Erika Pittella

Design, Realization, and Test of a UWB Radar Sensor for Breath Activity Monitoring

An analytical model of an ultrawideband range gating radar is developed. The model is used for the system design of a radar for breath activity monitoring having sub-millimeter movement resolution and fulfilling the requirements of the Federal Communications Commission in terms of effective isotropic radiated power. The system study has allowed to define the requirements of the various radar subsystems that have been designed and realized by means of a low cost hybrid technology. The radar has been assembled and some performance factors, such as range and movement resolution, and the receiver conversion factor have been experimentally evaluated and compared with the model predictions. Finally, the radar has been tested for remote breath activity monitoring, showing recorded respiratory signals in very good agreement with those obtained by means of a conventional technique employing a piezoelectric belt.

High-Gain S-band Patch Antenna System for Earth-Observation CubeSat Satellites

A novel S-band circularly polarized patch antenna system suited for earth-observing CubeSats is presented. The antenna consists of four rectangular patches properly excited in order to have the maximum gain in the boresight direction and produce circular polarization. The antenna has a compact size, and its geometry and characteristics are compatible with any CubeSat standard structure. A 57-mm-wide square window allows to accommodate imaging system optics in its center leading to a very compact overall system. A prototype of the designed antenna system has been used to validate simulation results that showed a gain of 7.3 dBi. Experimental measurements confirm that the antenna achieves good impedance match at the desired frequency of 2450 MHz, a directivity of 8.3 dBi, and 60° 3-dB beamwidth, in good agreement with the simulation results.

UWB pulse propagation into human tissues

In this paper the propagation of a UWB pulse into a layered model of the human body is studied to characterize absorption and reflection of the UWB signal due to the different body tissues. Several time behaviours for the incident UWB pulse are considered and compared with reference to the feasibility of breath and heartbeat activity monitoring. Results show that if the UWB source is placed far from the human body, the reflection coming from the interface between air and skin can be used to detect the respiratory activity. On the contrary, if the UWB source is placed close to the human body, a small reflection due to the interface between the posterior lung wall and the bone, which is well distanced in time from the reflections due to the first layers of the body model, can be used to detect lung and heart changes associated with the cardio-respiratory activity.

Complex Radar Cross Section Measurements of the Human Body for Breath-Activity Monitoring Applications

An experimental setup for complex mono-static radar cross section (RCS) measurements in the 1-10-GHz-frequency band, employing a suitably modified semianechoic chamber, is presented and characterized. The foreseen application is the measurement of the complex RCS of the human body during respiratory activity, to ease the design and optimization of ultrawideband (UWB) radar systems for breath-activity monitoring. The proposed RCS test range is calibrated by means of a readily available aluminum flat panel and its performance is tested against canonical targets, evaluating uncertainty in magnitude, and phase measurements. The setup is then employed to carry out investigations on the complex RCS of a volunteer, focusing on its changes resulting from breath activity. Applying the measured RCS patterns to a specifically developed model, the feasibility of the UWB radar approach for achieving a continuous contact-less monitoring of breath activity in a subject at rest is clearly demonstrated. Finally, experimental tests of the application of the proposed radar technique to real-world scenarios are shown, and the safety of RCS measurements and UWB radar monitoring, with reference to exposure of the monitored subject to the radiated electromagnetic fields, is evaluated.

Safety Aspects of People Exposed to Ultra Wideband Radar Fields

The safety aspects of people exposed to the field emitted by ultra wideband (UWB) radar, operating both in the spatial environment and on ground, for breath activity monitoring are analyzed. The basic restrictions and reference levels reported in the ICNIRP safety guideline are considered, and the compliance of electromagnetic fields radiated by a UWB radar with these limits is evaluated. First, simplified analytical approaches are used; then, both a 3-dimensional multilayered body model and an anatomical model of the head have been used to better evaluate the electromagnetic absorption when a UWB antenna is placed in front of the head. The obtained results show that if the field emitted by the UWB radar is compliant with spatial and/or ground emission masks, then both reference levels and basic restrictions are largely satisfied.

Monitoring of cardio-pulmonary activity with UWB radar: A circuital model

The aim of this work is to present a circuital model to design an ultra wide band radar for the monitoring of cardio-pulmonary activity. The model takes into account the signal source, the transceiver antenna properties, and the dispersive behavior of the thorax tissues. The model has been validated by comparing its results with those achieved with a commercial electromagnetic software. Finally it has been used to study the signal variations, both in air and at the antenna feed point, produced by the cardio-pulmonary activity.

Breath Activity Monitoring With Wearable UWB Radars: Measurement and Analysis of the Pulses Reflected by the Human Body

Objective: Measurements of ultrawideband (UWB) pulses reflected by the human body are conducted to evidence the differences in the received signal time behaviors due to respiration phases, and to experimentally verify previously obtained numerical results on the bodys organs responsible for pulse reflection. Methods: Two experimental setups are used. The first one is based on a commercially available impulse radar system integrated on a single chip, while the second one implements an indirect time-domain reflectometry technique using a vector network analyzer controlled by a LabVIEW virtual instrument running on a laptop. Results: When the UWB source is placed close to the human body, a small reflection due to the lung boundaries is present in the received pulse well distanced in time from the reflection due to the air-skin interface; this reflection proved to be linked to the different respiration phases. Conclusions: The changes in the reflected pulse could be used to detect, through wearable radar systems, lung movements associated with the breath activity. Significance: The development of a wearable radar system is of great importance because it allows the breath activity sensing without interfering with the subject daily activities.

Evaluation of the Electromagnetic Power Absorption in Humans Exposed to Plane Waves: The Effect of Breathing Activity

The safety aspects of the exposure of people to uniform plane waves in the frequency range from 900 MHz to 5 GHz are analyzed. Starting from a human body model available in the literature, representing a man in resting state, two new anatomical models are considered, representing different phases of the respiratory activity: tidal breath and deep breath. These models have been used to evaluate the whole body Specific Absorption Rate (SAR) and the 10-g averaged and 1-g averaged SAR. The analysis is performed using a parallel implementation of the finite difference time domain method. A uniform plane wave, with vertical polarization, is used as an incident field since this is the canonical exposure situation used in safety guidelines. Results show that if the incident electromagnetic field is compliant with the reference levels promulgated by the International Commission on Non-Ionizing Radiation Protection and by IEEE, the computed SAR values are lower than the corresponding basic restrictions, as expected. On the other side, when the Federal Communications Commission reference levels are considered, 1-g SAR values exceeding the basic restrictions for exposure at 4 GHz and above are obtained. Furthermore, results show that the whole body SAR values increase passing from the resting state model to the deep breath model, for all the considered frequencies.

A survey of radar systems for medical applications

A survey of radar systems used in the medical field is presented. First, medical applications of radars are described, and some emerging research fields are highlighted. Then, medical radars are analyzed in terms of block diagrams and behavioral equations and some implementations are shown as examples. A section is dedicated to the radiating structures used in these radars. Finally, human safety and environmental impact issues are addressed. The most investigated medical applications of radars are breast tumor diagnostics and remote monitoring of cardiorespiratory activity. New fields of interest are physiological liquid detection, and the monitoring of artery walls and vocal cord movements. Among the various topologies, continuous wave (CW) radars have been proven to yield the highest range resolution that is limited only by the system noise while the resolution of ultra wideband (UWB) and frequency modulated continuous wave (FMCW) radars is also related to the used frequency bandwidth. Concerning the maximum range, UWB radars have the best performance due to their ability to operate in the presence of environmental clutter. As for the radiating structures, planar antennas are preferred for diagnostic applications, due to their small dimensions and good matching when placed in contact with the human body. Radar systems for remote monitoring, instead, are designed by using high gain antennas and taking into account the complex radar cross section (RCS) of the body.

Design of a UWB radar system for remote breath activity monitoring

In this work a ultra wideband radar for breath activity monitoring has been designed taking into account the Federal Communications Commission (FCC) emission mask for medical imaging devices. The design has been performed by using a theoretical model that, starting from the characteristics of a specifically developed antenna and considering the FCC mask, allows the evaluation of the source signal shape, amplitude and repetition rate. Moreover, exploiting information on the human body radar cross section, the model has been used to predict the signal reaching the receiver after the body reflection. The designed radar has been implemented by using an indirect time domain reflectometry system and tested for breath activity monitoring. The radar has been able to monitor the breath activity of a subject in agreement with spirometry results.