• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.9 s.100
• /
• pp.926-931
• /
• 2005

In this paper, the printed-sleeve monopole antenna which has the small size and the broadband characteristics, is presented and its radiation characteristics are investigated. To conform the broadband characteristics of the proposed antenna, the experimental antenna is designed, fabricated, and its radiation characteristics are measured in PCS band (1.75 GHz${\~}$1.87 GHz). It is shown that the designed antenna has the non-directional pattern in the horizontal plane, the directional pattern in the vertical plane, VSWR less than 1.5, and gain in 2.14 dBi${\~}$3.4 dBi. From these results, the proposed antenna is conformed as a broadband antenna which can be used for the mobile communication indoor antenna extensively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.4
• /
• pp.386-392
• /
• 2002

This paper presents a basic characteristics of 4-element circular array dipole antennas for 4-sector beam steering. The coupled integral equations for the unknown current distributions on dipole elements are derived and solved by applying Galerkin's method of moments. The parasitic elements have been used to increase the directional gain and the beam is steered electronically either by sswitching between the parasitic elements or switching the position of the active element. The parasitic elements are switched short-circuited or open-circuited as required to steer a directional beam. In order to verify the theoretical analysis, the radiation pattern was compared with experiments.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2005.11a
• /
• pp.211-216
• /
• 2005

In this paper, we have designed, fabricated and measured a compact rectangular mono-cone antenna for ultra-wideband applications. The proposed antenna covers the entire UWB band (3.1 GHz $\sim$ 10.6GHz). The measured bandwidth is 8.2 GHz from 2.8GHz to 11 GHz for ${\mid}S_{11}{\mid}{\leq}-10dB$. From the measured results, the proposed antenna shows a good characteristics (linear phase, omni-directional pattern and very low gain variation) for UWB applications. Also, the measured results have a reasonable agreement with the simulated results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.10
• /
• pp.1097-1106
• /
• 2009

In this paper, the cross monopole antenna with branch element is presented and its radiation characteristics are investigated. To confirm the broadband characteristics of the proposed antenna, the experimental antenna is designed, fabricated, and its radiation characteristics are measured in PCS, WCDMA, WiBro and S-DMB band(1.750~2.655 GHz). It is shown that the designed antenna has the non-directional pattern in the horizontal plane, the directional pattern in the vertical plane, VSWR less than 1.5 and gain over 1.9 dBi in 1.72~2.82 GHz. From these results, the presented antenna is conformed as a broadband antenna which can be used for PCS, WCDMA, WiBro and S-DMB band.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.2
• /
• pp.249-254
• /
• 2014

We have studied on the possibility of railway stability system using RFID tag. UHF RFID tag was desinged, manufactured and tested. Proposed UHF tag antenna has PIFA type structure and inset feed multi matching technique was attempted for impedance matching of antenna. The impedance bandwidth (VSWR < 3) of the proposed tag antenna covers 917~923 MHz. Measured peak gain is 3.225 dBi and UHF band with an omni-directional radiation pattern. RFID reader and tag installed in motor car and track, respectively. Then, tag recognition rate according to velocity of car (under 45 km/h) represented 100 %.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.14 no.5
• /
• pp.7-14
• /
• 1977

Conventionally, a TIVT has been used for high power amplification in the microwave frequency range. However, an ultra-high-power amplifier in the 2GHz range has successfully been designed and fabricated employing high power transistors developed recently and available commercially. In the design of the amplifier, a balanced-pair configuration is adopted in order to obtain very high microwave power, and a good impedance matching is achieved by making use of microstripline techniques. For the RF power divider as well as combiner, an approach of stripline directional coupler isadopted because of its easiness in fabrication. The coupler so designed and fabricated indicates a satisfactory performance as a quadrature hybrie coupler. Measurements on the amplifier developed for an immediate commercial application also exhibit excellent overall performance characteristics RF power output, 14 watts, gain 14dB, frequency bandwidth, 160MHz, effciency 40%.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.9A
• /
• pp.934-940
• /
• 2008

In this paper, an antenna accessible to the Hepta-Band (GPS, DCS, PCS, UMTS, Wibro, Bluetooth and S-DMB) is designed and fabricated. To get broadband characteristics with small size, we propose a structure of Coplanar Waveguide-fed with Ground, which is based on a monopole antenna. Simulation is performed by adjusting the size of distance between a length of radiation patch and ground plane. The designed antenna satisfies the frequency bandwidth of 1.430Hz$\sim$2.9GHz(67.89%), the gain of $1.3{\sim}3.7dBi$ and an omni-directional radiation pattern at VSWR<2.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.22 no.2
• /
• pp.102-108
• /
• 2017

Proper design guides are proposed for a practical dual-active bridge (DAB) converter based on the mathematical model on the steady state. The DAB converter is popular in bidirectional application due to its zero-voltage capability and easy bidirectional operation for seamless control, high efficiency, and performance. Some design considerations are taken to overcome the limitation of the DAB converter. The practical design methodology of power stage is discussed to minimize the conduction and switching losses of the DAB converter. Small-signal model and frequency response are derived and analyzed based on the generalized average method, which considers equivalent series resistance, to improve the dynamics, stability, and reliability with voltage regulation of the practical DAB converter. The design of closed-loop control is discussed by the derived small-signal model to obtain the pertinent gain and phase margin in steady-state operation. Experimental results of a 3.3 kW prototype of DAB converter demonstrate the validity and effectiveness of the proposed methods.

• Journal of Korea Multimedia Society
• /
• v.19 no.8
• /
• pp.1345-1360
• /
• 2016

In this paper, we propose a new real-time human detection under omni-directional cameras for visual surveillance purpose, based on CNN with unified detection and AGMM. Compared to CNN-based state-of-the-art object detection methods. YOLO model-based object detection method boasts of very fast object detection, but with less accuracy. The proposed method adapts the unified detecting CNN of YOLO model so as to be intensified by the additional foreground contextual information obtained from pre-stage AGMM. Increased computational time incurred by additional AGMM processing is compensated by speed-up gain obtained from utilizing 2-D input data consisting of grey-level image data and foreground context information instead of 3-D color input data. Through various experiments, it is shown that the proposed method performs better with respect to accuracy and more robust to environment changes than YOLO model-based human detection method, but with the similar processing speeds to that of YOLO model-based one. Thus, it can be successfully employed for embedded surveillance application.

• Journal of Broadcast Engineering
• /
• v.20 no.2
• /
• pp.265-272
• /
• 2015

A new technology on video frame rate up-conversion (FRUC) is presented by combining the median filter and motion estimation (ME) with an occlusion detection (OD) method. First, ME is performed to have a motion vector. Then, the OD method is used to refine motion vector in the occlusion region. Since the wrong motion vector can be obtained with high possibility in the occluded area, a median filtering that less depends on the motion vector is applied to that area, and since the motion vector is continuous and robust in the non-occluded area, BDMC(Bi-Directional Motion Compensated interpolation) is applied to obtain interpolated image in that area. BDMC using the bi-directional motion vectors achieves good results when continuity and robustness of the motion vector is higher. Experimental results show that the proposed algorithm provides better performance than the conventional approach. The average gain of PSNR (Peak Signal to Noise Ratio) is approximately 0.16 dB in the test sequences compared with BDMC.