• JSTS:Journal of Semiconductor Technology and Science
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• 제3권2호
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• pp.89-95
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• 2003

In this paper, we have designed and fabricated high conversion gain Q-band active sub-harmonic mixers for a receiver of millimeter wave wireless communication systems. The fabricated active sub-harmonic mixer uses 2nd harmonic signals of a low local oscillator (LO) frequency. The fabricated mixer was successfully integrated by using $0.1{\;}\mu\textrm{m}$GaAs pseudomorphic high electron mobility transistors (PHEMTs) and coplanar waveguide (CPW) structures. From the measurement, it shows that maximum conversion gain of 4.8 dB has obtained at a RF frequency of 40 GHz for 10 dBm LO power of 17.5 GHz. Conversion gain from the fabricated sub-harmonic mixer is one of the best reported thus far. And a phase noise of the 2nd harmonic was obtained -90.23 dBc/Hz at 100 kHz offset. The active sub-harmonic mixer also ensure a high degree of isolations, which are -35.8 dB from LO-to-IF and -40.5 dB from LO-to-RF, respectively, at a LO frequency of 17.5 GHz.

• 천문학회지
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• 제55권6호
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• pp.207-213
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• 2022

The Seoul Radio Astronomy Observatory (SRAO) operates a 6.1-meter radio telescope on the Gwanak campus of Seoul National University. We present the efforts to reform SRAO to a Very Long Baseline Interferometry (VLBI) station, motivated by recent achievements by millimeter interferometer networks such as Event Horizon Telescope, East Asia VLBI Network, and Korean VLBI Network (KVN). For this goal, we installed a receiver that had been used in the Combined Array for Research in Millimeter-wave Astronomy and a digital backend, including an H-maser clock. The existing hardware and software were also revised, which had been dedicated only to single-dish operations. After several years of preparations and test observations in 1 and 3-millimeter bands, a fringe was successfully detected toward 3C 84 in 86 GHz in June 2022 for a baseline between SRAO and KVN Ulsan station separated by 300 km. Thanks to the dual frequency operation of the receiver, the VLBI observations will soon be extended to the 1 mm band and verify the frequency phase referencing technique between 1 and 3-millimeter bands.

• 대한전자공학회논문지TC
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• 제49권1호
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• pp.78-84
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• 2012

본 논문에서는 밀리미터파 탐색기에 사용되는 Ka-대역 수신기 모듈 설계 및 제작 기법을 제시하였다. 수신기 모듈은 안테나 연결을 위한 도파관, 순환기(Circulator) 및 모드 변환기, 수신기 보호를 위한 리미터 및 이득 제어 증폭기를 포함한다. 또한 모노 펄스 수신을 위한 합, 고각 및 방위각 채널로 구성되며 재밍 신호 확인을 위한 SLB(Sidelobe Blankin) 채널로 구성된다. 본 논문에서는 ADC(Analog to Digital Converter)의 비선형 특성에 따른 수신기 이득 및 이득 제어 범위를 분석하고, 넓은 수신기 동작 영역을 가지도록 설계되었다. 제작된 Ka-대역 수신기 측정 결과, 주파수 대역은 1 GHz, 잡음 지수는 8.2 dB 이하, 이득은 $56{\pm}2dB$, 동적 영역은 135 dB, 이득 제어 86 dB 이상, 채널간 격리도 35 dB 이상이다.

• Journal of electromagnetic engineering and science
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• 제18권3호
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• pp.188-198
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• 2018

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) was -97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.116-119
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• 2005

In this paper, we propose the PLL system of the local oscillator system for the millimeter wave band's radio astronomy receiving system. The development of the proposed local oscillator system based on the YIG oscillator VCO with 26.5 ${\sim}$ 40GHz specification. This system consists of the oscillator part including the YIG VCO, the harmonic mixer, and the isolator, the RF processing part including the triplexer, limiter, and RF discrimination processor. and the PLL system including YIG modulator and controller. Based on this configuration. we verify the frequency and power stability of the developed local oscillator system according to some temperature variation. From this test results we confirm the stable output frequency and power characteristic performance of the developed La system at constant temperature.

• 한국전자파학회논문지
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• 제25권1호
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• pp.130-136
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• 2014

본 논문에서는 최근 실리콘 기반의 소자를 이용하여 microwave 대역에서 millimeter wave 대역까지 동작하는 위상 배열 시스템 개발에 관한 연구를 리뷰하고자 한다. 우선 위상 배열 시스템의 중요한 부품인 위상 변위기를 CMOS 공정을 이용한 설계 방법에 대해 논의한다. 그리고 수동형 위상 변위기를 송수신 모듈에 적용하여 한 채널에서 16 채널까지 확장하여 실리콘 칩에 구현을 하였다. 35 GHz 대역에서 동작하는 4 채널 송수신 칩은 200 mW 이하의 저전력 성능을 보여주었다. 또한, 44 GHz 대역에서 16 channel로 확장하여 송신 출력과 선형성을 향상시킬 수 있었다. 능동형 위상 변위기는 Ku band 대역에서 동작하는 2-antenna 4-beam 수신기에 적용하였다. 한 칩에서 4개의 서로 다른 방향의 신호가 존재함으로 신호 간의 커플링을 최소화 하는 방법을 소개하고, 이를 측정을 통해 검증하였다.

• 한국전자파학회논문지
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• 제23권2호
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• pp.220-228
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• 2012

본 논문에서는 밀리미터파 탐색기의 수신기 보호용으로 사용할 낮은 누설 전력을 가지는 Ka 대역 능동 리미터 설계 및 제작 기법을 설명하였다. 낮은 누설 전력을 구현하기 위해서 송신 펄스 주기 신호와 입력 전력의 크기에 따라 리미터를 제어할 수 있는 능동 리미터 제어 회로를 제안하였다. 능동 리미터는 전형적인 2단 수동 리미터에 방향성 결합기, 검파기, 연산 증폭기 및 과전류 보호용 저항으로 구성된 궤환 회로로 구성되어진다. 제작된 Ka 대역 능동 리미터 측정 결과, 주파수 대역은 1 GHz, 약 신호 시 삽입 손실은 3.5 dB 이하, 능동 제어시 최대 감쇄량 46 dB, 4 W RF 입력 시 정상 누설 전력은 -7.5 dBm을 보였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1749-1753
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• 2003

We proposed several systems for 1Giga bit Modem. The first, Binary ASK(Amplitude Shift Keying) system has a high speed shutter transmitter and no IF(Intermediate Frequency) receiver only by symbol synchronization. The advantage of proposed system is that circuitry is very simple without IF process. The disadvantage of proposed system are that line spectrum occurs interference to other channels, and enhancement to 4-level system is impossible due to its large SNR degradation. The second, Binary phase modulation system has a high speed shutter transmitter and IF-VCO(IF-Voltage Controlled Oscillator) control by base-band phase rotation. Polarity of shutter window is changed by the binary data. The window should be narrow same as above ASK. The advantage of proposed system is which error rate performance is superior. The disadvantage of proposed system are that Circuitry is more complex, narrow pull-in range of receiver caused by VCO and spectrum divergence by the non-linear amplifier. The third, 4-QAM(Quadrature Amplitude Modulation)system has a nyquist pulse transmitter and IF-VCO control by symbol clock. The advantage of proposed system are that signal frequency band is a half of 1GHz, reliable pull-in of VCO and possibility of double speed transmission(2Gbps) by keeping 1GHz frequency-band. The disadvantage of proposed system are that circuit complexity of pulse shaping and spectrum divergence by the non-linear amplifier.

• 대한전자공학회논문지TC
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• 제42권11호
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• pp.45-52
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• 2005

본 논문에서는 밀리미터파 대역의 전파천문 관측용 수신시스템의 안정된 동작을 확보하기 위한 국부발진시스템을 제안하였다. 제안된 국부발진시스템은 $26.5\~40GHz$를 발진하는 YIG 발진기를 VCO로 하여 개발하였다. 이러한 국부발진 시스템은 YIG VCO, 고조파 믹서, 및 아이솔레이터 등을 포함한 발진부, triplexer, limiter, 및 RF 판별 기능 등을 포함하는 RF 프로세싱 부분과 YIG PLL을 위한 모듈과 제어기를 포함한 PLL 시스템으로 구성하여 설계, 개발하였다. 본 연구에서는 개발된 국부 발진시스템의 안정성을 확인하기위해서 온도변화에 따른 출력 주파수와 전력 안정도를 측정하였다. 이러한 실험결과로부터 개발된 국부발진시스템은 일정한 온도에서는 매우 안정된 출력 주파수와 전력특성이 확보됨을 확인하였다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.9-9
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• 2004