• Journal of the Korean Institute of Telematics and Electronics
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• v.12 no.4
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• pp.7-14
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• 1975

A significant new technique in the dsvelopment of micro-wave circuits is the process of untilization of coupled lines in the transverse electro-magnetic field. The bases for this technique are the application of even-and odd-mode characteristic impedances of the transmission line. This article describes the properties of directional couplers and explains a prccfdure usrd to design micro-strip directional couplers with the aid of the computer. The article also describes the experimental results obtained from seven microstrip couplers, which were built to verify the computer program and the approximate solutions. It can be seen that in cases at X-band where couplings of 10 to 20dB are required, the computer program and approximate solutions will produce good results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.3
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• pp.140-148
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• 2014

In this paper, We proposed Gaussian function as a basis of hybrid method. Hybrid method is to extrapolate late time and high frequency data using early time and low frequency data. This method takes advantages of both MOT and MOM as well as having shorter running time and smaller error. For this method a better basis function is required. We compared the performance of the result with proposed function and conventional basis including Hermite and Laguerre polynomial.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.02a
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• pp.163-166
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• 2008

이 논문에서는 MPEG-4 SVC 신호를 DVB-S2 전송시스템에 적용하여 Ka대역 위성방송서비스를 제공하는 전송방안에 대한 연구를 하였다. SVC신호는 계층 수를 2개로 제한하였으며, 이러한 다계층 신호를 DVB-S2 전송시스템에 적용하기 위하여, 성상도상에서 각 계층의 신호를 동기적으로 합치는 Hierarchical 변조방식과 각 계층의 전송스트림을 RF 주파수 상에서 비동기적으로 합치는 방식인 Layered 변조방식을 사용하였다. 각 전송방안에서 변조방식과 채널 부호율을 결합 소스/채널 부호화 방안에 따라 변화시켜 최적의 전송기법을 도출하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.149-154
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• 2021

Unlike or common images, Hyperspectral images were taken by continuous electromagnetic spectral into numerous bands according to wavelengths and are high-capacity high-resolution images. It has more information than ordinary images, so it is used to explore objects and materials. To reduce the amount of information in hyper-spectral images to be processed, band selection is utilized. Existing band selection techniques are heuristic techniques based on statistics, which take a long time and often lack generality and universality. To compensate for this, this paper utilizes quantization concept to draw representative bands through Discrete Range, we use them for band selection algorithm. Experimental results showed that the proposed technique performed much faster than conventional band selection methods, and that the performance accuracy was similar to that of the original even though the number of bands was reduced by one-seventh to one-tenth.

• Journal of Internet Computing and Services
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• v.18 no.5
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• pp.17-22
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• 2017

In a MPC coding using excitation source of voiced and unvoiced, it would be a distortion of speech waveform. This is caused by normalization of synthesis speech waveform of voiced in the process of restoration the multi-pulses of representation section. This paper present PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) used V/UV/S( Voiced / Unvoiced / Silence ) switching, position compensation in a multi-pulses each pitch interval and Unvoiced approximate-synthesis by using specific frequency in order to reduce distortion of synthesis waveform. Also, I was implemented that the PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) system and evaluate the SNRseg of PCFBD-MPC in coding condition of 8kbps. As a result, SNRseg of PCFBD-MPC was 13.4dB for female voice and 13.8dB for male voice respectively. In the future, I will study the evaluation of the sound quality of 8kbps speech coding method that simultaneously compensation the amplitude and position of multi-pulse source. These methods are expected to be applied to a method of speech coding using sound source in a low bit rate such as a cellular phone or a smart phone.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.58-66
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• 2011

In this paper, we propose a self-organized frequency allocation scheme for femto-cell deployment to avoid intercell interference, thereby reducing cell-registration failure. The proposed scheme follows two steps which if necessary manipulate frequency-band reallocation of existing femto-cells to accomodate newly incoming femto-cells. In the first step named "initial frequency allocation", each femto-cell collects neighboring femto-cells' frequency usage state by listening the broadcasting channels, and then selects one of interference-free frequency-bands. If no inference-free band is available, the second step named "frequency adjustment" starts, where frequency-band reallocation is properly performed from the aspect of overall performance improvement. Numerical results shows that the proposed scheme outperforms the best SINR scheme, which has been practically applied to femto-cell deployment, in terms of cell-registration failure probability and system overhead.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.185-190
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• 2015

In this paper we characterized and designed the waveguide antipodal finline transition at 57-65GHz frequency band in V-band for 5G mobile communication systems. Especially, we proposed the design method of spline taper for finline tapers by means of increasing curvature from linear taper. We could perform optimization more effectively by excluding improper regions for optimal performance from optimization using the method. Return losses and insertion losses of antipodal finline transitions were mainly affected by the taper shape of the finline. The resonances in the structure of the finline transition were the strongest enemies who deteriorate the performance of the transition. And we alleviated the resonances using semicircle shaped patch. The designed antipodal finline transition showed good performance as it showed less than -24.2dB of return loss and -0.24dB of insertion loss in the band(57-65GHz) which we suppose to use.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.69-75
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• 2004

In the paper, system is combined multiband system with DS-UWB techniques with properties including low peak-to-average power ratio, robustness to multiuser interference and excellent security. Because each sub-band is not satisfied with coherence bandwidth, rake receiver in each sub-band is applied to the Proposed system receiver. Output of rake receiver is combined by using Maximal Ratio combining technology. In this paper we mathematically analyse the BER of the DS-UWB system with singleband and multiband systems in the narrow interference channel condition and multi user interference channel condition, the simulation results show that proposed scheme is getting robuster with increasing of the number of subbands.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2674-2685
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• 1997

In this paper, the design and imprlementation of dual-band power amplifier which is used as a critical part for mobile phone to be simultaneously working at a dual band, 800MHz CDAM and PCS frequency band is described. DC operating point of power FET is limited to Class-B to enable long talk time considering that the tyupical power range of CDMA phones in working is around 10 to Class-B to enable long talk time considering that the typical power range of CDMA phones in working is around 10 to 15dBm, i.e., liner range. The power amplifier which employs two GaAs FETs with good linerity at a low operating point has duplexer cuplexer circuit to separate two frequency bands at input and output stage. Electromagnetic analysis for via holes and coupling between narrow transmission lines is included to design a circuit. Moduld size of 0.96CC($22{\times}14.5{\times}3mm^3$) and maximum module current of 130mA at output power range, 10 to 15dBm are attained. The power amplifer module has achieved ACPR performance with 2 to 3dB marging from IS-95 requirement at output powers, 23.5dBm for PCS and 28dBm for 800MHz CDMA respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.528-536
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• 2010

A monopulse feeder gives the most important impact upon the radiation pattern characteristics of a multi-function radar or a tracking radar which uses the space feed. It is described that the triple-mode type monopulse feeder which possesses the optimum aperture illumination for three monopulse channels is designed and measured in this paper. The measured results show that the designed feeder has not only the characteristics of the optimum aperture illimination in each channel and also very low return loss over the 10 % of fractional bandwidth at X-band. This means that the feeder provides the antenna system with low sidelobe level and high monopulse slope characteristics.