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- Evaluation of a low-cost COTS bio radar for vital signs monitoringPublication . Silva, Fábio; Almeida, Rita; Pinho, Pedro; Marques, Paulo; Lopes, Sérgio IvanWith the beginning of the COVID-19 pandemic, there was a need for the Health Care Workers (HCW) to pay more attention to the vital signs of their patients. One way for this to happen, while respecting the social distance, is using contactless technologies, e.g. the bio radar. This way, the HCW will be able to monitor the respiration and heart rates of the patient, without getting close to him. For this to be possible, the best radar configurations were studied, as well as other important aspects that should be taken into consideration while monitoring a patient, for the results obtained to be reliable.
- Improving LoRa network simulator for a More realistic approach on LoRaWANPublication . Francisco, Sérgio; Pinho, Pedro; Luís, MiguelNowadays, the need for information is rapidly increasing, urging the development of technology to obtain reliable information. Under the scope of Smart Cities, Low Power Wide Area Networks (LPWANs) have been seen as one of the enabling technologies for the data gathering process but, the evaluation of new methods and solutions in large-scale, real world-scenarios, is a challenging and sometimes an impossible task. Thus, the need to use tools enabling the simulation of such networks arose, triggering the development of different network simulators. In this work we focus on the simulation of LoRa networks. Resorting on the LoRa network simulator mostly used in the literature, the LoRaSim, we study the impact of different propagation and the capture-effect models in the performance of a LoRa network. In addition, an extension to LoraSim is implemented, offering the capability to tweak the network on a more detailed fashion, by supporting distinguished parameters (spreading factor, bandwidth, code rate and payload) on the end-devices. Results show that when applying a well-known propagation model (Okumura-Hata) and a more realistic capture-effect on a network that emphasizes the use of orthogonality among all devices, this heterogeneity greatly increases its efficiency and quality.
- 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.
- Substrate integrated waveguide cavity backed slot antennas for millimeter-wave applicationsPublication . Finich, Sanaâ; Salgado, Henrique; Pinho, PedroA low-cost single-layer substrate-integrated waveg uide (SIW) cavity-backed slot antenna is proposed for millimeter wave applications. The structure is designed to operate at the W-band. The T-shaped slot antenna is placed on the back-side of the SIW and fed by a grounded coplanar waveguide (GCPW) transmission line. A transition between the (GCPW) and the SIW is also designed. The simulated results provide that the antenna has a stable gain over the frequency range (98.79-100.56) GHz with a maximum value of around 6 dBi also high radiation efficiency.
- 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.
- 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.
- Textile antenna for bio-radar embedded in a car seatPublication . Loss, Caroline; Gouveia, Carolina; Salvado, Rita; Pinho, Pedro; Vieira, JoséA bio-radar system is presented for vital signs acquisition, using textile antennas manufactured with a continuous substrate that integrates the ground plane. Textile antennas were selected to be used in the RF (Radio Frequency) front-end, rather than those made of conventional materials, to further integrate the system in a car seat cover and thus streamline the industrial manufacturing process. The development of the novel substrate material is described in detail, as well as its characterization process. Then, the antenna design considerations are presented. The experiments to validate the textile antennas operation by acquiring the respiratory signal of six subjects with different body structures while seated in a car seat are presented. In conclusion, it was possible to prove that bio-radar systems can operate with textile-based antennas, providing accurate results of the extraction of vital signs.
- Study of physiological and structural variability in the acquisition of vital signs with Bio RadarPublication . Soares, Beatriz Lino; Pinho, Pedro; Albuquerque, Daniel; Gouveia, Carolina Teixeira de SousaThe monitoring of vital signals is usually carried out by sensors and electrodes. However, it may not be viable or the best solution for people with burn tissues or with more delicate skin, not to mention cases with infectious diseases, where contact should be kept to a minimum. Thus, vital signs monitoring using radar (Bio-Radar) has become a hot topic of research and development. Several studies state that there is variability in vital signs between people. However, in the Bio-Radar area, these issues have not been addressed. In this regard, this dissertation intends to verify if it is possible to evaluate the gender, age, Body Mass Index (BMI), and Chest Wall Perimeter (CWP) through the use of radar signals, namely Bio-Radar, used to the vital signs acquisition. In order to achieve this goal, the vital signs of 92 people (46 females and 46 males), aged between 18 and 50 years old were acquired. With this dataset, it was possible to develop a statistical study of relevant characteristics extracted from the signals. Later, three Machine Learning (ML) algorithms, namely Support Vector Machine (SVM), KNearest Neighbor (KNN) and Random Forest, were trained to identify gender, age, BMI and CWP. Finally, the relation between the respiratory amplitude and the respiratory rhythm is analyzed.
- 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.
- Design of an anechoic chamber for W-Band and mmWavePublication . Pinho, Pedro; Santos, Hugo; Salgado, HenriqueIn this paper, we describe the design of an electrically large anechoic chamber for usage on millimetre-wave bands. Ansys Savant sotware was used to perform a simulation of the chamber, using physical optics coupled with uniform theory of diffraction (PO/UTD). Moreover, a method based on an open waveguide probe is described in this paper to obtain the electrical properties of the RF absorbers at millimetre-wave frequencies. Two different source antennas were simulated in this work and the corresponding quiet zones predicted. The largest quiet zone was 30 mm x 30 mm x 50mm, for a chamber size of 1.2 m x 0.6 m x 0.6 m.