Use of the Analog Neural Networks in the Adaptive Antenna Control Systems

In the paper, original control system of adaptive antennas, which is based on Kalman filter, is presented and compared with earlier approaches to this problem. The designed control circuit eliminates some disadvantages of the control circuits based on the classical Kalman neural network and the Wang one, and enables a real time processing of quickly changing signals processed by adaptive antennas. Especially, the dependence of the convergence rate on ratio of eigenvalues and the risk of instability are significantly reduced

Multi-Objective Optimization of Wire Antennas: Genetic Algorithms Versus Particle Swarm Optimization

The paper is aimed to the multi-objective optimization of wire multi-band antennas. Antennas are numerically modeled using time-domain integral-equation method. That way, the designed antennas can be characterized in a wide band of frequencies within a single run of the analysis. Antennas are optimized to reach the prescribed matching, to exhibit the omni-directional constant gain and to have the satisfactory polarization purity. Results of the design are experimentally verified. The multi-objective cost function is minimized by the genetic algorithm and by the particle swarm optimization. Results of the optimization by both the multi-objective methods are in detail compared. The combination of the time domain analysis and global optimization methods for the broadband antenna design and the detailed comparison of the multi-objective particle swarm optimization with the multi-objective genetic algorithm are the original contributions of the paper

Multireflector Antennas - Cascaded Structures with Frequency Selective Surfaces

The problem of increasing the gain of directional multiband antennas is solved in the paper. A single-fed multiband (wideband) planar dipole is combined with cascaded (sandwiched) reflectors made of frequency selective surfaces. Each of those reflectors is placed in a quarter-wavelength distance from the dipole at the frequency of operation. The impedance matching is particularly achieved by active element properties, and impedance symmetrization. Further transformation is made by a planar circuit, placed on the active element plane. The antenna gain is set by the reflector elements amount (reflector plane dimensions). The antenna structure enables its setting into arrays with in-phase feeding

Modeling Broadband Microwave Structures by Artificial Neural Networks

The paper describes the exploitation of feed-forward neural networks and recurrent neural networks for replacing full-wave numerical models of microwave structures in complex microwave design tools. Building a neural model, attention is turned to the modeling accuracy and to the efficiency of building a model. Dealing with the accuracy, we describe a method of increasing it by successive completing a training set. Neural models are mutually compared in order to highlight their advantages and disadvantages. As a reference model for comparisons, approximations based on standard cubic splines are used. Neural models are used to replace both the time-domain numeric models and the frequency-domain ones

Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

Design and Implementation of Closed TEM Cells: Simulation-Based Approach

In the paper, a simulation-based design procedure for the implementation of a TEM cell (the Crawford cell) is presented. The empirical approach uses computer simulations carried out in the CST Microwave Studio to design the cell that operates in the frequency range from 100 kHz to 400 MHz. Following the developed procedure, the TEM cell was implemented, and the cell was tested experimentally. The TEM cell can be used for electromagnetic susceptibility (EMS) measurements, where the DUT is irradiated by the field in a wide frequency band. The DUT is tested to operate without the performance degradation under the influence of electromagnetic disturbances. In addition, the cell can be used for electromagnetic interference (EMI) measurements focused on interference emissions generated by the DUT

Multi-Band Planar Antennas: a Comparative Study

The classical patch antenna is a basic building block of compared antennas. The multi-band behavior is achieved by etching perturbation slots to the patch, which influence resonant current distributions. The antennas are designed for GSM bands (900 MHz, 1 800 MHz), and for the Bluetooth band (2 400 MHz)