Alfredo De Leo

Wireless Sensing for the Respiratory Activity of Human Beings: Measurements and Wide-band Numerical Analysis

An electromagnetic sensing system for the measurement of the respiratory activity is presented. The aims are to demonstrate the feasibility of the proposed approach and in particular to evaluate the effect on the measured signal of the distance between the subject and the sensing apparatus. Moreover, an electromagnetic model of the system, including the monitored subject, is proposed as a tool to solve the problem of selecting working parameters for system design. The sensing system is based on the measurement of the phase variation of the reflection coefficient caused by the respiratory activity. The phase signal compared with the thorax displacement measured by a reference instrument shows a high correlation () for different subject postures (sitting, standing, and lying) and a reduction of the signal amplitude with the distance  dB/cm is reported. The numerical simulations performed on a wide-band highlight the frequencies where the method exhibits the highest sensitivity to thorax movements. The sensitivity can be further improved by reducing the antenna beamwidth. Despite the signal amplitude reduction, the proposed system makes it possible to correctly operate at distances up to 2.5 m.

Design and Realization of an Electromagnetic Guiding System for Blind Running Athletes

Nowadays the technologies aimed at improving the quality of life of people affected by visual diseases are quite common; e.g., devices to support walking or reading. Surprisingly, there is a lack of innovative technologies aimed at helping visually impaired athletes during physical activities. An example is represented by blind runners who need to be physically linked to a sighted guide by means of non-stretchable tethers during races; with consequent limitations in terms of performance and independence. This paper wants to investigate the possibility of realizing a system able to guide blind runners along a complex path, paving the way for the realization of an innovative device designed to improve their independence during training or competitions. The system consists of: (1) a mobile unit, which is placed before the runner and generates two “electromagnetic walls” delimiting the way; (2) a receiving unit (worn by the athlete) that provides vibro-tactile warnings every time the user is going outside the safe area so as to encourage him to move toward the central position. The feasibility and the utility of the system proposed are demonstrated by means of tests carried out thanks to the collaboration of a blind volunteer.

Remote Measurement of the Respiration by Electromagnetic Sensing

Respiration activity is one of the fundamental functions of the human being (also known as vital signs) which is monitored for health purposes. Often it is required to operate the sensing of the respiration activity out of hospitals or clinical environments and without contact with the patient and possibly from a distance i.e. for the home monitoring of patients or for the ambient assisted living, AAL). Unfortunately, at present the sensing apparatus for respiration monitoring purposes are mainly based on the use of contact methods (chest belt, nasal temperature transducers, etc.) which appear to be not suited for such tasks. In this paper, the authors propose a novel approach based on the use of electromagnetic sensing of the respiration activity of subject. The proposed approach provide a remote, continuous measurement of the inspiration/expiration acts of a subject without requiring a contact; these features of the proposed system are suited for domestic monitoring and AAL.

Low-Frequency Theoretical Analysis of a Source-Stirred Reverberation Chamber

Theoretical analysis of a reverberation chamber excited through the source-stirring technique at low frequency is presented. A complete analytical solution returns quickly the electromagnetic field inside the chamber thanks to an efficient computation technique for the slowly convergent triple series. The stirring function is accomplished by 62 monopole antennas, irregularly distributed on the chamber walls, and subsequently, fed two at a time for a total of 1891 combinations. At first, the empty chamber is characterized, as usually it is done for any test site and then a receiving loop is considered in the chamber working volume to simulate a device under test (DUT) and the induced voltage is studied in terms of amplitude and phase. The analytical approach allows to account for all mutual couplings between transmitting antennas and the receiving structure through the computation of all self and mutual impedances. We demonstrate that the contribution of chamber irrotational modes cannot be neglected in the computation of both antenna input impedance and DUT-induced voltage. The present study highlights the capability of source stirring to change the field amplitude and orientation in the undermoded condition. This advantage takes also benefit from the use of an out-of-phase feeding for each pair of active antennas, achieving a higher DUT-induced voltage.

A feasibility study of a compact radar system for autonomous walking of blind people

In this contribution, recent developments in the design and development of a novel compact smart radar for visually impaired and blind users are described. Starting from previous studies and according to the specific user requirements, a new antenna (dimensions: 54mm × 8.4mm × 1.44mm) and an integrated Tx/Rx circuit board, working in the 24-26 GHz frequency band, have been designed; the aim of these improvements is twofold: the miniaturization of the whole system allowing its integration onto a traditional white cane and a drastic reduction of the dimensions, weight and final costs of the system by using existing and available technologies.

A novel measurement method for respiration rate by electromagnetic frequency sweep

The non-contact measurement of the respiration rate of a subject offers several interesting applications in hospital as well as in domestic environments. The use of electromagnetic waves has been proved to be a feasible approach to this purpose. In this paper, authors present a novel measurement method, based on the transmission of a frequency sweep and the measurement of the reflection coefficient (S11), to determine the respiration rate of the monitored subject without contact. The proposed method places itself at the half-way between continuous wave (CW) and ultra wide band (UWB) techniques, offering some advantages of both methods and improving its feasibility. Experimental tests have been carried out on voluntary subjects simultaneously measured with two reference systems in order to compare respiration frequency values. Results show a good correlation between the data measured during tests, proving that the proposed method is a valid approach to the issue of the noncontact assessment of the respiration rate both in clinical and domestic environments.

A Realistic Model for the Analysis of Heart Magnetic Stimulation

The aim of the paper is the development of an accurate numerical model to compute the current density flowing through the heart of a virtual human body, and induced by an external electric or magnetic excitation. The model has been experimentally validated and then applied to investigate the main characteristics of the heart magnetic stimulation. This has been carried out by comparing the current density induced in the cardiac region by an external magnetic pulse with the corresponding quantity due to the more traditional electric source. Magnetic stimulation is studied because it offers some advantages: in fact, compared with the electrical stimulation, this technique is contactless and might allow the stimulation of a dressed patient. The design constraint of the whole system is represented by the current density, whose waveform and intensity are a compromise between the strength of the magnetic induction field and the pulse rise time.

An Electromagnetic Sensor for the Autonomous Running of Visually Impaired and Blind Athletes (Part I: The Fixed Infrastructure)

Sport is one of the best ways to promote the social integration of people affected by physical disability, because it helps them to increase their self-esteem by facing difficulties and overcoming their disabilities. Nowadays, a large number of sports can be easily played by visually impaired and blind athletes without any special supports, but, there are some disciplines that require the presence of a sighted guide. In this work, the attention will be focused on marathons, during which athletes with visual disorders have to be linked to the sighted guide by means of a non-stretchable elbow tether, with an evident reduction of their performance and autonomy. In this context, this paper presents a fixed electromagnetic infrastructure to equip a standard running racetrack in order to help a blind athlete to safely run without the presence of a sighted guide. The athlete runs inside an invisible hallway, just wearing a light and a comfortable sensor unit. The patented system has been homemade, designed, realized and finally tested by a blind Paralympic marathon champion with encouraging results and interesting suggestions for technical improvements. In this paper (Part I), the transmitting unit, whose main task is to generate the two magnetic fields that delimit the safe hallway, is presented and discussed.

Electromagnetic Sensing of Obstacles for Visually Impaired Users

Vision impairment is a physical and sensory disability affecting a large number of subjects around the world. A large part of this subjects is aged 65 or older and their number grows faster than the overall population. In this work, a innovative sensing method, proposed by the research group of the Universita Politecnica delle Marche based on EM pulses, is presented together with some experimental results achieved in obstacles detection. The proposed approach accomplishes most of the operative requirements of electronic travel aids for visually impaired subjects and can provide additional information (height form the ground, distance and position of the obstacle) on obstacles respect to the available assistive technologies currently used by subjects affected by visual impairments.

Safety Investigation of a Magnetic Pulse Applicator for Heart Stimulation

The safety area around the applicator of a high current pulse generator, able to magnetically stimulate the human heart, is characterized in terms of allowable induced current. The magnetic field produced by the adopted coil is computed using a complete analytical model to determine the limit area allowed for medical operators. The International Commission on Non-Ionizing Radiation Protection recommendation is adopted for the occupational exposure limits. The presence of a ferrite tile close to the stimulation coil is also investigated. The ferrite tile enhances the field level on the patient side, making the magnetic stimulation more efficient. Experimental validation demonstrates the models reliability.