UWB RFID was analyzed for low power wireless signal transmission in brain-computer interface applications. The research investigated radio propagation inside the human body using a multilayer tissue model based on MRI scans. It was found that cerebellum and blood cause major absorption losses. Attenuation increases with frequency and cerebellum thickness variation. Absorption losses were less dependent on frequency than expected. Modifying UWB transmitters and receivers based on these results could improve energy efficiency and reduce power consumption.

1. [Systems][Enabling Technologies][Fundamental Knowledge]
UWB RFID for Low Power Wireless Signal Transmission in BBCI
Applications
Pragnesh V Patel1, Rutul Patel1, Dr. Santosh Nagaraj1, Dr. MahaSweta Sarkar1
1 Electrical and Computer Engineering, San Diego State University
Introduction
• To design any wireless communication system, the position of
Transmitter and Receiver and the channel through which the
signal propagates are important parameters.
• For in body communications human tissues are channel model.
This is because human body is a complex system consisting of
many different kinds of tissues.
• These tissues are constructed in a layered way where the
thickness is different for each tissue and differ for each human.
Therefore the tissues present in human torso have to be taken
into account for in body communication applications.
• The dielectric properties of human tissues is not only complex
but also frequency dependent. Moreover human tissues have
non zero conductivity. [1-2]
Results
• After studying the MRI scans of Human Brain of different age
people we found out the size of different medium through
which the signal will propagate.
• The absorption loss for all kind of thickness was investigated
and we found out that cerebellum and blood are major
contributor to absorption losses.
Table 1 Comparison of Attenuation for different size
Discussion
• From the results obtained we can show that as the frequency of
the signal increases the attenuation also increases irrespective
of size of medium.
• The attenuation due to variations in thickness of Cerebellum
causes big attenuation differences for all frequency bands.
• From the results it is investigated that the absorption losses are
not that frequency dependent as is expected and mentioned in
literature.
• For better energy efficiency and less power consumption the
Ultra Wideband Transmitter and Receiver can be modified
based on these results.
• Type of Antenna used and its directivity pattern along with
VSWR will have different effects on the results that are
obtained considering ideal conditions.
Conclusion
• In this research the radio propagation inside a human body has
been analyzed by investigating the physical characteristics of a
new developed multilayer model.
• In future work the influence of oblique incidence on the power
attenuations and reflections have to be investigated as well as
other effects as multipath and diffraction.
References
[1] Pahlavan, Kaveh, Yunxing Ye, Ruijun Fu, and Umair Khan.
"Challenges in channel measurement and modeling for RF
localization inside the human body." International Journal of
Embedded and Real-Time Communication Systems (IJERTCS) 3,
no. 3 (2012): 18-37.
[2] Gabriel, Camelia. Compilation of the Dielectric Properties of
Body Tissues at RF and Microwave Frequencies. KING'S COLL
LONDON (UNITED KINGDOM) DEPT OF PHYSICS, 1996.
[3] Pozar, MicroWave Engineering. Wiley, 2012
Method
• After studying the human brain we found out that Cerebellum
is best place to fit the electrodes to pick up the signal of neurons
and feed to transmitter.
• The transmitter sitting on cerebellum will transmit the signal to
receiver sitting outside the human head.
Figure 1 The Channel in Human Brain
• The losses that signal undergoes while propagating depend not
only on dielectric properties of human tissues but it also depend
on the size of the medium too. The medium through which the
signal propagates is shown in above figure. [3-4]
Tissue Thickness (mm)
Min Max Average
Cerebellum 30 50 40
Blood 8 10 9
Grey Matter 4 6 5
Bone 10 12 11
Scalp Fat 10 12 11
Skin 1 1.5 1.25
Total 63 91.5 77.25