• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.958-964
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• 2005

In this thesis, the matching network at the local oscillator port of the sub-harmonic mixer is optimized for reducing the conversion loss. A downconverter for point to point system applications is designed and fabricated using the such sub-harmonic mixer. The sub-harmonic mixer achieved the conversion loss of 11.8 dB at the 12 dBm input power of the local oscillator and the isolation of less than -40 dB. The downconverter achieved the IF output power flatness of 2 dB and the total noise figure of 5.9 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1198-1206
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• 2003

In this paper, a MMIC waveguide mixer module based upon the novel suggested mode converter for wave-guide-to-microstrip transition was fabricated and measured. The insertion and return losses of the mode converter was optimized by compensating the discontinuity effect between ridge and microstrip with the modification of 50 $\Omega$ microstrip line pattern. Due to the low loss nature of the mode converter, a millimeter wave MMIC mixer chip can be successfully applied as a waveguide module for mmW waveguide communication system. The measured results of the module showed the successful MMIC chip application in waveguide and the negligible degradation of the supplied chip specification.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.7B
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• pp.891-894
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• 2001

본 논문에서는 능동 배열 안테나에서 RF 대신 중간주파수를 이용하여 빔 추적을 하는 방법이 연구되었다. 안테나의 각 배열은 전압제어 발진기, 위상추적기, 혼합기와 결합되어 있으며 혼합기는 안테나 상에서 직접 RF 신호를 직접 중간주파수 신호로 변환시킨다. 전압제어 발진기 입력은 위상추적기에 의하여 조절되며 배열 안테나의 주사범위는 위상추적기와 전압제어발진기에 의하여 결정되었다.

• Journal of Energy Engineering
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• v.4 no.1
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• pp.85-94
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• 1995

본 연구에서는 최근 차량용 대체연료로서 주목받고 있는 천연가스의 연소특성을 규명하기 위해 밀폐된 정적연소실을 이용, 당량비, 초기압력 및 점화위치 변화에 따른 연소실험을 행하였으며, 그 결과 다음과 같은 결론을 얻었다. 메탄-공기 예혼합기의 화염전파과정은 이론혼합기 부근에서 구면형으로 진행되는데 반해, 과농 또는 과박 혼합기 그리고 점화위치가 연소실 벽면에 가까울수록 타원형으로 진행되며, 초기압력이 증가함에 따라 화염전파는 느려진다. 화염전파속도와 연소 속도는 초기압력이 낮고 점화위치가 연소실 중심에 가까울수록 빠르며, 당량비 1.0∼1.1 사이에서 최대치를 보인다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.53-60
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• 2002

Based on the analyses of the single transverse injection in supersonic flow fields, the mixing characteristics of dual transverse injection of hydrogen in supersonic air flow are studied with computational methods. Three-dimensional Navier -Stokes and the k-$\omega$ SST turbulence model were used. A parametric study is conducted with the variation of the distance between two injectors. The flow patterns and the mixing characteristics of two injection flows are very different from each other, and the flow patterns and the mixing characteristics of the rear injection flow are strongly influenced by those of the first injection flow. The increase of the distance between two injectors up to a specific distance results in the increase of mixing rate and penetration of fuel. However, the increase of the distance over the specific distance results in the decrease of mixing rate and penetration of fuel. From the results it can be stated that there exists a distance between two injectors for optimum mixing characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.472-478
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• 2003

In this paper, a near zero If mixer was designed in cascode structure by using two single-gate FETs. Since it is driven by the second order harmonic of LO signal, a sub-harmonic cascode FET mixer has good LO-RF port isolation characteristic. In order to solve DC offset of a homodyne system, near zero If is used instead of zero If and the mixer is driven by sub-harmonic of LO signal. As RF input power was -30 dBm and LO power was 6 dBm, the designed mixer had 6.7 dB conversion gain, 8.4 dB noise figure, 31.5 dB LO-RF port isolation, -1.9 dBm lIP3 and -2.8 dBm IIP2.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.533-539
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• 2015

In this paper, we designed a reconfigurable mixer for microwave broadband receiver. The proposed mixer using a anti-parallel diode is operated as a fundamental mixer or sub-harmonic mixer with respect to a control voltage. A fundamental mixer with a control voltage show a conversion loss of -10 dB, 1 dB compression point of 2.0 dBm at X-band/ Ku-band. On the other hand, it is performed as a sub-harmonic mixer with a conversion loss of -17 dB, 1 dB compression point of 2.0 dBm at Ka-band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1318-1323
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• 2010

A lot of demand for parts of millimeter wave band, as would be expected 57~63 GHz band down conversion mixer was designed and fabricated using IHP 0.25 um SiGe process. Designed and fabricated mixer was double balanced type and located reduced 3D balun at RF port and buffer amplifier at outport for suppression LO signal and conversion gain. Fabricated mixer measured conversion gain of 13.8 dB, $P1dB_{in}$ -17 dBm and 88 mA of current consumption characteristics, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1235-1239
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• 2010

In this work, a wideband technique has been proposed that improves the IF bandwidth of mixers and a 24-GHz down-conversion mixer employing the proposed technique has been designed and fabricated based on 0.13-${\mu}m$ RFCMOS technology. The mixer showed the conversion gain of $2.7{\pm}1.5$ dB from DC to 5.25 GHz IF for a fixed LO frequency of 24 GHz. Measured P-1dB and LO-RF isolation was -8.7 dBm and 21 dB, respectively. The mixer draws DC current of 10.6 mA from 1.3 V supply.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.540-549
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• 2017

A phase frequency detector(PFD) composed of logic circuits is widely used in a phase locked loop(PLL) due to the easy implementation for integrated circuits. A frequency locked loop(FLL) removes the reference oscillator in the PLL, and the resonator serves as a reference oscillator. A frequency detector(FD) is indispensable for the FLL configuration, and a FD, which is usually composed of a mixer is used to build an FLL. In this paper, instead of FD using mixer, a FD is constructed by using 1.175 GHz resonator composed of microstrip and PFD taking the versatility of PFD into consideration. Using the designed FD, FLL oscillating at a frequency of 1.175 GHz is composed. As a result of comparison with the FLL composed of FD using mixer, it was confirmed that the proposed FLL has better phase noise performance than FLL using mixer FD with FLL bandwidth.