scholarly journals Optimal Design of Aperiodic Reconfigurable Antenna Array Suitable for Broadcasting Applications

Electronics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 818 ◽  
Author(s):  
Ioannis P. Gravas ◽  
Zaharias D. Zaharis ◽  
Pavlos I. Lazaridis ◽  
Traianos V. Yioultsis ◽  
Nikolaos V. Kantartzis ◽  
...  
Keyword(s):  
Antenna Array ◽  
Optimization Methods ◽  
Base Station ◽  
Service Area ◽  
Center Frequency ◽  
Computational Time ◽  
Full Wave ◽  
Low Sidelobe ◽  
Full Wave Analysis ◽  
Velocity Mutation

An aperiodic reconfigurable microstrip antenna array is designed to serve as a DVB-T base station antenna operating in a single broadcasting channel. The antenna array is optimized at 698 MHz (center frequency of DVB-T channel 49) to concurrently achieve a particular radiation pattern shaping with high forward gain, main lobe tilting and null filling inside the service area, as well as low sidelobe level outside the service area, and low standing wave ratio at the inputs of all the array elements. To concurrently satisfy all the above requirements, both the geometry dimensions and the array feeding weights (amplitudes and phases) are optimized, thus leading to a complex multi-variable and multi-objective problem. The problem is solved by applying a recently developed particle swarm optimization (PSO) improved variant, called PSO with velocity mutation, in conjunction with the CST software package, which is employed by the PSOvm every time a full-wave analysis is required. Furthermore, all the optimization methods found in the CST environment are compared with the PSOvm. The results show that the PSOvm is capable of producing an antenna array geometry, which is closer to the predefined requirements than the geometries derived by the rest of the optimizers, in the least amount of computational time.

scholarly journals Estimating Electric Field and SAR in Tissue in the Proximity of RF Coils

2020 ◽  
pp. 293-307
Author(s):  
Rosti Lemdiasov ◽  
Arun Venkatasubramanian ◽  
Ranga Jegadeesan
Keyword(s):  
Electric Field ◽  
Computational Time ◽  
Rf Coils ◽  
Induced Current ◽  
Resonant Coupling ◽  
Simulation Tools ◽  
Full Wave ◽  
Rf Exposure ◽  
Simulation Based ◽  
Full Wave Analysis

AbstractMedical implants that require recharging typically use magnetic resonant coupling of transmit (external) and receive (internal) RF coils. Apart from magnetic field, the transmit coil creates a time-varying electric field that excites currents not only in the receive coil but also in the surrounding tissues. Radio frequency (RF) exposure assessment for inductive systems used in wireless powering and telemetry is done using electric field, specific absorption rate (SAR), and induced current as metrics. Full-wave analysis using RF simulation tools such as Ansys HFSS is generally used to estimate these metrics, and the results are widely accepted. However, such simulation-based analysis is quite rigorous and time-consuming, let alone the complexities with setting up the simulation.In this paper, we present a simple approach to estimating exposure (electric field, SAR, induced current) from fundamental electromagnetic principles enabling ability to arrive at results quickly. It significantly reduces the computational time in iterative approaches where multiple simulation runs are needed.

scholarly journals Design & Optimization of Large Cylindrical Radomes with Subcell and Non-Orthogonal FDTD Meshes Combined with Genetic Algorithms

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2263
Author(s):  
Enrique A. Navarro ◽  
Jorge A. Portí ◽  
Alfonso Salinas ◽  
Enrique Navarro-Modesto ◽  
Sergio Toledo-Redondo ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Antenna Array ◽  
Near Field ◽  
Antenna System ◽  
Curvilinear Coordinates ◽  
Ultraviolet Rays ◽  
Wave Analysis ◽  
Full Wave ◽  
Full Wave Analysis ◽  
Optimization Loop

The word radome is a contraction of radar and dome. The function of radomes is to protect antennas from atmospheric agents. Radomes are closed structures that protect the antennas from environmental factors such as wind, rain, ice, sand, and ultraviolet rays, among others. The radomes are passive structures that introduce return losses, and whose proper design would relax the requirement of complex front-end elements such as amplifiers. The radome consists mostly in a thin dielectric curved shape cover and sometimes needs to be tuned using metal inserts to cancel the capacitive performance of the dielectric. Radomes are in the near field region of the antennas and a full wave analysis of the antenna with the radome is the best approach to analyze its performance. A major numerical problem is the full wave modeling of a large radome-antenna-array system, as optimization of the radome parameters minimize return losses. In the present work, the finite difference time domain (FDTD) combined with a genetic algorithm is used to find the optimal radome for a large radome-antenna-array system. FDTD uses general curvilinear coordinates and sub-cell features as a thin dielectric slab approach and a thin wire approach. Both approximations are generally required if a problem of practical electrical size is to be solved using a manageable number of cells and time steps in FDTD inside a repetitive optimization loop. These approaches are used in the full wave analysis of a large array of crossed dipoles covered with a thin and cylindrical dielectric radome. The radome dielectric has a thickness of ~λ/10 at its central operating frequency. To reduce return loss a thin helical wire is introduced in the radome, whose diameter is ~0.0017λ and the spacing between each turn is ~0.3λ. The genetic algorithm was implemented to find the best parameters to minimize return losses. The inclusion of a helical wire reduces return losses by ~10 dB, however some minor changes of radiation pattern could distort the performance of the whole radome-array-antenna system. A further analysis shows that desired specifications of the system are preserved.

Rigorous full-wave analysis of the base-station antennas

2002 ◽  
Vol 19 (3) ◽  
pp. 324-328
Author(s):  
Shengbing Chen ◽  
Fushun Zhang ◽  
Yongchang Jiao ◽  
Baohua Sun
Keyword(s):  
Base Station ◽  
Wave Analysis ◽  
Full Wave ◽  
Base Station Antennas ◽  
Full Wave Analysis

Mobile network synthesis strategy

2019 ◽  
pp. 98-101
Author(s):  
V. Lyandres
Keyword(s):  
Average Distance ◽  
Mobile Network ◽  
Base Station ◽  
Service Area ◽  
Base Stations ◽  
Frequency Assignment ◽  
Network Synthesis ◽  
Universal Method ◽  
Synthesis Strategy ◽  
Adaptive Vector Quantization

Introduction:Effective synthesis of а mobile communication network includes joint optimisation of two processes: placement of base stations and frequency assignment. In real environments, the well-known cellular concept fails due to some reasons, such as not homogeneous traffic and non-isotropic wave propagation in the service area.Purpose:Looking for the universal method of finding a network structure close to the optimal.Results:The proposed approach is based on the idea of adaptive vector quantization of the network service area. As a result, it is reduced to a 2D discrete map split into zones with approximately equal number of service requests. In each zone, the algorithm finds such coordinates of its base station that provide the shortest average distance to all subscribers. This method takes into account the shortage of the a priory information about the current traffic, ensures maximum coverage of the service area, and what is not less important, significantly simplifies the process of frequency assignment.

Full-wave analysis of shielded coplanar waveguide short-end

1990 ◽  
Vol 26 (19) ◽  
pp. 1615 ◽  
Author(s):  
G. Bartolucci ◽  
J. Piotrowski
Keyword(s):  
Coplanar Waveguide ◽  
Wave Analysis ◽  
Full Wave ◽  
Full Wave Analysis
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