Outer-Wall Loop Antenna for Ultrawideband Capsule Endoscope System

Abstract

The capsule endoscopy system has been used to obtain an image from the inside of the human digestive tract. To acquire high-resolution images, a loop antenna with ultrawide bandwidth is proposed. It is part of the outer wall of the capsule, thus decreasing volume and increasing performance, and uses a meandered line for resonance in an electrically small area. The proposed antenna makes maximal use of the capsule's outer surface, enabling the antenna to be larger than inner antennas. The measured result shows that the gain of the proposed antenna is higher than that of inner antennas. Return loss and radiation pattern are investigated through simulation and measurement, showing that the proposed antenna has an ultrawide bandwidth of 260 MHz (from 370 to 630 MHz) for VSWR 2 and an omnidirectional radiation pattern. Using identical antenna pairs in the equivalent body phantom fluid, antenna efficiency is measured to 43.7% ( 3.6 dB).Index Terms-Capsule antenna, endoscopy system, loop antenna, meander, small antenna, wideband.

Design of Wideband Monopole Antenna Loaded With Small Spiral for Using in Wireless Capsule Endoscopy Systems

“…Thus, the spiral antenna plays the role of a load for the monopole antenna and leads to compression and impedance matching of antenna. The maximum gain of the antenna is −23 dB, which is 8 dB greater than that permitted for WCE transmitter antennas [9]. Table 2 compares the radiation characteristics of the proposed monopole antenna loaded with small spiral antenna with some other WCE antennas.…”

“…Also, the pattern of dual spiral antenna is omnidirectional, but the amount of S 11 < −14 dB is in the frequency band 350-450 MHz [8] which is too low for capsule antennas. The spherical helix and spherical spiral antennas [10] have appropriate radiation pattern, but the gains of these antennas are about −32 dB, which is lower than permitted gain for capsule antenna (−28 dB [9]). …”

“…The bandwidth must be high enough to improve the image resolution [9]. The other proposed antennas have satisfied this important requirement slightly.…”

Bandwidth Enhancement of an Implantable Antenna

“…However, lower profile would be preferred. Besides of fabricating on printed circuit board (PCB), another property for an implantable antenna design is conformal [9], [10], such as printing an antenna on the wall of a capsule [3], [4], therefore the capsule volume inside it can be saved for implanting the necessary sensors and electronic circuits. Additionally, the whole capsule surface can be fully used for the implantable antenna and therefore the radiation efficiency can be increased.…”

Design of an antenna for an ingestible capsule endoscope system

“…In Ref. [3], a loop antenna with meander pattern was suggested for the wideband 978-1-4673-2204-1/12/$31.00 ©2012 IEEE 62 ?peration. Since the performance of an antenna operated In the human body is strongly affected by the size of human body, location of implanted antenna, and tissue compositions [4], these factors must be considered to analyze the performance of antennas accurately.…”