Modulated scatterer technique probe for intra-body RF channel measurements

For sensing human body parameters, several sensors (implantable or digestible) can be located inside the body. Since intra-body locations are not physically accessible (or at least difficult and with some risks), wireless communication with the sensing nodes is required. This intra-body wireless communication is a very challenging area, mainly because of the unknown and very attenuated channel and its variation with different human subjects. The topic of this paper is enabling intra-body channel measurements for accurate channel modeling in order to allow for precise intra-body localization and efficient data transmission. We propose to measure the channel by using the modulated scatterer technique (MST). MST has several advantages over conventional techniques, in which a probe in receiver mode is employed, like low field perturbation, minimization, simplified design, minimized size due to simpler circuitry operation and lower power consumption allowing for self-powering. The topic of this paper is the design and measurement of a MST probe for intra-body applications. Measurements are presented using the proposed device over several frequencies of operation in order to evaluate the probe's performance. After initial testing in air and further testing in several tissue environments the probe's performance has been evaluated. The measurement results are matching the theory. Functionality is as predicted and efficient measurements are possible in the MICS and ISM operation bands.