Jointly Active and Passive Beamforming Designs for IRS-Empowered WPCN

This paper studies an intelligent reflecting surface (IRS)-empowered wireless powered communication network (WPCN) in Internet of Things (IoT) networks. In particular, a power station (PS) with multiple antennas uses energy beamforming to enable wireless charging to multiple IoT devices, in the downlink wireless energy transfer (WET) phase; then, during the uplink wireless information transfer (WIT) phase, these IoT devices utilise the harvested energy to concurrently transmit their individual information signal to a multi-antenna access point (AP), which equips with multi-user decomposition (MUD) techniques to reconstruct the IoT devices’ signal. An IRS is deployed to improve the energy collection and information transmission capabilities in the WET and WIT phases, respectively. To examine the performance of the system under study, We maximize the sum throughput with the aim of jointly designing the optimal solutions for the active PS energy beamforming, AP receive beamforming, passive IRS beamforming, and time scheduling. Due to the multiple coupled variables, the resulting formulation is non-convex, and a two-level scheme to solve the problem is proposed. At the outer level, a one-dimensional (1-D) search method is applied to find the optimal time scheduling, while at the inner level, an iterative block coordinate descent (BCD) algorithm is proposed to design the optimal receive beamforming, energy beamforming, and IRS phase shifts. In particular, the receive beamforming part is designed by considering the equivalence between sum rate maximisation and sum mean square error (MSE) minimisation, thereby deriving a closed-form solution. Furthermore, we alternately optimize the energy beamforming and IRS phase shifts using Lagrange dual transformation (LDT), quadratic transformation (QT), and alternating direction method of multipliers (ADMM) methods. Finally, numerical results are presented to showcase the performance of the proposed solution and highlight its advant..

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Tridimensional Yagi antenna: shaping radiation pattern with a non-planar array

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This work presents the concept and development of the tridimensional Yagi antenna, which is a novel type of Yagi antenna operating in P band. It is idealised from two other types of Yagi antennas: Quasi-Yagi and Yagi-Uda. The resultant antenna is based on a microstrip balun, as in the first, and its driver and directors are made from metal tubes, as in the second, both integrated to a reflecting plane. The key point of this new antenna model is its asymmetric and reconfigurable radiation pattern and therefore the possibility of a high rejection between sectors in a plane. This feature was accomplished with the new concept of progressive rotation of directors around the driver. The authors present a design methodology to adjust return loss and radiation pattern characteristics. The final prototype presents 9.4 dB gain at 450 MHz and 47% bandwidth centred at 425 MHz.4914341441Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Orbisat da Amazonia Industria e Aerolevantamento S/ACoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Wideband Omnidirectional Slotted-Waveguide Antenna Array Based on Trapezoidal Slots

This manuscript presents a novel approach for designing wideband omnidirectional slotted-waveguide antenna arrays, which is based on trapezoidal-shaped slots with two different electrical lengths, as well as a twisted distribution of slot groups along the array longitudinal axis. The trapezoidal section is formed by gradually increasing the slot length between the waveguide interior and exterior surfaces. In this way, a smoother impedance transition between waveguide and air is provided in order to enhance the array operating bandwidth. Additionally, we propose a twisting technique, responsible to improve the omnidirectional pattern, by means of reducing the gain ripple in the azimuth plane. Experimental results demonstrate 1.09 GHz bandwidth centered at 24 GHz (4.54% fractional bandwidth), gain up to 14.71 dBi over the operating bandwidth and only 2.7 dB gain variation in the azimuth plane. The proposed antenna array and its enabling techniques present themselves as promising solutions for mm-wave application, including 5G enhanced mobile broadband (eMBB) communications

Implementation and performance investigation of radio-over-fiber systems in wireless sensor networks

We report the performance investigation and implementation of four different radio-over-fiber (ROF) systems as backhaul for wireless sensor networks based on frequency shift keying modulation at 915 MHz. Its applicability was experimentally verified as a function of packet error rate, received signal strength indicator, and system reach. Furthermore, a performance noise analysis was carried out by taking into account the optical transmitter and receiver parameters, such as: equivalent input noise, noise figure, relative intensity noise, laser wavelength, and output power. The implementation of the proposed technical solution implies in a outstanding enhancement in the system reach, management, and flexibility. It has been achieved an improvement of 17.45 dB in the system performance by using high-quality pieces of equipment of ROF technology. (c) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:26692675, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.2716854122669267

PERFORMANCE ANALYSIS OF A RADIO OVER FIBER SYSTEM BASED ON IEEE 802.15.4 STANDARD IN A REAL OPTICAL NETWORK

We report on an implementation of a Radio over Fiber system based on IEEE 802.15.4 standard in a geographically distributed optical network. The system performance was analyzed under real conditions of temperature, pressure, humidity, and wind. Experimental results show no signal degradation and indicate frame error rates two orders of magnitude below the typical levels of wireless sensor networks. for distances tip to 160 kin. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1876-1879, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.244975181876187