• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.49-56
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• 2007

The IEEE 802.15.4 low rate wireless personal area network is a protocol suitable for wireless sensor networks. Thus there has been growing interest in the IEEE 802.15.4 protocol in the home automation networks. This paper proposes a scheduling scheme obtaining optimal parameters regarding the IEEE 802.15.4 frame and subframes in the home automation networks. Guaranteed time slots (GTS) are exploited for the delivery of real-time traffic. Given a set of the requirements for bandwidths and periods assigned to nodes in the network, the beacon interval and the active/inactive subframe duration satisfying the requirements are selected considering the low duty cycle by the proposed scheme. Based on these parameters, analytic results provide the way to efficient use of network resources including energy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1206-1212
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• 2005

In this paper, we propose a novel antenna structure which uses the electric and magnetic currents so as to eliminate nulls on their radiation pattern. The tag antenna was matched to the conjugate impedance of the commercial tag chip using the modified double T matching network. The radiation efficiency is about $90\%$, and the bandwidth($S_{11}< -10 dB$) is 848${\~}$926 MHz. Also it shows the gain deviation between the maximum and minimum gains about 4 dB at any direction of the tag antenna at the operating frequency. The readable range of the tag is 1.7${\~}$2.4 m for an arbitrary rotation angle of the tag with a commercial tag chip.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.223-230
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• 2008

A CRLH-TL based compact metamaterial antenna on a magneto-dielectric material is proposed. The proposed antenna is composed of two patches and vias, which is loaded by a magneto-dielectric material constructed by SRRs. The characteristic of SRRs is studied, and the size reduction of the antenna by using the magneto-dielectric material is confirmed. The simulated resonant frequency of the antenna has showed a decrease of 7.13 % at - 1st-order resonant mode, and 23.9 % at zeroth-order resonant mode. A zeroth-order resonant antenna is fabricated and measured, which has a resonant frequency of 1.888 GHz, a bandwidth of 0.48 %, a gain of 0.534 dBi, and an efficiency of 51.7 %.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.403-409
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• 2013

In this work, a CMOS two stage differential power amplifier which includes Marchand balun, transformer and injection-locked buffer is presented. The power amplifier is targeted for 70 GHz frequency band and fabricated using 65 nm technology. The measurement results show 8.5 dB maximum voltage gain at 71.3 GHz and 7.3 GHz 3 dB bandwidth. The measured maximum output power is 8.2 dBm, input $P_{1dB}$ is -2.8 dBm, output $P_{1dB}$ is 4.6 dBm and maximum power added efficiency is 4.9 %. The power amplifier consumes 102 mW DC power from 1.2 V supply voltage.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.10-14
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• 2017

A reverberation chamber is widely used in mobile handset measurements due to its faster and simpler measurement process compared to traditional anechoic chambers. We propose an ultra-wideband inverse conical antenna design suitable as a reference antenna in a reverberation chamber. Traditionally, multiple discone antennas are needed to cover more than 10:1 operation bandwidth of a reverberation chamber. The proposed inverse conical antenna offers wideband impedance matching bandwidth by virtue of the linear impedance transition along its oblique side. The antenna is feasible to mount on the conductive walls which can be utilized as a ground to improve the matching bandwidth, antenna gain and radiation patterns. The antenna geometry is optimized using a 3D electromagnetic simulation tool and fabricated using a 3D printer. The measured results show that the antenna reflection coefficient lower than -10dB and radiation efficiency more than 70% at the frequency range of 0.65~7 GHz.

• Journal of IKEEE
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• v.11 no.4
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• pp.187-192
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• 2007

Since wireless sensor networks (WSN) have relatively narrow bandwidth and have limited memory space. Mosaic by inlaying images transmitted by adjacent sensors can provide wider field of view and smaller storage memory. Most WSN are used for surveillance purpose, image acquisition period should be sufficiently short, so that mosaic algorithm has to be run in real time. Proposed algorithm is derived by using the fact that position of sensor nodes are fixed and known. Transformation matrix can be calculated by using distance between sensor nodes and distance between sensor nodes and predefined object. Simulation result shows that proposed algorithm provides very short processing time whereas it preserves image quality.

• Journal of IKEEE
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• v.24 no.2
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• pp.536-542
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• 2020

This paper presents a nature-inspired wideband sprout-leaf shaped antenna with end-fire radiation pattern. A sprout-leaf shape angled-radiator was designed for wide beamwidth radiation patterns for motion detection sensors. An extended and truncated ground plane was used as a reflector for end-fire radiation patterns. To feed the balanced radiator, a broadband microstrip (MS) to coplanar stripline (CPS) balun was utilized with excellent amplitude and phase balance. The proposed antenna demonstrates wide frequency bandwidth from 8.5 to 14.5 GHz with wide beamwidth and the radiation efficiency of 90%. The measured gain is from 4 to 5 dBi and front-to-back ratio was 10 to 20 dB. It has been shown that the proposed antenna can be used for imaging sensors, phased array systems, and radars that require a wide bandwidth and a directional radiation pattern.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.21-26
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• 2016

With the increased desire of TV consumers for interactivity and personalization, IPTV has been rapidly spread in recent years. IPTV can provide a variety of services through hundreds of channels, but the explosion of TV channels makes users even more difficult to find their desired contents. In addition, the channel zapping delay of IPTV is serious due to the limited network bandwidth. To resolve these problems, this paper distinguishes hot and cold channels by exploiting the real-time viewing rate as well as each user's viewing history, and then, maintains hot channels in the hot list, which is searched first during channel navigation and also prefetched to support the preview of channels. Experimental results show that the proposed scheme improves the IPTV channel seek time significantly compared to existing channel seeking interfaces.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.27-31
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• 2006

Millimeter over Fiber (MMoF) technique modulates millimeter wave signal optically to transmit it through an optical fiber for long distances with small loss. MMoF system usually uses optical single sideband (OSSB) modulation scheme to reduce fiber chromatic dispersion and obtain high bandwidth efficiency. The optical link of MMoF system using OSSB is treated as a nonlinear amplifier, and the AM/AM characteristic function of the amplifier is a Bessel function of the first kind of order 1. In this paper, we investigate the performance of OFDM MMoF system considering nonlinearity of OSSB modulation. We estimate a power of the nonlinear distortion noise to analyze the theoretical bit error rate(BER), and perform a simulation to verify the theoretical BER.

• Journal of Internet Computing and Services
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• v.11 no.2
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• pp.143-153
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• 2010

When providing high quality panoramic video across the Internet, mobile communications, and broadcasting areas, it requires a suitable video codec that satisfies both high-compression efficiency and random access functionality. The users must have high-compression efficiency in order to enable video streaming of high-volume panoramic data. Random access allows the user to move the viewpoint and direction freely. In this paper, we propose the parallel processing scheme under cell units in order to improve the performance of streaming service for large screen panoramic video in 10Mbps bandwidths based on H.264/AVC with high compression rate. This improved algorithm divides a screen composed of cells less than $256{\times}256$ in size, encodes it, and decodes it with the cells in the present view. At this point, encoding/decoding is parallel processed by the present cell units. Also, since the cells only included in the present view are packed and transmitted, the possible processing of not extricating blocks is proven by experiment.