Design of Microstrip Patch Antenna f Design of Microstrip Patch ... - IJRIT

IJRIT International Journal of Research in Information Technology, Volume 2, Issue 3, March 2014, Pg: 202-207

International Journal of Research in Information Technology (IJRIT) www.ijrit.com

ISSN 2001-5569

Design of Microstrip Patch Antenna for for Wireless Endoscopic Capsules Jincy Rachel Thomas1, Jeena Sara Thomas2, T. Mary Neebha3 and M. Nesasudha4 1

2

3

4

PG Scholar, Department of Electronics and Communication Engineering, Karunya University Coimbatore, Tamil Nadu, India [email protected]

PG Scholar, Department of Electronics and Communication Engineering, Karunya University Coimbatore, Tamil Nadu, India [email protected]

Assistant Professor, Department of Electronics and Communication Engineering, Karunya University Coimbatore, Tamil Nadu, India [email protected]

Associate Professor, Department of Electronics and Communication Engineering, Karunya University Coimbatore, Tamil Nadu, India [email protected]

Abstract A square spiral slotted microstrip patch antenna, and a small spiral patch antenna are designed and analyzed, in order to function as wireless endoscopic capsules. Wireless capsule endoscopy is presently, the best option for exploring inaccessible areas of the small intestine, or for the inspection of the gastrointestinal tract. The main constraint present during the design includes the size of the antennas. The antennas should be small enough to fit inside a capsule. FEKO software is used for the antenna design. Return loss or S11 is the main parameter that is analyzed, to test the efficiency of the antennas designed.

Keywords: Microstrip Patch antennas, Wireless capsule Endoscopy, FEKO, Return loss.

1. Introduction An antenna is defined as a transducer that is designed to transmit or receive electromagnetic waves. Microstrip antennas are highly advantageous over conventional microwave antennas and as a result, can be widely used in various practical applications. Compared with conventional antennas, microstrip patch antennas have many more advantages. The properties they possess include that they are lighter in weight, lower in volume, have lower costs, lower profiles, are smaller in dimension and are easier to fabricate. Since the advantages of the microstrip patch antenna are mainly to overcome de-merits such as complex design, bulky structure etc., it’s applications are in various fields such as medical, satellites and even in the military field like in rockets, aircrafts missiles etc. [1] and [2] show the designs of a pentagonal shaped, and a four spiral slotted microstrip patch antenna (MPA) used for wireless capsule endoscopy. [3], [4] and [5] display designs of patch antennas used for wireless applications. The design of a broadband microstrip monopolar patch antenna is done in [6]. [7] Jincy Rachel Thomas,

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also shows an endoscopic capsule antenna design. Antennas with slotted patches, and different geometries in the ground plane, are shown in [8], [9] and [10]. [11] shows a method for reducing surface waves in MPAs. [12] and [13] shows antennas used in the ISM band. [14] conducts a survey on MPAs, and [15] displays the design of a dual frequency MPA.

1.1 Wireless Capsule Endoscopy Wireless capsule endoscopy is presently, the best option for exploring even the most inaccessible areas of the small intestine, or for inspection of the gastrointestinal tract. This technique is much less painful compared to conventional endoscopy techniques and clearly reduces the risk of an operating method. Wireless capsule endoscopy system has become an accepted routine for inspection of gastrointestinal disorders such as cancers and polyps. In Wireless endoscopy system, an ingestible capsule is swallowed by the patient that consists of a camera, control unit and a microstrip patch antenna. This microstrip patch antenna is a low profile antenna, which is comparatively simple and inexpensive to fabricate, manufacture and design. The wireless endoscopy system comprises of three main modules: an ingestible capsule that is swallowed by the patient, an external control unit, and finally the display device for image display.

Fig. 1 Block diagram of Endoscopy Capsule Unit Fig.1 shows an endoscopy capsule unit. The main blocks in the entire process are - the capsule that is swallowed by the patient, and an external control unit. The capsule passes through the digestive track in which there is a camera, control unit and antenna. The capsule collects images of the gastrointestinal tract. The external control unit (with an antenna in it) collects data from the capsule and controls the operation of the capsule. The external unit is a wearable device that is carried by the patient. This unit can then be connected to a computer for enhanced image display and further analysis of the observed data.

2. Antenna Design Microstrip patch antennas are designed in order to function as wireless endoscopy capsules, in the ISM band. The microstrip patch antennas designed include: a square spiral slots microstrip patch antenna and a small spiral patch antenna – both intended to function inside endoscopy capsules.

2.1 Square Spiral Slotted Patch Antenna This antenna comprises of four spiral slots in the patch, a ground plane, a feed pin, and a dielectric layer. The antenna is designed with a high dielectric constant of εr=6.1 (Macor) and a thickness of h=0.6 mm. The spiral conductor shape is found to be a very efficient method to reduce the size of the microstrip antenna. The geometry is shown in Fig.2.

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Fig. 2 Square Spiral Slotted Patch antenna Table 1 displays the specifications of thesquare spiral slotted patch antenna. Table 1 PARAMETER VALUE (mm) A 8.25 B

8.25

C

0.50

D

0.75

Height of the Substrate

0.6

2.2 Small Spiral Patch Antenna Next, a small spiral antenna designed for an endoscopy capsule. The antenna is composed of a spiral PEC structure and a ground plane. The substrate is designed using air as the dielectric with εr=1 and the ground plane is taken to be PEC. As mentioned earlier, again, the spiral conductor shape is found to be a very efficient method to reduce the size of the microstrip antenna, as shown in Fig.3.


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Fig. 3 Small Spiral Patch antenna Table 2 displays the specifications of the small spiral patch antenna. Table 2 PARAMETER VALUE (mm) A 2 B

5

C

10

3. Results and Discussions We consider the reflection loss, S11 in each of the above mentioned antennas. Lower the value of S11, better is the impedance matching property of the antenna.

Fig. 4 Return loss of the Square Spiral slotted Patch antenna


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Fig. 5 Return loss of the Small Spiral Patch antenna Fig.4 and Fig.5 display the return loss (S11) graphs of the square spiral slotted patch, and the small spiral patch antennas, respectively.

Type Of Antenna

Table 3 Resonant Frequency

S11 (dB)

2.67GHz

-19.04

520.8MHz

-13.57

Square spiral slotted antenna Small spiral patch antenna

Table 3 displays the results obtained from the designed antennas. The square spiral slotted patch antenna is shown to display a better S11 value.

4. Conclusions There are some difficulties in designing endoscopic capsule antennas. Firstly, the human body is composed of a high dielectric and lossy material. Also, keeping the overall dimensions of the pill and the antenna, while tuning for lower frequencies – leads to the increase in the antenna size. This results in a reduced antenna efficiency and performance. However, the best antenna that can be used for endoscopy has been designed, and analyzed.

References [1]

[2]

Bondili Kohitha Bai, Anita Thakur, “Pentagonal shaped microstrip patch antenna in wireless capsule endoscopy system”, Natarajan Meghanathan, et al. (Eds): ITCS, SIP, JSE-2012, CS & IT 04, pp. 47–54, 2012 Huang Biao†, YAN Guo-zheng, LI Qian-ru, “A four spiral slots microstrip patch antenna for radiotelemetry capsules based on FDTD”, Journal of Zhejiang University SCIENCE A 8(10):15601567, 2007


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[3]

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[5]

[6]

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