121 research outputs found
Optimal Wideband LPDA Design for Efficient Multimedia Content Delivery over Emerging Mobile Computing Systems
An optimal synthesis of a wideband Log-Periodic
Dipole Array (LPDA) is introduced in the present study. The LPDA optimization is performed under several requirements concerning the standing wave ratio, the forward gain, the gain flatness, the front-to-back ratio and the side lobe level, over a
wide frequency range. The LPDA geometry that complies with the above requirements is suitable for efficient multimedia content delivery. The optimization process is accomplished by applying a recently introduced method called Invasive Weed Optimization (IWO). The method has already been compared to other evolutionary methods and has shown superiority in solving complex non-linear problems in telecommunications and electromagnetics. In the present study, the IWO method has been chosen to optimize an LPDA for operation in the frequency range
800-3300 MHz. Due to its excellent performance, the LPDA can effectively be used for multimedia content reception over future mobile computing systems
Evaluation of prediction accuracy for the Longley-Rice model in the FM and TV bands
Accurate geographical coverage predictions
maps for FM and TV are needed for channel and
frequency allocations and in order to avoid unwanted
interferences. The Longley-Rice model has been used
for this purpose over the last four decades and still
being used almost exclusively by the FCC in the
United States. In this work a comparison is presented
between the relative accuracy of this model in the
VHF-FM and UHF-TV frequency bands. Simulations
were made with accurate and up to date input data
(antenna height, location, gain, transmit power, etc.)
for the FM-TV stations provided by the ERT S.A.
public broadcaster in the region of Thessaloniki –
Greece. Finally, the calculated – simulated results
were confronted to field measurements using a Rohde
& Schwarz FSH3 portable spectrum analyzer and
high precision calibrated biconical and log-periodic
antennas, and the errors between predictions and
measurements were statistically analyzed in the two
frequency bands. It has been found in this study that
the Longley-Rice model, in general, overestimates
field-strength values, but this overestimation is much
higher in the VHF – FM radio band (88-108 MHz)
than in the UHF-TV band (470-790 MHz)
Comparative study of Radio Mobile and ICS Telecom propagation prediction models for DVB-T
In this paper, a comparative study between the results of a measurement campaign conducted in northern Greece and simulations performed with Radio Mobile and ICS Telecom radio planning tools is performed. The DVB-T coverage of a transmitting station located near the city of Thessaloniki is
estimated using three empirical propagation models (NTIA-ITS Longley Rice, ITU-R P.1546 and Okumura-Hata-Davidson) and one deterministic model (ITU-R 525/526). The best results in terms of minimum average error and standard deviation are obtained using the deterministic model and the NTIA-ITS
Longley Rice empirical model. In order to improve the results, the tuning options available in the ICS Telecom software are used on the Okumura-Hata-Davidson model, leading to a significant
increase in accuracy
Comparison of Evolutionary Optimization Algorithms for FM-TV Broadcasting Antenna Array Null Filling
Broadcasting antenna array null filling is a very
challenging problem for antenna design optimization. This paper
compares five antenna design optimization algorithms (Differential
Evolution, Particle Swarm, Taguchi, Invasive Weed, Adaptive
Invasive Weed) as solutions to the antenna array null filling
problem. The algorithms compared are evolutionary algorithms
which use mechanisms inspired by biological evolution, such as
reproduction, mutation, recombination, and selection. The focus of
the comparison is given to the algorithm with the best results,
nevertheless, it becomes obvious that the algorithm which produces
the best fitness (Invasive Weed Optimization) requires very
substantial computational resources due to its random search
nature
Optimization of log-periodic dipole antenna with LTE band rejection
This study presents an optimized design of a 10-dipole logperiodic antenna for UHF TV reception with LTE band rejection. The simulation of the antenna was performed in CST simulation software followed by optimization of the design using TRF (Trusted Region Framework) algorithm in the frequency range of 450 MHz-900 MHz. The parameters optimized are S11, realized gain and front-to-back ratio of the antenna. TV reception passband is 450 MHz-790 MHz and LTE band is 810 MHz-900 MHz. The proposed antenna design provides a good matching with a low S11 in the passband (470 MHz-790 MHz) and a high S11 in the stopband (i.e. LTE region of 810 MHz-900 MHz). The antenna provides a realized gain between 7 dBi and 8 dBi whereas front-to back ratio above 14 dB in the passband
Software Solutions for Antenna Design Exploration: A Comparison of Packages, Tools, Techniques, and Algorithms for Various Design Challenges
Numerous software packages exist for solving antenna design optimization problems, with many of these employing a variety of approaches, leading, in turn, to variations in optimization performance. Antenna designers, often not fully schooled in optimization, can be confused as to which algorithm in which software package should be used. A wrong choice can cause the failure of the optimization or the expending of considerable time on the computationally expensive 3D electromagnetic (EM) simulations involved. While it is true that the various algorithms, combined with the variety of complex challenges found in different real-world scenarios make a direct comparison among tools difficult, a robust attempt at such an evaluation is overdue
Accurate Antenna Gain Estimation Using the Two-Antenna Method
This paper demonstrates a simulation-assisted measurement technique to determine the gain of an antenna accurately in an open test site or anechoic chamber. The proposed technique is based on the two-antenna gain measurement method using Friis equation in far-field free-space conditions, with the actual measurement test setup modelled in CST Studio Suite for
simulation. An LTE-reject UHF TV log-periodic dipole antenna is used to validate the gain measurement technique in this paper. The simulation of the two-antenna gain measurement method is used in order to estimate an appropriate minimum separation distance between the two antennas that needs to be used for actual measurements to ensure far-field free-space conditions. Determining this minimum separation distance using several simulations instead of actual measurements saves time and effort because it eliminates the need to perform measurements at various separation distances. The measured realized gain obtained using this technique provides a good agreement with the simulation and thus validates the accuracy of this technique
Calibration of Free-Space Radiometric Partial Discharge Measurements
The present study addresses the calibration of four types of partial discharge (PD) emulators used in the development of a PD Wireless Sensor Network (WSN). Three PD emulators have been constructed: a floating-electrode emulator, and two internal PD emulators. Both DC and AC high-voltage power supplies are used to initiate PD, which is measured using concurrent free-space radiometry (FSR) and a galvanic contact method based on the IEC 60270 standard. The emulators have been measured and simulated, and a good agreement has been found for the radiated fields. A new method of estimating the absolute PD activity level from radiometric measurements is proposed
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