Improving the quality of healthcare and the prospects of "aging in place" using wireless sensor technology requires solving difficult problems in scale, energy management, data access, security, and ...privacy. We present AlarmNet, a novel system for assisted living and residential monitoring that uses a two-way flow of data and analysis between the front- and back-ends to enable context-aware protocols that are tailored to residents' individual patterns of living. AlarmNet integrates environmental, physiological, and activity sensors in a scalable heterogeneous architecture. The SenQ query protocol provides real-time access to data and lightweight in-network processing. Circadian activity rhythm analysis learns resident activity patterns and feeds them back into the network to aid context-aware power management and dynamic privacy policies.
In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer ...Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern.
This letter presents the design strategy and the experimental results on the Ku/Ka dual-band feed-horn developed within the Phase A/B1 study of the Copernicus imaging microwave radiometer, which is ...one of the new six expansion missions of the European Copernicus flagship program on Earth observation operating in five frequency channels. The radiometer requirements translate into a dense focal plane composed by compact and lightweight dual-band feed horns. The optimum illumination was derived in terms of Bloch waves and the applicability of piecewise-linear profile feed-horns for its synthesis in the case of two highly separated Ku--/Ka--frequency bands (1:1.95) was investigated. The presented feed-horn design was validated up to a technological readiness level of 6. The reported performances at antenna level for the complete Ku-/Ka-band feed cluster demonstrate the feasibility of dual-band smooth-wall feed-horns focal-planes meeting all the Earth observation requirements in terms of footprints, beam- and wide-beam efficiencies, and cross-polarization.
Radial transmission-line formalism is a generalization of Marcuvitz-Schwinger theory that permits to solve complex scattering problems in circular geometry. The formalism is exploited in this work ...for the analysis and design of ring loaded slots in circular waveguide whose applications span from microwave filters to mode converters. The scattering problem is formulated in terms of coupled magnetic field integral equations and solved using novel numerical schemes. The method is applied to study a choke flange and a stub filter in circular waveguide. A comparison with commercial software is reported to confirm the effectiveness of the approach.
A system for the automatic measurement of the circadian activity deviations in telemedicine has been developed within the framework of a "Health Integrated Smart Home Information System" (HIS/sup ...2/). HIS/sup 2/ is an experimental platform for the evaluation and the development of technologies in order to ensure the security and quality of life for patients who need home based medical monitoring. Location sensors are placed in each room of the HIS/sup 2/, allowing the monitoring of patient's successive activity phases within the patient's home environment. We proceeded with a sampling in an hourly schedule to detect weak rhythmic variations. Based on numerous measurements, we established a mean value with confidence limits. These also allowed us to define a zone within which the patient's activity is qualified to be "predictable." Alerts are set off if the patient's activity deviates from this zone.
This paper describes two small aperture array demonstrators called Medicina and Sardinia Array Demonstrators (MAD and SAD, respectively). The objectives of these instruments are to acquire experience ...and test new technologies for a possible application to the low‐frequency aperture array of the low‐frequency telescope of the Square Kilometer Array phase 1 (SKA1‐LOW). The MAD experience was concluded in 2014, and it turned out to be an important test bench for implementing calibration techniques based on an artificial source mounted in an aerial vehicle. SAD is based on 128 dual‐polarized Vivaldi antennas and is 1 order of magnitude larger than MAD. The architecture and the station size of SAD, which is along the construction phase, are more similar to those under evaluation for SKA1‐LOW, and therefore, SAD is expected to provide useful hints for SKA1‐LOW.
Key Points
Italian demonstrators of low‐frequency aperture array for radio astronomy
Aerial unmanned vehicle for the instrumental calibration of an aperture array
Technological solutions implemented in the receiving chain of a low‐frequency aperture array
A waveguide polarizer exploiting two different phase shift phenomena is presented in this letter. Iris-type discontinuities are in fact introduced in a waveguide structure having different ...propagation constants for the two principal polarizations. In this way, the required 90 differential phase shift is obtained combining the iris phase shift with the waveguide one. Several operative conditions arise from the combination of the two contributions. This approach has been used to design a broadband waveguide polarizer for the C-band antenna feed system of the Sardinia radio telescope with -40 dB reflection coefficients and a -35 dB cross polarization level in a 30% bandwidth.
This study presents the design and experimental results of a wide-band passive antenna-feed system developed for the C-band dual-circular-polarisation receiver of the Sardinia radio telescope (SRT). ...The latter is a 64 m diameter shaped radiotelescope under construction designed to operate with high efficiency from 300 MHz to over 100 GHz. The developed C-band antenna-feed system exhibits very high performances in a 30% band centred at 6.7 GHz; for example, the return loss at all electrical ports is higher than 30 dB and the cross-coupling between the two polarisations is lower than -34 dB. The design solutions of all the feed-system components, such as marker injector, polariser, transitions and the ortho-mode transducer (OMT), are reported in the study. In particular, the novel architecture of the OMT that provides an isolation between the two rectangular ports better than 70 dB is described in close detail. The computed and experimental results regarding both the complete system and its sub-assemblies are reported and discussed.
The joint of a large dielectric radome is described in terms of an equivalent transmission-line circuit thanks to the introduction of an equivalent periodic structure and by Floquet's modal analysis. ...In this framework, all the dielectric layers are modeled with their corresponding generalized scattering matrices, and the compensation grid is described as a parallel lumped admittance. Its value is the design parameter used to obtain the joint compensation. The measurements on a C-band prototype show a significant compensation effect for both polarizations.
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