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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.
- Dissipation factor and permittivity estimation of dielectric substrates using a single microstrip line measurementPublication . Gonçalves, Ricardo; Magueta, Roberto; Pinho, Pedro; Carvalho, NunoThe knowledge of the dielectric properties of materials, for the design of several components and circuits at high frequencies, is mandatory. In this paper, we present a simple method for the estimation of the dissipation factor (loss tangent) of dielectric materials based on the reflection measurement of a single microstrip line, which is applied to some common known materials, such as FR-4 and Rogers RO3010 laminates. The obtained results match well with the data on the literature for the considered materials.
- 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.
- 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.
- 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.
- A selective, tracking, and power adaptive far-field wireless power transfer systemPublication . Belo, Daniel; Ribeiro, Diogo C.; Pinho, Pedro; Carvalho, NunoThis paper proposes a selective, tracking, and power adaptive far-field wireless power transfer (WPT) system that may be integrated into passive wireless sensor networks (PWSNs). Both transmitter and receiving nodes are developed with features that allow them to cooperate. The system operates based on a backscattered pilot signal, which is used to control and focus the radiated energy. The transmitter may change between several states by turning on or off sets of antenna elements. Each of these states will transmit and consume a specific amount of power, and they will be selected based on the node's received signal strength (RSS). The receiving nodes are low complexity and battery-less devices, which use a small portion of the rectified energy to create an RSS-dependent modulation frequency, used to drive a backscatter modulator. Based on the nonlinear response of the rectifying devices, additional hardware was integrated into the nodes to activate/wake up them from specific wireless power signals. A complete system operating at 5.8 GHz for WPT and 3.6 GHz for the pilot signal is reported. It will be shown that effective far-field WPT links can be created with reasonable simplicity.
- Parasitic stacked slot patch antenna for DTT energy harvestingPublication . Moura, Tiago; Brás, Luís; Pinho, Pedro; Carvalho, Nuno; Gonçalves, RicardoIn this paper a rectangular patch antenna with two slots, integrated with a stacked parasitic antenna, is presented. These techniques allow a bandwidth (BW) and gain enhancement, two of the major limitations of traditional patch antennas. The antenna is designed to operate at 754 MHz for energy harvesting applications, from the Portuguese Digital Terrestrial Television (DTT) signal. The measured antenna BW is 22.5 MHz, representing an enhancement of around 17 MHz in respect to the simulated BW of the corresponding single patch configuration.