Showing papers in "Journal of Microwaves, Optoelectronics and Electromagnetic Applications in 2021"
TL;DR: In this paper, the authors presented the design and main electromagnetic characteristics of the novel compact microwave waveguide polarizer, which is based on a circular waveguide and anti-phase conducting posts located in it.
Abstract: This research presents the design and main electromagnetic characteristics of the novel compact microwave waveguide polarizer. The developed device's structure is based on a circular waveguide and anti-phase conducting posts located in it. The application of a circular waveguide instead of a square one allowed simple integration of a polarizer with corrugated horn antennas. The obtaining of required phase difference using a posts-based design provides the possibility of fine tuning of the developed circular waveguide polarizer after its manufacturing process. In addition, simultaneous adaptive operation at orthogonal circular and linear polarizations is available in the antenna system including a polarizer with posts. An automatic control of posts height must be applied in a waveguide in order to provide this option. Numerical simulation, optimization, manufacture and measurements of the polarizer's characteristics were carried out in the operating band 7.4-8.5 GHz. Measured characteristics proved that the suggested circular waveguide polarizer provides good matching and polarization performance. Developed circular waveguide polarizer can be integrated in corrugated horn antenna systems and applied in modern weather radars and satellite information systems.
17 citations
TL;DR: In this paper, a millimeter-wave printed quadrupole antenna is proposed, which consists of two symmetric printed dipoles that make the quad-rupole radiating power omnidirectionally.
Abstract: In this paper, a millimeter-wave printed quadrupole antenna is proposed. It consists of two symmetric printed dipoles that make the quadrupole radiating power omnidirectionally. Such an arrangement eliminates the influence of the ground as reflector. Simulation results show that the quadrupole antenna exhibits a broad impedance bandwidth and an enhanced gain compared to conventional dipoles. More interestingly, the configuration of the quadrupole includes an integrated feed network, making the design compact. Next, a novel omnidirectional array was designed, simulated, fabricated, and measured, exhibiting enhanced features like compactness, broad bandwidth, high gain, high efficiency, low cross-polarization, low cross-polarization level, low cost, and low profile.
5 citations
TL;DR: This application proves the effectiveness of using BIC techniques for modeling the communication channel by verifying an error reduction of about 80% concerning the metrics root-mean-square error and standard deviation.
Abstract: In this work, a new method employs Bioinspired Computational (BIC) optimization from the genetic algorithm, bat algorithm, and flower pollination algorithm. Robust and accurate modeling of the input parameters adjusts the propagation models Stanford University Interim, Electronic Communication Committee, and Floating Interception that consider environments with characteristics specifically of urban regions in the Amazon. The lack of research related to the development of propagation models for Amazonian environments motivated this work. Thus, this application proves the effectiveness of using BIC techniques for modeling the communication channel. Measurement campaigns were carried out in the city of Belem, Brazil, for large-scale channel modeling on the frequencies of 1.8 and 2.6 GHz, belonging to the long-term evolution or fourth-generation mobile communications system (4G). After being adjusted by the optimum values calculated by the BIC techniques used, the models showed better results compared to modeling without optimization. Additionally, it was verified an error reduction of about 80% concerning the metrics root-mean-square error and standard deviation.
5 citations
TL;DR: In this paper, a high gain, metamaterial based super wideband (SWB) antenna has been proposed, which has two inverted U slots which are responsible for two notches at 3.5 GHz and 5 GHz frequencies.
Abstract: The paper proposes a high gain, metamaterial based super wideband (SWB) antenna. The SWB antenna has two inverted U slots which are responsible for two notches at 3.5 GHz and 5.5 GHz frequencies. A flower-shaped slot is etched from the radiator to obtain the SWB characteristics. The super wideband antenna has dimensions of 30×35 ×1.5 mm3 with FR4 substrate. The antenna has a frequency bandwidth of 3.1 GHz - 15 GHz for S11 < -10dB. A metamaterial unit cell is designed and simulated for permittivity and permeability characteristics. This shows a negative refractive index in the band of 2.4 GHz to 8 GHz and 8.2 GHz to 9 GHz. A 3×3 array of metamaterial cells is used as a superstrate for the improvement of the gain characteristics. The fabricated prototype SWB antenna with superstrate has measured frequency bandwidth 3.1-15 GHz with notched bands at 3.5 GHz and 5.5 GHz. The experimental and simulated results are in line with each other.
5 citations
TL;DR: The overall results show that the adaptive intelligent techniques can effectively fix signal links under the dynamic weather conditions for both satellite and wireless networks in this region.
Abstract: The dynamic weather condition is a major concern for optimum channel utilization in recent times, especially at higher frequencies with larger bandwidth for 5G applications. Over the years, rain-induced attenuation among the hydrometeors has been linked as the major cause of signal impairment especially at the frequency, f ≥ 10 GHz. However, when f > 18 GHz, the significant impact of other hydrometeors; cloud/fog, and scintillation increases tremendously, especially for Low Earth Orbit, LEO satellites. LEO satellites find applications in fibre optics technology, scientific research, remote sensing, surveillance, meteorology, satellite imaging, and other applications. In this paper, the assessment of combined impairments based on 5-year (2012-2016) data has been carried out and a dynamic adaptive intelligent scheme (DAIS) has been adopted to achieve a good quality of service along the satellite channels operating at Ku-V band frequencies over five stations representing different climatic regions in Nigeria namely: Port Harcourt (PH), Akure, Ilorin, Zaria, and Kano. The proposed DAIS based on fuzzy logic was able to achieve a significant reduction in the transmitting power by about 70% and SNR by 50% across the frequencies considered without altering the information content of the downlink parameters, thereby improving the QoS significantly and adhere to Customer Service Level Agreements (CSLAs) irrespective of the weather dynamics. The overall results show that the adaptive intelligent techniques can effectively fix signal links under the dynamic weather conditions for both satellite and wireless networks in this region. Information from the results is timely because it will serve as the bedrock for the newly launched transformation to the digital video broadcasting (DVB) system in Nigeria for effective service delivery.
4 citations
TL;DR: A low-cost spectrum analyzer is presented, based on a commercial software defined radio and an open-source application package, deployed to overcome the hardware analog-to-digital converter limitation to monitor wide bandwidths.
Abstract: A low-cost spectrum analyzer is presented, based on a commercial software defined radio and an open-source application package. Fundamentals regarding the receiving operation and its sensitivity are presented, along with measurements, of two 8 and 12-bits software defined radio models. An application, run within GNU Radio, is presented, deployed to overcome the hardware analog-to-digital converter limitation to monitor wide bandwidths. Results are shown for two different frequency ranges, 200 MHz bandwidth.
4 citations
TL;DR: In this article, the authors presented the proposed structure and the simulation results from analytical and numerical modeling of two corrosion sensor elements in D-shaped optical fiber: one based on the lossy mode resonance (LMR) effect and the other based on surface plasmon resonance (SPR).
Abstract: This article presents the proposed structure and the simulation results from analytical and numerical modeling of two corrosion sensor elements in D-shaped optical fiber: one based on the lossy mode resonance (LMR) effect and the other based on the effect of surface plasmon resonance (SPR). In the first sensor element, a bilayer of titanium dioxide – aluminum (TiO2-Al) is deposited on the D-shaped region, operating in LMR conditions, while, in the second sensor element, an aluminum (Al) monolayer is deposited under D-shaped region, operating in SPR condition. The sensor elements can operate separately, enabling simultaneous two-parameter measurements at two different points, or they can operate in cascade configuration, increasing the operating range and sensitivity of the sensor set. The D-shaped region of the optical fiber is modeled with an analytical model based on the Fresnel formulation, and also with a numerical model, which uses the finite element method with the COMSOL Multiphysics 5.2 software. The transmission of light through the D-shaped region causes peculiar variations in each light polarization in each sensor element, depending on the metal thickness. Both regions are subject to a corrosive environment. The sensor elements are evaluated separately and in cascade configuration, using polarized and nonpolarized light. Finally, the obtained results show two resonance valleys for the same operating wavelength, resulting in a higher operating range with high sensitivity, compared to other corrosion sensor structures found in the literature.
3 citations
TL;DR: In this paper, a multiband magneto-dielectric resonator antenna with cylindrical geometry is proposed, which is composed of yttrium iron garnet (YIG) with chemical composition Y3Fe2(FeO4)3.
Abstract: A multiband magneto-dielectric resonator antenna with cylindrical geometry is proposed in this paper. The resonator is composed of yttrium iron garnet (YIG) with chemical composition Y3Fe2(FeO4)3. The final structure is built on a low-cost FR4 dielectric substrate. With only one resonator, the antenna is able to resonate in three distinct controlled frequency bands. These are the three propagation modes HEM11δ, TE01δ, and TM01δ, which are possible to be independently controlled at each input port of the resonator antenna. The resonator’s port was suitable designed to feed specific modes of the antenna using microstrip lines placed judiciously to excite each mode. Analytic, numerical, and experimental studies were performed and, after optimization, the final antenna design was obtained. The obtained simulated and measured S-parameters results are below -10 dB at the resonance frequencies 5.75 GHz, 6.86 GHz, and 8.37 GHz. The corresponding measured bandwidths are 370 MHz, 120 MHz, and 1060 MHz, respectively. The antenna has a total size of 32.5 × 32.5 × 8.35 mm3. Measured radiation patterns and gain are also presented and show good agreement when compared to simulated results.
3 citations
TL;DR: In this article, a new optical fiber corrosion sensor based on metallic bilayers is described, where the detection region is located at a fiber end facet and the authors present simulations as well as experimental results in controlled lab conditions for Ti(10 nm)/Al (10 nm) and Ni(5 nm/Al (5 nm) bilayers.
Abstract: In this paper, a new optical fiber corrosion sensor based on metallic bilayers is described. The detection region is located at a fiber end facet and we present simulations as well as experimental results in controlled lab conditions for Ti(10 nm)/Al(10 nm) and Ni(5 nm)/Al(5 nm) bilayers. We perform the characterization of the device by numerical simulations using the COMSOL Multiphysics software, and with an analytical model, which makes use of the Fresnel equations. According to the simulations, the change in the reflected optical signal over time is related to variations in the thickness of the metallic films by the corrosive process and, consequently, the corrosion rate in each metal of the bilayer can be obtained. Upon the simulation results, sensor devices were fabricated by depositing thin metallic films on the cleaved facet of the optical fiber using the sputtering method. We show that the use of a metallic bilayer as a transducer, instead of a monolayer, improves the sensor measuring interval (20 ± 1 nm) and provides information about the corrosion rate along the corrosion process.
3 citations
TL;DR: In this article, bandwidth enhancement of a microstrip patch antenna using a new kind of metasurface is discussed This new geometry is used to generate new resonances in antenna and with an optimal position of the metasuran in relation to antenna, we can overlap the resonances and obtain a large bandwidth.
Abstract: In this article, bandwidth enhancement of a microstrip patch antenna using a new kind of metasurface is discussed This new geometry is used to generate new resonances in antenna and with an optimal position of the metasurface in relation to antenna we can overlap the resonances and obtain a large bandwidth The proposed antenna showed a bandwidth from 51 GHz to 80 GHz what can it able to be applied in WiFi 5 and 6 Numerical results were obtained with Ansys HFSS software A prototype was built and measurements for S11, Smith chart and gain were performed Numerical and experimental results are in good agreement
2 citations
TL;DR: In this article, a wave matrix model was obtained by splitting the polarizer into separate structural elements, each element was described by its own wave transmission matrices, and the electromagnetic characteristics of the considered polarizer were obtained theoretically.
Abstract: The development of new mathematical model for guide polarization converter with diaphragms was carried out in the research by the method of wave matrices. In addition, numerical modeling of the performance of a polarizer with diaphragms is made by simulating the propagation of the fundamental modes with perpendicular linear polarizations. The wave matrix model was obtained by splitting the polarizer into separate structural elements. Each element was described by its own wave transmission matrices. As a result, a general wave scattering matrix was formed. Based on the elements this matrix the electromagnetic characteristics of the considered polarizer were obtained theoretically. In particular, complex reflection and transmission coefficients were calculated. Their modules and phases were analyzed in the frequency interval 10.7-12.8 GHz. To check the correctness of the obtained results an independent numerical simulation was carried out applying the finite element methodology in the frequency interval. The results of both approaches are in good agreement. The engineered converter of polarization with four diaphragms provides a reflection coefficient modulus of less than 0.14 and a transfer coefficient modulus of more than 0.99 for two orthogonal types of polarizations. As a result, a rigorous mathematical method was developed to analyze the elements of the scattering matrix of a waveguide polarizer with diaphragms. It can be used for the development of new broadband waveguide polarizers and waveguide filters based on diaphragm elements.
TL;DR: In this article, the authors proposed a new Damped Jacobi (NDJ) detector to improve the performance of the classical Jacobi linear algorithm for massive multiple-input multiple-output (MIMO) uplink.
Abstract: For massive multiple-input multiple-output (m-MIMO) uplink, the performances of the linear minimum mean-square error (MMSE) detector are considered near optimal, and they occupy benchmark place for most linear iterative detectors. However, the MMSE algorithm is known by its load computational complexity due to the implication of large-scale matrix inversions, and in other hand, iterative methods are often preferred in signal detection because of its low complexity. In this paper, we propose a New Damped Jacobi (NDJ) detector in order to improve the performance of the classical Jacobi linear algorithm. Starting from the classical Jacobi technique to our new proposal, we go through the development of two variants; one uses a damping factor and the other uses a stair-matrix. However, the NDJ incorporates a damping factor in its construction and basing also on stair matrix instead of diagonal matrix. The performances in terms of convergence and low complexity of each Jacobi variant studied in this paper are analyzed. Finally, some simulation examples are given to illustrate the advantages of the new proposed algorithm.
TL;DR: In this paper, the synthesis of a multi-band frequency selective surface (FSS) through bioinspired computing and a general regression neural network (GRNN) is addressed, which utilizes the multi-objective cuckoo search algorithm combined to a GRNN, determine the best physical dimensions of the FSS in order to achieve a multiband filtering at the 2.4, 3.5 and 5.8 GHz spectrums.
Abstract: This work addresses the synthesis of a multi-band frequency selective surface (FSS) through bioinspired computing and a general regression neural network (GRNN). This hybrid computational method, which utilizes the multi-objective cuckoo search algorithm combined to a GRNN, determine the best physical dimensions of the FSS in order to achieve a multi-band filtering at the 2.4, 3.5 and 5.8 GHz spectrums. Therefore, the results are to be applied to aid the propagation of Wi-Fi, WLAN, WiMAX and future sub-6 GHz 5G systems. The resonant frequencies were measured and a -10 dB cutoff value has been considered for the transmission coefficient. The triple rectangular loop conductor geometry of the device is printed upon a glass epoxy (FR-4) substrate. Measurements were made for different wave incidence angles, from 0° up to 45°, to demonstrate how signal incidence would affect the device’s functioning. The agreement between simulated and measured data display satisfactory results.
TL;DR: In this paper, the authors developed a mathematical analysis of how the signal source separation and the Karhunen-Loeve expansion affect the passbands of the maximum spatial eigenfilter.
Abstract: Maximum spatial eigenfiltering improves the accuracy of maximum likelihood direction-of-arrival estimators for closely-spaced signal sources but may interchangeably attenuate widely-spaced signal sources, producing a severe performance degradation. Although this behavior has been observed experimentally, it still lacks a mathematical explanation. In our previous work, we overcame these limitations using a differential spectrum-based spatial filter but this still caused a small degradation in the DOA estimate. In this paper, we develop a mathematical analysis of how the signal source separation and the Karhunen-Loeve expansion affect the passbands of the maximum spatial eigenfilter. The farther the sources, the less significant is the maximum eigenvalue of the spatial correlation matrix and its corresponding eigenvector. Then, the magnitude response of the maximum spatial eigenfilter no longer approximates the spatial power spectrum and is not guaranteed to place multiple passbands around the signal sources. Consequently, we propose a spatial filter built from the eigenvectors of the entire signal subspace. This filter showed an overall runtime smaller than that of our previous work. It also provides a significant reduction in the threshold signal-to-noise ratio for closely-spaced signal sources and does not hamper the estimation for widely-spaced signal sources.
TL;DR: There is an exponential growth in the number of publications about NIR, ranging from research in physics to medicine and the way research contribution in different countries is shown, in order to support the relevance of the topic in defining new tendencies for new investigations.
Abstract: While the amount of telecommunications services grows rapidly in the whole world, humans get potentially more exposed to Non-Ionizing Radiation (NIR) from a number of different sources. Measurements of NIR levels are relevant in order to compare the results with national and international standards, aiming at the preservation of human health. Thus, it is of great interest to explore a variety of topics regarding this subject. Based on this need, this paper has a number of goals, including monitoring radiation levels in an everyday situation, an investigation of how national and international regulations organs address NIR levels and a demonstration of scientific production trends regarding this topic. The work also presents a bibliometric study about the main scientific productions and trends related to NIR measurements, with focus on the field of Telecommunications. The analysis is based on the databases of Web of Science (WOS) and Scopus, computing publications in the last 10 and 3 years, showing a trend evaluation. Among the main results from this exploratory investigation, there is an exponential growth in the number of publications about NIR, ranging from research in physics to medicine. The way research contribution in different countries is also shown, in order to support the relevance of the topic in defining new tendencies for new investigations. Furthermore, the NIR exposure limits and measurement criteria are presented both in Brazilian and in international norms, demonstrating how different national regulations can be when compared to international guidelines. Another contribution is a case study in Natal, Brazil, where NIR levels were monitored in four distinct locations over a period of 24 hours each and compared to the current regulations. The result is a quantitative analysis of the amount of radiation that some populations might be exposed to in distinct moments of the day. Measurements were carried out in the proximity of an antenna spot, since it could represent a source of high NIR levels (a worst case of human exposure). This campaign differs from older studies by including a more intense usage of microwaves frequencies due to operating 4G and pre-5G systems in Brazil. Finally, a statistical study involving the measurements is conducted, concluding the analysis of how some population groups might be affected by NIR.
TL;DR: In this article, a low profile substrate integrated waveguide (SIW) based self-quadplexing antenna with high isolation is demonstrated for multiband wireless applications, where the SIW based resonator cavity is integrated with an X-shaped resonator and formed the four quarter mode cavities having the individual microstrip feed lines.
Abstract: In this paper, a low profile substrate integrated waveguide (SIW) based self-quadplexing antenna with high isolation is demonstrated for multiband wireless applications. Here the SIW based resonator cavity is integrated with an “X”-shaped resonator and formed the four quarter mode cavities having the individual microstrip feed lines. Each quarter mode cavity consists of “V”-shaped slots of different lengths; are in front to feed line and produce the four distinct resonant frequencies at 7.8 GHz, 8.5 GHz, 10.2 GHz, and 10.6 GHz, respectively. The working principle depends upon the perturbation of higher-order modes in a particular quarter mode cavity. The minimum intrinsic isolation of below than −26dB is attained between any of the two input ports by adequately modifying the antenna dimensions. Hence, a single antenna consists of four individual signals without interfering with each other, which determines the self-quadplexing property of the antenna. The proposed antenna is realized for maximum efficiency and minimum value of frequency ratio. The measured gain of the proposed antenna is 4.5 dBi, 5.28 dBi, 7.1 dBi, and 7.4 dBi at the four resonant frequencies, respectively.
TL;DR: In this paper, a configuration of a passive Q-switched Erbium-doped fiber laser (EDFL) using a Lutetium Oxide (Lu2O3) thin film as a saturable absorber (SA) is experimentally implemented to generate high pulse energy with a high signal to noise ratio.
Abstract: In this paper, a configuration of a passive Q-switched Erbium-doped fiber laser (EDFL) using a Lutetium Oxide (Lu2O3) thin film as a saturable absorber (SA) is experimentally implemented to generate high pulse energy with a high signal to noise ratio. A stable Q-switched pulse train is initiated at the input pump power of 30.442mW, and a maximum pulse energy of 16.11 nJ is obtained at an output power of 0.97 mW, which confirms the stability of the pulses. It was possible to increase the repetition rate of the Q-switched laser from 31.25 to 60.2 kHz as the pump power was raised from 30.442 mW to 71.652 mW. Moreover, the pulse width decreased from 11.4 µs to 4.27 µs and 66.4 dB of the received signal-to-noise ratio at the radio frequency spectrum was achieved.
TL;DR: A low-overhead lowcomplexity carrier phase tracking scheme for OFDM-based superchannel transmission system enabled by optical frequency combs and demonstrates experimentally the feasibility performance of the designed masterslave carrierphase tracking technique for comb-based OFDMbased superchannels.
Abstract: In this paper, we have designed a low-overhead low-complexity carrier phase tracking scheme for OFDM-based superchannel transmission system enabled by optical frequency combs. In this scheme, taking advantage of the broadband phase coherence provided by optical frequency combs among the OFDM-bands, the carrier phase retrieved from pilot-subcarriers of the OFDM-band on the central wavelength channel is reused for the OFDM-bands on the other wavelength channels. In this case, the overall pilot-subcarrier overhead and DSP complexity is significantly reduced since the pilot-subcarriers occupy a small fraction of the overall OFDM bandwidth. The feasibility of this joint-carrier phase tracking scheme has been verified successfully via comprehensive simulation, where results show that the BER threshold for soft-decision FEC could be achieved for 50GHz-spaced 5-band 4-QAM, 8-QAM, 16-QAM and 32-QAM OFDM-based superchannel signals with zero guard-band and both laser and nonlinear phase noise effects after 7000km, 4000km, 3000km and 2000km SSMF transmission respectively. The simulation results show that there exist chromatic dispersion-induced differential phase offset among the OFDM-bands whose impact on joint-carrier phase tracking depends on the modulation format, channel count and fiber length. Finally, we demonstrate experimentally the feasibility performance of the designed master-slave carrier phase tracking technique for comb-based OFDM-based superchannels.
TL;DR: In this article, the authors presented improvements to a telecommunication service planning tool for optimal positioning of base stations presented in a previous work, which includes the optimization of the positioning of the towers in order to meet the maximum coverage, prioritizing the locations considered most important.
Abstract: This work presents improvements to a telecommunication service planning tool for optimal positioning of base stations presented in a previous work. The tool uses a propagation loss model based on the K-Nearest Neighborhoods classifier since its conception. The original objective of this tool is to optimize the positioning of transmitting towers in the frequencies of 2.1 GHz and 2.6 GHz in a given environment, maximizing the coverage area. The improvement proposed in this article includes the optimization of the positioning of the towers in order to meet the maximum coverage, prioritizing the locations considered most important. The studied scenario is the campus of the Federal University of Para, with characteristics similar to some cities in the Amazon region. The analysis of the results was made by comparing the power data received from the measurement campaigns with the coverage estimates obtained with the improved tool. The improved methodology showed better results than those from the previous study, both in the positioning of the antennas and in the time spent. We obtained a reduction of up to 72% in the time to calculate the optimal solution compared to the original study.
TL;DR: An experimental analysis of the use of signals transmitted by Wireless Local Area Networks (WLAN) based on the IEEE 802.11b/g standards for Radio Frequency Energy Harvesting (RFEH) applications in indoor environments employing a Quasi-Yagi Rectenna (QYR) topology indicates that IEEE 802."11b" standards have great potential for applications in RFEH.
Abstract: This article presents an experimental analysis of the use of signals transmitted by Wireless Local Area Networks (WLAN) based on the IEEE 802.11b/g standards for Radio Frequency Energy Harvesting (RFEH) applications in indoor environments employing a Quasi-Yagi Rectenna (QYR) topology. This analysis is a crucial point to distinguish the use of the IEEE 802.11b/g standards for ambient RFEH applications and contributes to the debate on the use of different types of energy available for free in modern society. For it, a dedicated setup, developed in a controlled environment to avoid any external interference, was built to carry out the programmed measurements. The results obtained indicate that IEEE 802.11b/g standards have great potential for applications in RFEH, with the IEEE 802.11b average power four times higher than IEEE 802.11g at the rectifier output.
TL;DR: In this paper, a generalized scattering matrix (GSM) representation is obtained for relating the forward and backward modal field amplitudes in each of the waveguides in terms of coupling integrals representing the conservation of the reaction of the electromagnetic fields.
Abstract: In this paper, we present a mode-matching-based formulation for the electromagnetic analysis of multifurcated waveguide problems, that is, the junction of a number of input waveguides with an output region of larger cross-section area. A generalized scattering matrix (GSM) representation is obtained for relating the forward and backward modal field amplitudes in each of the waveguides in terms of coupling integrals representing the conservation of the reaction of the electromagnetic fields. Numerical results for several multifurcated coaxial waveguide devices are provided to validate the formulation. Comparisons against the finite-element method demonstrate that the present approach can accurately model multifurcated waveguide problems. The method introduced here provides useful matrix formulas that allow us to model multi-port waveguide devices by reusing well-known coupling integrals of two-port problems.
TL;DR: In this article, the performance of some models based on the Uniform Theory of Diffraction (UTD) for RF path loss prediction in such ridges is assessed. But the authors focus on a hybrid model in which the forest is a uniform layer over a wedge that represents the ridge, and its influence is incorporated into the diffraction coefficient.
Abstract: Irregular terrains covered with forest vegetation represent a challenging scenario for radio planning. A case of particular interest is the one where a forest-covered high hill or mountain is interposed to the link, for which typical diffraction loss models usually apply as good approximations, even disregarding the vegetation influence. Pragmatic approaches to incorporate the forest contribution, such as adding a clutter height, usually improve accuracy a little further. In this scope, this paper assesses the performance of some models based on the Uniform Theory of Diffraction (UTD) for RF path loss prediction in such ridges. Special attention goes to a hybrid model in which the forest is a uniform layer over a wedge that represents the ridge, and its influence is incorporated into the diffraction coefficient. The path loss predictions are compared with measurements from a mountainous region of the USA, and the statistical adherence of the models to the measured data is discussed. Overall, the slightly better performance of the models which incorporate the vegetation influence was confirmed, the hybrid model performing the best for frequencies below 910 MHz.
TL;DR: In this article, a planar printed microstrip line fed pentagonal shape ultra-wideband antenna with triple band-notched characteristics is proposed and investigated and measured results indicate that the proposed antenna having dimensions of 32 × 24 × 0.76 mm3 has a bandwidth over the frequency band 2.7-10.6 GHz with S11 ≤ -10 dB (VSWR ≤ 2), except in WiMAX band (3.27-3.85 GHz), WLAN band (5.6-5.95 GHz) and ITU-T band (
Abstract: In this paper, a compact, planar printed microstrip line fed pentagonal shape ultra-wideband antenna with triple band-notched characteristics is proposed and investigated. By incorporating a pair of mirrored Γ-shape, a pair of mirrored L-shape slots in the pentagonal patch and bent C-shape parasitic strip at the backside of a patch, the tunable band notched responses are realized. The proposed antenna is fabricated on Rogers RO3003 substrate with permittivity 3.0 and thickness of 0.76 mm. The measured results indicate that the proposed antenna having dimensions of 32 × 24 × 0.76 mm3 has a bandwidth over the frequency band 2.7-10.6 GHz with S11 ≤ -10 dB (VSWR ≤ 2), except in WiMAX band (3.27-3.85 GHz), WLAN band (5.6-5.95 GHz) and ITU-T band (7.84-8.46 GHz). The presented antennas show dipole- like patterns in E-plane and omnidirectional in H-plane, minor group delay variation, and nearly constant gain at operating frequencies.
TL;DR: In this paper, a circular patch microstrip antenna with a metamaterial resonator for 4G applications is proposed, where the resonator is inserted into the patch for some antennas, in different positions for a parametric study.
Abstract: In this article, a circular patch microstrip antenna with a metamaterial resonator for 4G applications is proposed. For the design of the circular antenna patch, an approximate calculation was performed. The circular resonator is inserted into the patch for some antennas, in different positions for a parametric study. When incorporating the resonator, the performance of the antenna is improved and analyzed through some parameters, when compared with the antenna without the resonator. To verify the influence of the resonator and validate its performance, simulated results were performed with the ANSYS HFSS® software and compared with the experimental results, through prototypes, in which they showed a good agreement.
TL;DR: In this paper, the authors presented the development of an inclinometer device based on a Mach-Zehnder interferometer considering the effects caused by temperature variations, and demonstrated the operation of a LPG-taper system for angle measurements.
Abstract: This article presents the development of an inclinometer device based on a Mach-Zehnder interferometer considering the effects caused by temperature variations. It was demonstrated the operation of a LPG-taper system for angle measurements. The practical results satisfactorily show reliable inclination measures, even with the cross sensibility effect caused by variable temperature.
TL;DR: From comparative studies carried out in an existing Otto chip, it is observed that PSO can be a very efficient approach for batch analysis and yields better results when compared with the traditional gradient-based regression method.
Abstract: Recently a surface plasmon resonance (SPR) optical sensor, based on the Otto configuration — the Otto chip — has been developed. One essential step in the quality control of the fabrication process is characterization of the active region of several devices in a batch. Characterization is done by measuring the angular spectrum of the optical re ectance on several points across the active region of the device, and determining parameters by regression analysis of the data. Traditional gradient methods used in the regression process are extremely dependent on an initial guess and are not very efficient for batch analysis of curves, when those include poorly defined SPR spectra, where an initial guess may be hard to infer. An alternative approach for the regression problem is to model the analysis as an optimization problem and using an efficient stochastic algorithm. In this paper one discusses the use of Particle Swarm Optimization (PSO) for characterization of Otto chip devices. From comparative studies carried out in an existing Otto chip, it is observed that PSO can be a very efficient approach for batch analysis and yields better results when compared with the traditional gradient-based regression method.
TL;DR: Several formulae for computing the direct coupling efficiencies from laser diodes to diffused channel waveguides, based on mathematic models for approximating the corresponding laser beams and the waveguiding modes, have been derived in this article.
Abstract: Several formulae for computing the direct coupling efficiencies from laser diodes to diffused channel waveguides, based on mathematic models for approximating the corresponding laser beams and the waveguiding modes, have been derived in this paper. Then, the authors utilize a simple shift-or-shrink (SOS) algorithm to seek their optimal coupling conditions, including the incident positions of the laser beams and the corresponding horizontal and vertical beam widths. The simulation results are presented and compared.
TL;DR: A parametric analysis of the positioning of HF monopole antennas on the upper bridge of a typical Navy frigate was presented, establishing recommended distances of decorrelation between the antenna and the main nearby objects.
Abstract: For vehicle tactical radio communications, positioning antennas along the structure is a complex task. In vessels, there are several radio systems installed operating from HF to SHF. Consequently, the antennas need to share the same restricted space while preserving electromagnetic compatibility. In this context, this work presents a parametric analysis of the positioning of HF monopole antennas on the upper bridge of a typical Navy frigate. A numerical antenna analysis tool was chosen to support the intended analysis. Six positioning scenarios were simulated, evaluating the performance change of figures of merit such as the reflection coefficient and gain, due to the mutual coupling between the antennas and the main metallic objects within their close range. Furthermore, from the analysis, it was possible to establish recommended distances of decorrelation between the antenna and the main nearby objects.
TL;DR: WCFD-MAC protocol allows two neighboring users to simultaneously participate in TNFD communication without interfering with each other by using directional transmission and a three-node angle condition (TAC).
Abstract: In this paper, we design full-duplex (FD) medium access control (MAC) protocol for co-existing wireless local area networks (WLANs) in 5G cellular networks (WCFD-MAC). Our design considers some significant features of 5G networks, exceptionally, beamforming and FD capabilities at both, the base station and user equipment. FD communications may generate interferences, namely self-interference (SI) in bidirectional FD (BFD) and inter-user interferences in three-node FD (TNFD). Several efforts have been performed to mitigate the SI in BFD communications. However, the inter-user interferences in TNFD are still considered as a major drawback in FD networks. These interferences must be mitigated by an efficient MAC protocol design. WCFD-MAC protocol allows two neighboring users to simultaneously participate in TNFD communication without interfering with each other by using directional transmission and a three-node angle condition (TAC). Directional transmission combined with TAC increases system throughput. WCFD-MAC protocol allows a new half-duplex (HD) communication scheme referred to as three-node HD (TNHD). This scheme may occur when bidirectional FD (BFD) and TNFD communications cannot occur. TNHD scheme includes device-to-device (D2D) communication and allows energy efficiency, which is one of the keys requirements of 5G wireless networks. Simulations results show that WCFD-MAC protocol achieves higher throughput than existing works in the literature.
TL;DR: The proposed scheme is based on indirect time-of-flight principle based on continuous-wave pseudorandom codes and incoherent detection for range evaluation and a measured range error of less than 0.6 % has been achieved for both single and dual-target detection.
Abstract: A LiDAR architecture for autonomous cars is presented and validated by numerical and experimental results. The proposed scheme is based on indirect time-of-flight principle based on continuous-wave pseudorandom codes and incoherent detection for range evaluation. The range ambiguity and resolution are controlled by the parameters of the pseudorandom code. Experimental results are reported for target detection ranging from 13 to 1,000 m, as well as a demonstration of a dual-target detection, demonstrating the efficiency of the proposed LiDAR architecture to operate in real scenarios of autonomous cars. A measured range error of less than 0.6 % has been achieved for both single and dual-target detection.