Abstract in English:

Abstract This experimental study discusses developing methodologies linked to optical fiber sensing (OFS), focused on structural health monitoring with sensors based on multimodal interference and the core diameter mismatch approach to monitor the flow of single and two-phase pipeline systems. Singlemode-multimode-singlemode (SMS), singlemode-nocore-singlemode (SNCS), singlemode-multimode-singlemode-multimode-singlemode (SMSMS), singlemode-multimode-erbium doped-multimode-singlemode (SMErDMS), and singlemode-multimode-dispersion compensation-multimode-singlemode (SMDCMS) were the five different heads sensors used in the sensor structure. Results showed that the polarization effect causes a spike in the sensitivity levels and alters the sensor's behavior with a polarizer among the optical source path. Sensitivity values of SMS sensor changed from 0.027 dBm/(h/m³) to 0.041 dBm/(h/m³) for the single-phase flow measurement tests; the SNCS structure's sensitivity changed from 0.093 dBm/(h/m³) to 0.221 dBm/(h/m³); and the SMSMS sensor's sensitivity changed from 0.862 dBm/(h/m³) to 1.122 dBm/(h/m³). The sensitivity values for the two-phase flow increased for the SMS from -0.126 dBm/(h/m³) to -0.288 dBm/(h/m³) and for the SMErDFMS from -0.028 dBm/(h/m³) to -0.929 dBm/(h/m³), respectively. All structures had a good acceptable coefficient of determination and the polarization mode maintained by a polarizer also to prevent random power coupling between the polarization modes and assisted in controlling the optical power.

Abstract in English:

Abstract Triangular trihedral corner reflectors (TTCRs) are widely used passive radar targets for evaluating radar system performance due to their high structural rigidity and predictable backscattering behavior. The Radar Cross Section (RCS) of a TTCR is critical for assessing system characterization parameters and understanding backscatter properties. This paper presents an RCS characterization of three different TTCR sizes under clear weather conditions, specifically considering an airport runway environment. A comprehensive analysis is conducted using both electromagnetic simulations in the 90–100 GHz millimeter-wave range and experimental measurements. Field measurements were carried out at Runway 2 of Kuala Lumpur International Airport using a 93.1 GHz Frequency Modulated Continuous Wave (FMCW) radar system. The study uniquely considers radar incident angles and runway transverse slope effects, contributing valuable insights into the real-world performance of high-frequency radar systems in airfield applications. The simulation models, experimental setup, and observed results are detailed to support future development of radar-based Foreign Object Debris (FOD) detection systems.

Abstract in English:

Abstract A miniaturized and highly sensitive plasmonic sensor based on surface plasmon resonance (SPR) in a photonic quasi-crystal fiber (PQCF) is proposed in this study. The sensor structure consists of a replicated and defect-modified quasi-periodic unit cell that forms a central core and two symmetrically arranged enlarged vertical cores. These cores are coated with a thin layer of gold to induce the plasmonic effect, allowing the detection of analytes inserted inside them. The combination of SPR and PQCF technologies provides accurate detection of the fields in the region with the analytes. In addition, the proposed sensor incorporates a temperature-sensitive liquid crystal strategically distributed in the microstructure, making the device also capable of detecting thermal variations in the analyzed material, expanding its functionality.

Abstract in English:

Abstract The zero forcing (ZF) and the and minimum mean square error (MMSE) conventional algorithms has been widely employed as near-optimal detectors for large-scale multiple-input multiple-output (LS-MIMO) systems, whereas their complexity is too high. In order to reduce the complexity of the MMSE algorithm while maintaining its performance in term of convergence speed, we develop in this paper a new fast detection scheme based on the joint of two low complexity iterative algorithms. The devised iterative scheme starts with an initial solution based on the inverse of diagonal matrix to calculate just one steepest decent (SD) iter-ation. So, this first solution is to be offered to the successive over-relaxation (SOR) algorithm which can use it to converge quickly with lower number of iterations. A better tradeoff between com-plexity and convergence speed compared to conventional methods is shown from theoretical investigation and simulation examples of our proposed algorithm.

Abstract in English:

Abstract Microstrip filters are widely employed in radio fre-quency and microwave circuits due to their efficiency, easy fabri-cation, and compatibility with printed circuit board technologies. In this scenario, this work addresses, for the first time, to the best of our knowledge, a comprehensive study that includes the design, software simulation, and prototype fabrication of ultra-wideband low-pass filters made with microstrip lines employing different topologies. The filters were designed and constructed at 7.5 GHz with four different topologies: Minimal Stubs, Split Stubs, Radial Stubs, and Stepped Impedance. The manufacturing methods employed were the computer numeric control milling in copper and printing with silver-based conductive ink. The manu-factured filters were Chebyshev I of order 9, which ensured rapid attenuation after the cutoff frequency. The results show that the filters fabricated with the Radial Stubs topology performed better than the other topologies investigated in terms of cutoff frequency, attenuation, and insertion loss. The experimental investigations also demonstrated a slightly better performance of the filters made of copper than those made of silver, with lower insertion loss values. The simulation results and experimental measurements are in good agreement for all topologies and fabrication methods investigated. Furthermore, all fabricated filters presented relatively flat group delays.

Abstract in English:

Abstract This manuscript presents the feasibility of designing a digital Lock-In Amplifier (LIA) for measuring experimental sys-tems through optical measurement techniques, from 32-bit micro-controller platforms, derived from the technology coming from the Internet of Things (IoT). As a proof of concept, the STM32F446RE microcontroller was used, in which the resident program uses the Direct Digital Synthesis (DDS) and synchronous detection tech-nique to promote lock-in processing from harmonic signals gener-ated in 2f. The digital LIA was tested to detect C2H2 (Acetylene) concentrations in a spectrometric cell by Wavelength Modulation Spectroscopy (WMS). The experimental setup also included a DFB laser and other optical components. The comparative analysis with the Signal Recovery® DSP7265 benchtop LIA showed that both systems effectively measured up to 54 ppm of C2H2. A strong Pearson correlation (r>0.8) was observed for all measurements performed. This confirms its potential for applications in situ nonlinear optical spectroscopy, especially WMS.

Abstract in English:

Abstract Currently, unmanned aerial vehicles (UAVs) are present in numerous sectors of the economy, which require them to carry out services with agility, safety and precision. This equipment can be designed in the multi-rotor concept, using several electric motors, normally with permanent magnets and radial flux. Another alternative would be to use axial flux electric motors, which have a potentially higher power density and help to reduce the weight of the UAV. In addition, the use of grain-oriented steel in the mo-tor stator contributed to reducing magnetic losses and increasing aircraft efficiency. Thus, this work proposes the development of a permanent magnet axial flux motor, using grain-oriented steel in a yokeless and segmented armature. The technical specifications for a UAV application in agriculture are presented, as well as the mathematical modeling required for optimized motor design. Finally, the developed project is validated through 3D finite element electromagnetic field simulations, demonstrating the feasibility of using rectangular teeth to simplify the stator assembly process.

Abstract in English:

Abstract This paper proposes a Defected Ground Structure (DGS) hairpin filter based on the Thue Morse sequence for Sband applications. The filter operates between frequencies ranging from 2.15 to 2.37 GHz and is built on a printed circuit board with a copper foil and FR-4 substrate, which has a permittivity of 4.4. The measured insertion losses were 1.79 dB, the measured insertion loss was 1.79 dB, the bandwidth was approximately 220 MHz, and the reflection coefficient reached -25 dB. Although there was a small shift in the response value for return loss between the measured and simulated values, the proposed filter can be applied to frequencies in the S range from 2 to 4 GHz.