Browsing by Author "Mendes, Carlos"
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- Bending effects on a textile microstrip antennaPublication . Amaro, Nuno; Mendes, Carlos; Pinho, PedroThis paper describes the design of a textile microstrip antenna for 2.4 GHz. Two different fabrics are used: one for the dielectric part and another one for the conductor part. The dielectric constant of the dielectric fabric is determined experimentally. The input matching is studied by electromagnetic simulation and experimentally. Since the antenna is meant to be incorporated in the user's clothe, the effect that the antenna bending has on the matching level is also investigated both theoretically and experimentally.
- A Dual-Mode Single-Band Wearable Microstrip Antenna for Body Area NetworksPublication . Mendes, Carlos; Peixeiro, CustódioDesign, fabrication, and test of a novel single-band wearable antenna with dual-mode operation (on-body and offbody) for body area network’s applications in the 2.45 GHz industrial scientific and medical band are presented. The on-body mode is achieved with a microstrip ring while the off-body mode is obtained with a compact meanderedmicrostrip patch placed inside the ring. The two antennas are fed separately but share a common ground plane and use only fabricmaterials facilitating the integration into the user’s clothes. The antenna operation is characterized when placed on a phantom mimicking a human torso. Input match, mutual coupling, radiation pattern, radiation efficiency, and path loss measurements are presented and show good agreement with simulations.
- Fabrication, measurement and time decay of the electromagnetic properties of semi-solid water-based phantomsPublication . Mendes, Carlos; Peixeiro, CustódioThis paper presents a complete and detailed description of the fabrication and measurement of the electromagnetic properties of water-based semi-solid phantoms with emphasis on the analysis of the time evolution of the complex permittivity of several samples stored in different conditions. A known recipe for a 2/3 muscle equivalent phantom is used as test material, and the several phantom sample properties are measured with an in-house developed coaxial probe technique. It is shown that the storing condition is of paramount importance to extend the lifetime of a given phantom. This behavior stems from the way the storing condition affects the water evaporation rate of the sample. In particular, while an unprotected sample can preserve its electromagnetic properties only for a few days, a very well-sealed one can last at least up to a year.
- Flexible RFID tag for bottle labellingPublication . Rodrigues, David; Pinho, Pedro; Mendes, CarlosThis paper describes the design, manufacturing and range measurement of an UHF (ultra high frequency) RFID (radio frequency identification) tag to apply on a glass bottle filled with water. To achieve this, a free-space matched RFID antenna is studied and modifications are made in order reduce its size drastically and to turn it functional when applied to a bottle with water. Later, range measurement tests are made on the fabricated tag.
- Limites fundamentais em antenas impressas pequenasPublication . Mendes, Carlos; Peixeiro, CustódioO objectivo desta comunicação é a análise de antenas impressas miniaturizadas utilizadas nos modernos e pequenos terminais portáteis dos sistemas de comunicações móveis. Começa-se pelo estudo do comportamento de antenas em geral, apresentando limites físicos fundamentais no que diz respeito à relação entre dimensão, ganho e largura de banda. É mostrado que a largura de banda, ganho e volume de uma antena estão relacionadas entre si e que o produto ganho - largura de banda é proporcional ao volume da antena. Apresentam-se ainda resultados de protótipos construídos anteriormente, e mostra-se que estes apresentam um desempenho que se encontra afastado do limite teórico, o que parece indicar que podem ainda ser mais optimizados.
- On-body off-body dual mode microstrip antenna for Body Area Network applicationsPublication . Mendes, Carlos; Peixeiro, CustódioThis paper describes the design, fabrication and test of a novel dual mode, on-body and off-body, planar microstrip antenna for Body Area Networks applications. The on-body antenna is obtained with a microstrip ring operating at a higher order mode while the off-body antenna is obtained with a meandered microstrip antenna. The antennas are fed separately but share a common ground plane and are disposed so that the occupied area is minimized.
- On-body transmission performance of a novel dual-mode wearable microstrip antennaPublication . Mendes, Carlos; Peixeiro, CustódioThe path loss established between several wearable antenas placed on a tissue-equivalent phantom is investigated through numerical simulations and measurements. The on-body performance of a previously proposed dual-mode wearable textile antenna, designed to operate in the 2.45 GHz industrial, scientific and medical band, is evaluated and compared with a wearable textile patch antenna. Simulation results of a _/4 resonant wire monopole are also presented to serve as a reference. Five different scenarios for the location of the transmitting and receiving antennas are analyzed: one with line of sight (LOS), two with non- LOS (NLOS), and the remaining two in the transition between LOS and NLOS. The transmission results are evaluated with the antenas mounted on the surface of a homogeneous phantom with 2/3 muscle properties mimicking the shape and physical macroscopic properties of a human torso. A general good agreement is obtained between numerical simulation and experimental results. It is shown that in the NLOS scenario, the proposed antenna has an equivalent path loss only about 3.4 dB higher than the monopole and about 10 dB lower than the patch.
- A performance measurement platform for C-ITS over 5GPublication . Serrador, António; Mendes, Carlos; Datia, Nuno; Cota, Nuno; Cruz, Nuno; Beire, Ana R.This paper aims to present a new performance measurement tool dedicated to mobile cellular networks, focussed on the new C-ITS applications and challenges. Called ISEL QoS-Network Performance Evaluation (IQ-NPE), developed under the European Union 5G-MOBIX project, it is a measurement performance tool that is able to extract a wide range of performance parameters at different levels: radio, network layers and application. This is a step further when comparing with classical tools, based on mobile terminals, because C-ITS applications take advantage of cellular modems using Multiple Input Multiple Output (MIMO) advanced systems, due to available space offered by vehicles. IQ-NPE is designed to test classical alongside with the new C-ITS applications (ITS-G5 based) performance running at the Multi-access/Mobile Edge Computing (MEC) node in the new 5G architecture. All the collected data can be exported, as integrated performance data, to further be analysed using business intelligence tools. Thus, this paper presents the IQ-NPE general architecture, its main components, probes (units composed by hardware and software subsystems), together with configuration input and output examples.
- Repetidor para ambientes interiores em CDMA2000Publication . Feiteira, Filipe; Assunção, João; Cota, Nuno; Fortes, Fernando; Silva, Henrique; Mendes, CarlosEsta comunicação descreve o desenvolvimento do protótipo de um repetidor para ambientes interiores, que será usado com a tecnologia CDMA2000 na faixa dos 460 MHz. O protótipo, que fica intercalado entre 2 antenas, consiste num módulo activo que efectua amplificação bi-direccional. Foram realizadas medidas de campo com este sistema, mostrando-se uma clara melhoria de cobertura.