• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.107-113
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• 2016

In this paper, we suggest a design method of a wide-band Butler matrix working at 5.9 GHz for V2X communication antennas. Since V2X communication needs beam-forming and beam-steering antennas to make transportation systems, mobile comm platforms, saturated frequency-resources, and signal TX-and-RX smart, multi-functional, resolved, and efficient utmost, respectively, the proper Butler matrix and its radiating elements as a low-profile geometry are realized. The constitutive components of the basic Butler matrix of a narrow band are designed first. And then, it is extended to a wide-band version to make its frequency-shift less affected by the event of the antenna system being mounted on a car body. The beam-forming and beam-steering performance is presented as the common feature tagged along with the different bandwidths of the frequency responses as the comparison between the narrow- and wide-band cases.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.151-164
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• 2003

In this paper, induction motor drives with low switching acoustic noise based on the 2 phase modulated RLL(Random Lead-Lag) PWM is proposed and implemented. The proposed switching method is much bettor than 3 phase modulated RLL-PWM from the standpoint of the broadening effect of the acoustic noise spectrum. Along with the randomization of PWM Pulses, SVM(Space Vector Modulation) is executed in the TMS320C31 DSP(Digital Signal Processor). To verify the validity of the proposed RPWM(Random PWM), the experimental study was tried. The experimental results show that the performance of the proposed method and the 3 phase center-aligned SVM / conventional RLL-PWM are nearly the same from the viewpoint of the constant v/f centrel. But, in case of the proposed 2 phase modulated RLL-PWM, the spectrum characteristics of the voltage and the switching acoustic noise are shown to have better broadening effect than 3 phase modulated one.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.525-532
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• 2007

Recently, broadband access networks have been competitively deployed all over the world with the development of various multimedia services for such a network. ETRI(Electronics and Telecommunications Research Institute) built the FTTH(Fiber-to-the-Home) service center to develop a next-generation equipment and a high-quality service/platform as well as to promote domestic industry in the field of optical communication. The FTTH service center has a variety of test equipments such as FTTH standard testbed for a BMT(Bench Mark Test), a network operation center, and IPTV service equipments. Also, ETRI deployed a new type of commercial optical access networks cooperating with ISP(Internet service provider). In this paper, we analyzed the quality degradation appeared in QoE(Quality of Experience), when IP data broadcasted from the FTTH service center is transmitted to subscribers through the commercial optical access network. Moreover, we proposed a noble solution to address this problem.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.81-88
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• 2011

This paper presents a design of spiral antenna with broad bandwidth for non-linear junction detector(NLJD). An elliptical patch as radiating element located on center position of radiating surface, as well as the spiral elements on radiating surface was designed for broad bandwidth of spiral antenna. An antenna ground structure generating the multi resonance by spiral slit inserted on ground surface was also proposed. In order to realize high directivity and high gain of the proposed antenna, the cavity wall made of Fr4-epoxy and the metal cap were considered in design. As a result, the calculated gain of antenna with metal cap was improved about 3 dB with comparison of antenna without metal cap and the measured main beam directivity toward -z axis direction agreed well with calculation result. The measured axial ratio satisfied the circular polarization within -z axis ${\pm}45^{\circ}$ at design frequency bands and showed reasonable agreement with prediction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.439-444
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• 2011

To determine the test gases for gas appliances of new gas group, the interrelation between gas interchangeability, including thermal efficiency, of 13A gas appliances and present 13A test gases was experimentally investigated. The test results show that the Wobbe indices in the case of incomplete combustion and the flame lifting limit gas for the new gas group are respectively 2% higher than the upper limit and 1% lower than the lower limit of the Wobbe index range. The most suitable composition of R gas is 96 mol% of methane and 4 mol% of propane; LNG could be also used as R gas. Further, analysis results showed that the hydrogen concentration of flash back limit gas could be lowered from 30 vol% to 23 vol%.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.4
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• pp.73-79
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• 2015

Enhanced bandwidths of the GPS microstrip patch antennas applied by a Wilkinson power divider and a quadrature hybrid were compared. The square patch was designed, and fed by the two port probes for the circuit application. The Wilkinson power divider and quadrature hybrid circuit were designed, and applied to the patch antenna. The designed patch and two circuits were implemented on the FR4 board, and combined together. The measurement of the bandwidth within a voltage standing wave ratio (VSWR) of 2: 1 were 36.5% (1,200~1,775 MHz) in the case of the Wilkinson power divider and 29.84% (1,230~1,700 MHz) in the case of the quadrature hybrid. Axial ratios (AR) in 3dB were 17.14% bandwidth (1,360~1,630 MHz) and 15.87% bandwidth (1,400~1,650 MHz), respectively. The application of the Wilkinson power divider is wider than that of the quadrature hybrid. The peak gains in the anechoic chamber at the GPS center frequency were measured as 2.84 dBi and 2.75 dBi, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.37-41
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• 2004

As mobile communication devices use wide bands for large data transmission, Low Temperature Co-fired Ceramic(LTCC) has been a candidate for module substrate, for it provides better electrical properties and enables various embedded passive devices compared to conventional PCB. The LTCC, however, has applied in limited area because of non-uniform shrinkage. Hybrid heating was developed to raise sample temperature uniformly in a short period of time This leads to unidirectional sintering which enables sample to be sintered layer by layer from the bottom, resulting in more stable shape of interconnection at the top surface of the sample than conventional electric furnace heating. When sintering properties of substrate and electrical/mechanical properties of interconnection were compared, hybrid heating showed possibility to be applicable to substrate miniaturization and interconnection densification superior to electric furnace heating.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.215-220
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• 2016

In this paper, a wideband antenna accomplished by adding a double sleeve of a rectangular planar monopole structure is proposed. In order to impedance matching of proposed antenna, the antenna performance was improved by adding two gap sleeves and outer sleeve for double sleeve structure. HFSS simulator of ANSYS corp. was used in order to confirm the antenna parameter characteristic. According to the simulation results, the VSWR was less than 2 for the range of 2.5GHz~10.5GHz. The frequency bandwidth is 8GHz. The frequency range of the actual fabricated antenna was 2.92GHz~10.32GHz, the frequency bandwidth is 7.4GHz. The measured radiation pattern frequency is 3GHz, 6GHz and 9GHz. The results are similar with dipole antenna pattern in all frequency. The antenna size is $40{\times}40mm^2$. The utilization possibility of the ultra-wideband planar monopole antenna could be confirmed according to compare and analyze the simulation and measurement data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1416-1426
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• 2008

In this paper, we present a small size and multiband directional dipole antenna for mobile communication repeaters. In the omni-directional dipole antenna, a planar reflector under the dipole provides improved directivity in front-direction with wide beamwidth. In order to miniaturize the directive dipole, the size of the reflector is reduced. A vertical stub on the reflector is proposed to enhance the front-directivity of the radiation pattern and mitigate the backward radiation due to the reduced reflector. Furthermore, we use horizontal stubs on edge of vertical stub to obtain additional reduction of the antenna size. To meet the current demand of wireless communication service, the designed antenna shows wideband characteristic by employing electromagnetic coupled two-dipoles with dual-resonance frequencies.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.376-380
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• 2014

In the present study, oblique L-shaped monopole slot antenna with broadband characteristic is newly proposed. For bandwidth enhancement as well as size reduction, L-shaped slot with two open-terminations on the ground edge is used. The lower part of L-shaped slot comprises oblique form for bandwidth enhancement in low frequency band, whereas its higher part comprise tapered form for its enhancement in high frequency band. The short-circuit terminated microstrip line which is generally known to be more useful for bandwidth enhancement than open-circuit termination is used. The measured impedance bandwidth($S_{11}{\leq}-10dB$) and gain of the fabricated antenna have been observed to be 4.72 GHz (2.28~7 GHz) and more than 3dBi over the passband respectively.