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.