• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.47-51
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• 2013

In this paper, we present design and test results of a Ka-band dual-band ortho-mode transducer (OMT) for use in a feed assembly for the very small aperture terminals (VSATs). The designed ortho-mode transducer have wideband characteristics to separate the signals that have two orthogonal linear polarizations operating at 20GHz of receive frequency band and at 30GHz of transmit frequency band. In addition, in order to reduce the volume of the feed assebly, a Boifot based ortho-mode transducer has been designed with a dual-band. Experimental results for the design verification, the return loss in the receive band and in the transmit band for the horizontal polarization showed over 20dB and 21dB, respectively, and for the vertical polarization showed over 20dB and 24dB, respectively. The port isolation for the horizontal polarization and the vertical polarization showed over 43dB and 52dB, respectively, in the receive band and in the vertical band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.66-69
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• 2016

In this paper, we suggests a Ka-band LNB considering next-generation UHD satellite TVRO. Since Ka-band has grater attenuation than Ku-band in atmosphere, we designed the low-noise down-converter to improve receiving sensitivity and to extend a dynamic range of receiver. It aims to compensate a quality of ultra high definition transmission signal for rainfall. The low-noise block diagram consists of a three-staged amplifier (LNA), band-pass filter for deleting image (BPF), mixer and IF when considering nonlinear characteristics in the receiver RF front end module. Also, we showed a LNB through optimization processes affecting dynamic range directly in receiver FEM. Asa resuly of experiment, the gain of low-noise down-converter show between 58.5dB and 60.7dB, the noise figure has a high characteristic as 1.38dB. Finally, the phase noise of local oscillator is -63.10dBc at 100MHz offset frequency.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.40-49
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• 2008

A Frequency synthesizer for mobile-DTV applications is implemented using $0.18{\mu}m$ CMOS process with 1.8V supply. PMOS transistors are chosen for VCO core to reduce phase noise. The measurement result of VCO frequency range is 800MHz-1.67GHz using switchable inductors, capacitors and varactors. We use varactor bias technique for the improvement of VCO gain linearity, and the number of varactor biasing are minimized as two. VCO gain deterioration is also improved by using the varactor switching technique. The VCO gain and interval of VCO gain are maintained as low and improved using the VCO frequency calibration block. The sigma-delta modulator for fractional divider is designed by the co-simualtion method for accuracy and efficiency improvement. The VCO, PFD, CP and LF are verified by Cadence Spectre, and the sigma-delta modulator is simulated using Matlab Simulink, ModelSim and HSPICE. The power consumption of the frequency synthesizer is 18mW, and the VCO has 52.1% tuning range according to the VCO maximum output frequency. The VCO phase noise is lower than -100dBc/Hz at 1MHz at 1MHz offset for 1GHz, 1.5GHz, and 2GHz output frequencies.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.28-33
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• 2011

Recently, the investigation of the cognitive radio (CR) system is actively progressed as one of the methods for using the frequency resources more efficiently. In CR systems, when the frequency band allocated to the incumbent user is not used, the unused frequency band is assigned to the secondary user. Thus, the FFT input signals corresponding to the actually used frequency band by the incumbent user are assigned as '0'. In this paper, based on the fact that there are many '0' input signals in CR systems, a low-power FFT design method for NC-OFDM is proposed. An efficient zero flag generation technique for each stage is first presented. Then, to increase the utility of the zero flag signals, modified architectures for memory and arithmetic circuits are presented. To verify the performance of the proposed algorithm, 2048 point FFT with radix-24SDFstructureisdesignedusingVerilog HDL. The simulation results show that the power consumption of FFT is reduced considerably by the proposed algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1038-1044
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• 2011

In this paper, the multichannel intermediate frequency transceiver for broadband multimedia system is designed and the experimental results are analyzed. Basic elements of the transceiver such as frequency synthesizer, amplifier, mixer, automatic gain control amplifier are introduced. The analysis technique described here applies not only to amplifier but also to any other nonlinear components such as mixers and frequency doubler. Through the investigation of the power spectrum density of the transmitted signal, the phase noise of the local oscillator is evaluated below 70 dBc/kHz. The frequency characteristics of the modulated signal is flat within the system bandwidth. Also the effects of adjacent channel interference and supurious emission are analyzed. And the function of automatic gain control amplifier is well operated.

• The KIPS Transactions:PartB
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• v.10B no.3
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• pp.311-320
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• 2003

The Optimal filter yielding optimal texture feature separation is a most effective technique for extracting the texture objects from multiple textures images. But, most optimal filter design approaches are restricted to the issue of supervised problems. No full-unsupervised method is based on the recognition of texture objects in image. We propose a novel approach that uses unsupervised learning schemes for efficient texture image analysis, and the band-pass feature of Gabor-filter is used for the optimal filter design. In our approach, the self-organizing neural network for multiple texture image identification is based on block-based clustering. The optimal frequency of Gabor-filter is turned to the optimal frequency of the distinct texture in frequency domain by analyzing the spatial frequency. In order to show the performance of the designed filters, after we have attempted to build a various texture images. The texture objects extraction is achieved by using the designed Gabor-filter. Our experimental results show that the performance of the system is very successful.

• 전기의세계
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• v.14 no.4
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• pp.22-27
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• 1965

우리나라의 speaker제작의 역사는 얼마되지 않을 뿐더러 자급자족의 영역을 못 벗어나고 있다. Weston speaker, 자사내에서 자급자족하고 있는 금성사제 speaker등 완전히 질량의 단계에 못들어가고 있는 실정이다. 그나마 성능면에서도 뒤떨어짐을 면할 수 없는 실정이다 .부속품 예컨데 자철 coil접착제등 거이 매매회사에서 직수입하고 있는 형편인것 같다. 물론 종합공업이 발달해야만 되겠기에 단편적 발달은 기하기 어려울 줄 안다. 그러나 speak의 조립 공정에서 끝마치고 있는 형편이고 보면 한심할 지경이다. 물론 speaker제작이라고 하는 것은 극히 delicacy한 면을 가지고 있다. 즉 효율은 $B^{2}$에 비례하는것은 당연하지만 효율을 높이고저 공기부하의 저항을 크게 할려면 corn의 입경이 크게 되므로 자연적으로 진동계의 질량이 크게되며 또 voice coil의 저항을 적게하자니 coil가 필연적으로 굵게되어 길이가 짧게 될 뿐만아니라 air gap 이 크게되어 자속밀도 B가 적게 되는 상반관계가 있다. Cabinet, baffle, corn, corrugation, speaker system등을 가장 합리적으로 설계할 필요가 있다. 이 실험결과를 보고함으로서 speaker연구에 대한 욕구를 갖고 의욕적인 계기가 되었으면 한다. Voice coil 의 turn수를 바뀌었을때 impedance을 측정하였으며 turn수와 음압level 및 주파수 관계를 알아보았다. 그리하여 중형 speaker의 주파수특성을 알아 설계에 기여하고저 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.290-293
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• 2007

RFID 시스템은 주파수마다 다른 인식 거리를 가지며, 장거리 시스템의 900MHz의 경우 1m에서 최대 10m까지 인식 범위를 가진다. 주파수는 거리에 의하여 해당 파장이 감쇠하는 현상이 생하며, PSK 질문기에서 발생하는 전파는 1/4파장 변화에 의하여 출력 신호 극성이 반전되며 허용 인식범위 내 응답기에서도 적합한 통신이 안되는 영역이 발생하였다. 본 연구에서는 900MHz RFID 장비를 기본으로 안테나와 태그의 위치를 변경하여 테스트를 진행하여 어떤 지정에서 음영구역이 발생하는지 테스트를 진행하고, 문제점이 발생하는 원인에 대하여 논하며 이런 문제점을 해결하기 위하여 일본에서 2.4GHz RFID 응답기에서 사용하는 베이스 밴드 FSK 변조회로를 기반한 900MHz RFID 응답기 설계방안을 제안한다.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2004.06a
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• pp.106-111
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• 2004

밀리미터파 대역(30∼300GHz)의 전파에 대한 관심이 증가하면서 NRD(Non Radiative Dielectric)에 대한 관심이 커지고 있다. NRD Guide 에서는 평행한 평판 전도체의 간격을 반 파장 이하로 좁게 함으로써 공기 영역에서는 차단 상태가 되고 유전체 내에서는 차단상태가 해소되어 밀리미터파의 신호가 방사되지 않고 전송 될 수 있는 특성을 가진다. 밀리미터 웨이브를 발진시키기 위해 밀리미터파 대역에서 쉽게 동작하고 비교적 손쉽게 구할 수 있는 Gunn 발진기의 발진소자인 Gunn Diode를 사용한다. 본 논문에서는 실험을 통해 스트립 금속 공진기로 공진 주파수를 미조정하여 비방사유전체선로를 통한 밀리미터파 대역의 주파수특성을 분석하고 이러한 특성을 이용하여 60GHz 대역 송신기의 발진회로 설계를 다루었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.5
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• pp.340-348
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• 1986

The design of two-dimensional zero-phase FIR digital filters by transformations is a popular and well-developed technique, but is suffers from the disadvantage that in its current form the filters with only four quadrant symmetry can not be designed exactly circular symmetry at frequencies far from the origin. it is shown how symmetry requirement for the filters with any number of dimensions can be fulfilled with arbbitrary percision by adapting transformation with the appropriate series expansions. this transformation has been known generally as the McClellan transformation. In this paper, a simple method for ensuring exelent circular symmetry at frequencies far from the origin is presented. This method which employs the Modified Mcclellan trnsformation for the design of 2-D FIR filter form 1-D FIR filters is quite useful for the design of 2-D FIR filters with multiple cutoff boundaries such as band-pass filters.