Ik-Jae Hyeon

Bio: Ik-Jae Hyeon is an academic researcher from Chung-Ang University. The author has contributed to research in topics: Insertion loss & Surface micromachining. The author has an hindex of 5, co-authored 13 publications receiving 115 citations.

Circular/Linear Polarization Reconfigurable Antenna on Simplified RF-MEMS Packaging Platform in K-Band

Abstract: A linear-polarization (LP)/circular-polarization (CP) switchable reconfigurable antenna using a radio frequency micro-electro-mechanical-system (RF-MEMS) switch is proposed and a novel package platform is introduced. Since the package substrate of the novel package platform is used as a radiation aperture substrate of the antenna structure, the fabrication process can be simplified, and degradation of radiation performance can be prevented. As the radiation aperture exists on the top side of the package substrate, an aperture-coupling feed structure is employed. To implement the LP-CP-switchable antenna based on the package platform, a stub, acting as the other feed, is added to a slot ring and is connected to the RF-MEMS switch with an on/off state. The proposed antenna is simulated using the Finite-Element Method, after which it is fabricated and measured. The measured 10 dB impedance bandwidths (BWs) are 22.90% (LP state) and 28.43% (CP state). The measured 3 dB axial ratio BW is 13.07% in the CP state. The measured gains at 21 GHz are 2.63 dBi (LP state) and 3.90 dBi (CP state).

Silicon/quartz bonding and quartz deep RIE for the fabrication of quartz resonator structures

Abstract: In this paper, silicon/quartz bonding and quartz deep RIE (DRIE) processes have been developed to fabricate micromechanical quartz resonator structures. A low temperature (< 300degC), plasma-assisted silicon/quartz bonding condition that can provide the maximum bonding shear strength of 10 MPa has been experimentally constructed. The bonded silicon wafer was first applied to an etch mask of quartz, and thick quartz microstructures (~ 50 mum) have been fabricated by deep RIE of quartz with a gas mixture of C4F8 and He. In addition, a simple fused-quartz freestanding cantilever structure has been successfully fabricated by using the bonded silicon wafer not only for an etch mask layer but also for a substrate for quartz structures. The developed bonding and deep RIE processes, in combination with a proper metallization technique, are expected to be used for the wafer-level fabrication of freestanding quartz resonators.

Fabrication of Electrostatically-Actuated, In-Plane Fused Quartz Resonators using Silicon-on-Quartz (SOQ) Bonding and Quartz Drie

Abstract: This paper reports a novel process to fabricate electrostatically-actuated, in-plane micromechanical resonators made of fused quartz for high-Q microsensor applications. Two key processes - low temperature plasma-assisted Silicon-on-Quartz (SoQ) direct bonding and quartz DRIE using C 4 F 8 /He plasma - have been used in combination with thin metallization to fabricate fused quartz resonators driven by electrostatic force. The proposed method enables wafer-level fabrication of fused quartz resonators readily mounted on the substrate, which is advantageous over the conventional fabrication method of quartz crystal resonators. By using the proposed process, 40-?m-thick laterally-driven fused quartz cantilever resonators have been successfully fabricated. The measured Q-values of the metal-coated fused quartz cantilevers are 21,700~48,900 according to the length of the cantilever.

Millimeter-Wave Substrate Integrated Waveguide Using Micromachined Tungsten-Coated Through Glass Silicon Via Structures

Abstract: A millimeter-wave substrate integrated waveguide (SIW) has been demonstrated using micromachined tungsten-coated through glass silicon via (TGSV) structures. Two-step deep reactive ion etching (DRIE) of silicon vias and selective tungsten coating onto them using a shadow mask are combined with glass reflow techniques to realize a glass substrate with metal-coated TGSVs for millimeter-wave applications. The proposed metal-coated TGSV structures effectively replace the metallic vias in conventional through glass via (TGV) substrates, in which an additional individual glass machining process to form micro holes in the glass substrate as well as a time-consuming metal-filling process are required. This metal-coated TGSV substrate is applied to fabricate a SIW operating at Ka-band as a test vehicle. The fabricated SIW shows an average insertion loss of 0.69 ± 0.18 dB and a return loss better than 10 dB in a frequency range from 20 GHz to 45 GHz.

Design of Polarization Reconfigurable Antenna Using Metasurface

Abstract: A planar polarization-reconfigurable metasurfaced antenna (PRMS) designed using metasurface (MS) is proposed. The PRMS antenna consists of a planar MS placed atop of and in direct contact with a planar slot antenna, both having a circular shape with a diameter of 78 mm (0.9 $\lambda_{0}$ ), making it compact and low profile. By rotating the MS around the center with respect to the slot antenna, the PRMS antenna can be reconfigured to linear polarization, left-hand and right-hand circular polarizations. An equivalent circuit is used to explain the reconfigurability of the antenna. The PRMS antenna is studied and designed to operate at around 3.5 GHz using computer simulation. For verification of simulation results, the PRMS antenna is fabricated and measured. The antenna performance, in terms of polarization reconfigurability, axial-ratio bandwidth, impedance bandwidth, realized boresight gain and radiation pattern, is presented. Results show that the PRMS antenna in circular polarizations achieves an operating bandwidth of 3.3–3.7 GHz (i.e., fractional bandwidth 11.4%), a boresight gain of above 5 dBi and high-polarization isolation of larger than 15 dB. While the PRMS antenna in linear polarization achieves a gain of above 7.5 dBi with cross-polarization isolation larger than 50 dB.

Polarization Reconfigurable Wheel-Shaped Antenna With Conical-Beam Radiation Pattern

Abstract: This paper introduces a polarization reconfigurable wheel-shaped antenna with wide bandwidth and conical-beam radiation pattern. A wideband circular-monopolar patch surrounded by eight reconfigurable coupling loop stubs can generate conical-beam radiation patterns with different polarizations. This polarization reconfigurable characteristic is realized by controlling PIN diodes on the coupling loop stubs. The center-fed circular patch operates with the vertically-polarized conical-beam radiation and the coupling loop stubs radiate the horizontally-polarized wave propagation. With choosing proper magnitudes and phase differences between the two orthogonal radiations from the monopolar patch and the loop stubs, a circularly-polarized conical-beam radiation can be obtained. In addition, the presence of a back reflector yields a wide axial ratio bandwidth, enhances the front-to-back ratio of the radiation pattern, and avoids EM interferences between DC biasing lines and the antenna. This proposed antenna can generate three types of polarizations with the conical-beam radiation pattern including vertical polarization, left-handed circular polarization, and right-handed circular polarization by controlling the PIN diodes. Measured impedance and axial ratio bandwidths are 28.6% (3.45 to 4.6 GHz) and 15.4% (3.6 to 4.2 GHz), respectively, for the two CP modes. The maximum CP gain is 4.4 dBic. Furthermore, a dual-band operation (3.35 to 3.44 GHz and 4.5 to 4.75 GHz) can be observed for the LP mode. The antenna can operate at the downlink of standard C band (3.625 to 4.2 GHz) for geostationary satellite communication.

Multi-Polarization Reconfigurable Antenna for Wireless Biomedical System

Abstract: This paper presents a multi-polarization reconfigurable antenna with four dipole radiators for biomedical applications in body-centric wireless communication system (BWCS). The proposed multi-dipole antenna with switchable 0°, +45°, 90° and −45° linear polarizations is able to overcome the polarization mismatching and multi-path distortion in complex wireless channels as in BWCS. To realize this reconfigurable feature for the first time among all the reported antenna designs, we assembled four dipoles together with 45° rotated sequential arrangements. These dipoles are excited by the same feeding source provided by a ground tapered Balun. A metallic reflector is placed below the dipoles to generate a broadside radiation. By introducing eight PIN diodes as RF switches between the excitation source and the four dipoles, we can control a specific dipole to operate. As the results, 0°, +45°, 90° and −45° linear polarizations can be switched correspondingly to different operating dipoles. Experimental results agree with the simulation and show that the proposed antenna well works in all polarization modes with desirable electrical characteristics. The antenna has a wide impedance bandwidth of 34% from 2.2 to 3.1 GHz (for the reflection coefficient ${\leq}$ −10 dB) and exhibits a stable cardioid-shaped radiation pattern across the operating bandwidth with a peak gain of 5.2 dBi. To validate the effectiveness of the multi-dipole antenna for biomedical applications, we also designed a meandered PIFA as the implantable antenna. Finally, the communication link measurement shows that our proposed antenna is able to minimize the polarization mismatching and maintains the optimal communication link thanks to its polarization reconfigurability.

A Reconfigurable Polarization Converter Using Active Metasurface and Its Application in Horn Antenna

Abstract: This paper proposes a reconfigurable polarization converter based on a p-i-n diode controlled active metasurface (AMS). The AMS consists of a thin dielectric substrate and is tuned by two identical layers of elliptic split rings loaded with p-i-n diodes. The p-i-n diodes are positioned between the split gaps and biased through the interconnected elliptic split rings without extra bias network. The active design achieves conversion from linear to circular polarization when the p-i-n diodes are OFF, whereas no conversion takes place when the diodes are ON. A prototype of the proposed design is fabricated, and the operational characteristics are measured. Both the simulated and the experimental results verify the viability of the design. Subsequently, the converter is applied to a linearly polarized horn antenna as a superstrate, making the polarization of the antenna reconfigurable.

Pattern-Reconfigurable Microstrip Patch Antenna With Multidirectional Beam for WiMAX Application

Abstract: A parasitic planar patch antenna capable of multi directional pattern reconfiguration is presented. The antenna structure consists of a driven element surrounded by four parasitic elements that act either as reflector(s) or director(s) depending on the switching arrangement. Beam reconfiguration is achieved by using four p-i-n diode switches where the effect of switching technique on the overall element performance is investigated numerically and experimentally. The proposed antenna achieves nine distinguished main beam angular positions. Moreover, the proposed antenna has achieved excellent realized gain levels at all configuration scenarios with a minimum value of 7 dBi. Simulation and measurement results show good agreement and promising applications of such antenna structure in enhanced WiMAX systems.