• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1085-1090
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• 2010

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as Cellular CDMA and Korean PCS. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum UWB source and an impulse radio UWB source, to a Cellular CDMA and K-PCS digital transmission system. The average frame error rate degradation of each system arc presented. From these experimental results, we show that in all practical cases UWB system can coexist with Cellular CDMA and K-PCS terminal without causing any dangerous interference.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.11a
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• pp.98-99
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• 2004

(1) Using high-frequency induction heating sintering and spark plasma sintering method, the densification of WC-Ni hard materials was accomplished using ultra fine power of Ni and WC. (2) Nearly fully dense WC-Ni could be obtained within 1 min. (3) Relative density and mechanical properties of WC-Ni obtained by HFIHS were high than those obtained by SPS. And WC grain size made by HFIHS was smaller than that made by SPS. (4) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by HFIHS were $13MPa{\cdot}m^{1/2}\;and\;1950kg/mm^2,\;13.5Mpa{\cdot}m^{1/2}\;and\;1810kg/mm^2,\;14.4MPa{\cdot}m^{1/2}\;and\;1690kg/mm^2$, respectively for 60MPa and an induced current for 90% output of total capacity, 15KW. (5) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by SPS were $12.2MPa{\cdot}m^{1/2}\;and\;1796kg/mm^2,\;12.9MPa{\cdot}m^{1/2}\;and\;1725kg/mm^2,\;13.6MPa{\cdot}m^{1/2}\;and\;1597kg/mm^2$, respectively for 60MPa and the electric current of 2500 A

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.7-11
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• 2009

An Ultra-WideBand(UWB) Low-Noise Amplifier(LNA) is proposed and is implemented in a $0.18-{\mu}m$ CMOS technology. The proposed UWB LNA provides excellent wideband characteristics by combining a High-Pass Filter (HPF) with a conventional resistive-loaded LNA topology. In the proposed UWB LNA, the bell-shaped gain curve of the overall amplifier is much less dependent on the frequency response of the HPF embedded in the input stage. In addition, the adoption of fewer on-chip inductors in the input matching network permits a lower noise figure and a smaller chip area. Measurement results show a power gain of + 10 dB and an input return loss of more than - 9 dB over 2.7 to 6.2 GHz, a noise figure of 3.1 dB at 3.6 GHz and 7.8 dB at 6.2 GHz, an input PldB of - 12 dBm, and an IIP3 of - 0.2 dBm, while dissipating only 4.6 mA from a 1.8-V supply.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.209-212
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• 2001

A flame detector responds either to radiant energy visible to the human eye or outside the range of human vision. Such a detector is sensitive to glowing embers, coals, or flames which radiate energy of sufficient intensity and spectral quality to actuate the alarm. An infra-red detectors can respond to the total IR component of the flame alone or in combination with flame flicker in the frequency range of 5 to 30 Hz. A major problem in the use of infrared detectors receiving total IR radiation is the possible interference of solar radiation in the infrared region. When detectors are located in places shielded from the sun, such as vaults, filtering or shielding the unit from the sun's rays is unnecessary. In this study, we proposed method for redue a false alarm with using filtering & sensor technology for distinguish of causes of raise a false alarm and pure flame.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.421-427
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• 2012

To improve the lubricity of ultra low sulfur diesel, vegetable oil-based alkanol amide derivatives were prepared and their lubricity properties were studied. To synthesize the alkanol amides, we conducted the amidation reaction of diethaolamine High Frequency Reciprocating Rig (HFRR) and the fatty acid methyl esters, obtained by the continuous transesterification of methanol and several vegetable oil, such as soybean oil, palm oil and coconut oil. The synthesized amides were soluble in ultra low sulfur diesel in the concentration range of ca. 1 wt%; the lubricating properties of ultra low sulfur diesel containing 120 ppm of amides were measured using an HFRR method. It was found that the wear scar diameter in the pure ultra low sulfur diesel decreased significantly from 581 ${\mu}m$ to 305~323 ${\mu}m$ upon the addition of the amides, indicating that lubricating properties of the diesel were improved. On the other hand, the types of vegetable oils did not affect the wear scar diameters, implying that lubricating properties of the diesel did not depend strongly on the structures of alkyl groups of alkanol amide derivatives. When we measured the lubricating properties of the one type of diesels containing various amounts of alkanol amide, we observed that the wear scar diameter decreased drastically with increasing the amide concentration, meaning that the lubricity improved with the amide concentration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1161-1167
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• 2004

The conventional PLL(phase locked loop) frequency synthesizer takes a long switching time because of the inherent closed-loop structure. The digital hybrid PLL(DH-PLL) which includes the open-loop structure into the conventional PLL synthesizer has been studied to overcome this demerit. It operates in high speed, but the hardware complexity and power consumption are the serious problem because the DLT(digital look-up table) is usually implemented by the ROM which contains the transfer characteristic of VCO(voltage controlled oscillator). This paper proposes a new DH-PLL using a very simple DLT-replacement digital logic instead of the complex ROM-type DLT. Also, a timing synchronization circuit for the very small over-shoot and shorter settling time is designed for the ultra fast switching speed at every frequency synthesis. The hardware complexity gets decreased to about $28\%,$ as compared with the conventional DH-PLL. The high speed switching characteristic of the frequency synthesis process can be verified by the computer simulation and the circuit implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.145-152
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• 2009

Ultra-wideband communication systems for impulse radio have merits that are possible for either high resolution ranging system or radio determination. Conventionally, in order to accomplish these functions, the rapid analog to digital convertor (ADC) is necessary to apply radio determination system operating in time domain. However, considering that low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces the high resolution ranging system operating in frequency domain with using low sampling rate ADC, and a new non-coherent ranging scheme utilizing analog Frequency Modulation (FM) mode for the frequency domain transformation. To verify the superiority of the proposed ranging algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• Journal of Advanced Navigation Technology
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• v.22 no.1
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• pp.31-36
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• 2018

In this paper, we designed and implemented an ultra wideband(UWB) antenna with band rejection characteristics. The proposed antenna consists of a planar radiation patch with slots and ground planes on both sides. Due to the slots in the radiation patch, the antenna shows band rejection characteristics. U-type slot contributes for wireless local area network(WLAN, 5.15~5.825 GHz) band rejection and n-type slot contributes for X-Band(7.25~8.395 GHz) band rejection. To make voltage standing wave ratio(VSWR) less than 2.0 for UWB frequency band except rejection bands, the shapes of planar radiation patch and ground plane was modified. The Ansoft 's high frequency structure simulator(HFSS) was used for the design process and simulations of the proposed antenna. The simulated antenna showed VSWR less than 2.0 for all UWB band excepts for dual rejection bands of 5.15 ~ 5.94 GHz and 7.02 ~ 8.45 GHz. And measured VSWR for the implemented antenna is less than 2.0 for all UWB band of 3.10~10.60 GHz excluding dual rejection bands of 5.12~5.95 GHz and 7.20~8.58 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.178-184
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• 2015

This paper proposes a hardware architecture for high performance Deblocking filter(DBF) in High Efficiency Video Coding for UHD(Ultra High Definition) videos. This proposed hardware architecture which has less processing time has a 4-stage pipelined architecture with two filters and parallel boundary strength module. Also, the proposed filter can be used in low-voltage design by using clock gating architecture in 4-stage pipeline. The segmented memory architecture solves the hazard issue that arises when single port SRAM is accessed. The proposed order of filtering shortens the delay time that arises when storing data into the single port SRAM at the pre-processing stage. The DBF hardware proposed in this paper was designed with Verilog HDL, and was implemented with 22k logic gates as a result of synthesis using TSMC 0.18um CMOS standard cell library. Furthermore, the dynamic frequency can process UHD 8k($7680{\times}4320$) samples@60fps using a frequency of 150MHz with an 8K resolution and maximum dynamic frequency is 285MHz. Result from analysis shows that the proposed DBF hardware architecture operation cycle for one process coding unit has improved by 32% over the previous one.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.728-732
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• 2010

GIS(Gas insulated switching gear) is power equipment with excellent dielectric strength and is economy merit in high confidence and stability. Recently, because equipment of GIS was occurring problem of confidence used for a long time, partial discharge on-line diagnosis systems have been importantly recognized. Partial discharge (PD) detection is an effective means for monitoring and evaluation of dielectric condition of gas insulated system (GIS). The ultra-high-frequency (UHF) PD detection technique can detect and locate the PD sources inside GIS by detecting electromagnetic wave emitted from PD source. Therefore, real-time diagnostic system using UHF detection method has been developed for this application is being expanded gradually. However, the signal of partial discharge occurring in SF6 gas is very weak and susceptible to external noises which mainly consist of PD in air. Thus, it is important to distinguish the PD in SF6 gas more sensitively from the external noises. Unfortunately, these external noise signals and the partial discharge signals have very similar characteristics. Therefore, to solve this problem, we need the signal processing method for distinguish partial discharge signals with external noise signals for improvement of SNR(signal to noise ratio) and sensitivity. In this paper, we proposed internal signal processing method for removing external noise signals with built-in pre.amplifier and frequency conversion circuit.