biomedical applications of antenna
Post on 18-Dec-2014
1.865 Views
Preview:
DESCRIPTION
TRANSCRIPT
Biomedical Applications of Antenna
Gunjan Gupta – 10BEC112
Pratik Bhanawat- 10BEC113
Institute of Technology, Nirma University
INTRODUCTION:
In this report we are talking about Antenna and its application in the field of Biomedical
Science. These days we are using different electronic gadgets like mobiles, radio, Wi-
Fi, etc. which include antenna for reception and transmission of signals. These gadgets
also affects our Body while receiving and transmitting signals. These effects may be
good one which we are going to discuss in terms of Biomedical Application and there
is also bad effects which we know in terms of daily life hazards. But before this it is
important to know about Body Area Network (BAN).
Body area network (BAN) research [1], which uses the human body as a transmission
channel, has recently attracted considerable attention globally. Illustrations of the
electric field streamlines around the human body and wearable devices with electrodes
were drawn. In the pictures, the electrodes of the wearable devices constitute a closed
circuit with the human body and the earth ground. The results suggest that earth ground
has little influence on the human body and wearable devices. Only when the human
body is directly grounded, the electric field near the feet area will decrease. The input
impedance of the transmitter is approximately the same, and the received open-circuit
voltage and current of the receiver are also the same.
Figure 1: Transmission system using the human body as a transmission channel [2].
Figure 2: Electric field stream line model of PAN [2].
Body-centric communication takes its place firmly within the sphere of personal area
networks (PANs) and (BANs). The content of a BAN or PAN contains a range of
communications needs and requirements. [4] These can be classified as:
Off-body: because the channel is off of the body and in the surrounding space,
only one antenna in the communications link is on the body. This is referred to
as the off-body domain.
On-body: most of the channel is on the surface of the body and both antennas
will be on the body. This is called the on-body domain.
In-body: a significant part of the channel is inside the body and implanted
transceivers are used. This is called the in-body domain.
This nomenclature implies a partitioning of the PAN and BAN space into three areas.
The first is where most of the channel is off the body and in the surrounding space, and
where only one antenna in the communications link is on the body, which we call the
off-body domain. The second is where most of the channel is on the surface of the body,
and both antennas will be on the body, called the on-body domain. The last is where a
significant part of the channel is inside the body and implanted transceivers are used,
and we call this the in-body domain. While this is not a perfect subdivision, it does
serve to highlight some of the different challenges for antennas and propagation in the
body-centric system.
Challenges to Body Area Network are:
Power
Absorption (SAR): specific allowances of radiation
Signal integrity
Body is a lossy, complex medium for signal propagation
Distortion of radiation pattern close to human?
Wireless PANs in Medical Applications
The aim is the creation of a patient-cantered RF hub that can receive vital signs from
patients, concentrate them and send them to a base station in a relatively short range
via a wireless personal area network (WPAN). WPANs can be used for connecting to
a higher level network and the Internet (uplink) and even for wireless communication
among the ECG sensors themselves (intrapersonal communication).
The criteria that are mostly considered for the selection of the most appropriate and
efficient protocol in this area are:
Data rate
Range
Low battery power requirement
Safety and reliability
Security
Data Latency
One very widely spreading application in Biomedical Science is Non-Invasive Method
Investigation for Blood Pressure Measurements. The old traditional way of checking
Blood Pressure is called Cuff method and this new method is done with Arterial
tonometer which is a biomedical application of Antenna.
Cuff
Accurate
Non-continuous monitoring
Discomfort from pressure
Arterial tonometer
Applies constant pressure on artery at
the wrist
Constant pressure creates discomfort
Fig 3 & 4: Cuff Method and Arterial Tonometer investigation
for Blood pressure [3]
Challenges of coughless methods
Pulse Transit Time method (PTT) o The time taken for one arterial pulse pressure wave to travel from aortic
valve to peripheral site.
o Two different blood pressures have to be induced in order to make the
method work
Detect PTT o Pulse Oximeter
Diodes emits light and detect absorption of light.
Light absorption differ due to SpO2 level and vessel
expansion.
o Impedance sensor
Sends current between 2 points to detect impedance change
from arterial pulse.
Current LifeSync system already contains impedance
sensor for detecting respiration.
o Issues with impedance detection
Impedance change can result from stretching skin as in
respiratory.
How to isolate the change from breathing and blood pulse?
Liquid Antennas for Bio-monitoring Applications
Fig 5: Liquid Antennas for Bio-Monitoring Applications [3]
We see there are various applications of Antenna in field of Biomedical Science. As
this is a very diverse field, so more and more scientist and researchers are working to
develop the use of Antenna and its properties for healthy purposes.
References:
1. Effect of Earth Ground and Environment on Body-Centric Communications in the MHz Band Katsuyuki
Fujii and Yasuyuki Okumura
2. K. Fujii, M. Takahashi, and K. Ito, “Electric field distributions of wearable devices using the human body as a
transmission channel,” IEEE Transactions on Antennas and Propagation, vol. 55, no. 7, pp. 2080–2087, 2007
3. ATHENA Research Group-Biomedical Application – Georgia Institute of Technology
4. Book: Antennas and Propagation for Body-Centric Wireless Communications Second Edition Peter S. Hall Yang Hao
top related