Modulated scatterer technique probe for intra-body RF channel measurements

Abstract

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.

Development of aMSTsensor probe, based on aSP3Tswitch, for biomedical applications

“…The three different resistive loads not only are used to maximize r , 16 the MST probe retrieve the information and the electric characteristic of the media surrounding the antenna tag as detailed in Refs. 21–24.…”

“…MST probes demonstrated their potentialities 16,17 especially in biomedical applications where they have been used for breast cancer detection 18 and different microwave imaging systems. 19,20 In particular, MST probes able to retrieve the dielectric characteristics of materials in which they are embedded, [21][22][23][24] could be very useful in biomedical applications such as the detection of skin tumors. 25,26 MST probes make use the scattering properties of small passive antennas, 16,27 thanks to this they can be strongly miniaturized making them suitable for biomedical devices.…”

“…Another interesting key of force of MST systems is that they can be easily integrated in an existing microwave systems such as RFIDs or radars. Multiports MST sensors are able to retrieve the electrical properties of materials, 17,21,23,24 these characteristics make multiports MST probes particularly suitable for biomedical applications. The structure of a MST sensor is quite simple it consists of a transmitting/receiving antenna connected with different resistive loads by mean of an electronic switch, and a control unit.…”

Fabrication of Implantable Capsule-Type Channel Sounders for the High-Accuracy Measurement of the Signal Loss of Out-Body to In-Body Channels

“…A channel sounder comprises a pair of devices that are used to discretely generate and receive a test signal to measure the channel parameters. For the out-body to inbody channel, the channel measurement can be performed using a wired channel sounder, where twisted pairs or coaxial cables are connected between the channel transmitter and the receiver in the channel sounder [5][6][7]. Such a cable connection causes interference during the channel measurement of the out-body and in-body channels.…”