Wood-based composite materials for ultralight lens antennas in 6G systems

Extremely high frequencies used in future wireless communication systems such as 6G require low loss materials to avoid wasting power and maintain acceptable efficiency . Furthermore, especially in the internet...

Passive Measurements of the Refractive Index of Liquid Nitrogen and Free-flowing substances by the Prism Method in the Millimeter Wavelength Range

It is proposed to use the classical prism method in the millimeter wavelength range for measuring the refractive index of liquid and free-flowing substances, including mixtures with particle sizes comparable to the wavelength. The method is implemented using a hollow radio transparent rectangular prism filled with a test substance. The measurements were carried out in the thermal radiation mode using radiometers with horn-lens antennas at frequencies of 37.5 and 94 GHz. To measure the deflection of the refracted beam, a linear scanner with a black body mounted on it, cooled with liquid nitrogen, was used. The distance between the prism and the scanner was 1 m. The refractive index of liquid nitrogen, sand, gravel, marble chips and granular polyethylene were measured. Using the refractive formula and the Landau-Lifshitz-Looeng formula for calculating the dependence of the refractive index of binary mixtures on the bulk density of particles, estimates of the refractive index of the material of the particles that make up the substances under study are obtained. They are in satisfactory agreement with the known experimental data for quartz, feldspar, granite, and marble.

Study and Design of Array and Beamsteering Antennas for Millimeter Wave Band Application

Millimeter wave (mmWave) communication systems have attracted significant interest regarding supporting high data rate of Gigabit/s communications for the new generation of wireless communication networks. MmWave communication systems have frequency ranges in between 30 and 300 GHz wherein an enormous amount of unused bandwidth is available. Although the available bandwidth of mmWave frequencies is promising for high data rate communications, the propagation characteristics of mmWave frequencies are significantly different from microwave frequency band in terms of path loss, diffraction and blockage, and atmospheric absorption. In general, the overall losses of mmWave signals are significantly larger than that of microwave signals in point-to-point wireless communications. To compensate the high propagation losses, due to the limited output power that the current RF active components can deliver in millimeter waves, the use of directional and beam-steerable antennas become necessary in mmWave wireless systems. The use of directional antennas can effectively alleviate the signal interference in mmWave communications. High-gain directional antennas can be used at both the transmitting and receiving ends, resulting in a significantly enhanced Signal-to-Noise ratio (SNR) and improved data security, and can be used in long-range mmWave point-to-point communications. Moreover, directional antenna beams with limited spatial coverage need to be steered either electronically or mechanically to obtain a better substitute link for non-Line of Loss (LOS) communications. Therefore, this dissertation mainly focuses on antenna design for mmWave frequency band applications. High gain and beam-steerable antennas with the merits of low profile, high gain, high efficiency and low cost are studied to address the new challenges of high frequency band antennas. First, waveguide-based technology is employed to propose a new wideband high gain antenna for 60 GHz band applications. Then, for beam-steerable antenna applications to steer the antenna beam in a specific direction, different structures of cylindrical lens antennas are studied. First, a compact two-dimensional lens antenna is designed and proposed at 28 GHz, and then a possible design of a wideband beam-steerable lens antenna is discussed and presented. Finally, a fully metallic wideband metasurface-based lens antenna is explored. The antenna is realized based on an array of periodic unit-cells to reduce the loss of the dielectric part in the conventional lens antennas. This property is exploited to design wideband cost-effective fully metallic antenna at mmWave frequencies.

SWITCHING SCANNING ANTENNA SYSTEM BASED ON A FLAT LUNEBERG LENS WITH CONCENTRIC RINGS

Антенные системы с возможностью широкоугольного сканирования довольно часто используются в современных системах беспроводной связи и радиолокационных системах гражданского и военного назначения. Особое внимание привлекли Smart-антенны (антенны с коммутируемым лучом и адаптивные антенные системы), а также фазированные антенные решетки (ФАР). В работе рассмотрен вариант построения ФАР с коммутационным сканированием с диаграммообразующей схемой в виде плоской линзы Люнеберга, состоящей из системы концентрических диэлектрических колец, размещенных на подложке из материала Rogers 5880. Исследованы влияние кронштейна крепления для ФАР на диаграмму направленности, уровень излучения, снижение коэффициента направленного действия и уровня сектора сканирования в азимутальной плоскости. Максимальный диаметр ФАР 160 мм, полная высота такой антенны получилась 38 мм. Запитка осуществляется при помощи коаксиальных кабелей с волновым сопротивлением 50 Ом. Диаметр самой линзы Люнеберга был выбран 80 мм; полная высота линзы мм. Подложка имеет толщину мм, склеенная слоем клея толщиной 0.025 мм. Концентрические кольца на этой подложке имеют высоту 0.787 мм. Минимальная ширина концентрического кольца (внешнего) мм (при резке УФ лазером минимальная ширина перегородки между отверстиями равна 0.05 мм). Полосковые трансформаторы расположены на плате из материала Rogers 5880 и имеют толщину равную мм Scanning antennas with wide-angle scanning capabilities are widely used in the areas such as modern wireless communications and military and civilian radars. Among them, lens antennas with switched beams and phased array antennas (PHAR) attracted considerable attention. In this paper, we consider a variant of the construction of switching scanning PHAR with a diagram-forming scheme in the form of a flat Luneberg lens consisting of a system of concentric dielectric rings placed on a substrate made of Rogers 5880 material. We studied the effect of the PHAR mounting bracket on the presence of its influence on the radiation pattern, the radiation level, the decrease in the directional coefficient, and the level of the scanning sector in the azimuth plane. The maximum diameter of the PHAR is 160 mm, the full height of this antenna is 38 mm. The power supply is carried out using coaxial cables with a wave resistance of 50 Ohms. The diameter of the Luneberg lens itself was chosen 80 mm; the full height of the lens is H =0.939 mm. The substrate has a thickness of t =0.127 mm, glued with a layer of glue, 0.025 mm thick. The concentric rings on this substrate are 0.787 mm high. Minimum width of the concentric ring (external) d - W =0.25 mm (when cutting with a UV laser, the minimum width of the partition between the holes is 0.05 mm). Strip transformers are located on the board made of Rogers 5880 material and have a thickness of H =0.939 mm

Probabilistic characteristics of a two-channel detector with two inertial single-photon photoemission devices and a logical adder

Analytical expressions are obtained for calculating the probabilities of correct detection of a two-channel inertial detector of pulsed optical radiation in the photon counting mode, containing a receiving optical complex of two lens antennas, two single-photon photoemission devices and a logic adder.