Ick Chang Choi

Kyungpook National University

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Hyun Deok Kim

Kyungpook National University

Young Cheol Kim

Pusan National University

S. Ahmad

Kyungpook National University

Byoung‐Ju Yun

Kyungpook National University

Duk‐jin Kim

Seoul National University

Tae Gu Kim

Kyungpook National University

Chul Hyun

Intelligent Image and Information System

Hyun Deok Kim

Kyungpook National University

Changmin Ahn

Kyungpook National University

Hyeok Woo Son

Kyungpook National University

Cooperative Institutions

Kyungpook National University

Pusan National University

Seoul National University

Korea Advanced Institute of Science and Technology

Kyungpook National University Hospital

Korea Institute of Materials Science

Korea Institute of Machinery and Materials

Korea Automotive Technology Institute

Soongsil University

Ajou University

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Analysis of the scalability of the video-overlay system

Asia Optical Fiber Communication and Optoelectronics Conference (2007)

Ick Chang Choi Byoung‐Ju Yun Hyun Deok Kim

We have derived an analytic expression for the scalability of the video-overlay system in the FTTH network and shows that the scalability strongly depends on both the optical amplifier noise and the configuration of the distribution network.

Overlay network

10.1109/aoe.2007.4410839

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Citations (0)

Double‐tuned RF receiver coil for detecting both ¹ H and ³¹ P elements in 4.7 T MRI system

Electronics Letters (2015)

S. Ahmad Young Cheol Kim Ick Chang Choi Hyun Deok Kim

A novel double‐tuned radio‐frequency (RF) receiver coil for use in magnetic resonance imaging (MRI) systems has been demonstrated based on a birdcage‐type circuit. The receiver coil utilises the end‐ring current as well as the leg current of the birdcage‐type circuit to detect the nuclear magnetic resonance (NMR) signals of different elements simultaneously. It was designed to detect the NMR signals of both 1 H and 31 P elements in a 4.7 T MRI system. The coil showed an excellent frequency response and provided clear magnetic resonance images of a Na 2 HPO 4 phantom when used with the 4.7 T MRI system.

10.1049/el.2015.1086

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Citations (4)

Saw-tooth shaped legs birdcage RF coil for small animal NMR imaging at 1.5T MRI system

Jungmin Kim S. Ahmad Ick Chang Choi Young Cheol Kim Hyun Deok Kim

In this paper we are demonstrating a novel method of designing and implementing a modified birdcage type Radio Frequency (RF) coil for small animal Nuclear Magnetic Resonance (NMR) imaging. This RF coil is basically a band pass type birdcage coil which is specifically designed to perform the whole body NMR imaging of small animal at 1.5T MRI systems. The designed RF coil contains the saw tooth shaped pattern as the leg conductors. The magnetic field produced at 63.85 MHz resonance frequency by this designed saw toothed shape leg pattern RF coil is significantly stronger than the magnetic field produced by a conventional straight leg band pass type birdcage coil designed with the same dimension. A full wave 3D electromagnetic simulation is carried out to optimize the RF coil dimensions, capacitor values and to study the RF coil electromagnetic characteristics.

Radiofrequency coil

10.1109/apmc.2013.6694858

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Birdcage type NMR receiver coil sensor with integrated detuning circuit for 3T MRI system

IEEE Sensors (2015)

S. Ahmad Young Cheol Kim Ick Chang Choi Hyun Deok Kim

A novel birdcage type Radio Frequency (RF) receiver coil sensor with passive type detuning circuits integrated on the end-rings of the coil sensor has been implemented. A simulation model of the RF receiver coil sensor with the passive type detuning circuits has also been proposed. The simulation model completely explains the working principle of the RF receiver coil sensor with the passive type detuning circuits. The RF coil sensor was designed to perform the Nuclear Magnetic Resonance (NMR) imaging of small animal at 3T Magnetic Resonance Imaging (MRI) system. The integrated detuning circuits of the RF coil sensor eliminate the noises induced by the mutual inductance between receiving and transmitting coils. We have confirmed the performances of the RF coil sensor through experiments, which agreed well with those of the simulations.

Radiofrequency coil

RF probe

Coil noise

RLC circuit

10.1109/icsens.2015.7370638

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Citations (4)

Remotely powered sensor network over CATV infrastructure

Duk‐jin Kim Ick Chang Choi Byoung‐Ju Yun Hyun Deok Kim

The CATV infrastructure has been deployed in most houses and buildings and the coaxial cables of the CATV infrastructure usually can provide sufficient bandwidth to accommodate other services as well as CATV service. We have proposed and demonstrated a novel remotely powered sensor network over the existing CATV infrastructure composed of coaxial cables, splitters and so on. The proposed sensor network has been implemented by using the wasted bandwidth of the coaxial cable (VHF and UHF bands) of the conventional CATV network without any change of the existing infrastructure. Furthermore, it supports a convenient remote power feeding from a central node to end nodes (sensor nodes) by using coaxial cable. We have developed transceiver for the wired sensor network matched the characteristics impedance of the coaxial cable of the CATV network. We also have developed protocol stack of the transceiver to interface with wired cable instead of air and to support the remote power feeding to the end nodes. We have confirmed the performance of the proposed sensor network by measuring the packet error rate (PER) for various data rates when the end nodes were remotely powered. The maximum transmission distance between the central node and the end node of the wired CATV network was about 265 m when the 128 sensor nodes were joined the network at the operating data rate of 250 kb/s.

Coaxial cable

Transceiver

Coaxial

10.1109/icce-berlin.2011.6031841

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Dual resonant RF coil for 1.5T and 3T MRI systems employing FPCB etched sub-legs

Asia-Pacific Microwave Conference (2011)

S. Ahmad Hyeok Woo Son Ick Chang Choi Young Cheol Kim Yongmin Chang

Radio frequency coil is the core component used in the detection of nuclear magnetic resonance signal. Usually the radio frequency coil is designed for operation on a specific magnetic field strength based magnetic resonance imaging system. This paper describes the method of implementing a modified birdcage type receive only radio frequency coil which has the ability to detect the nuclear magnetic resonance signal of 1H nuclei at 64 MHz and 128 MHz resonance frequency for 1.5T and 3T magnetic resonance imaging systems respectively. This dual resonance is achieved by dividing each coil leg into pair of sub-legs. This radio frequency coil is designed to perform the whole body nuclear magnetic resonance imaging of small animal. The coil performance has been verified via simulation and electrical parameter measurements.

Radiofrequency coil

SIGNAL (programming language)

Coil noise

Source

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Fast and Efficient Birdcage Coil Design Process for High Field MRI System by Combining Equivalent Circuit Model and 3D Electromagnetic Simulation

S. Ahmad Young Cheol Kim Ick Chang Choi Sungwoo Choi Tae Gu Kim

A novel method has been established to mitigate the complexity of a birdcage coil design process for use in a MRI (Magnetic Resonance Imaging) system. It can reduce the time consumptions of the typical coil design process based on 3D (three-dimensional) simulations. The method combines an equivalent circuit model and a 3D electromagnetic simulation. It makes it possible to understand the coil properties intuitively and to solve the major engineering problems by using just the circuit model not by using the complex 3D simulation. The concept of the dominant resonance path length of the coil has also been introduced, which facilitates the design process by considering the skin effect of the coil. We have verified that the skin effect of the birdcage coil can be evaluated through a simple circular loop circuit instead of the whole 3D geometry. Base on the design proposed method, we also have successfully demonstrated that the birdcage coil based on a FPCB (Flexible Printed Circuit board) technique can be used in high filed (3.0 T and 4.7 T) MRI systems for small animal NMR (Nuclear Magnetic Resonance) imaging.

Electromagnetic simulation

Radiofrequency coil

10.1109/ams.2017.37

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Citations (2)

Recent Progress in Birdcage RF Coil Technology for MRI System

Diagnostics (2020)

S. Ahmad Young Cheol Kim Ick Chang Choi Hyun Deok Kim

The radio frequency (RF) coil is one of the key components of the magnetic resonance imaging (MRI) system. It has a significant impact on the performance of the nuclear magnetic resonance (NMR) detection. Among numerous practical designs of RF coils for NMR imaging, the birdcage RF coil is the most popular choice from low field to ultra-high field MRI systems. In the transmission mode, it can establish a strong and homogeneous transverse magnetic field B1 for any element at its Larmor frequency. Similarly, in the reception mode, it exhibits extremely high sensitivity for the detection of even faint NMR signals from the volume of interest. Despite the sophisticated 3D structure of the birdcage coil, the developments in the design, analysis, and implementation technologies during the past decade have rendered the development of the birdcage coils quite reasonable. This article provides a detailed review of the recent progress in the birdcage RF coil technology for the MRI system.

Radiofrequency coil

Larmor precession

10.3390/diagnostics10121017

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Citations (25)

Enhancement of sensor network lifetime based on simple transmission power control technique

2023 IEEE International Conference on Consumer Electronics (ICCE) (2012)

Duk‐jin Kim Ick Chang Choi Byoung‐Ju Yun Hyun Deok Kim

A simple transmission power control technique has been proposed and demonstrated to realize an energy efficient sensor network over existing CATV infrastructures. The sensor network has been implemented by using the wasted bandwidth of the coaxial cables of a conventional CATV network and supports automatic transmission power control to enhance the network lifetime. The transmission power control technique can enhance the lifetime of sensor network by a factor of 1.7 times with a 42% improved power saving efficiency.

Power transmission

Coaxial

10.1109/icce.2012.6161928

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Sensor network over CATV infrastructure

2023 IEEE International Conference on Consumer Electronics (ICCE) (2011)

Chul Hyun Duk‐jin Kim Ick Chang Choi Byoung‐Ju Yun Hyun Deok Kim

A novel sensor network by using the coaxial cable infrastructure of the CATV network has been demonstrated. The sensor network has been implemented by using the wasted bandwidth of the coaxial cable (900-MHz band) of the CATV network without any change of the existing infrastructure. We have confirmed the performance of the sensor network by measuring the packet error rate (PER) for various data rates and verified that there was no sensitivity degradation due to the transmission over the CATV infrastructure. The maximum transmission distance between the coordinate node and the sensor node of the network was about 364 m w hen 128 sensor nodes were joined the sensor network at the operating data rate of 256 kb/s. The sensor network over the CATV infrastructure inherently guarantees a reliable networking between the nodes with excellent securities. Furthermore it is free from the interferences from other wireless services, which is especially useful in massive wireless environments such as in house or building.

Coaxial cable

10.1109/icce.2011.5722750

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Citations (2)