• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.41 no.5
• /
• pp.53-62
• /
• 2004

In this study, an improved post-processing technique for correcting MRI artifact due to the unknown respiratory motion in the imaging plane is presented. Respiratory motion is modeled by a two-Dimensional linear expending-shrinking movement. Assuming that the body tissues are incompressible fluid like materials, the proton density per unit volume of the imaging object is kept constant. According to the introduced model, respiratory motion imposes phase error, non-uniform sampling and amplitude modulation distortions on the acquired MRI data. When the motion parameters are known or can be estimatead a reconstruction algorithm based on biliner superposition method was used to correct the MRI artifact. In the case of motion parameters are unknown, first, the spectrum shift method is applied to find the respiratory fluctuation function, x directional expansion coefficient and x directional expansion center. Next, y directional expansion coefficient and y directional expansion center are estimated by using the minimum energy method. Finally, the validity of this proposed method is shown to be effective by using the simulated motion images.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.36T no.4
• /
• pp.94-102
• /
• 1999

This paper is related with the compensation of communication channel characteristics using predistorter, and the considered characteristic is the additive noise, phase rotation and frequency selective fading which occurred in communication channel. Predistorter can minimize the effect of obstacle element which occured in channel at receiving side by transmitting the predistortion of signal after modulation, the coefficient of inverse electrical charateristic of communication channel is performed at transmitting side. For this purpose, the predistorter is designed by using Tricepstrum Equalization Algorithm which is adaptive equlizer algorithm, and the receiving side must transmit the probing signal to transmitting side. Using the probing signal, the transmitting side can obtain the inverse characteristic coefficient of communication channel, and this probing signal must be transmitted periodically. We assumed that the channel characteristic do not change during this one period. As a result of computer simulation, we confirmed that the performance of predistorter was fairly good as same as the adaptive equalizer, and this technique have a effectiveness that can be used in the forward channel of mobile communication in order to achieve high speed transmission.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.11 no.2
• /
• pp.145-150
• /
• 2016

The capability of accurate positioning and tracking is necessary to implement an unmanned autonomous driving system. The moving-baseline GPS Technique is a promising candidate to mitigate positioning errors of conventional GPS system. It provides accurate positioning data based on the phase difference between received signals from multiple GPS antennas mounted on the same platform. In this paper, we propose a dual-band dual-circularly-polarized antenna suitable for the moving-baseline GPS. The proposed antenna operates at GPS L1 and L2 bands, and fed by the side of the antenna instead of the bottom. The antenna is firstly designed by calculating theoretical values of key parameters, and then optimized by means of 3D full-wave simulation software. Simulation and measurement results show that the optimized antenna offers 6.1% and 3.7% bandwidth at L1 and L2, respectively, with axial ratio bandwidth of more than 1%. The size of the antenna is $73mm{\times}73mm{\times}6.4mm$, which is small and low-profile.

• Journal of the Microelectronics and Packaging Society
• /
• v.24 no.1
• /
• pp.57-65
• /
• 2017

The electronic components in mobile device are composed of electronic chips and various other materials. These components become extremely thin and the constituent materials have different coefficient of thermal expansion, so that considerable warpages occurs easily due to temperature change or external load. Shadow $moir{\acute{e}}$ is non-contact, whole field technique for measuring out-of-plane displacement, but the measurement sensitivity is not less than $50{\mu}m/fringe$, which is not suitable for measuring the warpage of the electronic components. In this paper, we implemented a measurement method with enhanced sensitivity of $25{\mu}m/fringe$ by investigating and optimizing various experimental conditions of the shadow $moir{\acute{e}}$. In addition, four $moir{\acute{e}}$ fringe patterns recorded by the phase shift are processes to obtain a $moir{\acute{e}}$ fringe patterns with a sensitivity four times higher. The measurement technique is applied to small electronic components of a smart phone for measuring warpage with a high sensitivity of $5{\mu}m/fringe$ at room temperature and at the temperature of $100^{\circ}C$.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.1
• /
• pp.1-6
• /
• 2003

Since the scale in pipes reduces the flow rate, a quantitative evaluation of the scale is essential for the proper maintenance of pipes. Guided waves were employed to estimate the amount of scale in water supplying pipes. Using variable angle wedge, several modes of guided waves wire generated and their propagation charcteristics along the pipes with stale were analyzed. It was experimentally observed that the amplitude of F(M,2) modes at $f{\times}d=1.5MHz\;mm$ decreased significantly with increasing amount of scale. The present study showed that F(M,2) modes were optima) to evaluate the scale in water supplying pipes.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.2 no.2 s.3
• /
• pp.1-12
• /
• 2003

DAB(Digital audio broadcasting) is a next generation radio broadcasting system which provides CD quality audio, various data services and superior reception ability when moving. Also, it can show traffic informations and news literally or graphically. In this paper, we design and fabricate the DAB tuner for ITS service that follows Eureka-147 and ETSI 300 401 specifications. This small-sized tuner can be adopted to mny electronic equipments such as a Hi-Fi audio, DVD player, car audio system etc.. The overall performance of the tuner depends on a phase noise of VCO and the sensitivity of the receiving system is influenced by LNA, image rejection filter and channel selection filter. All our measurement results satisfy the specification for a DAB system with the return loss of 9dB, the noise figure of 6dB for both Band 111 and L-band and the sensitivity of -97dBm.

• Korean journal of communication and information
• /
• v.60
• /
• pp.172-192
• /
• 2012

Over the last ten years, media convergence and multiple platform expansion have affected the ways that people watch conventional television. In the post-TV era, the growing use of the Internet and mobile multi-media devices, such as smart phones, as well as the availability of abundant television content, allows television consumption to be more personalized, diversified, and linked with various media activities, especially social media uses. This study attempts to examine how television viewing experiences have been transformed with the development of the trans-media uses. Based on Walter J. Ong's concept of relation-ism, which posits that new media transform the meanings and relevance of old media rather than making old media obsolete, this study will pay particular attention to how the cultural meanings of television viewing have been redefined in the post-TV era. For the examination, this study has looked at concrete cases of the television viewing experiences of 29 young people in their twenties. Based on in-depth interview data, this study discusses the newly emerging characteristics of television viewing, its temporal and spatial experiences, and the significance of television as a medium and as a social place.

• Journal of IKEEE
• /
• v.18 no.4
• /
• pp.559-565
• /
• 2014

A 3 dB coupler has been designed and implemented using the most commonly used double-sided FR4 boards. The coupling and the bandwidth of the coupler are enhanced with the enlarged overlapped area of the coupler. Major design parameters are plotted as a design guide and the parameters are verified by simulation and measurement. The size of the manufactured coupler is $30{\times}14mm^2$. Its measured insertion loss and phase difference are 0.6 dB and $90.5^{\circ}$ at center frequency of 2.5 GHz, respectively. The operating frequency range is 1.72 GHz to 3.08 GHz for $3.6{\pm}0.5dB$ insertion loss. The coupler has the performance similar to that of conventional Lange coupler, and implementation of the coupler is easy and cheap with wide metal width and spacing and no additional wire bonding process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.1
• /
• pp.47-55
• /
• 2012

This paper describes the developed HILS and test equipment in order to test the performances of MMW(Millimeter-Wave) seeker which can detect and track a high speed of short-range ballistic missile and aircraft. This system is used to 141 horn antenna array, array switching, and gain and phase control algorithm to simulate various kind of targets and trajectory of high speed and maneuver moving target. In addition, it simulates not only velocity and range for these targets but also clutter and jamming environments. System configuration and implementation and the measurement results of major subsystems such as target motion simulator, simulation signal generator, high speed data aquisition unit, and central control unit are presented. These systems could verify the detection and tracking performance of MMW seeker through dynamic real-time test based on simulation flight scenario.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.17 no.5
• /
• pp.22-28
• /
• 2003

This paper describes the frequency dependence of the grounding impedance. In order to propose the evaluation method of the transient response of powered grounding systems, the grounding impedances were measured with varying the frequency of incoming currents by way of the variable frequency inverter and band pass filter. The magnitude and phase of the grounding impedance were analyzed in the frequency range of 20 [Hz]∼2.1[kHz]. The grounding impedance were increased with increasing the frequency of the test current. The grounding impedance at the frequency of 2[kHz] in the actual 22.9[kV] substation grounding system was approximately 3 times as large as the 60[Hz] grounding impedance. It was found that the frequency dependence of the grounding impedance is mainly subject to the inductive reactance of the grounding conductors. As a result, it is critical to determine the shape and size of grounding grid reducing the resultant inductance in grounding systems for lightning surge protection.