• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1159-1164
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• 2006

Broadband antennas have late-time ringing by multi-reflections between feed points and 0pen ends of the antennas, which indicates the narrowband nature of the antenna. The resistive loading has been used to reduce the late time ringing that is important for ground penetrating radar and resonance detection systems in order to prevent masking of target. In this paper, we design an ultra wide band antenna with resistive loading technique to reduce the internal reflections within the antenna.. The designed antenna is implemented and tested to show inIproved characteristics.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.1
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• pp.19-24
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• 2003

A very small size 2.4 GHz ISM band BPF(Band Pass Filter) is realized using LTCC Multi-layer technology. Proposed design method enables to achieve BPF size $2.0\times1.2\times0.8mm^3$. A $lambda/4$ resonator with shunt-to-ground loaded capacitor is used to shorten resonator length, achieving higher quality factor. Also this resonator enables BPF to improve out-of-band rejection. Coupling coefficients between coupled strip-line resonators and external quality factor (Qe) of a resonator are derived and applied to the filter design. The measured results show good agreement with simulated data.

• Fire Science and Engineering
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• v.30 no.2
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• pp.62-67
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• 2016

In this study, the optical depth is analyzed with the effects of droplet size distribution of the water curtain nozzle to attenuate the radiative heat transfer. The HELOS/VARIO equipment is used for the measurement of the droplet size distributions. The spray characteristics are quantified by the investigation of Deirmenjian's modified gamma distribution function. The distribution constant of the nozzle can be obtained as ${\alpha}=1$ and ${\gamma}=5.2$. The generalized equation of the optical depth related with the droplet size distribution is introduced. These results will be applicable to the analysis of the design condition of the water curtain nozzle.

• Journal of the Korea Computer Industry Society
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• v.10 no.4
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• pp.135-142
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• 2009

In this thesis, we designed and implemented a tracking filter which can be used for FH/2-FSK communication system in band of 40~60[MHz]. After measuring a performance of a tracking filter, an insertion loss was measured from 3.7 to 4.3 dB, depending upon a hopping center frequency. The 3 dB bandwidth of a tracking filter was specified 5.1 to 5.33% depend upon a hopping and 30/3 dB shape factor indication for interrupting property of a filter shows 6.828 to 6.98 satisfying a required specification. Also the attenuation $2{\times}f_0$, the characteristic parameter for interference degree, was specified 46~52dB, not satisfying a required specification.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.2
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• pp.93-100
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• 2008

In this paper, Low Noise Block down converter(LNB) is designed for a Ka-band satellite television receiver only(TVRO) using commercially available MMIC. Designed Low Noise Block down-converter is composed of three stage amplifiers involving input noise matched at first amplification stage, image reject band pass filter, frequency mixer and intermediate frequency amplification. Through LNB Module power budget to obtain gain and attenuation, Optimum LNB devices satisfying Ka-band LNB technical specification are selected. Experimental results of designed Ka-band LNB yields conversion gain of over $58{\pm}1dB$, noise figure of less than 1.5dB and phase noise of -94.6dBc @10KHz.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.56-61
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• 2007

In this paper, a circulating current reduction approach for the parallel operation of fuelcell systems with Z-source inverters is investigated. The carrier phase shifted SPWM(Sinusoidal Pulse Width Modulation) is used as a modulation method since it has an advantage in reducing output current harmonics. However, when this technique is applied to the parallel operation of Z-source inverters, it additionally produces circulating currents. A coupled circulating current reactor is used to reduce circulating current generated by the parallel operation of Z-source inverters and to reduce output current harmonics. The proposed circulating current reduction approach using coupled circulating current reactors is verified through simulation and experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.563-568
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• 2003

In this paper, a miniaturized parallel coupled bandpass filter using multi-layered LTCC(Low Temperature Co-fired Ceramics) substrate for SOP(System-On-Package) is proposed for applications to wireless communication systems. The fabricated BPF is composed of five 106${\mu}{\textrm}{m}$ thick LTCC layers and its size is 5.24mm x 4.3mm x 0.53 mm. The measured characteristics of the BPF show the center frequency of 5.8GHz, bandwidth of 200MHz, insertion loss of 2.326dB and return loss of 13.679dB. In addition, the attenuation is 28.052dB at 4.7GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.98-105
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• 2011

Reduced complexity codebook searching for Quantized Equal Gain Transmission(QEGT) is proposed over MIMO-OFDM systems. QEGT codebook is divided into M groups of Q index members. Each group has a representative index. At the 1st stage only the representative indices are searched then the best index is selected. At the 2nd stage the optimum index is determined only among the group of the selected representative index. This strategy reduces the overall index search algorithm comparing to the conventional methods. Monte-Carlo simulation shows that the searching complexity is reduced, but the link-level performance is still almost the same as the conventional methods when the number of transmission antennas are 3 to 7.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.395-402
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• 2003

The capacity of a CDMA cellular system is determined by the amount of interference, therefore the exact estimation of interference is important to evaluate the system performance. In this paper, we propose an approximated equation which calculates reverse link other cell interference in the CDMA cellular systems. The equation using Riemann-Zeta function has a property that it is useful in case of any radio propagation loss exponents. And we compare calculation results with simulation results in other to verify it's usefulness. The upper bound of system capacity calculated with the proposed approximated equation gives almost alike result with the simulation. The proposed interference bound is useful to calculate system capacity and to evaluate some algorithm in a hierarchical cellular system which must be considered various propagation exponents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.725-734
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• 2006

As a sequel to Part 1, the performance characteristics of the cell averaging (CA), greatest of (GO), and smallest of (SO) constant false alarm rate (CFAR) processors in nonhomogeneous environment are obtained and compared when receiving antenna diversity is employed in the pseudonoise (PN) code acquisition of direct-sequence code division multiple access (DS/CDMA) systems. Unlike in homogeneous environment, the GO CFAR processor is observed to exhibit the best performance in nonhomogeneous environment, with the CA CFAR processor performing the second best.