Jong-Gwan Yook

Bio: Jong-Gwan Yook is an academic researcher from Yonsei University. The author has contributed to research in topics: Microstrip antenna & Patch antenna. The author has an hindex of 38, co-authored 556 publications receiving 6433 citations. Previous affiliations of Jong-Gwan Yook include Gwangju Institute of Science and Technology & University of Michigan.

Interference mitigation using uplink power control for two-tier femtocell networks

Abstract: This paper proposes two interference mitigation strategies that adjust the maximum transmit power of femtocell users to suppress the cross-tier interference at a macrocell base station (BS). The open-loop and the closed-loop control suppress the cross-tier interference less than a fixed threshold and an adaptive threshold based on the noise and interference (NI) level at the macrocell BS, respectively. Simulation results show that both schemes effectively compensate the uplink throughput degradation of the macrocell BS due to the cross-tier interference and that the closed-loop control provides better femtocell throughput than the open-loop control at a minimal cost of macrocell throughput.

Biosensing using split-ring resonators at microwave regime

Abstract: A split-ring resonator (SRR) array is experimentally demonstrated for a biosensing device at microwave frequencies Each SRR in the array is excited by a time-varying H-field component through a microstrip transmission line in which microwaves propagate in the quasitransverse electromagnetic mode It is found that the resonant frequency changes due to the binding of biotin and streptavidin onto the surface of the SRRs The observed change values represent around ΔfB=120MHz and ΔfB-S=40MHz, respectively Finally, the SRR-based biosensing device suggests a few improvements for increasing sensitivity and describes its possible application

Application of time-frequency domain reflectometry for detection and localization of a fault on a coaxial cable

Abstract: In this paper, we introduce a new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains. The approach rests upon time-frequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. This latter capability is of particular interest when testing communication cables and systems. Sensitivity in detecting the reflected signal is provided by a time-frequency cross-correlation function. The approach is verified by experimentally locating various types of faults, located at various distances, in RG 142 and RG 400 coaxial cables.

Wideband Microstrip Patch Antenna With U-Shaped Parasitic Elements

Abstract: A wideband U-shaped parasitic patch antenna is proposed. Two parasitic elements are incorporated into the radiating edges of a rectangular patch whose length and width are lambdag/2 and lambdag/4, respectively, in order to achieve wide bandwidth with relatively small size. Coupling between the main patch and U-shaped parasitic patches is realized by either horizontal or vertical gaps. These gaps are found to be the main factors of the wideband impedance matching. The proposed antenna is designed and fabricated on a small size ground plane (25 mmtimes30 mm) for application of compact transceivers. The fabricated antenna on a FR4 substrate shows an impedance bandwidth of 27.3% (1.5 GHz) at 5.5 GHz center frequency. The measured radiation patterns are similar to those of a conventional patch antenna with slightly higher gains of 6.4 dB and 5.2 dB at each resonant frequency

A planar split-ring resonator-based microwave biosensor for label-free detection of biomolecules

Abstract: In this study, a planar split-ring resonator (SRR)-based RF biosensor was developed for label-free detection of biomolecules such as the prostate cancer marker, prostate specific antigen (PSA), and cortisol stress hormone. The biosensor has a resonance-assisted transducer and is excited by a time-varying magnetic field component of a local high-impedance microstrip line. The resulting device exhibits an intrinsic S 21 resonance with a quality-factor (or Q-factor) of 50. For the biomolecular interaction, anti-PSA and anti-cortisol were immobilized on the gold surface of the resonator by a protein-G mediated bioconjugation process and corresponding frequency shifts of Δ f 1 p = 30 ± 2 MHz (for anti-PSA) and Δ f 1 c = 20 ± 3 MHz (for anti-cortisol) were observed. The additional frequency shift of each PSA and cortisol antigen with a 100 pg/ml concentration was about 5 ± 1.5 MHz and 3 ± 1 MHz, respectively. From the experimental results, we confirmed that our device is very effective RF biosensor with a limit of detection (LOD) of 100 pg/ml and has sufficiently feasibility as a label-free biosensing scheme.

Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

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Massive MIMO Networks: Spectral, Energy, and Hardware Efficiency

Abstract: Massive multiple-input multiple-output MIMO is one of themost promising technologies for the next generation of wirelesscommunication networks because it has the potential to providegame-changing improvements in spectral efficiency SE and energyefficiency EE. This monograph summarizes many years ofresearch insights in a clear and self-contained way and providesthe reader with the necessary knowledge and mathematical toolsto carry out independent research in this area. Starting froma rigorous definition of Massive MIMO, the monograph coversthe important aspects of channel estimation, SE, EE, hardwareefficiency HE, and various practical deployment considerations.From the beginning, a very general, yet tractable, canonical systemmodel with spatial channel correlation is introduced. This modelis used to realistically assess the SE and EE, and is later extendedto also include the impact of hardware impairments. Owing tothis rigorous modeling approach, a lot of classic "wisdom" aboutMassive MIMO, based on too simplistic system models, is shownto be questionable.

Femtocells: Past, Present, and Future

Abstract: Femtocells, despite their name, pose a potentially large disruption to the carefully planned cellular networks that now connect a majority of the planet's citizens to the Internet and with each other. Femtocells - which by the end of 2010 already outnumbered traditional base stations and at the time of publication are being deployed at a rate of about five million a year - both enhance and interfere with this network in ways that are not yet well understood. Will femtocells be crucial for offloading data and video from the creaking traditional network? Or will femtocells prove more trouble than they are worth, undermining decades of careful base station deployment with unpredictable interference while delivering only limited gains? Or possibly neither: are femtocells just a "flash in the pan"; an exciting but short-lived stage of network evolution that will be rendered obsolete by improved WiFi offloading, new backhaul regulations and/or pricing, or other unforeseen technological developments? This tutorial article overviews the history of femtocells, demystifies their key aspects, and provides a preview of the next few years, which the authors believe will see a rapid acceleration towards small cell technology. In the course of the article, we also position and introduce the articles that headline this special issue.