This paper presents the numerical modeling of a switchable reflecting metasurface designed for operation in the Ku band. The proposed structure is based on a reflective architecture in which the phase shift of the reflected wave is controlled by applying a bias voltage to cuvettes filled with liquid crystal. By varying the voltage, the effective dielectric permittivity of the liquid-crystal medium changes, which in turn modifies the local response of the metasurface and enables controlled beam steering. The simulations were performed using parameters of a commercially available liquid-crystal mixture, GT5-26001 manufactured by Merck. The obtained results demonstrate a smooth dependence of the beam-deflection angle on the permittivity gradient formed across the metasurface. Within the investigated range of tuning parameters, the reflected beam can be steered from 10° to 59°. These results indicate that liquid-crystal-based metasurfaces are a promising low-profile and energy-efficient solution for reconfigurable beam control in practical satellite communication systems.

Antennas suitable for 6G applications can potentially operate in the W-band (75-110 GHz), which requires fine manufacturing accuracy, particularly for fine surface processing. Such antennas with fine surfaces can be produced using many different techniques, such as chemical etching, milling, and additive manufacturing. However, even fine manufacturing leads to certain imperfections on the antenna surface that lead to the performance degradation of an antenna. As a result, an undesirable difference between the numerical and experimental results can occur. To study this effect, we performed electromagnetic simulations of surface roughness in multiple conventional electromagnetic devices suitable for 6G applications. As antennas under investigation, we have chosen a horn antenna and a patch antenna. In addition, we consider a rectangular WR-10 waveguide and a 50 Ohm microstrip transmission line. Surface roughness has been implemented as a set of hemispheres, which are randomly distributed, added, or subtracted on the surface of the antenna. After performing a set of simulations, we evaluated the S-parameters, antenna efficiency, and directivity patterns. The results are then compared with reference devices with ideal surfaces to find the optimal surface requirement for antenna manufacturing.

Satellite communication systems for mounting on vehicles are commonly based on phased array antennas with electronical beam steering. In this work we develop active metasurface-based receive-transmit antenna arrays for newly deployed satellite constellation system running in Ku-band. Both receive and transmit subarrays are based on patch-antenna elements driven in circular polarization using 90 circle hybrids. In both subarrays we optimized elements sizes and array period to have optimal ellipticity, gain, side lobe level. In electromagnetic simulations we achieved realized gain of 32.2 dBi for the Rx subarray and 33.4 dBi for the Tx subarray obtained in a broad scanning angle range from -15 circle to + 45 circle.

Modern phased array antennas with electronic beam steering are commonly based on planar antennas. In this work, we develop a separate receive-only, transmit-only antenna array for a newly deployed satellite constellation system operating in the Ku-band. Both receive-only and transmit-only arrays are based on circular polarized patch-antenna elements with the directors. In both arrays, we optimized element sizes and array period to have optimal ellipticity, gain, and sidelobe level. In addition, we added an inter-element metallic screen to improve the isolation between the elements. In electromagnetic simulations, we achieved a realized gain of 32 dBi for the receive-only array and 33 dBi for the transmit-only array obtained in a broad elevation angle range of +/- 45 degrees.

A simulated and manufactured broadband antenna array of 2x2 meta-elements operating in the range of 2.5-4.5 GHz is presented. The characteristic size of the aperture of this sample is two wavelengths, but its realized gain exceeds 11.3 dBi in the entire range and reaches a peak of 14.3 dBi at the frequency of 3.2 GHz. Such results become possible by the successful combining electric and magnetic multipoles of the meta-elements, slightly spaced in frequency. As a trade off in accuracy and manufactring costs we use additive manufacturing: 3D printing of meta-elements on a photopolymer printer and subsequent metallization of their surface were involved in the manufacture of the antenna array.

In this paper, we investigate a novel subwavelength scatterer, the layout of which is inspired by the Mo-bius strip. The characteristic size of the proposed particle is about 10 mm. So that we consider the frequency range from 1 to 30 GHz in numerical simulation for field distribution calculation of scattering task using finite element method. The results of spectral analysis of multipolar coefficients of far electric field allows us to conclude that with certain specified geometric parameters of the scatterer, co-directional electric and magnetic dipole moments are simultaneously excited in it. Due to this behav-ior at multiple frequencies, the proposed particle is transparent to one circular polarization, while the other is effectively scattered. Due to the reciprocity principle, such scatterer can also be used as an an-tenna with a predictable radiation pattern in several frequency ranges.

This work is devoted to the analysis of how, knowing the macroscopic characteristics of the antenna's far field, such as the radiation pattern and axial ratio, to determine the microscopic ones: the amplitude and phase of the electric field. The paper presents both the results of analytical calculations and several numerical examples. The results of this work are of particular value in problems of far field multipolar decomposition, since to implement the algorithm it is necessary to know exactly the electric field of the antenna, while in engineering problems it is more convenient to operate in terms of diagrams on.

With the rapid development of automated systems, it became necessary to use wireless communication systems to monitor a variety of different parameters. Wireless sensors are actively used in many modern intelligent systems to track and control various characteristics of the system and its environment. The task of developing compact sensors with high sensitivity and measurement accuracy is extremely urgent in this field. In this paper, two microwave sensor designs based on dielectric resonators, whose parameters are optimized for quasi-BIC mode maintenance, have been proposed. Furthermore, the application of these sensors extends to the realm of temperature tracking, water temperature control, and impurity detection, showcasing their potential in manufacturing processes, wireless power transfer, and various other industrial applications.

In this manuscript, we investigate the accuracy of electromagnetic simulations of surface roughness in multiple conventional antennas for the W-band. Because the roughness of surface processing becomes comparable to the size of the antenna at such a high frequency, it is important to study the impact of this surface roughness on the performance of some conventional antennas. As a reference antenna, we have chosen a horn antenna and a patch antenna. In addition, we considered a rectangular WR-10 waveguide and microstrip transmission line. Surface roughness was implemented as a set of hemispheres randomly distributed, added, or subtracted across the antenna's surfaces. After conducting a set of simulations, we assessed and compared antenna performance to references antennas with ideal surfaces to find an optimal surface requirement for antenna manufacturing.

High‐gain directive antennas are used to support point‐to‐point long‐range wireless communication channels. In typical designs, the array factor plays the key role, while individual elements’ layout is simplified. Herein, a four‐element phased array is demonstrated, where a volumetric form factor of each element is taken as an advantage to elevate the antenna gain while keeping the device footprint small. The two‐step design process, encompassing a genetic topology optimization and finite tuning with a particle swarm algorithm, is applied and subsequently demonstrated. This shows that exploring the third dimension allows obtaining more than 25 dB isolation between adjacent radiating elements and, at the same time, grants them highly directive radiation patterns. This operation principle is verified by demonstrating a large number of resonating multipoles constructively interfering to create a directional beam. The antenna with aπλ2aperture demonstrates more than 13 dB gain around 3 GHz frequency range. Antenna elements are 3D printed in resin and then metallize electrochemically. Additive manufacturing of complex volumetric architectures with a small interelement spacing allows implementing new devices, encompassing the advantages of resonant approaches and arrays factors. Miniaturized 3D antenna array devices can be used in wireless communications where controllable beam properties are demanded.

We propose a transceive element of a phased array antenna for satellite communications systems operating in Ku frequency band. The proposed element based on a magneto-electric dipole antenna. A substrate-integrated waveguide and a cruciform slit of a special shape are used as a feeding element. We aim to drive the circular polarization at two sub bands simultaneously. We performed electromagnetic simulations and optimization of the single element and applied array factor to evaluate beam steering, directivity and cross-polarization. The antenna elements were optimized using 8 criteria to obtain acceptable S-parameters and ellipticity. As a results, we obtain satisfactory cross-polarization for R-x-band of <-20 dB. For T-x-band we obtained value <-14.2 dB for oblique beam position and of -20.1 dB for normal beam position. The developed geometry meets the requirements of manufacturing on printed circuit boards. The results obtained indicate the prospects of using such broadband transceive elements in phased arrays.

This paper presents a phased array antenna with volumetric elliptical elementary radiators optimized with genetic and swarming algorithms. The emitters themselves were manufactured using the SLA method. The presented geometry is compact (the aperture is only 2 wavelengths) and has a high gain about 11–14 dBi in a wide operating band (2.5–4.5 GHz). To describe inner modal structure and understand far field formation properties of this array, multipole decomposition is used.

Radio-frequency identification (RFID) is a widely used technology for wireless data transfer between tags and readers. Passive ultrahigh-frequency (uhf) RFID architecture is a compromise between cost and performance in numerous retail applications, in which multiple goods must be labeled and simultaneously interrogated from a distance. Furthermore, for robust operation, passive tags must be visible from any direction and for any polarization to compensate for their accidental misalignments with respect to the reader's antenna. Obtaining long-range omnidirectional operation with miniaturized tags remains a challenge, which limits the scope of emerging applications, including the Internet of small things. Here we develop the concept of resonance cascading and demonstrate a new architecture based on a high-index ceramic resonator. Taking advantage of frequency hopping between communication channels, we design several mutually orthogonal spectrally separated dipolar resonances to enable omnidirectional operation inside an RFID frequency band, instead of using traditional single-band quasi-isotropic antennas. As a result, we experimentally demonstrate a compact 28.5 \ifmmode\times\else\texttimes\fi{} 27.5 \ifmmode\times\else\texttimes\fi{} 27 mm$^{3}$ device, which can be omnidirectionally interrogated from a distance of over 10 m, which is further than has been previously achieved in the field of long-range omnidirectional uhf RFID tags. The concept of resonance cascading and spectral sharing can be further employed in a variety of wireless communication applications.

In this paper, the possibility of using a mobile phone as a ripeness sensor is considered. The concept of differentiation based on changes in the dielectric constant of the product as it matures (increase in sugar content) is proposed. A scheme is considered in which one device plays the role of a base station and transmits a Wi-Fi signal at a frequency of 2.4 GHz, and another device uses a specially developed mobile application to analyze this signal and determine by its changes whether a fruit located in the near field of a telephone antenna is edible. The results of the distinctness of different types of products, as well as different degrees of ripeness (unripe/ripe) for one product (avocado) are presented. The sensitivity of the method is also evaluated based on comparison with laboratory measurements using high-quality patch antennas.

The emerging need for green technologies motivates the development of new approaches to manufacture electronic consumables. In case of low-cost mass-production sensors, the problem becomes even more severe due to the generation of environmental waste. Here we demonstrate an RFID-type sensor based on a caramel substrate with a micron-scale conductive layer. The device, being primarily made of sugar, attracts insects, which consume it almost completely. As an application, we demonstrate a tag that can be applied for remote pest monitoring. In the experiment, a long-range UHF RFID communication channel is established and monitored over time. An RFID-on-caramel tag consumed by insects loses its connection with a reader, indicating the presence of pests. We show the new caramel-based devices to communicate with a reader over a 10-meter distance, paving the way to remote crop monitoring. Such low-cost biodegradable sensors are highly promising for smart agriculture, warehouse management, and stock monitoring approaches.

Additive technologies show promising results in 6G antennas operating in W-band. However, quality of additive manufacturing strongly depends on many crucial factors related to the manufacturing process. In this work we perform electromagnetic simulations to study an impact of surface roughness to the performance of some conventional antennas suitable for 6G applications. Finally, we could define the surface roughness requirements for the additive antennas.

Capabilities to monitor the purity and mixture composition of liquids with the aid of low-cost portable devices can grant essential advantages in maintaining personal health safety. The overwhelming majority of consumer wireless devices operate at relatively small operational bandwidth, thus not allowing for retrieving material composition via dispersion characteristics. To mitigate the bandwidth limitations, resonant methods, granting precision in a small frequency window, might be of use. Here, we demonstrate a liquid sensor able to provide 90.5 kHz/RIU sensitivities owing to a resonator, supporting high-quality factor quasi-bound states in the continuum. The sensor's architecture encompasses a high-permittivity ceramic resonator and a capillary wrapped around it. The volumetric design increases the overlap between the electromagnetic mode and the liquid under test while maintaining resonant conditions within a relatively narrow frequency band. To demonstrate the capabilities of the proposed method, the UHF RFID band was considered, and temperature dependence of the distilled water permittivity was retrieved. Interfacing standalone low-cost electromagnetic sensors with widely available consumer-level wireless devices offers promising opportunities that contribute to the paradigm shift toward IoT.

Optical theorem, being the manifestation of the energy conservation law, relates the total scattering cross-section of a structure with its scattering in the forward direction. However, there are no fundamental restrictions on other directions. Strong asymmetric reflection and backscattering can be achieved in structures with magneto-electric coupling, taking place between constitutive elements. Here scattering properties of single meta-particles, based on near-field coupled electric and magnetic dipoles, and their arrays are analyzed. It is shown that dissipation is the key mechanism, responsible for the asymmetric backscattering behavior. While far-field scattering can serve as a sufficient loss mechanism in the case of single structures, ohmic dissipation should be added in the case of periodic arrays (metasurfaces). In this case, the practical realization is based on split-ring resonators, loaded with resistance, and wires, both printed on a PC board.

Radio frequency identification (RFID) is a widely used approach for a short-range contactless data exchange, i.e., employed in billing systems. During the last years, unauthorized access has become an issue, as it has been proven on numerous unpleasant occasions. A typical theft scheme is based on approaching a victim with a card reader. However, a straightforward adaptation of the reader's antenna elements allows performing the attack from a distance, opening a severe security loophole. Here, we propose and demonstrate hardware-based protection capable of preventing a far-field attack of this kind. Our solution is based on an RFID chip shielding with an opaque metal. The Faraday type of the enclosure has a small aperture, which suppresses electromagnetic field leakage from the device. This property affects both up and down interrogation links, virtually making the far-field attack impossible. Activation of the card is done by holding it in hand-this way, it is made accessible to an authorized readout, which still remains wireless. The physical principle of the operation is placing a high-index dielectric structure next to a subwavelength aperture, making it electromagnetically larger and, as a result, supporting the field leakage. Our experimental prototype, validated by several different users, shows the capability to diminish far-field attacks on ultrahigh frequency (UHF) RFID tags. This hardware security solution can find usage in numerous applications, such as biometric passports, credit cards, and many others, where unauthorized access to sensitive data is highly undesirable.

In this work, a highly sensitive temperature sensor based on bound states in the continuum (BIC) was proposed. A ceramic resonator with a half-cylindrical shape placed above a ground plane and designed to support high-quality factor supercavity modes. Experimentally, the sensor has been demonstrated to operate in a wide temperature range, from 25 to 105 ºC, with a resolution of 0.2 °C. The sensor's high-precision performance is based on the use of high-quality ferroelectric ceramics capable of supporting the confined modes with a high quality factor of more than 1000.