3D Inductive Frequency Selective Structures Using Additive Manufacturing and Low-Cost Metallization

The use of additive manufacturing and different metallization techniques for prototyping radio frequency components such as antennas and waveguides are rising owing to their high precision and low costs. Over time, additive manufacturing has improved so that its utilization is accepted in satellite payloads and military applications. However, there is no record of the frequency response in the millimeter-wave band for inductive 3D frequency selective structures implemented by different metallization techniques. For this reason, three different prototypes of dielectric 3D frequency selective structures working in the millimeter-wave band are designed, simulated, and manufactured using VAT photopolymerization. These prototypes are subsequently metallized using metallic paint atomization and electroplating. The manufactured prototypes have been carefully selected, considering their design complexity, starting with the simplest, the square aperture, the medium complexity, the woodpile structure, and the most complex, the torus structure. Then, each structure is measured before and after the metallization process using a measurement bench. The metallization used for the measurement is nickel spray flowed by the copper electroplating. For the electroplating, a detailed table showing the total area to be metallized and the current applied is also provided. Finally, the effectiveness of both metallization techniques is compared with the simulations performed using CST Microwave Studio. Results indicate that a shifted and reduced band-pass is obtained in some structures. On the other hand, for very complex structures, as in the torus case, band-pass with lower loss is obtained using copper electroplating, thus allowing the manufacturing of inductive 3D frequency selective structures in the millimeter-wave band at a low cost.

A method of measuring transmittance of radiation from the film of ice 0 in the IR wave band deposited on a dielectric plate

A method of measuring transmittance of radiation from the film of ice 0 in the infrared wave band is described. Ice 0 is formed from supercooled water at the temperature below –23°C. This ice is ferroelectric and forms a highly conductive layer of the nanometric order of thickness at the boundary with dielectric. The complexity of the experiment consisted in the necessity of using low intensities of the probing signal and considering radiation of the cooled parts of the installation. In order to obtain a thin film of ice, the method of depositing water vapor on a substrate cooled in nitrogen was used. The method rules out formation of condensate in cooling. Deposition of water vapor is possible only in heating, when delivery of cold nitrogen vapor into the chamber with the sample is excluded. To ensure exposure of the film to IR radiation, two sources of infrared radiation were considered: a halogen lamp with a broad radiation spectrum (on the surface of heated glass) and a CO2 laser with the radiation wavelength of 10.6 µm. In the first case, spectral measurements are possible when filters are used. In the installation based on a CO2 laser, an intense signal is emitted, requiring consideration of sample heating. Components of the installation have been elaborated and investigated, on which transmittance of radiation from the film of ice 0 is planned to be measured.

Ultra-high-energy Gamma-Ray Radiation from the Crab Pulsar Wind Nebula

It has been long debated whether the high-energy gamma-ray radiation from the Crab Nebula stems from leptonic or hadronic processes. In this work, we investigate the multiband nonthermal radiation from the Crab pulsar wind nebula with the leptonic and leptonic–hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recently observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative components generated by the electrons and protons in the Crab Nebula. The modeling results indicate that the pure leptonic origin model with the one-zone only can partly agree with some segments of the data from various experiments (including the PeV gamma-ray emission reported by the LHAASO and the other radiation ranging from the radio to very-high-energy gamma-ray wave band), and the contribution of hadronic interaction is hardly constrained. However, we find that the hadronic process may also contribute, especially in the energy range exceeding the PeV. In addition, it can be inferred that the higher energy signals from the Crab Nebula could be observed in the future.

Millimeter-wave band subsurface sounding module

Radio-wave devices are used for many environmental and material research tasks. These devices and the development of relatively simple and affordable quasi-optic radio wave receivers and transmitters of millimeter and terahertz bands are important for numerous applications. Results of the design of a terahertz-band quasioptical transmitter-receiver module are presented. The module is intended for the remote detection of various objects and for measuring the depolarized field components backscattered by various long objects hidden behind obstacles (building materials and/or everyday items that prevent visual contact with the objects). These may be interfaces between materials with different dielectric constants, fiber optic cables, electric cables, and otherobjects. Results of full-scale experimental testing of the module on the detection of electric cables buried under plater in the wall of a building are presented.

Evaluation of 5G Positioning Performance Based on UTDoA, AoA and Base-Station Selective Exclusion

Accurate and reliable positioning solution is an important requirement for many applications, for instance, emergency services and vehicular-related use cases. Positioning using cellular signals has emerged as a promising solution in Global Navigation Satellite System (GNSS) challenging environments, such as deep urban canyons. However, harsh working conditions of urban scenarios, such as with dense multipath and Non-Line of Sight (NLoS), remain as one of the key factors causing the detriment of the positioning estimation accuracy. This paper demonstrates that the use of joint Uplink Time Difference of Arrival (UTDoA) and Angle of Arrival (AoA) gives a significant improvement in the position accuracy thanks to the use of antenna arrays. The new advances of this technology enable more accurate user locations by exploiting angular domains of propagation channel in combination with time measurements. Moreover, it is shown that a better localization is achieved by combining the joined UTDoA and AoA with a base-station selective exclusion method that is able to detect and eliminate measurements affected by NLoS. The proposed approach has been tested through simulations based on a deep urban deployment map, which comes with an experimental data file of the user’s position. A sounding reference signal of 5G new radio operating in the centimeter-wave band is used. The obtained results add value to the use of advance antennas in 5G positioning. In addition, they contribute towards the fulfillment of high-accuracy positioning requirements in challenging environments when using cellular networks.

Performance of SVM technique for DoA Estimation in 5G mm-Wave band

Applying Machine Learning algorithms in wireless communication has shown increasing interest due to the increase of demand on capacity, the increase of the number of users, and equipment sharing the limited frequency spectrum resources. Also, the need for a reduction in power consumption at base stations and the optimization of radio coverage make ML an attractive and promising technique. In this paper, we investigate the usage of Support Vector Machine (SVM) technique for Direction of Arrival (DoA) estimation in the millimeter-wave band. The objective is to predict the location of a user in a given area by analyzing the received signals at an array of antennas, using an SVM-based model. The first phase of this technique consists of the training phase that aims to identify the characteristics of each class, and that is based on a set of training samples. The second phase consists of testing the trained model using a set of samples/users. We have carried out a set of simulations based on the developed model. The results are promising in terms of the accuracy of determining the DoA, taking into consideration a channel with noise and multipath.

A compact high gain wideband millimeter wave 1 × 2 array antenna for 26/28 GHz 5G applications

Purpose This paper aims to present the design, fabrication and analysis of a wideband, enhanced gain 1 × 2 patch antenna array with a simple profile structure to meet the desired antenna traits, such as wide bandwidth, high gain and directional patterns expected for the upcoming fifth-generation (5G) wireless applications in the millimeter wave band. To enhance these parameters (bandwidth and gain), a new antenna geometry by using a T-junction power divider is presented. Design/methodology/approach The theory behind this paper is connected with advancements in the 5G communications related to antennas. The methodology used in this work is to design a high gain array antenna and to identify the best possible power divider to deliver the power in an optimized way. The design methodology adopts several steps like the selection of proper substrate material as per the design specification, size of the antenna as per the frequency of operation and application-specific environment condition. The simulation has been performed on the designed antenna in the electromagnetic simulation tool (high-frequency structure simulator [HFSS]), and optimization has been done with parametric analysis, and then the final array antenna model is proposed. The proposed array contains 2-patch elements excited by one port adapted to 50 Ω through a T-junction power divider. The 1 × 2 array configuration with the suggested geometry helps to improve the overall gain of the antenna, and the implementation of the T-junction power divider provides enhanced bandwidth. The proposed array designed using a 1.6 mm thick flame retardant substrate occupies a compact area of 14 × 12.14 mm2. Findings The prototype of the array antenna is fabricated and measured to validate the design concept. A good agreement has been reached between the measured and simulated antenna parameters. The measured results confirm its wideband and high gain characteristics, covering 24.77–28.80 GHz for S11= –10 dB with a peak gain of about 15.16 dB at 27.65 GHz. Originality/value The proposed antenna covers the bandwidth requirements of the 26 GHz n258 band (24.25–27.50 GHz) to be deployed in the UK and Europe. The suggested antenna structure also covers the federal communications commission (FCC)-regulated 28 GHz n261 band (27.5–28.35 GHz) to be deployed in America and Canada. The low profile, compact size, simple structure, wide bandwidth, high gain and desired directional radiation patterns confirm the applicability of the suggested array antenna for the upcoming 5 G wireless systems.

Waveguide Manufacturing Technologies for Next-Generation Millimeter-Wave Antennas

Some recent waveguide-based antennas are presented in this paper, designed for the next generation of communication systems operating at the millimeter-wave band. The presented prototypes have been conceived to be manufactured using different state-of-the-art techniques, involving subtractive and additive approaches. All the designs have used the latest developments in the field of manufacturing to guarantee the required accuracy for operation at millimeter-wave frequencies, where tolerances are extremely tight. Different designs will be presented, including a monopulse antenna combining a comparator network, a mode converter, and a spline profile horn; a tunable phase shifter that is integrated into an array to implement reconfigurability of the main lobe direction; and a conformal array antenna. These prototypes were manufactured by diverse approaches taking into account the waveguide configuration, combining parts with high-precision milling, electrical discharge machining, direct metal laser sintering, or stereolithography with spray metallization, showing very competitive performances at the millimeter-wave band till 40 GHz.

A Multiroute Signal Control Model considering Coordination Rate of Green Bandwidth

Oriented to characteristics of the inflow and outflow of routes in urban road network, we modified the classical fundamental green wave bandwidth model, in which separate turning green wave band is available for traffic flow from subarterials merging into an arterial, and this variable green wave band can be more flexible to service the commuting traffic. Moreover, with the analysis of the mapping characteristics of the phase coordination rate, the concept of the coordination rate of green wave bandwidth was proposed, with which as the objective function, a multiroute signal coordination control model was established, and this model is a mixed integer linear programming problem with the overall optimal coordination rate of inbound, outbound, and turning movement as the objective. Finally, a case study was given with road network in Suzhou Industrial Park, Jiangsu Province, China. From the simulation results, we can conclude that the coordinated distribution of the model proposed in this study is more stable; the fluctuation range is 0.09, which is less than that of optimization scheme in classical signal timing software Synchro, which is 0.33; and the total route delay can also be reduced by 15% compared to the current situation and 3.3% compared to Synchro optimization solution.

Verification of the Radio Wave Absorption Effect in the Millimeter Wave Band of SWCNTs and Conventional Carbon-Based Materials

Using a sample coated with three types of carbon-based paints, namely single-wall carbon nanotube (SWCNTs), carbon black, and graphite, the amount of radio wave absorption for each was measured. SWCNTs proved to have the superior radio wave absorption effect in the millimeter band. Considering the change in the amount of radio wave absorption depending on the coating amount, three different coating thicknesses were prepared for each test material. The measurement frequency was set to two frequency bands of 28 GHz and 75 GHz, and the measurement method was carried out based on Japanese Industrial Standard (JIS) R1679 “Radio wave absorption characteristic measurement method in the millimeter wave band of the radio wave absorber.” As for the amount of radio wave absorption in the 28 GHz band, a maximum amount of radio wave absorption of about 6 dB was obtained when 35 m of CNT spray paint was applied. It was confirmed that the carbon black paint came to about 60% that of the SWCNT, and the graphite paint did not obtain much radio wave absorption even when the coating thickness was changed. Furthermore, even in the 75 GHz band, the radio wave absorption was about 7 dB when 16 μm of CNT spray paint was applied, showing the maximum value. Within these experimental results, the CNT spray paint has a higher amount of radio wave absorption in the millimeter wave band than paints using general carbon materials. Its effectiveness could be confirmed even with a very thin coating thickness of 35 μm or less. It was also confirmed that even with the same paint, the radio wave absorption effect changes depending on the difference in coating thickness and the condition of the coated surface.