This paper introduces an artificial intelligence (AI) methodology designed to enhance the output of two-dimensional (2D) electromagnetic imaging systems, specifically tailored for the imaging of conductive objects utilizing inductive sensors. The core of our imaging system comprises a commercial data acquisition board, alongside custom-made multilayer planar coils developed by conventional printed circuit board technology. By leveraging recent advances in AI and machine learning, our approach significantly improves the resolution and clarity of electromagnetic images. The paper uses a multi-layer perceptron (MLP) classifier to process the raw electromagnetic data captured by the imaging system. These algorithms are trained to recognize patterns and anomalies in electromagnetic field data, which are often indicative of conductive objects. The enhanced imaging capability is demonstrated through a series of experiments that compare the AI-enhanced outputs with the ground truth.

Power amplifiers in wireless communication systems can introduce nonlinear distortion, degrade signal transmission quality, and increase power consumption. The paper presents a BiLSTM-CNN-based model for modelling power amplifier behaviour to address this issue. The model uses BiLSTM layers to capture temporal information from the signal data and incorporates a multi-head attention mechanism to focus on different temporal features. Additionally, convolutional layers process global features and reduce model parameters through weight sharing. Using this model, a digital pre-distortion (DPD) model is proposed to linearise the power amplifier through an indirect learning approach. The results show that the BiLSTM-CNN model achieves a normalised mean square error (NMSE) of -40.3dB, and the DPD model enhances the adjacent channel power ratio (ACPR) of the communication system by 18dB, demonstrating the model's feasibility. Comparative analysis with other network models indicates that BiLSTM-CNN outperforms traditional methods of fitting performance and convergence speed, showcasing its superiority.

This work derives exact expressions for the voltage and current induced into a two conductors non-isolated transmission line by an incident plane wave. The methodology is to use the transmission line radiating properties to derive scattering matrices and make use of reciprocity to derive the response to the incident wave. This methodology to derive receiving characteristics from the radiation properties via a scattering matrix is novel, and we already started to implement it to additional cases. An immediate advantage we obtained from this method is the derivation of a very simple analytic expression for the voltage and current for a matched transmission line. The analysis is in the frequency domain, and it considers transmission lines of any small electric cross section, incident by a plane wave from any direction and polarization. The analytic results are validated by successful comparison with ANSYS commercial software simulation results, and compatible with other published results.

For the purpose of fifth-generation and beyond communication applications, broadband circularly polarized (CP) & high gain AI-tuned metantenna operating in the 5 GHz band is presented in this article. So, an linearly polarized (LP) printed monopole antenna is being taken into consideration in the initial stage. To initiate CP from LP, a metallic strip that functions as a dynamic switching mechanism is utilized to short one of the parasitic conducting strips (PCS) with partial ground plane. The objective is to enhance the impedance (IBW) and axial bandwidths (ARBWs) as well as the antenna gain in order to make it a suitable candidate for ambient RF energy harvesting/wireless energy harvesting application. To achieve this, AI-tuned metasurface is placed below the monopole radiator at a height of 0.33λ_o. With a measured 49.84% IBW, 22.36% ARBW, CP gain > 8 dBic, antenna efficiency > 70%, fabricated on an FR-4 substrate with 1.3λ_o x 0.9λ_o x 0.02λ_o, it is suitable for the technological deployments in a current wireless technology, assuring resilience in networks. To meet the ever-increasing requirements of the current scenario, wireless communication landscape is on a paradigm shift. This transformation is brought by the utilization of metasurfaces offering customized, effective, and typical control of electromagnetic waves keeping with the desired frequency conditions.

Optimal placement of wireless base stations in urban areas allows for maximum coverage and performance whilst maintaining minimal cost. In this paper, we propose a novel machine learning approach to place base stations rapidly in an urban environment for 5G communications and beyond. This is a noteworthy approach as 5G, especially those that involve millimeter wave frequencies tend to require significantly higher number of base stations for any particular area, unlike their counterpart low frequencies where a small number of base station is sufficient to cover a good geographical area. Our machine learning empowered path loss model is developed to tackle this change in gameplay head-on, and it bridges the gap between empirical and ray tracing methods where we achieve accuracy closer to ray tracing yet at a significantly lower computation cost. Promising preliminary results are obtained, with a minimum coverage area of 80% with potential for future improvements.

This paper presents a coaxially fed, miniaturized tri-band circularly polarized (CP) antenna with a single layer patch configuration. Broadside radiation is achieved in the L5 band (1.176 GHz), L1 band (1.575 GHz), and S band (2.49 GHz), through the strategic excitation of higher-order modes (TM20 and TM30). The antenna design integrates slots and capacitors to reduce the operating frequency, efficiently excite all three modes, and achieve circular polarization within the designated bands. Each frequency band can be independently tuned with minimal effect on the performance of other bands. Moreover, it also facilitates the tuning of polarization sense (from RHCP to LHCP and vice versa) across all three bands. The proposed antenna radiates RHCP at L5, L1, and S bands, with a gain of 1.3 dBi, 1.5 dBi, and 2.7 dBi, respectively. A prototype with dimensions of (0.15λ_L5 × 0.15λ_L5) has been developed and fabricated to validate the antenna's performance.

In the paper, an optically transparent wideband antenna is proposed for wearable off-body communications. It consists of two identical asymmetric dipoles connected by parallel metal plates, and is directly fed through the feeding cable. The dual-dipole system allows for the realization of high front-to-back ratio (FBR) without the need of the ground as a reflecting surface, and size reduction can be obtained. The asymmetric dipole can generate two resonant frequencies, thereby expanding the operated bandwidth. In addition, optical transparency is achieved by slotting the dipole and embedding it in the silicone dielectric. For validation, a prototype is fabricated, which exhibits a size of 0.41λ₀ x 0.14λ₀ x 0.13λ₀. The results show that the prototype has a 10-dB fractional bandwidth (FBW) of 34%, an FBR of more than 14.1 dB, and a cross-polarization ratio of more than 20.8 dB. Within the bandwidth, the gain is larger than 2.79 dBi with the average efficiency of over 60 %.

This research explores the versatility of a miniature reconfigurable antenna designed for a variety of wireless applications: 5G (IEEE 802.15.3), WLAN (IEEE 802.11), V2X (IEEE 802.11 p), WiMAX (IEEE 802.166), Wi-Fi 6E (IEEE 802.11 ax), Wi-Fi 7 (IEEE 802.11 be), C-band (from 4 GHz to 8 GHz), and X-band (from 8 GHz to 12 GHz). The antenna utilizes an FR4-Epoxy substrate with a thickness of 1.6 mm and a relative permittivity of 4.3. To enable frequency reconfigurability, the patch is equipped with two PIN diodes, which can be positioned at different locations to adjust the antenna's operational frequency range. This reconfigurability allows the antenna to maintain its size while changing its frequency range according to the state of the PIN diodes. The strength of our work lies in achieving exceptional electrical performance while maintaining a small size, cost-effective, and compact design. The antenna demonstrates an almost omnidirectional radiation pattern across all frequency ranges. Additionally, the simulated reflection coefficient remains within the ideal range for every frequency band. The antenna's overall dimension is 22 × 18 × 1.6 mm³ (λ_o/4 × λ_o/5 × λ_o/56) (with λ_o being the free space wavelength at the lowest resonating frequency and for the proposed antenna its value equal to 91.18 mm) with a miniaturization rate equal to 75.25%. This compact antenna is designed to operate across multiple frequencies, making it suitable for various applications, particularly in wireless communication systems. Its versatility also makes it a promising candidate for future portable devices, sensor networks, and telecommunication applications. The performance metrics, including return loss and radiation pattern, are presented, demonstrating strong performance across these parameters. The analyses were conducted using the CST Studio Suite, which provided detailed insights into the antenna's functionality and effectiveness.

The development of adaptable and efficient antenna designs has been required due to the growing demand for high-performance wireless communication systems driven by the increasing availability of online video streaming and multimedia devices. The design and implementation of a compact, reconfigurable C-shaped patch antenna that is specifically designed for 5G applications in the sub-6 GHz spectrum is presented in this paper. The antenna, which measures 20 × 30 mm², can operate at five resonance frequencies within the 4 to 6 GHz range. Laser treatment is applied to optimize bandwidth and gain. Following the treatment, the antenna attained a bandwidth of 1100 MHz and an improved gain of 5.2 dBi at 5 GHz, as opposed to its initial gain of 4.3 dBi. The system functioned effectively since the reflection coefficient was less than -10 dB over the desired frequency ranges. The design's stable performance, compact integration, and varactor diode frequency adjustment make it desirable for wireless applications. Results exhibited a considerable match between simulated and measured data, demonstrating the promise of this reconfigurable antenna for next-generation wireless communication systems.

This contribution presents the design and validation of a portable and low-cost experimental setup of a sounder for channel characterization at the millimeter wave band for 5G systems (Frequency Range 2 - FR2). Unlike the high cost application-specific equipment employed by many research groups, universities and telecommunication companies, which also requires adequate mounting and transport to and within the measurement sites, our channel sounder integrates several hardware and software components that result in a lightweight and convenient device for manual operation. Our device enables measurements at 26 GHz, a band earmarked for the upcoming deployment of 5G systems in the millimeter wave band in Colombia. We present channel measurements to validate the performance of the experimental setup and to assess the adherence to the predictions of the 3GPP (3rd Generation Partnership Project) TR (Technical Report) 38.901 standard propagation model, achieving favorable results.

The rate at which powerline communication (PLC) impulsive noise arrives and lasts in the channel determines the severity of signal degradation, with impulsive noise bursts capable of causing complete signal loss. Consequently, the PLC impulsive noise requires an appropriate description to enhance the reliability and effective utilisation of the PLC channel. This paper employs the queuing theory approach to analyse and model the PLC impulsive noise inter-arrival and service time distribution, where the impulsive noise is categorised into single-impulse noise events and burst-impulse noise events. The Erlang-k distribution is proposed for modelling both the inter-arrival and service time distributions for the PLC impulsive noise with the process viewed as an infinite queue with a single server. The impulse noise events are assumed to traverse k stages before entering the PLC network and also pass through k stages before leaving the PLC network, with each of the stages following an exponential distribution. The proposed models are then validated through measurements from different indoor environments and compared to the exponential distribution model, commonly employed in modelling inter-arrival and duration of PLC impulsive noise. The E_k/E_k/1 queue model is determined to adequately model the burst-impulse noise events. In regards to the single-impulse noise events, the exponential distribution is observed to provide a suitable fit for the inter-arrival time distribution. The occurrence of PLC impulsive noise events is also found to achieve a state of equilibrium for all the measurement data under study.

This paper introduces a MIMO antenna featuring a complementary folded-line metamaterial (CFL-MTM) design, it wants to reduce mutual interaction among very close microstrip patch antenna components. The antenna elements have an edge-to-edge spacing of roughly 0.0933λ₀ (7 mm). By integrating CFL-MTM elements into the antenna structure, the antenna achieves negative permittivity and permeability characteristics, resulting in a compact size of 37 × 44 × 1.6 mm³. The antenna is suitable for S band applications, covering a bandwidth of approximately 3.121-4.277 GHz (1156 MHz). The incorporation of CFL-MTM results in a negative refractive index area, which effectively controls and reduces mutual coupling between the antenna parts. The antenna's dimension is optimized by keeping the CFL-MTM smaller than the resonant wavelength. Furthermore, the characteristics of the suggested MIMO antenna, such as ECC, CCL, and TARC, are assessed to show that it is suitable for S band applications.

This research focuses on the integration of an opto-satellite system based on Free Space Optical Communication (OWC) within DVB-RCS2 chains, implementing 16-QAM modulation techniques and Optical Time Division Wavelength Multiplexing (OTDMWDM). A co-simulation framework combining the MATLAB and OptiSystem environments is adopted to evaluate the system's performance. Key performance indicators, such as Bit Error Rate (BER) and Q factor, are meticulously analyzed to quantify the effectiveness of the proposed approach. The results obtained demonstrate notable improvements in transmission reliability and signal quality, highlighting the potential of OWC to optimize DVB-RCS2 standards. This study contributes significantly to the development of innovative solutions in the field of satellite communications, paving the way for more efficient and resilient systems.

In this paper, a reconstruction methodology for the field emitted by an electronic equipment in a CISPR 25 standard environment is developed. It is based on an inverse method to determine equivalent dipoles representative of the electromagnetic sources. Positions and dipolar moments of equivalent dipoles are obtained via a hybrid optimization method, using a Genetic Algorithm (GA) followed by a Pattern Search (PS) method. First, the validity of the approach is verified with a numerical 3D model of a microstrip line. Then, an experimental protocol, corresponding to the setup of the CISPR 25 standard, is proposed and validated with a monopole antenna as a radiating source. As expected, the measurements obtained with the rod antenna yield some numerical errors related to the equivalent dipoles. However, such a compact model predicts the radiated field with sufficient accuracy to be useful for analyzing several EMC constraints in an automotive context.

A simple technique for generating single and multiple beams from antenna arrays is presented. The approach is based on the multistage sequential rotation technique. A new feature in using multistage sequential rotation is provided. It is demonstrated that by applying a controlled second sequential rotation, circularly polarized antenna arrays operating alternately in a single-beam mode M1 and multi-beam mode M2 in the same frequency band can be designed. Proof-of-concept is provided mathematically and through numerical simulations in light of case studies. The approach can not only be applied to large antenna arrays following a modular principle adapted to the array size and needed applications without loss of generality, but it also paves the way for the manufacture of circularly polarized antennas operating alternately or simultaneously in both modes in the same frequency band. In addition, antennas designed using the proposed approach may have a wide range of applications ranging from monopulse radar to antennas for compensation of interference and blockage in dynamic communication environments.

A reconfigurable reflectarray antenna (RRA) is proposed with beam steering capability at 1.1 THz. The element of reflectarray is composed of vanadium dioxide (VO-2) and a gold bilayer model designed on a unit cell of 0.45λ, in which temperature variations produce different reflection phases due to the dependence of VO-2 on ambient conditions. The proposed reflectarray antenna has an aperture of 3100 μm and when particular cells of the array are exposed to temperature over 340K, it causes the phase in those unit cells to alter, eventually acting as 1-bit RRA. The radiation pattern shows a maximum gain of 24.3 dBi and a sidelobe level of -14.4 dB with an aperture efficiency of 21.7%. The maximum gain in case of offset is over 21 dBi with side lobe levels less than -10 dB up to 80-degree beam steering range. The proposed reconfigurable reflectarray antenna shows a beam steering capability of up to 100 degrees, which is sufficient for indoor communications. The designed antenna with its performance is optimum for the development of 6G RIS-based communication systems.

Traditional touchscreens, popular for their adaptability and ease of maintenance, typically use capacitive technology where finger contact alters an electrostatic field. Here we demonstrate a touch keyboard configuration, based on a resonant-based system encompassing split-ring resonators (SRRs). These resonators, operating at the GHz spectral range, detect a finger's proximity, changing resonance frequency, but remain unaffected by distant objects - thus allowing for a parallel and independent readout of multiple keys. Specifically, 14 independent keys have been demonstrated, and the frequency-sharing protocol for parallel acquisition of sequences has been successfully implemented. The readout is performed in parallel by monitoring the transmission through a microstrip line, which is equipped with a series of distinct SRRs that resonate at different frequencies. The system has been implemented on an extremely low-cost platform, which can be transformative for similar tasks.

In the work presented in this paper, a microwave sensor is investigated for estimating the glucose level in the blood of a diabetic patient. The microwave sensor consists of a planar microstrip transmission line printed on one side of the substrate while four Circular Complementary Split Ring Resonators (CCSRR) arranged in compact beehive arrangement are etched out from the ground plane on the other side, thus forming a Defected Ground Transmission Line (DG-TL). It is well known that the dielectric properties of blood to a large extent depend on the intrinsic glucose concentration. Placing the fingertip on the CCSRR cells is expected to disturb the electric field in the vicinity by changing the inductance-capacitance of the configuration and thus mirroring a change in the S-parameters of the transmission line. The changes, a shift in the resonance frequency and a change in the amplitude, is proportional to the dielectric strength of the adjacent medium which in turn is proportional to the blood glucose level. To mimic a human finger, a tiny glass container containing aqueous glucose solution is placed on the CCSRR configuration and by varying the glucose concentration; the changes in the S-parameters were observed. The sensor has planar dimensions of 60 mm x 20 mm and offers a resolution of 0.75 MHz per mg/dL of glucose concentration. Simulations and measurements indicate the applicability of the design for identifying glucose levels in the blood.

This article introduces an inscribed hexagonal-slot square patch antenna developed in the field of RFID technology for reader applications. The proposed structure is energized with one feeding element. This study proposes a high-gain microstrip antenna for ISM band applications at 5.8 GHz. FR4 material is utilized in design and fabrication of the antenna. The resulting design achieves a −10 dB impedance bandwidth of around 3.6% in the ISM band. The proposed design is determined to be compact in comparison to several contemporary designs and has dimensions of 0.43 λ x 0.43 λ x 0.03 λ (λ = wavelength at 5.8 GHz). The measurement reveals that the antenna can operate across the frequency band 5.67 GHz−5.88 GHz having a maximum gain value 4.58 dBi at 5.77 GHz. The satisfaction of the propagation test in different environments and the reading distance value of 2.81 cm at the ISM band supports the application of the structure as a short-range RFID reader.

In this paper, a high-speed frameless torque permanent magnet synchronous motor is designed to determine the optimal structure of the rotor by comparing the air gap magnetism, cogging torque and output torque of the motor through finite element analysis. The effects of different material rotor sheaths on eddy current loss are compared and analyzed, and the copper shield is used to optimize the rotor eddy current loss of the high-speed frameless torque motor. Through the analytical method, based on the theory of thick-walled cylinder, the stress calculation is carried out on the multilayer rotor structure of the high-speed permanent magnet synchronous motor with copper shielding layer, and a comparative analysis is carried out with the simulation results to verify the validity of the analytical calculations and the reasonableness of the optimization of the rotor eddy current loss.