Jungsuek Oh

Bio: Jungsuek Oh is an academic researcher from Seoul National University. The author has contributed to research in topics: Antenna (radio) & Coaxial antenna. The author has an hindex of 13, co-authored 49 publications receiving 474 citations. Previous affiliations of Jungsuek Oh include University of Michigan & Samsung.

Low Profile, Miniaturized, Inductively Coupled Capacitively Loaded Monopole Antenna

Abstract: A novel high-gain low-profile miniaturized antenna with omnidirectional vertically polarized radiation, similar to a short dipole is presented. The proposed design focus is on increasing the gain and improving the polarization purity of the radiated field in the horizontal plane. The gain and polarization improvement are achieved by isolating the feed structure from a miniaturized resonant radiating structure composed of an in-plane capacitor and a structurally embedded transformer. The antenna topology is developed, based on circuit model and through full-wave simulations the equivalence is established. The equivalent circuit model assists in the initial design, and then minor modifications are required to achieve the desired frequency of operation. The initial topology of the proposed antenna, the so-called Inductively Coupled Capacitively Loaded Monopole Antenna (ICCLMA), consists of two metal layers, a feeding pin and a shorting pin. The performance of the proposed antenna is compared to that of an ordinary inverted F antenna and a more recent low profile vertically polarized antenna (LMMMA) . It is shown that the gain of ICCLMA is 9 dB and 4 dB higher than that of the conventional inverted-F antenna and the LMMMA, respectively. To simplify the fabrication process a modified single-layer ICCLMA topology is presented and optimized. Finally, a design procedure to further reduce the lateral dimension of ICCLMA is presented. A procedure for accurate measurement of antennas with small ground planes is also presented.

Extremely Small Two-Element Monopole Antenna for HF Band Applications

Abstract: This paper presents a novel antenna architecture to achieve an extremely small form factor for HF band applications. The approach is based on manipulating the topology of a short monopole antenna without utilizing a high index material. A new architecture incorporating two radiating elements is configured, which allows significant gain enhancement. It is shown that such architecture can render a miniaturized HF antenna on air substrate having lateral and height dimensions as small as 0.0115λ0 × 0.0115λ0 × 0.0038λ0 (150 mm× mm × 50 mm for operation at 22.9 MHz). It is found that the measured gain of such architecture can be as high as - 18.1 dBi, which is 16.7 dB higher than a reference inverted-F antenna realized on a high index material (eR = 10.2) having exactly the same dimensions. The proposed antenna architecture is composed of two in-phase radiating vertical elements connected to two inductors between which a capacitive top load is connected to achieve the desired resonant condition. The two vertical elements act effectively as a monopole having increased height. It is also shown that the gain of the antenna can be increased monotonically by increasing the quality factor (Q) of the phase shifter. High Q air-core inductors that can be accommodated in electrically small monopole antenna are designed and incorporated in the phase shifter to achieve a gain value of - 17.9 dBi. Details about the proposed design approach, simulation, and measurement results are discussed.

A Topology-Based Miniaturization of Circularly Polarized Patch Antennas

Abstract: A novel approach for the miniaturization of circularly polarized patch antennas is presented. This enables a size reduction of as high as 75%, compared to a conventional corner-truncated circularly polarized patch antenna. The proposed design procedure consists of a number of intermediate steps, each of which produces antenna miniaturization as well as the desired polarization and impedance matching properties. This is very challenging in miniaturizing circularly polarized probe-fed patch antennas. It is shown that two resonant frequencies can be tuned independently to produce a dual band antenna with two orthogonal polarizations. Finally, two circularly polarized miniaturized patch antennas with different miniaturization factors are fabricated, and their input impedances, radiation patterns and axial ratios are discussed.

Low Profile Vertically Polarized Omnidirectional Wideband Antenna With Capacitively Coupled Parasitic Elements

Abstract: This communication presents a low profile and electrically small wideband antenna with omnidirectional radiation pattern and vertical polarization. A novel design approach manipulating the topology of a low profile folded monopole antenna with capacitively coupled parasitic elements in the same plane is presented to achieve omnidirectional radiation pattern. The 10-dB return loss fractional bandwidth of 43% is achieved with the dimension of 0.2λLF ×0.2λLF ×0.06λLF where λLF is the wavelength at the lowest frequency of the operation. Unlike the convention wideband λ/4 monopole antennas utilizing inductively coupled parasitic elements, the λ/2 folded monopole antenna allows for positioning the capacitively coupled parasitic elements in the middle of the antenna where maximum electric stored energy is formed. This, together with reducing the lateral dimension of the folded monopole antenna, enables the cancellation of radiated fields from electric currents in the horizontal plane of the proposed antenna, which is essential to achieve vertically polarized omnidirectional radiation. The compact parasitic elements introduce additional resonances that significantly increase the antenna bandwidth. Effects of design parameters on two resonant frequencies and impedance matching to a 50 Ω feed are investigated using the equivalent circuit model of the parasitic element and full-wave electromagnetic (EM) simulations. Based on this analysis, a design procedure to optimize the antenna topology is established.

Compact, Low Profile, Common Aperture Polarization, and Pattern Diversity Antennas

Abstract: This paper presents compact and low profile two-port antennas that can provide polarization or pattern diversity schemes from a common aperture. The proposed antennas make use of a novel small microstrip antenna topology with an open area at its waist. The two sections of the small-size microstrip antenna are connected through a magnetic coupling mechanism facilitated by two vertical metallic strips connecting the top plates to the ground plane. This allows for placement of another small antenna element within the same aperture having either polarization or pattern that is orthogonal to the microstrip antenna with low envelope correlation. Topologies of polarization and pattern-diversity antennas are optimized for size reduction and minimum envelope correlation. Although the proposed diversity antenna consists of two antenna elements with different polarizations or radiation patterns, they just occupy about 30% of the area of a conventional microstrip antenna over the same substrate. It is shown that the envelope correlation between radiation patterns of the two antenna elements is lower than -30 dB over the 10-dB return loss bandwidth of the proposed antenna.

What should 6G be

Abstract: The standardization of fifth generation (5G) communications has been completed, and the 5G network should be commercially launched in 2020. As a result, the visioning and planning of 6G communications has begun, with an aim to provide communication services for the future demands of the 2030s. Here, we provide a vision for 6G that could serve as a research guide in the post-5G era. We suggest that human-centric mobile communications will still be the most important application of 6G and the 6G network should be human centric. Thus, high security, secrecy and privacy should be key features of 6G and should be given particular attention by the wireless research community. To support this vision, we provide a systematic framework in which potential application scenarios of 6G are anticipated and subdivided. We subsequently define key potential features of 6G and discuss the required communication technologies. We also explore the issues beyond communication technologies that could hamper research and deployment of 6G. This Perspective provides a vision for sixth generation (6G) communications in which human-centric mobile communications are considered the most important application, and high security, secrecy and privacy are its key features.

What should 6G be

Abstract: The standardization of fifth generation (5G) communications has been completed, and the 5G network should be commercially launched in 2020. As a result, the visioning and planning of sixth generation (6G) communications has begun, with an aim to provide communication services for the future demands of the 2030s. Here we provide a vision for 6G that could serve a research guide in the post-5G era. We suggest that human-centric mobile communications will still be the most important application of 6G and the 6G network should be human centric. Thus, high security, secrecy, and privacy should be key features of 6G and should be given particular attention by the wireless research community. To support this vision, we provide a systematic framework in which potential application scenarios of 6G are anticipated and subdivided. We subsequently define key potential features of 6G and discuss the required communication technologies. We also explore the issues beyond communication technologies that could hamper research and deployment of 6G.

Dielectric Resonator Antennas: A Historical Review and the Current State of the Art

Abstract: This article presents a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades. Major research activities in each decade are highlighted. The current state of the art of dielectric-resonator-antenna technology is then reviewed. The achievable performance of dielectric resonator antennas designed for compactness, wide impedance bandwidth, low profiles, circular polarization, or high gain are illustrated. The latest developments in dielectric-resonator-antenna arrays and fabrication techniques are also examined.

Optically transparent composites reinforced with plant fiber-based nanofibers(ABSTRACTS (MASTER THESIS FOR GRADUATE SCHOOL OF AGRICULTURE))

Abstract: The fibrillation of pulp fiber was attempted by two methods, a high-pressure homogenizer treatment and a grinder treatment. The grinder treatment resulted in the successful fibrillation of wood pulp fibers into nanofibers. The nanofibers demonstrate promising characteristics as reinforcement material for optically transparent composites. Due to the size effect, the nanofiber-reinforced composite retains the transparency of the matrix resin even at high fiber content such as 70 wt %. Since the nanofiber is an aggregate of semi-crystalline extended cellulose chains, its addition also contributes to a significant improvement in the thermal expansion properties of plastics while maintaining its ease of bending. Cellulose nanofibers have tremendous potential as a future resource since they are produced in a sustainable manner by plants, one of the most abundant organic resources on earth.

Hybrid Fractal Shape Planar Monopole Antenna Covering Multiband Wireless Communications With MIMO Implementation for Handheld Mobile Devices

Abstract: A hybrid fractal shape planar monopole antenna covering multiple wireless communication bands is presented for multiple-input-multiple-output (MIMO) implementation for handheld mobile devices. The proposed structure is the combination of Minkowski island curve and Koch curve fractals. It is placed with edge to edge separation of 0.16λ0 at 1.75 GHz. The T-shape strip is inserted and rectangular slot is etched at top side of ground plane, respectively to improve the impedance matching and isolation between the antennas. A measured impedance matching fractional bandwidths ( S11 ≤ -10 dB) are 14% from 1.65 GHz to 1.9 GHz for the band 1 and 80% from 2.68 GHz to 6.25 GHz for the band 2. Acceptable agreement is obtained between the simulated and measured antenna performance parameters. These characteristics demonstrate that the proposed antenna is an attractive candidate for handheld mobile devices.