• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.10
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• pp.1131-1137
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• 2014

In this paper, oscillator with compact hairpin resonator is used to design the local oscillator of X-band radar system. The proposed hairpin resonator is minimized by increasing capacitance of line end of conventional one. By this method, size can be minimized about 40% compared with the conventional resonator and also can improve phase noise characteristic. The result of oscillator using proposed hairpin resonator is measured in oscillating frequency of 9.05 GHz, output power of 2.47 dBm, and phase noise of -101.4 dBc/Hz. The fabricated oscillator in this paper can minimize design and it's planar structure makes it easy to design MMIC.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.7
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• pp.51-57
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• 1995

The theoretical analysis for AlInAs/GaInAs resonant tunneling diodes (RTDs), which have shown the improved negative differential resistance (NDR) characteristics, has scarcely been made in comparison with AlGaAS/GaAs RTDs. In this paper, the static current-voltage relation of Al$_{0.48}In_{0.52}As/Ga_{0.47}In_{0.53}$As RTDs were numerically estimated by using a self-consistent method. Assuming a simplified RTD with single quantum well structure and spacer layers, the peak current density (J$_{P}$) and the peak-to-valley current ratio (PVCR) were analysed as the function of the thickness of the well, the barrier and the spacer layer, and temperature. As the results, the peak current density and the peak-to-valley current ratio indicated a reciprocal relation roughly in respect to the thicknesses of the well and the barrier, and it was theoretically predicted that it be not attainable to provide a high peak current desity (J$_{P}$) over 1${\times}10^{5}A/cm^{2}$ as well as the large peak-to-valley current ratio (PVCR) over 10 that were the the critical conditions for the practical use.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.77-80
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• 2008

In this paper, low phase noise VCO using novel compact microstrip spiral resonator is proposed. A spiral resonator has super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff and a large coupling coefficient value, which makes a high Q value, and has reduced the phase noise. To increase the tuning range of VCO, varactor diode has been connected at the tunable negative resistance in VCO. This VCO has presented the oscillation frequency of $5.686{\sim}5.841GHz$, harmonics -29.83 dBc and phase noise of $-115.16{\sim}-115.17dBc/Hz$ at the offset frequency of 100 KHz.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.54-58
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• 2006

A new design for easily controlling operating frequency of an antenna-integrated planar oscillator is introduced. The oscillator circuit of a broadband negative-resistance active part and a passive load including a patch antenna. The patch resonance is used for determining the oscillation frequency. This design reduces the possibility of mismatch between antenna radiation and oscillation frequencies. To achieve optimum output power, load-pull simulation for the negative-resistance circuit is used. The load-pull simulation shows the feed point and the delay of feed line can affect the oscillation power. Two negative-resistance circuits capable of supporting oscillation over full C-band and X-band are fabricated. The oscillation frequency, output power and phase noise for different patch antennas are measured.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.847-853
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• 2007

In this paper, a novel push-push voltage-controlled oscillator(VCO) using microstrip square open loop resonator and tunable negative resistance is presented. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced phase noise of VCO. The VCO with 1.8V power supply has phase noise of $-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$ in the tuning range, $5.744{\sim}5.859 GHz$. The FOM of this VCO is $-202.83{\sim}-201dBc/Hz\;@\;100 kHz$ in the same tuning range. When it has been compared with single-ended VCO using microstrip square open loop resonator, and push-push oscillator using microstrip line resonator, the reduced phase noise has been -8.51dB, and -33.67dB, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.193-196
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• 2005

유기발광소자의 발광층의 두께에 따른 임피던스의 변화를 살펴보았다. 임피던스는 두께에 따라 저항의 변화에 따른 의존성을 보이며, 그에 따른 임피던스와 Cole-Cole 반원의 변화, 두께에 따른 $1/\tau$ 의 변화를 살펴보았다. 발광층의 두께는 각각 100, 200, 300 nm의 두께로 열증착하여 실험하였고, 소자의 구조는 $ITO/Alq_3/Al$의 구조로 측정 하였다. 유기발광소자의 발광층인 $Alq_3$의 두께가 증가함에 따라 임피던스의 크기가 증가하고, 위상각의 크기는 100nm의 경우 0V에서 용량성을 보이다가 6~10V까지 부성저항특성을 나타낸 후 약 22V에서 저항성을 나타내고, 200과 300 nm의 경우 12V까지 용량성을 나타내다 이후 22V 근방에서 $0^{\circ}$에 가까워지며 저항성을 나타내는 것을 알 수 있었다. 또한 두께에 따른 Cole-Cole 반원을 살펴보면 두께가 증가할수록 반원의 크기가 증가하는 것을 알 수 있으며, 이를 통해 간단한 등가회로를 예측할 수 있었다. 그리고 벌크내의 용량성$(C_p)$을 측정하여 두께의 증가에 따라 $C_p$ 값이 감소하는 것을 알 수 있었다.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.239-241
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• 2006

본 논문에서는 Liquid crystal display (LCD) Backlight module중에 Cold cathode fluorescent lamp (CCFL)를 포함한 인버터가 가지고 있는 기생 용량 측정 방법을 고안하였다. CCFL의 부성 저항 특성을 고려하여 램프의 정적 저항 성분을 일정하게 유지시키고 입력 전압 대 출력 전압의 비 중 최대 Gain을 갖는 주파수를 찾아내 기생 용량을 계산하는 Algorithm을 완성하였다. 시뮬레이션과 실험 결과를 통해 비교 검증함으로써 측정 방법의 유효성을 입증하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.481-482
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• 2005

유기발광소자의 발광층의 전압에 따른 임피던스의 변화를 살펴보았다. 임피던스는 전압의 변화에 따른 의존성을 보이며, 그에 따른 임피던스와 Cole-Cole 반원의 변화를 전기전도기구와 비교하여 살펴보았다. 소자의 구조는 ITO/$Alq_3$/Al의 구조로 발광층의 두께는 60 nm로 열증착하여 실험하였다. 실험에서 전기전도기구의 Ohmic 영역, SCLC 영역, 부성저항영역, TCLC 영역에서 각각 임피던스를 측정하였고, 전압의 증가에 따라 임피던스의 크기가 감소하고, 위상각은 0V에서 용량성을 보이다가 발광영역에서 저항성을 나타내는 것을 알 수 있었다. 또한 전압에 따른 Cole-Cole 반원을 살며보면 전압이 증가할수록 반원의 크기가 감소하는 것을 알 수 있으며, 이를 통해 간단한 등가회로를 예측할 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.482-487
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• 2005

In this paper, we propose the control method of output impedance of each cascode unit cell of distributed amplifier by connecting varactors in the gate-terminal of common gate. Compared to common source unit cell, cascode unit cell has many advantages such as high gain and high output impedance as well as negative resistance loading. But if the transistor model which is used in design is inaccurate and process parameter is changed, oscillation sometimes can occur at band edge in which the gain start to drop. Therefore, we need control circuit which can prevent oscillation, although the circuit has already fabricated, and varactor connected to gate-terminal of common gate of cascode gain cell can play that part. Measured result of fabricated distributed amplifier shows the capability of contol of gain characteristic by adjusting of value of varactors, this can guarantee the stability of the circuit. The gain is $8.92\pm0.82dB$ over 49 GHz, the group delay is $\pm9.3 psec$ over 41 GHz. All transistor which has $0.15{\mu}m$ gate length is GaAs based p-HEMT, and distributed amplifier is put together with 4 stages.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.8
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• pp.45-51
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• 2007

We designed and fabricated the planar graded-gap injector GaAs Gm diodes with $1.6{\mu}m$ active length for operation at 94 GHz. The fabrication of the Gunn diode is based on MESA etching, Ohmic metalization, and overlay metalization. The measured negative resistance characteristics of the graded-gap injector GaAs Gunn diodes are examined for two different device structures changing the distance between the cathode and the anode electrodes. Also, we discuss the DC results under the forward and the reverse biases concerning the role of the graded-gap injector. It is shown that the structure having the shorter distance between the cathode and the anode electrode has higher peak current, higher breakdown voltage, and lower threshold voltage than those of the larger distance.