The Wideband Implantable Antenna with Circular Polarization for

Monitoring the Thyroid

Jaya Prakash M., Kishore A., Shiyam P., Ramasamy K. and Sapna B. A.

Department of Electronics and Communication Engineering, KIT‑Kalaignarkarunanidhi Institute of Technology,

Coimbatore, Tamil Nadu, India

Keywords: Implantable Antenna, Broadband, Circular Polarized Antenna, Thyroid Monitoring.

Abstract: A small circularly-polarized implantable antenna for long-term thyroid monitoring. The dual port loop

structure proposed antenna covers a bandwidth of Wide band frequency 0.03 MHz - 6.02 GHz and it resonates

at frequency of 2.45 GHz and 5.8 GHz which are mostly adopted for the WBAN and the medical telemetry

applications. Antenna covers a super ultra-wide bandwidth due to the large operation band. An RO6010/droid

6010LM is selected as the substrate and the superstrate material within the compact design and its high

dielectric constant and low loss are employed to minimize the size and improve the performance. The antenna

footprint is 5 mm × 5 mm and its thickness are 0.57 mm in total. It demonstrates return losses of -22.45 dB at

2.45 GHz and -14 dB at 5.8 GHz. The antenna is -13dB (-19dB) at lower (upper) resonance frequency. SAR

is studied by placing the antenna on the neck of human head model for human safety. The signal is well

fastened yet dynamic in a dynamic environment, as a result of circular polarization. The simulation results

exhibit satisfactory impedance matching and reasonable radiation efficiency, implying the proposed antenna

is suitable to be used for the thyroid detection in biomedical applications.

1 INTRODUCTION

Implant antennas play a key role in biomedical

applications, offering real-time health monitoring

capabilities with minimal invasiveness. Recent

research has demonstrated significant advancements

in the design and performance of such antennas for

deep-tissue applications. For instance, a study by

Varvari (2024) focuses on the development of RF

sensors for thyroid tracking, showcasing their

effectiveness in early disease detection. Similarly,

Asif introduced a wide-band tissue-deeply

implantable antenna optimized for RF-powered

medical devices, ensuring efficient signal

transmission and power delivery. Metamaterial-based

antennas have also gained traction due to their

enhanced performance in miniaturized biomedical

systems. Shaw (2019) explored a metamaterial

implantable antenna with superior impedance

matching and improved radiation efficiency. In the

field of capsule endoscopy and deep-tissue

monitoring, Shah (2024) developed four-port triple-

band MIMO antenna, addressing the challenges of

high-data-rate communication within human tissues.

Additionally, Song proposed a dual-band circularly

polarized implantable antenna, ensuring robust signal

transmission in biomedical telemetry applications. A

comprehensive review by Jasim et al. (2025)

highlights the various design considerations,

fabrication techniques, and challenges associated

with implantable antennas for biomedical

applications. Their study provides valuable insights

into the evolution of implantable antennas,

emphasizing health considerations and geometric

optimizations for enhanced biocompatibility and

performance. An ultra-wideband compact meander

line antenna for brain implants and biotelemetry

application in 2.45 GHz ISM band is presented in

2024 by Mohan and Kumar. Their study

demonstrates the feasibility of miniaturized, high-

performance antennas for deep-tissue

communication, reinforcing the need for advanced

implantable antenna designs in biomedical

applications. These advancements underline the

growing importance of implantable antennas in

medical diagnostics and treatment. This paper

introduces a wideband implantable antenna tailored

for thyroid monitoring, integrating circular

polarization for improved signal stability. The

subsequent sections detail the antenna’s structural

100

M, J. P., A, K., P, S., K, R. and B A, S.

The Wideband Implantable Antenna with Circular Polarization for Monitoring the Thyroid.

DOI: 10.5220/0013892700004919

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Research and Development in Information, Communication, and Computing Technologies (ICRDICCT‘25 2025) - Volume 3, pages

100-104

ISBN: 978-989-758-777-1

design, performance analysis, and SAR evaluation to

validate its suitability for biomedical applications.

This paper introduces an implantable antenna with

broadband capabilities for thyroid monitoring. The

introduction section provides an overview of antenna

types used in implantable devices. Segment 2

describes the structure of the proposed antenna.

Segment 3 presents a detailed analysis of the

antenna's performance, followed by the conclusion in

Segment 4.

2 ANTENNA DESIGN

2.1 Antenna Structure

This implantable antenna is designed with a dual-port

feeding mechanism is utilized within a symmetrical

square layout of 5 mm × 5 mm and a total thickness

of 0.57 mm, shown in figure 1 making it well-suited

for integration into space-constrained medical

devices. Rogers RO6010/duroid 6010LM, selected

for its high permittivity (10.2) and low dielectric loss,

serves as both the substrate and superstrate, ensuring

effective miniaturization and improved operational

efficiency. The optimized dimensions are outlined in

the Table 1.

Table 1: Parameters of Antenna.

Antenna

Parameters

L W W1 W2 W3 L1 H

Dimension (mm) 5.0 5.0 0.30 1.0 0.20 0.850 0.254

Figure 1: Patch and Port View.

2.2 Feeding Mechanism

A dual-port feeding mechanism is utilized, where

rectangular strips interconnect at opposite ends to

form a closed-loop structure. This configuration

allows for precise excitation control, facilitating

circular polarization with a broad bandwidth. The

resulting stable wireless communication is critical for

dynamic implantable applications.

2.3 Design Evolution

Figure 2: Top View of Antenna Across Each Iterative

Cases.

The antenna design underwent four iterative

modifications to refine its performance. The initial

design used a Jerusalem cross-shaped patch, which

was later optimized by introducing L-shaped and

meandered slots to enhance impedance matching and

return loss. The last incarnation had much better

bandwidth and reflection coefficients. Each stage had

a small change to the patch to improve the bandwidth,

as well as the return loss of the antenna. The S 11 for

all four bands were compared as shown in Figure 3,

evidencing a gradual performance improvement

through the design procedure. The first patch had bad

TLRL (return loss) due to high reflect and loss and

only was excited at 5.58GHz. Strategic cuts and

variations of the dimensions of the patch in forms 2

and 3, resulted in an appreciative enhancement of

return loss. The topology-double negative materials

(DNGM)-TL SRR-R antenna and its parameters

inherited from iteration 4 (form 4), as is embodied in

figure 4, were designed, conducting a perfect

impedance matching, over a wider range of higher

frequencies from 39 kHz to 6 GHz with return loss of

The Wideband Implantable Antenna with Circular Polarization for Monitoring the Thyroid

101

-39.0 dB at 2.8 GHz and -43.0 dB at 5.36 GHz. Figure

2 shows Top View of Antenna Across Each Iterative

Cases. The combined graph highlights the iterative

enhancement purpose and confirms the success of

design.

Figure 3: Iterative Levels Return Loss.

3 PERFORMANCE

EVALUATION

3.1 Reflection Coefficient Analysis

Figure 4: S11 Parameter.

Simulations conducted using HFSS confirmed the

antenna performance in both free space and a

phantom model simulating human tissue. The return

loss values of -23.0 dB at 2.45 GHz also -14.0 dB at

5.8 GHz confirm a wide bandwidth extending from

0.03 MHz to 6.2 GHz. Figure 4 shows S11 parameter.

The current flow plots illustrate the 180-degree phase

shift, ensuring effective circular polarization

displayed in Figure 5. The current direction changes

by 180 degrees, indicating that the antenna operates

with CP, which offers the advantage of easily sensing

signals from all directions.

Figure 5: Flow of Current in the Antenna.

3.2 Radiation Performance

Figure 6 illustrates Radiation pattern simulations at

the frequencies (as we mention in abstract) indicate

stable circular polarization with minimal back. The

gain performance of the antenna has been evaluated

across its working frequency range, showcasing

stable radiation characteristics. It achieves -19 dB and

-13 dB ensuring reliable functionality within the

intended frequency bands. Figure 7 shows Antenna

Gain plot.

Figure 6: Field Pattern of the Antenna.

ICRDICCT‘25 2025 - INTERNATIONAL CONFERENCE ON RESEARCH AND DEVELOPMENT IN INFORMATION,

COMMUNICATION, AND COMPUTING TECHNOLOGIES

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Figure 7: Antenna Gain Plot.

3.3 SAR (Specific Absorption Rate)

To ensure compliance with safety regulations, the

specific absorption rate (SAR) was evaluated at input

power levels of 1 W and reduced to maintain safe

exposure limits.

The maximum SAR values of 1.59 W/kg at 2.45

GHz and 1.58 W/kg at 5.8 GHz confirm the design's

suitability for biomedical applications with minimal

thermal effects on thyroid tissues. The input power

was reduced, resulting in maximum allowable input

power values of 5 mW at 2.45 GHz and 3.2 mW at

5.8 GHz. The simulated SAR, shown in Figure 8, was

calculated using a human head phantom with the

antenna placed in the neck region. The SAR analysis

demonstrates that the antenna meets medical safety

standards, effectively minimizing thermal impact on

nearby thyroid tissues. Literature compared in Table

Figure 8: SAR Analysis of Antenna.

Table 2: Reference is compared with the antenna.

Ref. no Fre

(

GHz

)

Bandwidth Dimension

(

mm³

)

Gain

(

)

SAR

(

W/k

1 5 300 MHz 13.38 × 18.24 × 1.52 5.8 NA

3 2.45 NA 12 × 12 × 3 -14.07 8.72

4 0.915 9.7% 10.5 × 7.5 × 0.127 -37.3 251

1.780 7.8% -30.3 211

2.45 8.3% -27.9 252

5 0.915 220 MHz π × 0.0142 × 0.0027 -29.5 585.1

2.45 230 MHz -19.5 462.2

WORKED ANTENNA 2.45 5.97 GHz 5 × 5 × 0.57 -19.0 1.59

5.8 -13.0 1.58

4 CONCLUSIONS

Wideband implantable antenna with circular

polarization for monitoring the thyroid is operates

across 0.03 MHz to 6.0 GHz offering a total

bandwidth of 5.970 With compact dimensions of 5

mm × 5 mm × 0.57 mm, it ensures efficient

integration within biomedical applications. The

evaluation of both simulation and experimental

results confirms optimal impedance matching, with

S11 of -23.0 dB at 2.45 GHz and -14.0 dB at 5.8 GHz.

SAR analysis validates with medical safety standards,

maintaining maximum allowable power levels of 5.10

mW and 3.2 mW at the respective frequencies,

ensuring biocompatibility and minimal tissue heating.

This study confirms the antenna's suitability for

thyroid detection in biomedical applications, ensuring

stable and secure wireless communication. Future

advancements may focus on integrating it with

implantable sensors and further reducing its size to

expand its usability in diverse medical fields.

ACKNOWLEDGEMENTS

File No.8-122/FDC/RPS/POLICY-1/2021-2022.

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REFERENCES

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antennas for biomedical applications: Health

considerations, geometries, fabrication techniques, and

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Mohan, Archana, and Niraj Kumar. "Implantable antennas

for biomedical applications: a systematic review."

BioMedical Engineering OnLine 23(1) (2024): 87.

Mohan, Archana, and Niraj Kumar. "An ultra–wideband

compact meander line antenna for brain implants and

biotelemetry applications in the 2.45 GHz ISM band."

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Samanta, Gopinath, and Debasis Mitra. "Dual-band circular

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Shah, Syed Manaf Ali, et al. "Four-port triple-band

implantable MIMO antenna for reliable data telemetry

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COMMUNICATION, AND COMPUTING TECHNOLOGIES

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