Sangbok Park

A Wideband Spiral Antenna for Ingestible Capsule Endoscope Systems: Experimental Results in a Human Phantom and a Pig

This paper presents the design of a wideband spiral antenna for ingestible capsule endoscope systems and a comparison between the experimental results in a human phantom and a pig under general anesthesia. As wireless capsule endoscope systems transmit real-time internal biological image data at a high resolution to external receivers and because they operate in the human body, a small wideband antenna is required. To incorporate these properties, a thick-arm spiral structure is applied to the designed antenna. To make practical and efficient use of antennas inside the human body, which is composed of a high dielectric and lossy material, the resonance characteristics and radiation patterns were evaluated through a measurement setup using a liquid human phantom. The total height of the designed antenna is 5 mm and the diameter is 10 mm. The fractional bandwidth of the fabricated antenna is about 21% with a voltage standing-wave ratio of less than 2, and it has an isotropic radiation pattern. These characteristics are suitable for wideband capsule endoscope systems. Moreover, the received power level was measured using the proposed antenna, a circular polarized receiver antenna, and a pig under general anesthesia. Finally, endoscopic capsule images in the stomach and large intestine were captured using an on-off keying transceiver system.

A new receiver antenna with buffer layer for wireless capsule endoscopy in human body

This work proposes the CP dual pentagon loop antenna with the buffer layer to receive a power generated by transmitting antenna placed in wireless endoscopy in human body. Experiments have been performed to know abilities for the proposed antenna with a buffer layer. The advantages of the antenna with a buffer layer have been identified in terms of a power transmitted to a receiver antenna.

Simple Technique for Measurement of Complex Permittivity and Detection of Small Permittivity Change Using Partially Open Cavity

This letter presents a measurement methodology of the complex permittivity of liquid using a partially open cavity in narrow band. The partially open cavity (POC) can measure dielectric small changes caused by the temperature variation of the liquid inside the cavity as well. Using the resonance frequency and unloaded quality factor of the proposed POC, the complex permittivity is evaluated. The apertures on the walls of the cavity are designed to circulate the liquid inside to outside of the POC and located at the corner area of the cavity to minimize the disturbance of field distribution at the dominant mode. The results measured by the proposed POC were compared with those by the conventional open-ended probe and Cole-Cole equation. The POC showed better performance in measuring small dielectric constant changes than the open-ended probe.

Design of the buffer layer and absorber for enhancement of receiving sensitivity for wireless endoscopy

Many trials of small sensors inserted into the human body, which are to detect and treat diseases of internal organs, are being performed in many areas. As these are new wireless communications which are taking place inside the human body, it is different from most communications which are performed in air. Firstly, relative permittivity and loss caused by internal organs has to be considered for an exact analysis. In FCC, relative permittivity of internal organs is expressed as one layer which includes multi-reflection for each of them has been given to simply analyze the wave propagation in human body. When relative permittivity of human body is about 58, a reflection due to a mismatch of impedance occurs. Because of this problem, we have proposed a buffer layer to reduce the reflection.

A New Simultaneous Measuring Method of Complex Permittivity and Permeability using Two-Port Probe

Simultaneous measuring method for complex permittivity and permeability is proposed. The proposed two-port probe has a simple structure which is composed of uncovered transmission line to complement a conventional two-port probe which measures only one unknown material within it. The proposed method has a wideband feature and can take an accurate measurement. Using the equivalent circuit model for the proposed probe, the unknown complex epsivr and mur can be extracted. To compensate errors generated by structure, it needs the reference materials which have epsivr and mur calculated by Cole-Cole equation. Then it will be compared with results of another samples derived by Cole-Cole equation. The proposed method can measure complex epsivr and mur for liquids, soft solid substances and gases.

Design of a single body type repeater antenna for isolation enhancement at IMT-2000 band

In this work, we have used the opened waveguide cavity to enhance the isolation. The proposed reflector with the donor and receptor antenna satisfied the isolation, more than 80 dB as well as the gain and return loss of the antennas. Also the size of the reflector is reduced considerably compared with conventional reflectors.

Development of a V-band rotman lens using thin-film dielectric

This paper proposed a microstrip Rotman lens which is enables beam steering at mm-wave. The lens which has three beam ports and five array ports has two dummy ports at beam curve in order to reduce multi reflection from inside of the Lens, and side wall of the Lens was minimized. Also array curve is designed without a dummy port in order to reduce insertion loss. The lens which has magnitude deviation less than plusmn2 dB and phase aberration less than plusmn5deg over 58 GHz- 62 GHz has been employed as a feeder of five linear array antennas with spaced 0.6lambda (3 mm), showing beam steering angle of -7deg, 0deg, +7deg and HPBW of 15deg.

A study on non-invasive hyperthermic lipolysis using microwave

Non-invasive hyperthermic ablation technique of adipose tissue under skin using microwave is proposed, which exploits dielectric heating to heat up the adipose tissue using a circular antenna. We select an operating frequency 5.8 GHz, ISM band, for concentrating EM power radiated from the external antenna to the adipose tissue and for minimizing it to inner organs of the body. In order to protect skin from heat, a cooling system used a fan, which bring wind to it, is developed. And using obese rats, an experiment was performed to validate the proposed non-invasive hyperthermic ablation technique. We show that weight of each obese rats applied the proposed system was reduced.

Development of a V-band Rotman Lens using thin-film substrate with a flip-chip interconnection

This paper proposed the symmetry Rotman Lens which is enabled beam steering at mm-wave. The Lens which has four beam ports and eight array ports has four dummy ports at beam curve in order to reduce multi reflection from the inside of the lens, and the side wall of the lens was minimized. Also the array curve is designed without a dummy port in order to reduce insertion loss. The lens has been employed as a feeder of eight linear array antennas with spaced 0.5lambda (2.5 mm), showing beam steering angle of -20deg, -6deg, +4deg, +18deg and HPBW of 11deg~13.5deg. The beam steering antenna module is mounted a antipodal fin line transition, SP4T switch, and PA on metal jig, showing gain of 17.3 dB~18 dB and SLL of 7.3 dBc.

Subcutaneous fat thickness measurement using rectangular waveguide by approximation of waveguide admittance to plane wave admittance

In this paper, we propose a fast algorithm to measure skin and subcutaneous fat thickness. To reduce a computational complexity in mode matching method, an aperture admittance of a waveguide attached to human body which consists of materials with high dielectric constant and loss is approximated to the characteristic admittance of the plane wave. In order to estimate the thickness of skin and subcutaneous fat, maximum likelihood estimation (MLE) method is used. For accurate estimation, the permittivities of pork composed of skin, fat and muscle were measured by open ended coaxial cable. The proposed algorithm is verified by measuring the thickness of skin and fat and comparing the result with ultrasound scanning.