Journal Papers by Carlos A Fernandes
Vaquero, Á.F.; Pino, M.R.; Arrebola, M.; Matos, S.A.; Costa, J.R.; Fernandes, C.A. Evaluation of a Dielectric-Only Transmitarray for Generating Multi-Focusing Near-Field Spots Using a Cluster of Feeds in the Ka-Band. Sensors 2021, 21, 422., Jan 2001
A transmitarray antenna is evaluated to generate a multi-focusing spot area in the Fresnel region... more A transmitarray antenna is evaluated to generate a multi-focusing spot area in the Fresnel region of the antenna in the Ka-band. The antenna is designed to focus the radiated field at a certain point using a central feeding configuration. The number of feeds is increased to create as many focusing spots as feeds. The feeds are placed along an arc defined in the principal planes of the transmitarray, radiating independent near-field spots and providing a solution with a wide-angle spot scanning without an antenna displacement and a high isolation between feeds. To validate this concept, a transmitarray based on dielectric-only cells is designed and simulated under full-wave conditions. Then, this design is manufactured using a 3D printing technique, and the prototype is measured in a planar acquisition range. Measurements are performed for different feed positions in order to validate the multi-focusing capability of the antenna. Measurements and simulations show a high agreement and validate the proposed design technique.
IEEE Transaction on Antennas and Propagation, 2018
— Many wireless communication applications such as satellite communications use circularly polari... more — Many wireless communication applications such as satellite communications use circularly polarized (CP) signals, with the requirement for easy switching of the polarization sense between uplink and downlink. Specifically, in satellite communications , the trend is also to move to higher frequencies and integrate the receiving and transmitting antennas in one dual-band terminal. However, these simultaneous demands make the design and fabrication of the composing parts very challenging. We propose, here, a dual-band dual-linear polarization (LP)-to-CP converter that works in the transmission mode. The working principle of this polarizer is explained through an example for Ka-band satellite communications at 19.7–20.2 and 29.5–30 GHz. The LP-to-CP converter is a single panel composed of identical unit cells with a thickness of only 1.05 mm and a size of 5.3 mm × 5.3 mm. Due to its operation in the transmission mode, the polarizer can be combined with a simple dual-band dual-LP antenna to obtain the desired dual-band dual-CP single antenna. However, the unique property of this polarizer is yet the fact that it converts a given LP wave, e.g., x-polarization, to orthogonal CP waves at the two nonadjacent frequency bands, e.g., left-handed CP at lower band and right-handed CP at higher band. The polarizer is tested both with 20 and 30 GHz LP rectangular horns to illuminate a dual-band transmit array (TA) to obtain wide-angle steering of CP beams. The performance of the polarizer and its association with the TA is evaluated through simulation and measurements. We also present design guidelines for this type of polarizer. Index Terms— Antenna–filter–antenna, circular polarization (CP), dual-band antennas, frequency selective surfaces, periodic structures, polarization conversion.
Surface plasmons polaritons are collective excitations of an electron gas that occur at an interf... more Surface plasmons polaritons are collective excitations of an electron gas that occur at an interface between negative-ε and positive-ε media. Here, we report the experimental observation of such surface waves using simple waveguide metamaterials filled only with available positive-ε media at microwave frequencies. In contrast to optical designs, in our setup the propagation length of the surface plasmons can be rather long as low loss conventional dielectrics are chosen to avoid typical losses from negative-ε media. Plasmonic phenomena have potential applications in enhancing light– matter interactions, implementing nanoscale photonic circuits and integrated photonics.
In this paper, we propose a ball grid array (BGA) module with an integrated 3-D-printed plastic l... more In this paper, we propose a ball grid array (BGA) module with an integrated 3-D-printed plastic lens antenna for application in a dedicated 130 GHz OOK transceiver that targets the area of 5G backhaul/fronthaul systems. The main design goal was the full integration of a small footprint antenna with an energy-efficient transceiver. The antenna system must be compact and cost effective while delivering an approximately 30 dBi gain in the working band, defined as 120 to 140 GHz. Accordingly, a 2 × 2 array of aperture-coupled patch antennas was designed in the 7 × 7 × 0.362 mm 3 BGA module as the feed antenna of the lens. This achieved a 7.8 dBi realized gain, broadside polarization purity above 20 dB, and over 55% total efficiency from 110 to 140 GHz (20% bandwidth). A plastic elliptical lens 40 mm in diameter and 42.3 mm in height was placed on top of the BGA module. The antenna achieved a return loss better than −10 dB and a 28 dBi realized gain from 114 to 140 GHz. Finally, active measurements demonstrated a >12 Gbps Tx/Rx link at 5 m with bit error rate (BER) < 10 −6 at 1.6 pJ/b/m. These results pave the way for future cost-effective, energy-efficient, high-data rate backhaul/fronthaul systems for 5G communications. Index Terms— 3-D printing, 5G, backhaul/fronthaul links, ball grid array (BGA), dielectric lens, millimeter-wave (mmw) antennas, organic module.
Transmit array design is more challenging for dual-band operation than for single band, due to th... more Transmit array design is more challenging for dual-band operation than for single band, due to the independent 360° phase wrapping jumps needed at each band when large electrical length compensation is involved. This happens when aiming at large gains, typically above 25 dBi with beam scanning and F/ D ≤ 1. No such designs have been reported in the literature. A general method is presented here to reduce the complexity of dual-band transmit array design, valid for arbitrarily large phase error compensation and any band ratio, using a finite number of different unit cells. The procedure is demonstrated for two offset transmit array implementations operating in circular polarization at 20 GHz(Rx) and 30 GHz(Tx) for Ka-band satellite-on-the-move terminals with mechanical beam-steering. An appropriate set of 30 dual-band unit cells is developed with transmission coefficient greater than −0.9 dB. The full-size transmit array is characterized by full-wave simulation enabling elevation beam scanning over 0°−50° with gains reaching 26 dBi at 20 GHz and 29 dBi at 30 GHz. A smaller prototype was fabricated and measured, showing a measured gain of 24 dBi at 20 GHz and 27 dBi at 30 GHz. In both cases, the beam pointing direction is coincident over the two frequency bands, and thus confirming the proposed design procedure.
This paper illustrates the role of additive manufacturing (AM) as enabling technology to realize ... more This paper illustrates the role of additive manufacturing (AM) as enabling technology to realize high-performance low-cost antennas for Ka-band applications. In addition to the inherent electromagnetic challenges implicit in the conception of such complex devices, this paper also points out the stringent limitations that appear when opting for classical fabrication techniques, based on assembled split-block models. AM emerges in this context as a change of paradigm, allowing mono-lithic fabrication and design freedom, which result in substantial improvements in terms of compactness, mass, simplicity, cost, and production time. Two different antennas for Ka-band satellite communications are presented here, namely a wideband horn and a dual-band circular cavity. Both prototypes are fabricated using a stereolithographic (SLA) AM process followed by metal coating. This fabrication approach is especially well suited to the implementation of these designs, since they have internal shapes that are inaccessible to conventional machining tools. The experimental results are not only in very good agreement with the theoretical predictions but also demonstrate improvements over the performances achieved by traditional milling and assembly fabrication approaches, thereby confirming the validity and great potential of SLA for Ka-band satellite communications.
A shaped double-shell dielectric lens is evaluated as a primary feed for a multibeam single-refle... more A shaped double-shell dielectric lens is evaluated as a primary feed for a multibeam single-reflector system operating in the satellite uplink and downlink Ka-bands, complying with gain and edge-of-coverage (EoC) directivity requirements. An assembly of dual-band printed feeds is integrated at the base of a single lens, each feed producing a virtual focus far behind the lens base and coincident with the reflector focal arch. The used double-shell lens approach, instead of a single-material lens, allows an extra degree of freedom to accommodate an aberration mitigation condition. This primary feed system is proposed as a low-complexity solution to enable fitting more beams per solid angle than conventional single-feed-per-beam systems based on a cluster of focal-plane horns. A proof-of-concept lens prototype with 87 mm diameter and 62 mm height, fed by a linear arrangement of five dual-band printed feeds, was fabricated and tested at the Ka-band. The lens measured radiation patterns were post-processed to evaluate the combined performance of the lens with an offset F/D 1 reflector system designed for 45-dBi EoC directivity. It is shown that it duplicates the reflector aperture efficiency compared to horn-fed systems with same feed separation. Index Terms—Dual-band antenna, multibeam antennas, reflector antennas, shaped double shell-lens antenna.
We successfully assess the feasibility of a passive body-implantable sensor antenna concept to re... more We successfully assess the feasibility of a passive body-implantable sensor antenna concept to reach 750 Mbps using impulse radio (IR) in the near-field. It is based on a uniplanar printed antenna configuration, operating in the 1.4-to 4.2-GHz band. The analysis includes the effect of the implant media, the performance in terms of data rate transmission (theoretical and experimental) and feasibility of a " passive " sensor concept in terms of power constraints associated with specific absorption rate (SAR) limits, Federal Communications Commission (FCC) power mask, energy scavenging circuit minimum activation energy, and signal-to-noise ratio (SNR). Finally, we prove the potential of the overall system integrated with an electronic chip model and bio-compatible material. To our knowledge there is no explicit study in the literature that fully demonstrates an implantable system with this kind of data rates addressing all the above. Index Terms—Body-area communication, high data rates, impulse radio (IR), link power budget, passive antenna, phantom, pulse fidelity, specific absorption rate (SAR).
A ball grid array-module (BGA-module) incorporating a low-cost shaped dielectric lens is proposed... more A ball grid array-module (BGA-module) incorporating a low-cost shaped dielectric lens is proposed for wireless communications in the 60-GHz WiGig band between a smart eye-wear, where it is integrated and facing a laptop or TV. The module, which is codesigned with a 60-GHz transceiver, consists of two separate identical antennas for transmitting (Tx) and receiving (Rx). The in-plane separation of these elements is 6.9 mm both being offset from the lens focus. This poses a challenge to the lens design to ensure coincident beam pointing directions for Rx and Tx. The shaped lens is further required to narrow the angular coverage in the elevation plane and broaden it in the horizontal plane. A 3-D-printed eyewear frame with an integrated lens and a recess for proper BGA-module integration is fabricated in ABS-plastic material. Measurements show a reflection coefficient below −12 dB in the 57–66 GHz band. A maximum gain of 11 dBi is obtained at 60 GHz, with 24 • and 96 • beamwidth at 5-dBi gain, respectively, in the vertical and horizontal planes. The radiation exposure is evaluated for a homogeneous SAM head phantom and a heterogeneous visible human head. The simulated power density values for both models are found to be lower than the existing standards.
A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-b... more A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-band satellite and high altitude platform (HAP) providing broadband access services. The wide-angle elevation beam steering is achieved by in-plane translation of a thin offset flat lens in front of a stationary primary feed while full azimuth coverage is obtained by simple 360º rotation of the lens. A new strategy is also proposed to reduce the effective F/D of the focusing system and consequently the total antenna height without increasing beam distortion: a second small flat lens is added on top of the primary feed to create a virtual focus located well below the feed phase center. The challenge is to conciliate high gain both with wide beam scanning and reduced antenna height. Design rules are presented for this antenna concept along with a 27.3-dBi gain fabricated example for the up-link Ka-band (29.5–30 GHz), with circular polarization, 0◦ to 50◦ 20 elevation scan, better than 2.8-dB scan loss and an effective F/D of only 0.55. Both lenses are 3.35-mm thick, formed by a suitable assembly of phase shifting unit cells with less than 0.4 dB of transmission loss in simulation. The main lens dimensions are 195 mm × 145 mm and its weight is 215 g. Total antenna height, including the feed is 26 84 mm.
The design of a micromachined polyethylene lens for WiGig modules is described and its electromag... more The design of a micromachined polyethylene lens for WiGig modules is described and its electromagnetic characteristics are measured. The lens is electromagnetically fed by linearly polarized Tx and Rx patch antennas integrated in an existing ball-grid-array (BGA) organic module. Antennas are separated from each other by a distance of 4.45 mm (0.89lambda at 60 GHz). The goal of the lens is to increase the gain of each antenna while lowering the beam depointing effect due to their offset position regarding the focal point of the lens. A geometrical optics/physical optics (GO/PO) hybrid method is applied to the design and analysis of the lens shape for noncollimating purpose. Using a lens height of 30 mm for both Tx and Rx antennas, a 13-dBi minimum realized gain from 54 to 66 GHz is obtained. Compared to an elliptical lens providing an equivalent realized gain over the same bandwidth, the depointing angle from the boresight direction is reduced from 15° to 4°. Full-wave simulations are verified by measurements.
A complete UHF radio-frequency identification (RFID)-based system capable of localizing individua... more A complete UHF radio-frequency identification (RFID)-based system capable of localizing individual blood bags inside storage cabinet drawers is presented. It was developed to demonstrate the improvement possibility of current blood stock management systems and as the submission to the 2014 IEEE AP-S Student Design Contest: Antennas for RFID Application. The system is composed of a cabinet model, a transceiver unit, and a PC with the controlling software. A new implementation of pseudolocalization principle is used to localize the blood bags that are equipped with dedicated passive tags designed to be resilient to blood proximity and small size. The detector antennas are placed at the drawers bottoms and additional passive tags are utilized to identify individual locations in each drawer. The transceiver unit is made from off-the-shelf commercial electronic boards and wirelessly controlled by software run on the PC. The entire system is small, transportable, battery powered, and low cost.
A simple low-cost mobile ground terminal antenna for Ka-band satellite communications is presente... more A simple low-cost mobile ground terminal antenna for Ka-band satellite communications is presented. The antenna is composed of a shaped dielectric lens which tilts and rotates in front of a feed to direct the beam. The wideband feed system is composed of a quad-ridged horn with a 45° slant aperture and a coaxial-to-quad-ridged circular waveguide transition. The lens allows simple mechanical beam steering from 0° to 65° in relation to the zenith and 360° in azimuth by rotating both the lens and the feed slanted aperture. Performance measurements of a manufactured prototype prove the beam tilting capabilities in elevation with a maximum gain of 22 dBi and scan loss below 3 dB at 20 GHz and 24 dBi gain with less than 4.5 dB scan loss at 30 GHz.
Starting from a challenge in the early 1990s to develop a highly shaped beam dielectric lens ante... more Starting from a challenge in the early 1990s to develop a highly shaped beam dielectric lens antenna for a pilot 150 Mb/s cellular mobile broadband system operating in the 60-GHz band, several new developments have been accomplished over more than 20 years at Instituto de Telecomunicações [1] in the areas of millimeter-wave shaped dielectric lens antennas and planar metamaterial lenses. We review here a few representative examples with numerical and experimental results, covering applications in mobile broadband communications, radiometry, satellite communications, multigigabit short-range communications, and sublambda near-field target detection.
Applied Physics Letters, Oct 1, 2008
Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes, Phys. Rev. B, 78, 0... more Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes, Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of crossed metallic wires may behave as a nonresonant material with extremely large index of refraction at microwaves, and may enable the realization of ultra-subwavelength waveguides.
Dielectric lens antennas are proposed for wireless broadband communication systems in the mm-wave... more Dielectric lens antennas are proposed for wireless broadband communication systems in the mm-wave range. Two lens antenna configurations for base station applications are presented and evaluated in terms of radiation characteristics, feeding system, input reflection loss, bandwidth and fabrication tolerances. The system requirements to provide optimum power distribution over the cell and good control of the cell boundaries are achieved.
Microwave Theory and Techniques, IEEE Transactions on, Mar 1, 2004
In this paper, we propose a new hybrid method to characterize the band structure of three-dimensi... more In this paper, we propose a new hybrid method to characterize the band structure of three-dimensional metallic crystals. We formulate an auxiliary problem that has the same spectrum as the metallic crystal. We prove that the spectrum of the auxiliary problem can be efficiently computed using the plane-wave method and the method of moments. Thus, the band structure of the metallic crystal can also be efficiently calculated. Our approach is much more effective than root-searching methods, because all of the eigenvalues are obtained at once and degenerate cases pose no difficulty. This is a generalization of a previously proposed method for two-dimensional structures.
Ieee Transactions on Antennas and Propagation, 2011
A new wideband compact slot antenna array for indoor WLAN access points (AP) is described, coveri... more A new wideband compact slot antenna array for indoor WLAN access points (AP) is described, covering several wireless communication services from 2.4 to 4.8 GHz, that is especially designed to enhance MIMO system capacity. The array topology provides both spatial and polarization diversity. Despite very close packing of the array elements, these exhibit very low mutual coupling and low cross-polarization, greatly favoring MIMO diversity gain. A detailed MIMO performance comparison is conducted against a common array of patches in indoor environment, based both on simulation and indoor measurements: the new antenna shows a clear improvement in terms of channel capacity.
IEEE Transactions on Antennas and Propagation, 2013
There is a growing interest for simultaneous identification and centimetre-resolution localizatio... more There is a growing interest for simultaneous identification and centimetre-resolution localization of multiple targets in indoor environments. A hybrid passive UHF/UWB RFID concept has been recently proposed that conciliates the potential from high resolution UWB impulse radio with the typical range from UHF-RFID identification systems. This paper proposes a new planar antenna for hybrid passive tag systems, which operates both in the UHF-RFID band and in the FCC UWB band. The co-designed UHF and UWB antenna elements are printed back-to-back on each side of a common substrate with appropriate topology for future integration with a single UHF-UWB RFID chip. Experimental tests have shown that both UHF-RFID and UWB performance of the hybrid antenna are comparable to available commercial solutions that work just on a single band. The antenna is adequate for lowcost mass production of hybrid passive tags. It aims at low-cost passive RFID systems combining the ability of item identification with precise tracking in indoor environments.
IET Microwaves, Antennas & Propagation, 2014
Viability of a conformal single-layer monopole antenna is studied for a wall-embedded tag in an u... more Viability of a conformal single-layer monopole antenna is studied for a wall-embedded tag in an ultra-wideband (UWB) suitcase localisation application based on impulse radio UWB. The performance of the embedded antenna is simulated and confirmed experimentally in real-time localisation (RTL) experiments carried out in a cluttered laboratory environment. Evaluation in the main planes shows average suitcase positioning error around 8 cm for worst-case conditions. RTL tests are made when the suitcase is empty, when it is filled with common travelling items and also when it is shadowed by a second suitcase. A vector network analyser-based measurement set-up is used for target localisation error evaluation. Additionally, the same tests are repeated using portable commercial time-domain transceivers with similar results.
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Journal Papers by Carlos A Fernandes