Doo-Yeong Yang

Analysis of unit cells for filter design using CRLH transmission line

In this paper, unit cells using coplanar waveguide transmission line with composite right and left-handed structure are proposed. The characteristics of the unit cells are analyzed in order to design low-pass filter and high-pass filter in small sizes. By changing the sizes of these unit cells, the parameters of right-handed and left-handed immittance components are changed and the desired characteristics of the unit cells are achieved. The equivalent circuits of the unit cells are extracted and analyzed either. As a result, the simulation results of the unit cells and the equivalent circuits are almost identified. In the end, the movement and energy distributions of electromagnetic field are shown to compare the characteristics of the two unit cells.

A Dual-Channel MAC Protocol with Directional Antennas for Mobile Ad-Hoc Networks

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual-channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual-channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out-of-band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator. Keywords: Ad hoc MAC protocol, directional antennas, tone, dual-channel, deafness.

Development of Mobile Context Awareness Restaurant Recommendation Services

Mobile network evolution and development of USN technologies introduce new business model based on context awareness. Cellular operators provide friend finding service using cell based location information and telematics service using GPS location information. Recently cellular operators provide yellow page service based cell based location information. In this paper, we develop mobile tour application on WIPI platform based on location information. Mobile tour information services provide the best information based on context awareness using user location information from LBS(Location Based Service) Platform, season, weather conditions, time from Web server, and personal preference information stored in database. Mobile tour information service application is developed on WIPI platform.

Design and Fabrication of an End-Launched Rectangular Waveguide Adapter Fed by a Coaxial Loop

An end-launched adapter combining a coaxial loop within a rectangular waveguide has been analyzed and designed. The accurate electromagnetic modeling of input impedance for the adapter design has been developed using a modal analysis method. Also, design parameters to improve the end-launched adapter have been investigated. Numerical and experimental results of the proposed model have been compared with the results of previous works, and verified by an electromagnetic simulator of High Frequency Structure Simulator (HFSS). The input voltage standing wave ratios (VSWRs) are smaller than 2 over the wide frequency band from 7.5 GHz to 10.5 GHz.

Analysis of unit cells for high pass filter using left-handed transmission line

In this paper, two novel unit cells using folded coplanar waveguide transmission line with left-handed structure are proposed, which have high-pass property. The characteristics of the unit cells are analyzed in different sizes, in order to recognize the characteristics of optimal design parameters. Also, equivalent circuits of the unit cells are extracted and equations to estimate the values of the immittance components in the equivalent circuits are formulated. The simulation results of the unit cells agree well with the results of the equivalent circuits. Energy distributions of electromagnetic field are shown to prove the property of left-handed structure. Finally, measurements of the proposed unit cells are shown to identify the characteristics.

The AODV Routing Protocol based on Location Information for Inter-Vehicle Communication

In order to realize Intelligent Transport System (ITS) without any road facilities support, Inter-vehicle Communication (IVC) is increased attention. IVC makes it possible to exchange real-time information among vehicles without centralized infrastructure. The IVC systems use multi-hop broadcast to disseminate information. In this paper, we propose the improved AODV routing protocol based on location information. The proposed AODV routing protocol transmits Hello packet with location information to calculate the distance between nodes. Then it achieves fast link recovery. We confirm the throughput performance of the proposed AODV routing protocol compared with the AODV routing protocol using Qualnet ver.3.8 simulator.

RFID Reader Antenna with Hilbert Curve Fractal Structure over Partially Grounded Plane

In this paper, UHF band RFID reader antenna using filbert curve fractal structure and adding the partially grounded plane at the bottom of antenna, which has a resonant frequency at 910MHz, is proposed. Input impedance of antenna is matched with the feed line of 50ohm by varying the length and width of line segment making up the antenna, and by moving the position of via hole. The gain and directivity of antenna is enhanced as varying the dimension of the partially grounded plane and adding the line segment. The size of fabricated antenna is . The impedance band width(VSWR. The return loss and the gain of fabricated antenna are -18.2dB, 5.3dBi at 910MHz.

Genetic algorithm optimization of a corrugated conical horn antenna

This paper presents a design procedure for a wideband corrugated multi-sectional conical horn using a genetic algorithm (GA). The GA optimizes the length, number of sections, flare angles, and depth of the first slot in each horn section in order to match the admittance, reduce the voltage standing wave ratio (VSWR), and generate the desired copolarization and cross-polarization patterns. A VSWR < 1.6 is obtained from 11 GHz to 18 GHz.

D-CRLH Based Band Rejection Filter using a Concavo-Convex Coupled CPW Transmission Line

In this paper, the use of a dual composite right/left-handed coplanar waveguide (CPW) transmission line is proposed for the design of a band rejection filter. The notch property of the filter is achieved by combining the convex signal line with the shorted concave meander line, and the equivalent circuit model is extracted from the geometry of the unit cell for organizing the band rejection property. Then the equivalent parameters of the unit cell are analyzed to identify those behaviors. And the dispersion characteristics and energy distributions are simulated. In the end, the band rejection filter is manufactured by cascading two proposed unit cells. We show that the measurement result for the resonant frequency demonstrates good agreement with the simulation result and the band rejection filter provides a rejection performance of 17.5 dB at the stopband frequency ranging from 869 MHz to 894 MHz.

Triple-band Multiplexer for a Low Power Portable Base Station

In this paper, a triple-band multiplexer using a microstrip transmission line was designed and fabricated to make use of a low power portable base station. This multiplexer was used in the triple-band including the cellular, WCDMA and LTE mobile frequency band, and designed to have an insertion loss of 0.8 dB, low SWR of 1.5 in the passband and a band rejection of 15 dB in the stopband. From the measured results obtained by a confidence test for the fabricated multiplexer samples, the maximum insertion loss and SWR of the fabricated multiplexer samples in all passbands of 824-894MHz, 1920-2170 MHz and 2500-2600 MHz were below 0.71 dB and 1.38, and the attenuations in the stopbands were better than 15 dB. Therefore, the triple-band multiplexer has good performance and satisfies the design specifications.