Presented is a noncontact model and radiometric sensor developed to facilitate core body temperature extraction. The system has been designed as a close-proximity sensor to detect thermal emissions radiated from deep inside the human body. The radiometer uses a cavity-backed slot antenna (CBSA) designed to account for performance degradation which occurs in the near field of the human body. Tissue-simulating materials with electrical properties similar to the human body have been identified, and layered configurations of these phantoms are used to mimic the electromagnetic characteristics of a human stomach volume: hence, defines the core model. Positioned approximately 7 mm from the core model, the sensor tracks the change in brightness temperature as the subsurface physical temperature is varied. A mathematical noncontact model (NCM) is subsequently used to correlate the observed brightness temperature to the subsurface temperature, accounting for artifacts induced by the sensor's remote positioning from the specimen. The accuracy of the NCM is validated through an analysis of the measurement data extracted from the test bed before and after applying the model. The results illustrate that the measurement is highly sensitive to the antenna impedance match and atmospheric temperature. The measurement is less sensitive to the physical temperature of the instrument and emissivity of the specimen. The results of this study demonstrate that radiometric sensors are capable of close proximity, subsurface extraction of biological data given that certain parameters are closely monitored. Index Terms-Closeproximity health monitoring, near-field biomedical sensing, noncontact biomedical sensing, noninvasive biomedical monitoring. 1530-437X/$26.00 John Gerig, photograph and biography not available at the time of publication. Thomas M. Weller (S'92-M'95-SM'98) received the B.S., M.S., and Ph.D. degrees in electrical engineering in 1988, 1991, and 1995, respectively, from the University of Michigan, Ann Arbor.

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Presented is a Cavity Backed Slot Antenna (CBSA) designed for integration into a biomedical radiometric sensor. The sensor is intended for close proximity health monitoring applications. An internal probe feed adds a novel approach to biomedical antenna design by isolating antenna feed currents from the body and providing frequency tuning of ~50MHz/mm as a function of probe length. Measurements and simulations performed with the CBSA in close proximity to a skin tissue phantom confirm that the antenna is a good candidate for the intended applications.

An end loaded planar open sleeve dipole (ELPOSD) antenna over an electromagnetic band gap (EBG) high impedance surface is presented. An ELPOSD consists of a printed dipole with two parasitic elements (sleeves) along its sides and capacitive loading at the end. This antenna is fed from beneath the ground plane by live vias connected to a microstrip to coplanar strip balun. The EBG structure is based on the Jerusalem Cross geometry and is sandwiched between two 1.27 mm-thick substrate layers, resulting in a total antenna thickness (excluding the feed layer) of ~λ/50. Measured performance of the antenna demonstrates a bandwidth of 30 MHz at 2.45 GHz, with a gain of ~3.5 dB. IntroductionHerein a low-profile planar antenna operating at 2.45 GHz with uni-directional radiation is presented. The goal of this effort was to establish a baseline approach for realizing a flexible antenna with moderate bandwidth that can be used in applications such as bodyworn sensors. For electromagnetic sensing, e.g. in the case of radiometric sensors, reduction in backside radiation is important in order to maximize the detection sensitivity. Accordingly, a design incorporating a backing ground-plane is appropriate. Furthermore, in this particular effort, the ability to tune the operating frequency is desirable as this allows real-time adjustment of the sensing depth. For this reason, the architecture has been conceived with the aim of facilitating eventual integration of varactor-based tuning.Among the choices for antenna elements satisfying the above criteria are various forms of microstrip patch antennas. Standard, single-layer patches are typically narrow-band [1] and tuning approaches usually involve devices that are exposed on the outer surface [2], contrary to the embedded solution that is desired in this work. Multi-layer patches may offer instantaneous bandwidth covering the frequency range of interest [e.g. 3] however the thickness conflicts with the desire to achieve a flexible, low-profile design.The approach taken in this work was to integrate an end-loaded planar open sleeve dipole (ELPOSD) into a multi-layer substrate that includes a back ground-plane and an intervening high-impedance, electronic band-gap (EBG) layer. The ELPOSD is naturally broad-band, typically ~25% bandwidth, and compact in size. The Jerusalem Cross Frequency Selective Surface (JC-FSS) geometry was selected for the EBG layer, due to its wide angular stability and the potential for convenient frequency tuning and substrate thickness reduction. Previous authors have investigated the combination of an ELPOSD with patch-type electronic band-gap (EBG) layers [e.g. 4, 5]. Antenna Design and PerformanceThe ELPOSD antenna design consists of a printed dipole that is loaded with two parallel sleeves, and has parasitic capacitive loading at the ends of the dipole arms; the loading 978-1-4244-4968-2/10/$25.00 ©2010 IEEE elements offer design miniaturization. The dipole was designed for a 1.27 mm-thick Rogers RT6010 substrate, with a dielectric constant of 10.2, that...