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- 3D printed lens antenna for wireless power transfer at Ku-bandPublication . Gonçalves, Ricardo; Pinho, Pedro; Carvalho, NunoIn this paper we present the design of an antenna, operating in the Ku-band, conceived for wireless power transfer systems. It comprises an hemispherical dielectric lens, fabricated using 3D printing technology, fed by a microstrip patch antenna array. The conjugation of the dielectric lens with the microstrip patch array allows the development of a compact high gain antenna. The antenna presents a matched bandwidth between 12.7 and 13.15 GHz and a maximum gain of 18.1 dBi at each element.
- 3D antenna characterization for WPT applicationsPublication . Jordão, Marina; Pires, Diogo; Belo, Daniel; Pinho, Pedro; Carvalho, Nuno BorgesThe main goal of this paper is to present a three-dimensional (3D) antenna array to improve the performance of wireless power transmission (WPT) systems, as well as its characterization with over-the-air (OTA) multi-sine techniques. The 3D antenna consists of 15 antenna elements attached to an alternative 3D structure, allowing energy to be transmitted to all azimuth directions at different elevation angles without moving. The OTA multi-sine characterization technique was first utilized to identify issues in antenna arrays. However, in this work, the technique is used to identify which elements of the 3D antenna should operate to transmit the energy in a specific direction. Besides, the 3D antenna design description and its characterization are performed to authenticate its operation. Since 3D antennas are an advantage in WPT applications, the antenna is evaluated in a real WPT scenario to power an RF-DC converter, and experimental results are presented.
- Evaluation of planar elliptical antenna array with inner counter-elliptical slotPublication . Pinho, Pedro; Carvalho, NunoThis paper presents and analyzes a low profile planar antenna array of elliptical elements with inner counter-elliptical slots. The antenna has single feed and provides two main directive radiation components (front and back), with gain higher than 7 dBi and circular polarization (CP) over the entire 5 GHz ISM& UNII bands. This approach also cancels the null over the elevation plane, which makes it suitable for bidirectional communications, also for proximity coverage. The inner slot of elliptical shape provides three additional degrees of freedom to match the planar monopole and/or array in impedance and polarization over the desired frequency band. An electromagnetic (EM) model of the proposed antenna is developed for numerical analysis and optimization. The principle of operation and parametric study of the antenna are provided. The antenna is fabricated and experimental results are presented. The number of elements in the array are chosen according to the desired gain and the inner elliptical slot parameters (major radius, elliptical ratio and rotation) scaled for impedance and polarization matching.
- Challenges in resource-constrained IoT devices: energy and communication as critical success factors for future IoT deploymentPublication . Pereira, Felisberto; Correia, Ricardo; Pinho, Pedro; Lopes, Sérgio I.; Carvalho, Nuno BorgesInternet of Things (IoT) has been developing to become a free exchange of useful information between multiple real-world devices. Already spread all over the world in the most varied forms and applications, IoT devices need to overcome a series of challenges to respond to the new requirements and demands. The main focus of this manuscript is to establish good practices for the design of IoT devices (i.e., smart devices) with a focus on two main design challenges: power and connectivity. It groups IoT devices in passive, semi-passive, and active, giving details on multiple research topics. Backscatter communication, Wireless Power Transfer (WPT), Energy Harvesting (EH), chipless devices, Simultaneous Wireless Information and Power Transfer (SWIPT), and Wake-Up Radio (WUR) are some examples of the technologies that will be explored in this work.
- 5.8 GHz Microstrip antennas and array for microwave power transferPublication . Carvalho, António; Carvalho, Nuno; Pinho, Pedro; Georgiadis, Apostolos; Constanzo, AlessandraWireless power transmission presents itself as being a solution to some common problems of the extensive use of electronic devices such as the removal of parasitic components present in feeding pads and the constant charge of electronic devices without the need of wires. This solution becomes attractive, for example, as a means of increasing the flight time of battery dependent unmanned aerial vehicles. Microstrip antenna due to their ease of manufacturing, low fabrication cost, support of different polarizations and conformability to irregular surfaces and different substrates, seem very advantageous in being used for microwave power transmission. This paper presents a linearly polarized 16-element antenna array with uniform amplitude and phase excitation proposed for power transmission while both a linearly and circularly polarized single element patch are proposed for reception.
- 3D antenna array for SWIPT Sensing with WPT capabilitiesPublication . Pires, Diogo; Belo, Daniel; Jordão, Marina; Pinho, Pedro; Carvalho, NunoIn this work, the design and development of an alternative three-dimensional array is presented. This arrangement aims to improve Simultaneously Wireless Information and Power Transfer (SWIPT) systems and to provide advantages when integrated into a Wireless Sensor Network (WSN) architecture. The conceived 3D antenna array consists of eight antenna elements operating at 5.65 GHz that are attached in a 3D printed heptagonal prism. With this structure, it is intended to achieve as close as possible to an omnidirectional radiation pattern with considerable gain, avoiding power losses. The experimental measurements carried out are in line with the performed electromagnetic simulations and validate the array operation. A full azimuth coverage was ensured with an average realized gain of 6.7 dBi. For some azimuth directions, this gain can reach approximately 8.35 dBi. This array proves to be a reliable solution to fed multiple low-power sensors that are placed over the 360 azimuth angles.
- Small size antennas mountable on mettalic gas cylindersPublication . Pereira, Felisberto; Carvalho, Nuno; Pinho, PedroThis paper presents a solution to integrate a metallic gas cylinder in an Internet of Things (IoT) network. The work briefly explains the different attempts made, then focusing on describing the final solution. The discussion has in account the simulated and measured results. The final result is a small antenna (dimensions lower than 90mm x 35mm) capable of taking advantage of the metallic surface of the gas cylinder without compromising its input impedance.
- Beam steering antenna and network design for WPT applicationsPublication . Costa, Andreia; Gonçalves, Ricardo; Pinho, Pedro; Carvalho, NunoThe Internet of Things (IoT) is increasingly present in our daily routine. It allows to use technology in a more efficient way. Important enabler of it is Wireless Power Transmission (WPT) as an alternative to electrical conductors (wires and cables). Given these aspects a linear microstrip antenna array was developed for 2.45 GHz ISM band, with Circular Polarization (CP). The main objective of this array is to create a beam to power up wireless sensors within a specific area of a room. The steering performance of the antenna is simulated using CST tool. Simulation results are found to be in good agreement with measurements.
- When backscatter communication meets vehicular networks: boosting crosswalk awarenessPublication . Pereira, Felisberto; Sampaio, Hugo; Chaves, Ricardo; Correia, Ricardo; Luís, Miguel; Sargento, Susana; Jordão, Marina; Almeida, Luís; Senna, Carlos; Oliveira, Arnaldo S. R.; Carvalho, Nuno BorgesThe research of safety applications in vehicular networks has been a popular research topic in an effort to reduce the number of road victims. Advances on vehicular communications are facilitating information sharing through real time communications, critical for the development of driving assistance systems. However, the communication by itself is not enough to reach the most desired target as we need to know which safety-related information should be disseminated. In this work, we bring passive sensors and backscatter communication to the vehicular network world. The idea is to increase the driver (or vehicle) awareness regarding the presence of pedestrians in a crosswalk. Passive sensors and backscatter communication technologies are used for the pedestrians’ detection phase, while the vehicular network is used during the dissemination of the detection information to surrounding vehicles. The proposed solution was validated through end-to-end experimentation, with real hardware and in a real crosswalk with real pedestrians and vehicles, demonstrating its applicability.
- 3D antenna for wireless power transmission aperture coupled microstrip antenna with dielectric lensPublication . Dias, Gonçalo; Pinho, Pedro; Gonçalves, Ricardo; Carvalho, NunoNowadays 3D printers are useful for the development and rapid prototyping of dielectric structures for radiation manipulation and support of antennas. This is possible since the materials used in this machines are essentially dielectric. These can be used as radiating elements (dielectric resonators), as radiation handlers (lenses) or as a supporting base for applying conductive material to radiation (substrates). In this paper we explore 3D printing technology to develop a lens antenna for wireless power transfer operating at 20 GHz. The design, simulation and measurement of an aperture coupled microstrip antenna with dielectric lens is presented and discussed. The lens is used to focus the beam of lower gain feed antenna to produce a highly directive pattern with low side lobe.
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