Łukasz Januszkiewicz

The paper proposes a Pareto meta-front approach for the multi-objective design of reconfigurable millimeter-wave passive reflectors. For each value of a generalized cost parameter, such as wave frequency, a conventional Pareto front is generated by simultane-ously maximizing the Radar Cross Section (RCS) and minimizing the physical surface area of the array. The utopia point is then determined, and the Pareto-optimal solution with the minimum Euclidean distance from it is selected as the best compromise. Repeating this procedure over the parameter range yields the Pareto meta-front, defined as the locus in the objective space that tracks the evolution of the preferred trade-off across a family of Pareto fronts indexed by different values of the generalized cost parameter. The solutions associ-ated with points on this curve are referred to as meta-optimal solutions. The proposed method is applied to a reconfigurable passive dipole array for intelligent reflecting surface applications. The array employs variable element lengths and switchable reactive loads to control the phase distribution and electronically steer the reflected beam. Array geometry and load values are jointly optimized over the 50–70 GHz frequency range to maximize the RCS while minimizing reflector area and maintaining performance over a broad angular range. In the proposed frequency-indexed formulation, the incident-wave frequency serves as the generalized cost parameter. The resulting meta-front identifies frequency-dependent configurations that provide an effective compromise between reflectivity and physical size, establishing a systematic frequency-indexed multi-objective framework for wideband elec tromagnetic wave redirection.

This paper presents a knitted coplanar waveguide (CPW) transmission line for wearable wireless systems operating in the 5G NR n71 band. The line is intended to candidate RF interconnect for future integration into wearable systems covering the n71 downlink band of 617–652 MHz and uplink band of 663–698 MHz. Unlike printed, sewn, embroidered, multilayer, or coaxial textile transmission lines, the proposed CPW structure is formed directly during a single knitting process using only one machine. The line was designed for 50 Ω impedance and experimentally characterized with the use of S-parameter measurements. The results show impedance matching better than |S11| < −15 dB within the investigated frequency range and transmission coefficient |S21| > −2 dB at 600 MHz. These results confirm the feasibility of using knitwear as a functional RF transmission medium for fully textile-integrated sub-GHz 5G wearable communication systems.

This paper presents the design of an inverted-F antenna intended for integration into a smartwatch operating in the 2.4 GHz band. The antenna design addresses spatial constraints imposed by the device’s miniaturized form factor and the proximity of electronic components, including the printed circuit board, display, and battery. The influence of the user’s body on the antenna’s performance characteristics was considered during the design phase through numerical simulations employing the Finite-Difference Time-Domain (FDTD) method with a heterogeneous human body model. Simulation results and measurements of a fabricated prototype antenna are presented, demonstrating satisfactory performance in terms of impedance matching with VSWR below 1.5 in the whole band and gain of −1 dBi.

This paper presents a dual-band antenna designed for integration into eyewear. The antenna is intended for a system supporting visually impaired individuals, where a wearable camera integrated into glasses transmits data to a remote receiver. To enhance system reliability within indoor environments, the proposed design supports both fifth-generation (5G) wireless communication and Wi-Fi networks. The compact antenna is specifically dimensioned for integration within eyeglass temples and operates in the 3.5 GHz and 5.8 GHz frequency bands. Prototype measurements, conducted using a human head phantom, validate the antenna’s performance. The results demonstrate good impedance matching across the desired frequency bands and a maximum gain of at least 4 dBi in both bands.

The paper presents the optimization of a reflector-backed Vivaldi antenna which was designed to operate at the 1.8, 2.1, and 3.5 GHz frequencies used in the fourth and fifth generation of wireless systems. Reducing antenna back radiation is the primary goal of the optimization; at the same time, however, antenna impedance matching has to be preserved for the considered set of frequencies, this way generating a conflict of goals. The proposed design method is based on a minimax formulation of each goal against frequency and a Pareto-like tradeoff of solutions. Both goals were achieved as a consequence of the optimization process, and the antenna now exhibits a voltage standing wave ratio below 3, front-to-back ratio of 14 dB and a gain in the front direction not smaller than 8 dBi.

This paper introduces a novel approach to fabricating textile microwave transmission lines through knitting techniques. These textile-based transmission lines, capable of transmitting high-frequency signals between wearable transceivers and antennas, offer significant potential for the development of advanced wearable electronics. By leveraging a single technological process, our proposed method enables the creation of flexible and wearable devices. To demonstrate the feasibility of this approach, we present the design and numerical modeling of a microstrip line operating within the gigahertz frequency range. A prototype structure was fabricated and experimentally characterized, revealing moderate attenuation of less than 5 dB for frequencies below 2.5 GHz. However, a major challenge in the field of wearable electronics is the real-time applicability of such devices. Our work aims to address this challenge by providing a flexible and scalable solution for integrating wireless communication capabilities into wearable systems. Future research will focus on further optimizing the design and fabrication processes to enhance performance and minimize signal loss, ultimately enabling the realization of practical and user-friendly wearable devices.

This paper summarizes the possibility of employing knitted textile barriers as a shield against electromagnetic fields to protect the human body from their negative impact. Ten variants of knitted fabrics made of electrically conductive yarns, steel, and copper wire that differed in stitch pattern, structural parameters, and raw material, were designed, manufactured, and tested. The knitted fabrics produced differed in structural parameters, including course and wale density, surface density, thickness, thread length in the loop, wale and course take-up, volume cover factor, and surface porosity. These parameters were examined in accordance with the research methodology used in knitting. Barrier measurements were taken in the direction of the wales and in the direction of the courses for two frequencies of electromagnetic fields: 2–4 GHz and 4–7 GHz. It was observed that the shielding effectiveness of the manufactured materials depends on the structural parameters of the fabric, the stiches applied, and the type of yarn.

The article examines the shielding effectiveness of fabrics with conductive fibres in the microwave frequency range. Because of the limited size of the samples and high frequency range, the methods presented in literature could not be applied in this research. The method proposed, using a special measurement setup, demonstrated practicality for smaller textile samples. The results showed an angular dependence of shielding effectiveness, suggesting the need for perpendicular orientation of conductive fibres in fabrics to maximize shielding. This research provides knowledge on tailored solutions to mitigate electromagnetic interference in modern electronic technologies.

In this work, three textile antennas with the same geometry were produced using three different technologies: magnetron sputtering (PVD), ink-jet printing and embroidery using electroconductive yarn. In all three cases, the electrically conductive medium was the same, which was silver, known for centuries for its very good conductive properties. In order to show how the method of manufacturing antennas affects their operational parameters, the following measurements were carried out: surface resistivity, impedance, standing wave coefficient of antenna radiators, and their radiation characteristics were assessed. The surface resistivity value of the antenna paths obtained ranged from 0.05 to 1.2 Ωm/m.