Browsing by Author "Gouveia, Carolina"
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- Design of a Cardiopulmonary antenna for vital signs monitoring robust to different subjectsPublication . Cardoso, João; Pinho, Pedro; Gouveia, Carolina; Albuquerque, DanielWith the advancement of wireless diagnosis and treatment technologies, antennas deployed close to the human body are now widely used. The use of on-body antennas, along with other technologies, presents itself as an innovative method for detecting and monitoring vital signs. These antennas can be attached directly on the body or on clothes, making it comfortable to use and less invasive when compared to conventional methods, allowing at-home monitoring of elderly patients or high risk workers with a single antenna. In this paper, a robust high bandwidth patch antenna was developed to operate in the dedicated Industrial, Scientific and Medical frequency band, namely at 2.45 GHz, capable of monitoring vital signs in any subject. This work presents the design and results of a robust cardiopulmonary antenna, to be further used to monitor the respiratory rate of five different subjects, each one with different physiognomy.
- Different antenna designs for non-contact vital signs measurement: a reviewPublication . Gouveia, Carolina; Loss, Caroline; Pinho, P.; Vieira, JoséCardiopulmonary activity measured through contactless means is a hot topic within the research community. The Doppler radar is an approach often used to acquire vital signs in real time and to further estimate their rates, in a remote way and without requiring direct contact with subjects. Many solutions have been proposed in the literature, using different transceivers and operation modes. Nonetheless, all different strategies have a common goal: enhance the system efficiency, reduce the manufacturing cost, and minimize the overall size of the system. Antennas are a key component for these systems since they can influence the radar robustness directly. Therefore, antennas must be designed with care, facing several trade-offs to meet all the system requirements. In this sense, it is necessary to define the proper guidelines that need to be followed in the antenna design. In this manuscript, an extensive review on different antenna designs for non-contact vital signals measurements is presented. It is intended to point out and quantify which parameters are crucial for the optimal radar operation, for non-contact vital signs' acquisition.
- Dynamic digital signal processing algorithm for vital signs extraction in continuous-wave radarsPublication . Gouveia, Carolina; Albuquerque, Daniel; Vieira, José; Pinho, PedroRadar systems have been widely explored as a monitoring tool able to assess the subject's vital signs remotely. However, their implementation in real application scenarios is not straightforward. Received signals encompass parasitic reflections that occur in the monitoring environment. Generally, those parasitic components, often treated as a complex DC (CDC) offsets, must be removed in order to correctly extract the bio-signals information. Fitting methods can be used, but their implementation were revealed to be challenging when bio-signals are weak or when these parasitic reflections arise from non-static targets, changing the CDC offset properties over time. In this work, we propose a dynamic digital signal processing algorithm to extract the vital signs from radar systems. This algorithm includes a novel arc fitting method to estimate the CDC offsets on the received signal. The method revealed being robust to weaker signals, presenting a success rate of 95%, irrespective of the considered monitoring conditions. Furthermore, the proposed algorithm is able to adapt to slow changes in the propagation environment.
- Influence of radiation pattern in the performance of bio-radarPublication . Gouveia, Carolina; Malafaia, Daniel; Vieira, José; Pinho, PedroThe bio-radar system can measure vital signals accurately, such as the respiratory signal, by using the Doppler effect principle that relates the received signal properties with the distance change between the radar antennas and the person's chest-wall. In this paper, the antenna radiation pattern influence on the quality of the received signal is analysed. Moreover, we show that the antenna with a narrow beam leads to a better signal to noise ratio.
- Limits of WPT through the human body using Radio FrequencyPublication . Duarte, Rodrigo; Gouveia, Carolina; Pinho, Pedro; Albuquerque, DanielRecently, the medical community has been devel oping new technologies to enhance medical treatments and diagnosis means, having in mind the patients’ comfort and safety. Implantable medical devices are an example of such solutions. Nonetheless, these devices present some disadvantages, namely need of batteries. Hence, these implants have a limited lifetime, and require periodical surgical interventions to change or to recharge. In order to solve this problem, systems based on Radio Frequency (RF) has been developed to transfer energy inside the organism. However, transmitting power to inside the human body must be performed carefully, since high power levels might be prejudicial to the subject. In this context, the goal of this work is to study the performance of the Wireless Power Transfer (WPT) to inside the human body, while respecting the Specific Absorption Rate (SAR) limits. Therefore, the levels of absorbed power in different body parts were verified by simulation, in order to reach conclusions about the user’s safety. More specifically, two biological models that represent the thigh and the arm were considered. The simulation results led us to conclude that it is possible to transmit approximately 140 mW on the limbs location, while respecting the SAR limits. In turn, it is possible to receive a power superior to 93 µW inside the human body. Additionally, real tests were also carried out in three subjects to verify the power attenuation related to each body structure.
- Motion detection method for clutter rejection in the bio-radar signal processingPublication . Gouveia, Carolina; Vieira, José; Pinho, PedroThe cardiopulmonary signal monitoring, without the usage of contact electrodes or any type of in-body sensors, has several applications such as sleeping monitoring and continuous monitoring of vital signals in bedridden patients. This system has also applications in the vehicular environment to monitor the driver, in order to avoid any possible accident in case of cardiac failure. Thus, the bio-radar system proposed in this paper, can measure vital signals accurately by using the Doppler effect principle that relates the received signal properties with the distance change between the radar antennas and the person’s chest-wall. Once the bio-radar aim is to monitor subjects in real-time and during long periods of time, it is impossible to guarantee the patient immobilization, hence their random motion will interfere in the acquired signals. In this paper, a mathematical model of the bio-radar is presented, as well as its simulation in MATLAB. The used algorithm for breath rate extraction is explained and a method for DC offsets removal based in a motion detection system is proposed. Furthermore, experimental tests were conducted with a view to prove that the unavoidable random motion can be used to estimate accurately the DC offsets and thus remove them successfully.
- A review on methods for random motion detection and compensation in bio-radar systemsPublication . Gouveia, Carolina; Vieira, José; Pinho, PedroThe bio-radar system can measure vital signals accurately, by using the Doppler effect principle, which relates the received signal properties to the distance change between the radar antennas and the subject chest-wall. These systems have countless applications, from short range detection to assist in rescue missions, to long-term applications as for the continuous sleeping monitoring. Once the main applications of these systems intend to monitor subjects during long periods of time and under noisy environments, it is impossible to guarantee the patient immobilization, hence its random motion, as well as other clutter sources, will interfere in the acquired signals. Therefore, the signal processing algorithms developed for these applications have been facing several challenges regarding the random motion detection and mitigation. In this paper, an extended review on the already implemented methods is done, considering continuous wave radars. Several sources of random motion are considered, along with different approaches to compensate the distortions caused by them.
- Study on the usage feasibility of continuous-wave radar for emotion recognitionPublication . Gouveia, Carolina; Tome, Ana; Barros, Filipa; Soares, Sandra C.; Vieira, José; Pinho, PedroNon-contact vital signs monitoring has a wide range of applications, such as in safe drive and in health care. In mental health care, the use of non-invasive signs holds a great potential, as it would likely enhance the patient's adherence to the use of objective measures to assess their emotional experiences, hence allowing for more individualized and efficient diagnoses and treatment. In order to evaluate the possibility of emotion recognition using a non-contact system for vital signs monitoring, we herein present a continuous wave radar based on the respiratory signal acquisition. An experimental set up was designed to acquire the respiratory signal while participants were watching videos that elicited different emotions (fear, happiness and a neutral condition). Signal was registered using a radar-based system and a standard certified equipment. The experiment was conducted to validate the system at two levels: the signal acquisition and the emotion recognition levels. Vital sign was analysed and the three emotions were identified using different classification algorithms. Furthermore, the classifier performance was compared, having in mind the signal acquired by both systems. Three different classification algorithms were used: the support-vector machine, K-nearest neighbour and the Random Forest. The achieved accuracy rates, for the three-emotion classification, were within 60% and 70%, which indicates that it is indeed possible to evaluate the emotional state of an individual using vital signs detected remotely.
- Textile antenna array for bio-radar applicationsPublication . Gouveia, Carolina; Loss, Caroline; Raida, Zbynek; Lacik, Jaroslav; Pinho, Pedro; Vieira, JoséIn this paper, a 2 x 2 antenna array operating at 5.8 GHz is presented for vital signs acquisition using a radar-based system, also known as bio-radar. Since these non-contact systems have multiple applications, their front-end design should take into account the monitoring environment of each specific application. In this sense, the antenna design has a crucial role to guarantee the proper integration of the full system, considering different materials. In this work, the antennas were made using textile materials, in order to integrate the bio-radar system in a car seat cover. This work presents the design of the antenna and the results achieved through measures in the anechoic chamber. Furthermore, respiratory signals were also acquired with the manufactured antennas and they are herein presented for validation purposes.
- 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.