Seung Sik Lee

Bio: Seung Sik Lee is an academic researcher from Electronics and Telecommunications Research Institute. The author has contributed to research in topics: Signal & Phase-locked loop. The author has an hindex of 7, co-authored 25 publications receiving 521 citations.

A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics

Abstract: A planar monopole antenna with a staircase shape and small volume (25times26times1 mm3) is proposed in this paper. With the use of a half-bowtie radiating element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9-14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omnidirectional radiation pattern is obtained. The group delay which is an indication of linearity between two proposed antennas is less than 1 ns. The electrical characteristics in terms of frequency and time domains and physical ones of the proposed antenna make it attractive for use in ultrawideband (UWB) systems

Method and apparatus for acquiring reception synchronization in local wireless communication system

Abstract: In a local wireless communication system, a reception signal including an STF (short training field) in which a plurality of patterns are repeatedly transmitted is received, the STF including a first number of STF patterns and a second number of STF patterns, the second number of STF patterns having an opposite code to that of the first number of STF patterns. In a first frequency offset estimation and correction process and a second frequency offset estimation and correction process, frequency offset estimation is performed on a plurality of STF patterns to acquire a phase error of each sample constituting the STF patterns, and the frequency of the STF patterns is corrected based on the acquired phase error. Cross correlation is performed on a predetermined number of STF patterns, among a plurality of STF patterns output subsequent to the frequency offset estimation and correction, to detect frame timing.

Base station, terminal, and operating method thereof

Abstract: A base station and a terminal for supporting a low power mode are provided. The base station transmits a first type of beacon signal for a terminal operating in a normal mode, a second type of beacon signal for a terminal operating in a low power mode, and a charging signal for a terminal in a low power mode. The terminal harvests energy from a charging signal and receives the second type of beacon signal using the harvested energy. The terminal confirms a communication request through the second type of beacon signal, enters into an active period, and communicates with the base station.

Real time video watermarking method using frame averages

Abstract: The present invention relates to a watermarking method for protecting the copyright of digital data, which includes the step of dividing each of two successive frames into at least two sub-groups, the step of adding and subtracting a value, which varies according to pixel locations, to and from a specific component value at each pixel location of the sub-groups using Just Noticeable Difference (JND) values and averages of the specific component value at pixel locations of corresponding sub-groups of the two successive frames, the step of adaptively embedding watermark information while modifying embedment intensity of the watermark information, the step of calculating the averages of the specific component values of the sub-groups, and the step of extracting watermark information using the calculated averages.

Digital phase-locked loop apparatus using frequency shift keying and method of controlling the same

Abstract: A digital phase-locked loop apparatus using FSK includes a PFD detecting phase differences between a reference clock and a frequency-divided signal, and a first adder for generating first digital control codes by adding first digital codes, second digital codes, and channel frequency codes including channel information to each other, the first digital codes being converted from time differences between first and second pulses. The apparatus further includes a digital filter correcting errors of the first digital control codes to generate second digital control codes, a DCO for varying an oscillating frequency in accordance with a digital tuning word based on the second digital control codes, and a dual modulus division unit dividing the oscillating frequency into a frequency-divided signal.

A Compact Ultrawideband Antenna With 3.4/5.5 GHz Dual Band-Notched Characteristics

Abstract: We propose a compact planar ultrawideband (UWB) antenna with 3.4/5.5 GHz dual band-notched characteristics. The antenna consists of a beveled rectangular metal patch and a 50 Omega coplanar waveguide (CPW) transmission line. By etching two nested C-shaped slots in the patch, band-rejected filtering properties in the WiMAX/WLAN bands are achieved. The proposed antenna is successfully simulated, designed, and measured showing broadband matched impedance, stable radiation patterns and constant gain. An equivalent circuit model of the proposed antenna is presented to discuss the mechanism of the dual band-notched UWB antenna. A UWB antenna and a single band-notched one are also provided for references.

Compact Printed UWB Diversity Slot Antenna With 5.5-GHz Band-Notched Characteristics

Abstract: A novel compact printed ultrawideband (UWB) slot antenna for MIMO/diversity applications is presented in this letter. The antenna consists of two modified coplanar waveguides (CPWs) feeding staircase-shaped radiating elements for orthogonal radiation patterns, where a rectangle stub is placed at 45° between the CPW to ensure high isolations. By etching two split-ring resonator (SRR) slots on the radiators respectively, the band-notched property is achieved. Results show that this antenna meets a 10-dB impedance bandwidth and 15 dB isolation from 2.5 to 12 GHz, with a notched band at 5.5 GHz. The measurements of the radiation patterns and envelope correlation coefficient (ECC) denote that the antenna is suitable for multiple-input-multiple-output (MIMO)/diversity systems. Furthermore, it has a compact size of 48 × 48 mm2, which has been significantly reduced, and it is a good candidate for portable devices.

UWB Elliptical Monopoles With a Reconfigurable Band Notch Using MEMS Switches Actuated Without Bias Lines

Abstract: Two CPW-fed elliptical monopoles were fabricated on liquid crystal polymer (LCP) with reconfigurable rejection band (band-notch) characteristics in the frequency range between 5 and 6 GHz. The first antenna uses a lambda/2 long, U-shaped slot and the second antenna uses two symmetrically placed lambda/4 long, inverted L-shaped stubs as resonating elements. Microelectromechanical system (MEMS) switches are used to activate and deactivate the resonating elements without the need of dc bias lines due to a novel design of the switch geometry. Transmission line models and surface current distributions are used to explain the effect of the added resonating elements. Reflection coefficient radiation pattern and gain measurements are presented to verify the design concepts featuring a very satisfactory performance.

A Band-Notched Ultrawideband Printed Monopole Antenna

Abstract: In this letter, a band-notched ultrawideband (UWB) antenna is presented and the notched-band characteristic is realized by a compact coplanar waveguide (CPW) resonant cell (CCRC). The antenna with a total size of 46 mm $,times,$30 mm operates in a band from 2.67 to over 12 GHz, and shows omnidirectional radiation patterns. Measurements indicate that the antenna presents a notched band from 5.10 to 5.94 GHz for $ VSWR ge 3:1$, which covers the wireless local area network (WLAN) band. The time-domain behaviors and the CCRC are discussed and the group delay is given experimentally. Also, parametric studies are performed numerically in the end.