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Abstract In this paper, an implanted CPW fed slot

monopole antenna for ISM band applications is proposed.

The antenna has a simple structure with low profile and is

placed on human tissues like Muscle, Fat and Skin. The

designed antenna is made compatible for implantation by

embedding it in a FR4. The proposed antenna is simulated

with help of method of moments software IE3D by

assuming the predetermined dielectric constant for the

human muscle tissue, fat and skin. The antenna works in

the short distance communication band (Electronic

Communications Committee approved the frequency band- 688

MHz) and Industrial, Scientific and Medical (ISM Bands,

2.43GHz). Simulated maximum gains attain -18dBi and -

14.77dBi in the two desired frequency ranges, respectively.

The return loss, VSWR, radiation pattern, Z-parameter

and current distribution of these antennas were examined

and characterized.

Index TermsISM Band (2.4 2.48 GHz), Coplanar Wave

Guide Structure, Biomedical Applications.

I. INTRODUCTION

The implantable antennas promise large improvements in

patients care and quality of life. Pacemaker communication,

glucose monitoring, endoscopy and insulin pumps are just a

few examples of medical treatments that could take advantage

of wireless control [1]. The Medical Implant Communication

Service band (MICS, 401406 MHz) has been recently

allocated to this purpose [2]. Among all the components

necessary for implanted telemetry applications, the antenna

plays a key role in obtaining robust communication. Modern

technological advances in wireless networking,

microelectronics integration and miniaturization, sensors, and

the internet allow us to fundamentally modernize and change

the way health care services are deployed and delivered. The

range of medical devices being used on and into the human

body are increasing rapidly and implanted device are of

special interest in new sensing and monitoring device for

healthcare. During the last few years there has been a

significant increase in the number of wearable and

implantable health monitoring devices, activity monitors and

portable Holter monitors, to refined and expensive implantable

devices.

In most cases, implanted devices interface with the outside

world in terms of both powering and telemetry. Powering is

the delivery of useful energy to the implant from the external

world in order to make it operate. Telemetry includes sensed

data transmission from the implanted device to an external one

and vice versa [5].

The human body's effect on RF wave propagation is

complicated by the fact that the body consists of components

that each offers different degrees, and in some cases different

types, of RF interaction. To erect a reliable wireless

communication links from/to the human body, the body has to

be characterized as a medium for wave propagation. To

characterize the human body as a medium for radio frequency

wave propagation, the electrical properties of the body tissues

should be known for the frequency of interest. In this paper an

implanted CPW fed slot monopole antenna for the human

body medical device, their characteristics, and human body as

a medium for radio frequency propagation at 2.43GHz are

studied. All the results in this work were obtained with the

Method of Moments by IE3D Simulator ver.15.

II. DESIGNOFANTENNA

Fig. 1 shows the geometry of Implantable CPW-fed slot-

monopole hybrid antenna for 688MHz and 2.43GHz dual-

band biomedical applications. The antenna is printed on a 5030 mm FR4 substrate with thickness of 1.6 mm and relative

permittivity of 4.4. A 50 CPW transmission line of a signal

strip width of 3mm, with a gap distance of 0.9mm between the

strip width and the coplanar ground plane is used for feeding

the antenna. L-shaped monopoles with slots are designed for

dual-band biomedical operations.

Fig.1 Antenna Structure (All dimensions are in mm)

Implantable CPW fed Slot Monopole Antenna for Biomedical Applications

S. Ashok Kumar1and T. Shanmuganantham

2

1Research Scholar, Department of Electronics Engineering, Pondicherry University, Pondicherry2Assistant Professor, Department of Electronics Engineering, Pondicherry University, Pondicherry

[email protected] [email protected]

30

0.9

3

3.1

4

16

60.1

50

4.5

0.1

20

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III. SIMULATIONRESULTS

A. Return Loss

Fig. 2 shows the simulated return loss against frequency

with different monopole length. It is seen that dominantly

affects the lower frequency. The lower band of the proposed

antenna has an impedance bandwidth of 75 MHz (660735MHz). Moreover, the upper band has an impedance bandwidth

of 200MHz (22902490MHz), which is sufficient for the

biomedical application.

Fig.2Return Loss vs. Frequency

B.

Voltage Standing Wave Ratio (VSWR)

The calculated 2:1 VSWR bandwidths cover a frequency

range from 660 MHZ to 725MHz and 2.29GHz to 2.49GHz

with a bandwidth of 75MHz and 200MHz respectively as

shown in fig.3.

Fig.3 VSWR vs. Frequency

C. Reflection Gain

Fig.4 shows simulated antenna gains against frequencies.

The simulated gain of the lower band varies in a range of

-18.99 to -18.51 dBi and upper band varies in a range of

about -15.30 to -15.77 dBi. The result that the proposed

antenna has larger gain in the high band is mainly because

the antenna gain is a function of its electrical dimensions

relative to the wavelength of interest, current/fielddistribution and radiation pattern.[3]

Fig.4 Reflection Gain vs. Frequency

D. Effective Quality Factor

The effective quality factor is defined as the ratio of

imaginary part of input impedance to the real part of input

impedance.Im( )

Re( )

ineff

in

ZQ

Z (1)

This definition leads to effQ becomes zero at resonance. In

this paper the quality factor of 688MHz and 2.43GHz is 0.51

and 0.08 respectively. The effective quality factor is shown in

the fig.5.

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Fig.5 Quality Factor vs. Frequency

E.

3D Current Distribution

Fig.6 shows 3D current / field distribution as shown. The

green colour shows maximum current distribution in

antenna structure.

Fig.6 3D Current Distribution

F.

Radiation Pattern

Fig.7 and Fig.8 shows the simulated radiation pattern of

elevation pattern and azimuth pattern at 688MHz and

2.43GHz respectively. At low band, the radiation pattern is

obtained in the E-Plane and a nearly omnidirectional

radiation pattern in the H-plane.

Fig.7(a) Elevation Pattern at 2.43GHz

Fig.7(b) Azimuth Pattern at 2.43GHz


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Fig.8(a) Elevation Pattern at 688MHz

Fig.8(b) Azimuth Pattern at 688MHz

IV. CONCLUSIONANDDISCUSSION

An implantable CPW fed slot monopole antenna for

biomedical applications is presented. The proposed antenna

was analyzed by mentor graphics software. The antenna

occupies a surface area of 350 30 1.6mm and has a

impedance bandwidth of 1.07% and 8.33% of frequency at

688MHz and 2.43GHz within 2:1 VSWR. The antenna

simulated results of lower return loss (-12dB and -25dB for688MHz and 2.43GHz respectively), better impedance

matching (around 50) and maximum gain -18dBi and

14.7dBi for 688MHz and 2.43GHz respectively. It should be

noted that while a homogeneous tissue model is sufficient for a

basic design, a more realistic model of the human body will

give more exact representation of the actual operating

scenario. In future, experiments will be conducted to validate

these numerical calculations.

REFERENCES

[1]

S.Ashok Kumar and T.Shanmuganantham Implanted CPW fedMonopole Antenna For Biomedical Applications AIAA-2012 (SpringerBook Series)Springer InternationalConference, vol-178, pp. 97-105,2012.

[2]

W. C. Liu, F. M. Yeh, and M. Ghavami, Miniaturized implantable

broadband antenna for biotelemetry communication, Microwave Opt

Techno Lett... Vol. 50, pp. 24072409, 2008.

[3]

Chih-Yu Huang and En-Zo Yu, A Slot-Monopole Antenna for Dual-

Band WLAN Applications IEEE Antennas and Wireless Propagation

Letters, Vol. 10, 2011.

[4]

H.Jasik, Antenna Engineering Handbook. New York: McGraw-Hill,

1961, pp. 13.

[5]

A.Kiourti, Biomedical telemetry: Communication between implanted

devices and the externalworld,Opticon1826, no.8, pp. 17, 2010.

[6]

Inder Bahl, Lumped Elements for RF and Microwave Circuits Artech

House Microwave Library, 2003.

[7]

Fu-Jhuan Huang, Chien-Ming Lee, Chia-Lin Chang, Liang-Kai Chen,

Tzong-Chee Yo, and Ching-Hsing Luo, Rectenna Application of

Miniaturized Implantable Antenna Design for Triple-Band Biotelemetry

Communication IEEE Transactions on Antennas and Propagation , Vol.

59, no. 7,July2011

[8]

Tutku Karacolak, Robert Cooper, James Butler, Stephen Fisher, and

Erdem Topsakal, In Vivo Verification of Implantable Antennas Using

Rats as Model Animals IEEE Antennas and Wireless Propagation

Letters, Vol. 9,2010

[9]

Electronic Communications Committee (ECC) within the European

Conference of Postal and Telecommunications Administrations (CEPT)

Cluj Napoca, September 2010.


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