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최재연 남서울대학교출판국 2009 남서울대학교 정보통신 논문집 Vol.6 No.2
In this paper, a internal antenna for mobile handsets is proposed. The proposed antenna is low-profile for mounting in limited inner space of a handset. It consists of three open points with quarter wave length for multi-band operation. The ground plane below the patch is removed for wide-bandwidth without the variation of antenna size and the slot is added at the center of the patch for convenient matching in high frequency band.
최재연 남서울대학교 2010 남서울대학교 논문집 Vol.16 No.1-1
Microwave application development has made it necessary to conceive special materials capable of highly absorbing such radiation. An experimental multi-layer active microwave absorber in described. The absorber is a planar structure which is analyzed by modified Powell's method. In case of four dielectric layers with inequality constraints in design variables. The optimal radar absorbing materials' are designed by setting the relative permittivity and the loss tangent of the dielectrics as a function of the frequency over 5~20GHz. Key Words : Absorber, active, adaptive, Powells' method
최재연 남서울대학교 1997 남서울대학교 논문집 Vol.3 No.-
The broadside coupled coplanar waveguide(BCCPW) shielded with the rectangular waveguide is analyzed by applying the Galerkin's method in the spectral domain. Characteristic parameters are obtained respectively when BCCPW is symmetric and unsymmetric with regard to the suspended dielectric substrate. Characteristic impedances and effective dielctric constants of BCCPW are also obtained by varying the height of the dielectric substrate and the width of the center and the ground strip in terms of transmission modes.
최재연 남서울대학교출판국 2008 남서울대학교 정보통신 논문집 Vol.5 No.1
In this paper, we propose All-Optical WDM Buffer System for resolving contention problem of packets in Optical Packet Switching System. The proposed system consists of tunable wavelength converters based on SOA, N×N AWG, and fiber delay lines. This structure can reduce ASE and cross-talk noise because the buffering is achieved from passing packets through each different delay line determined by converting the wavelength of input packet. We also perform buffering experiment for two 50ns optical pulses, and it proves that the proposed system works as expected.
최재연 남서울대학교 2009 남서울대학교 논문집 Vol.15 No.2
The designed PCS antenna exhibits the better radiation characteristics widely used monopole antenna. The performance characteristics of an antenna are analyzed by commercially available simulation tool. The main objectives of the designed antenna are to reduce the size and to increase the efficiency. In this paper, we introduce two types of antenna. They are small antenna and in-house antennas. The basic idea of a small antenna is the usage of dielectric material covering the wire radiator to reduce the size and to improve the gain. A PIFA is designed to use as an in-house antenna for PCS. The analysis results show that their radiation characteristics and gain are better than those of a monopole. Key Words : Small Antenna, PIFA, in-house Antenna, PCS
최재연 남서울대학교 2010 남서울대학교 논문집 Vol.16 No.2
In this study, impedance transformation characteristic for the broadband TEM horn antenna is analyzed. The moment method can be applied to analyze the TEM horn antenna. The balun feeding the TEM horn is needed for impedace matching between antena which is balanced circuit and coaxial cable which is unbalanced circuit. The balun is composed of the Lange coupler with the two-stage cascaded connection and the impedance transformer designed by the short-linear matching method and the linear double taper method. At the antenna operating at the frequency band , 1.5 - 3 GHz, the measured data agree well with the calculated results. Key Words : impedance transformation, TEM, horn antenna
최재연 남서울대학교 2007 남서울대학교 논문집 Vol.13 No.3
A software-defined radio (SDR) system is a radio communication system which can tune to any frequency band and receive any modulation across a large frequency spectrum by means of programmable hardware which is controlled by software. An SDR performs significant amounts of signal processing in a general purpose computer, or a reconfigurable piece of digital electronics. The goal of this design is to produce a radio that can receive and transmit a new form of radio protocol just by running new software. The hardware of a software-defined radio typically consists of a superheterodyne RF front end which converts RF signals from analog IF signals, and analog to digital converter and digital to analog converters which are used to convert a digitised IF signal from and to analog form, respectively. Software-defined radio can currently be used to implement simple radio modem technologies. In the long run, software-defined radio is expected by its proponents to become the dominant technology in radio communications. It is the enabler of the cognitive radio. This paper introduces the Software defined radio technology for the next generation communication system. Key Words : Software defined radio, wireless communication
최재연 남서울대학교 2007 남서울대학교 논문집 Vol.13 No.4
The antenna emits radio signals to activate the tag and to read and write data to it. Antennas are the conduits between the tag and the transceiver, which controls the system's data acquisition and communication. Antennas are available in a variety of shapes and sizes. RFID tags are categorized as either active or passive. Active RFID tags are powered by an internal battery and are typically read/write, i.e., tag data can be rewritten and/or modified. Passive RFID tags operate without a separate external power source and obtain operating power generated from the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. The coupling method between passive tag and the reader is considered. Key Words : RFID, tag, reader, passive tag coupling