Changhyeong Lee

A planar 8-way radial power-splitter combined flat ap-antenna with increased h-plane gain

A method to make the access-point(AP) antenna flat and create multiple beams with good gains in the horizontal plane is proposed to overcome the drawbacks of the monopole antenna. The monopole antenna has a relatively high profile and low H-plane gain due to the imbalance in elevation. Considering 8 beams around the circle, the input power is divided by a thin 8-way radial power-splitter which requires technical treatment on very high impedance as large as 400 Ω. This is connected to 8 quasi-Yagi antennas. The experiment shows the desired power-splitting and the improvement of the horizontal-plane gain as a flat antenna structure.

Metamaterial-embedded beamforming phased-array antennas for degradable GPS links

This paper presents an approach to enable a typical GPS receiver to be much less susceptible to intentional disruption such as jamming and change in link environment. Beamforming GPS receivers comprising 4×4 elements or 8×8 ones are designed using metamaterials, for the placement on the body of an aircraft as an airborne vehicle, to cope with the varying angle of incidence with good antenna gain and the low inter-element interference to make the system more robust and adaptive. The design results show the antenna gain much higher than 5 dBi, and the movable circularly polarized beam with the excellent axial ratio at the resonance frequency and low mutual coupling between the elements.

Investigating electromagnetic power transfer ratio of circular polarizing planar metasurface lens

We designed an antenna structure with the circular polarization metamaterial superstrate which increases the directivity of the primary antenna as a lens. The metamaterial superstrate removes the necessity of the array antenna and complicated feed. Plus, it provides the Fabry-perot cavity with the circular polarization. With regard to the primary antenna, a CRLH antenna is adopted to have the size-reduction from the conventional half-wavelength patch antenna.

Electromagnetics computational modelling of magnetic metamaterials for wireless power transfe

We design a compact metamaterial structure enabling the wireless power transfer(WPT) system to enhance its function and model it for electromagnetic characterization. To couple the transmitting and receiving loops of the system compliant with the A4WP requirements, the metamaterial should resonate at a very low frequency as an effectively magnetic device. Additionally, they must be substantially small for the low frequency far below 10 MHz, taking into account the integration to practical handheld devices. The miniaturized structure is simulated through a full-wave method, and its magnetic properties are investigated through the so-called retrieval algorithm to extract its effective permeability. The analysis results present the relationship between the WPT coupling device and metamaterial constitutive parameters.

Low-SAR metasurface-based dipole and its beamforming array

This paper suggests a new planar metamaterial-based dipole with a low SAR. The artificial magnetic conductor(AMC) lies below the dipole through a thin AMC to prevent a high SAR as well as secure a good impedance match, which will become poor near the human tissue by the conventional techniques. The design is conducted for 2.4 GHz WBAN frequency, and shows the strengths at volume miniaturization, return loss and SAR. Also, this method is extended to the beamforming characteristics in an array configuration aiming to build adaptive wearable equipment