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.

In this paper, a miniaturized coplanar waveguide (CPW) to rectangular waveguide (RGW) transition using integrated resonators and variable housing is proposed. By properly designing the dimensions of the integrated resonators and variable housing, a compact and broadband transition can be accomplished. The -15-dB fractional bandwidth of the transition is as broad as 45.2%, which ranges from 8.21 GHz to 13 GHz, covering the whole X-band (8.2-12.4 GHz). Besides, the transition size is as small as 3.94 mm. To reduce the mechanical complexity, the housing height is from 24.5 mm to 22.86 mm, which is equal to the height of the rectangular waveguide. The -15-dB fractional bandwidth of the transition is as broad as 45.5%, which ranges from 8.18 GHz to 13 GHz, encompassing the whole X-band. Besides, the transition size is still as small as 3.94 mm. To verify the simulations, a back-to-back CPW-to-RWG transition is fabricated and measured. The simulation and measurement results are in good agreement.

A novel filtering crossover featuring flexibly allocated center frequencies based on ridged substrate integrated waveguide (RSIW) is proposed. Two TE₁₀₁-mode SIW cavities, two loading single ridge SIW (SRSIW) cavities and a loading triple ridge SIW (TRSIW) cavity are used to realize the filtering crossover. Good transmission and isolation responses can be achieved based on orthogonal degenerate TE₁₀₂ and TE₂₀₁ modes in the centered TRSIW cavity. The frequency ratio of the TE₁₀₂ and TE₂₀₁ modes can be significantly improved by adjusting the aspect ratio and the dimensions of ridges in the centered TRSIW cavity. A prototype operating at 4.98 GHz/10.1 GHz is fabricated and measured. The measured results demonstrate excellent agreement with the simulated one.

Multiple-Input Multiple-Output (MIMO) antennas are essential for transmitting and receiving information in Vehicle to Everything (V2X) communication. However, the MIMO antenna designs at V2X are complex because of the mutual coupling problem. Several approaches have been designed to improve antenna isolation. However, these approaches have drawbacks like gain, bandwidth, and radiation efficiency reductions. This work introduces a compact four-port MIMO antenna that operates at a 5.85 GHz to 5.9 GHz frequency range for V2X communication. Here, the slotted circular microstrip patch MIMO antenna is considered. The antenna's length, width, and patch are optimized by metaheuristic optimization called Aquila Optimization (AO). A substrate Rogers RT5880, which has a defected ground structure (DGS) and a parasitic patch, is used to design the antenna. F-shaped parasitic elements are placed near each antenna element to improve isolation. The DGS with a U-shaped parasitic element minimizes the mutual coupling among the adjacent antenna elements. The considered overall dimension has a compact size, and it achieves better envelope correlation coefficient (ECC < 0.5), total active reflection coefficient (TARC < -10 dB), diversity gain (DG > 9.9 dB), channel capacity loss (CCL < 0.4), and mean effective gain (MEG < 3 dB) at 5.88 GHz. Hence, it is proposed that the developed design is useful for applying V2X communications.

In this paper, we propose some suggestions for unsolved problems in classical and quantum electromagnetics. We aim to explain these problems in the simplest way possible. Some issues like the quantum computer may need a lot more work. The subject matter is interdisciplinary needing international collaboration in many different areas such as physics, math, engineering, and material science.

In this contribution, two antennas for microwave imaging are described and validated. The first solution is a slot antenna designed when it works a direct contact with human head. However, the air-gap issues and hair layer degrade the antenna performances. These limitations are overcome with the cylindrical brick antenna containing coupling liquid medium. Basically, this antenna consists of a ground plane hosting a wide slot and a microstrip feed line with a fork-like tuning stub inserted within the circular container. Numerical examples show that the proposed antenna exhibits S₁₁ below -10 dB over the selected frequency band from 1 to 2 GHz, in agreement with microwave brain imaging systems. Moreover, the antenna is assessed in terms of transmission coefficients and field penetration. In particular, it is shown that such a feature holds true when the antenna is placed in different positions over the head, when it is located on both the skin and the hair. Experiments on a few real humans confirm the numerical results. The transmission coefficient, which is the only one used in imaging systems to streamline the hardware complexity, is of comparable level of other similar antennas already present in literature. However, the proposed antenna is lighter and smaller in size.