic reduction-order selection algorithm for macromodels in finite-element analysis is presented. The algorithm is based on a goal-oriented a posteriori error estimator that operates on low-order reduced blocks of matrices, and hence, it can be evaluated extremely quickly.

Investigation of continuous wave jamming in an IEEE 802.15.4 network

This paper presents how continuous wave jamming affects IEEE 802.15.4 network. To this end, an office-based measurement setup has been proposed. Within the measurement area, 25 nodes have been set up in order to create a IEEE 802.15.4 tree-based test network structure. A dedicated jamming device that generates and transmits a continuous wave signal has been developed. Several tests have been conducted and presented to demonstrate the network's vulnerability to jamming attacks for different jammer power levels and its positions across the scene.

RSS-Based DoA Estimation Using ESPAR Antenna Radiation Patterns Spline Interpolation

In this paper, it is shown how power pattern crosscorrelation (PPCC) algorithm, which relies on received signal strength (RSS) values recorded at electronically steerable parasitic array radiator (ESPAR) antenna output port, used for direction-of-arrival (DoA) estimation, can easily be improved by applying spline interpolation to radiation patterns recorded in the calibration phase of the DoA estimation process. The proposed method allows one to measure ESPAR antenna's radiation patterns during the initial calibration phase with much coarser angular resolution than required for linearly interpolated radiation patterns. Simulation results indicate that the overall DoA estimation accuracy can be kept at the similar level even for a few number of points, which, when applied in anechoic chamber calibration procedure of wireless sensor network (WSN) nodes equipped with ESPAR antennas, will have a noticeable influence on the overall calibration time and therefore also on deployment costs in practical WSN applications.

An algorithm for enhancing macromodeling in finite element analysis of waveguide components

G. Fotyga , K. Nyka – 2017
An algorithm for enhancing the finite element method with local model order reduction is presented. The proposed technique can be used in fast frequency domain simulation of waveguide components and resonators. The local reduction process applied to cylindrical subregions is preceded by compression of the number of variables on its boundary. As a result,the finite element large system is converted into a very compact set of linear equations which thus can be solved extremely fast.

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 system’s bandwidth.

Efficient analysis of structures with rotatable elements using model order reduction

This paper presents a novel full-wave technique which allows for a fast 3D finite element analysis of waveguide structures containing rotatable tuning elements of arbitrary shapes. Rotation of these elements changes the resonant frequencies of the structure, which can be used in the tuning process to obtain the S-characteristics desired for the device. For fast commutations of the response as the tuning elements are rotated, the 3D finite element method is supported by multilevel model-order reduction, orthogonal projection at the boundaries of macromodels and the operation called macromodels cloning. All the time-consuming steps are performed only once in the preparatory stage. In the tuning stage, only small parts of the domain are updated, by means of a special meshing technique. In effect, the tuning process is performed extremely rapidly. The results of the numerical experiments confirm the efficiency and validity of the proposed method.

Measurement of distance, velocity and angle of arrival using FMCW-CW combined waveform

A procedure of tacking small flying object based on a general principle of FMCW and Doppler radar is presented. In order to increase measurement range, this technique uses active signal source on the moving object. For simultaneous measurements of distance, radial velocity and direction (AoA) as well as simplified synchronization a combined FMCW-CW waveform is proposed. The presented measurement system was realized and verified in the field during flight tests of a research rocket.