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