No abstract

Internet of Things (IoT) technology is rapidly emerging in medical applications as it offers the possibility of lower-cost personalized healthcare monitoring. At the present time, the 2.45 GHz band is in widespread use for these applications but in this paper, the authors investigate the potential of the 915 MHz ISM band in implementing future, wearable IoT devices. The target sensor is a wrist-worn wireless heart rate and arterial oxygen saturation (SpO2) monitor with the goal of providing efficient wireless functionality and long battery lifetime using a commercial Sub-GHz low-power radio transceiver. A detailed analysis of current consumption for various wireless protocols is also presented and analyzed. A novel 915 MHz antenna design of compact size is reported that has good resilience to detuning by the human body. The antenna also incorporates a matching network to meet the challenging bandwidth requirements and is fabricated using standard, low-cost FR-4 material. Full-Wave EM simulations are presented for the antenna placed in both free-space and on-body cases. A prototype antenna is demonstrated and has dimensions of 44 mm × 28 mm × 1.6 mm. The measured results at 915 MHz show a 10 dB return loss bandwidth of 55 MHz, a peak realized gain of −2.37 dBi in free-space and −6.1 dBi on-body. The paper concludes by highlighting the potential benefits of 915 MHz operation for future IoT devices.

In this article, a method for the assessment of the performance and for the design of a 2-D-array for multiple input multiple output (2-D-MIMO) radar applications is presented. The proposed approach is based on the analysis of the ambiguity function associated with the array. Such analysis leads to the definition of an area in the 2-D-angular field-of-view of the radar, denoted as ambiguity-free region, characterized by a low probability to obtain ambiguities in direction of arrival estimation. Simulations of a basic 2-D-MIMO array are used to explain the proposed method, which is then employed as the main criterion for the optimization of a 2-D-MIMO sparse array composed of four transmitters and eight receivers. The optimization is performed through a genetic algorithm. The resulted element positions guarantee an ambiguity-free region span in the azimuth and elevation angles greater than 120 • and angular resolutions of 8 • and 5.9 • on the azimuth and elevation angles, respectively. The optimized positions are then used to realize a 2-D-MIMO sparse array that is integrated in a radar system operating at a center frequency of 76.5 GHz. Such an array is calibrated, and comparisons between the simulated and measured ambiguity functions show the effectiveness of the proposed method.

This is a cross-sectional survey on the health conditions of railways workers active in 258 interconnection and conversion substations all over Italy. Measurements performed in both kinds of substations operating at 220 kV have shown that maximum levels of the electric field strength and of the magnetic flux density at 50 Hz are of the order of 5 kV/m and 15 microT, respectively. Three subject groups, differently exposed (1, 10, 20 h/week), and an unexposed control group, for a total number of 627 workers, constitute the population at study. All subjects underwent a general medical examination, laboratory investigations, and a series of selected examinations relative to three systems (nervous, cardiovascular, and haematopoietic) considered at higher risk. No differences have been found between the exposed and the control groups. It is concluded that workers exposed to ELF electromagnetic fields of moderate strength do not show the presence of clear effects on their state of health.

No abstract