• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.1-8
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• 1998

An MMIC single-balanced upconverting mixer for PCS application has been successfully developed using an MMIC process employed by 1 .mu. ion implanted GaAs MESFET and passive lumped elements consisting of spiral inductor, Si3N4 MIM capacitors and NiCr resistors. The configuration of the mixer presented in this paper is two balanced cascode FET mixers with common-source self-bias circuits for single power supply operation. The dimension of the fabricated circuit including two active baluns intermodulation characteristic with two-tone excitation are also measured, showing -28.17 dBc at IF power of -30 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.876-885
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• 2000

A new and simple method is presented for determining the parasitic resistances of MESFET and HEMT from the measured S-parameters under normal active bias without depending on additional DC measurements or iteration or optimization process. The presented method is based on the fact that the difference between source resistance(Rs) and drain resistance(Rd) can be obtained from the measured Z-parameters under zero bias condition. It is possible to define the new internal device including intrinsic device and 3 parasitic resistances by elimination the parasitic inductances and capacitances from the measured S-parameters. Three parasitic resistances are calculated easily from the fact that the real parts of Yint,11 and Yint,12 of intrinsic Y-parameters are zero theoretically and the relations between S-,Z-, Y-matrices. The calculated parasitic resistances using the presented method and successively calculated equivalent circuit parameters give modeled S-parameters which are in good agreement with the measured S-parameters up to 400Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.13-21
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• 1997

In this paper, the oscillator type active antenna used as an element of active phased array antenna is designed and fabricated using slot coupling. The radiating element and active circuit are fabricated on each layer respectively and coupled electromagnetically through slot on the ground plane. This structure can solve the problems such as narrow bandwidth of microstrip antenna, spurious radiation by active circuits, and spaces for integration of the feeding circuits which are caused by integrating antennas with oscillator circuits in the same layer. The active antenna in this paper, the oscillation frequency can be tuned linearly by controlling the drain bias voltage of FET. The frequency tuning range is between 12.37 GHz to 12.65 GHz when bias voltage is varied from 3V to 9V, thus frequency tuning bandwidth is 280 MHz (2.24%). The output power of antenna is uniform within 5dB over frequency tuning range. Therefore this active antenna can be used as an element of linear or planar active phased array antennas.

• Journal of IKEEE
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• v.20 no.3
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• pp.251-259
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• 2016

This paper describes that how to enhance the robustness of semiconductor TRM(Transmitter and Receiver Module) through the bias sequencing and tuning the switching time. Previous circuit designs focused on improving the MDS(Minimum Detection Signal) performance. Because TRM has critical problem which transmission output signal leak into receiver by it's compact design. Under this condition, TRM was frequently broken down within the MTBF(Mean Time Between Failure). This study proposes the bias sequencing and tuning the switching time to improve above problem. At first, we collected major failure symptom and infer it's cause. Second, we demonstrated it's effect by derive the improvement method and apply it to our system. And finally we can convinced that the proposed method clear the frequent failure problem with its lack of isolation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.897-903
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• 2011

This paper presents a highly linear power amplifier MMIC, having an output power level of about 1 watt, based on InGaP/GaAs hetero-junction bipolar transistor(HBT) technology for the 900 MHz band. The active bias circuit is applied to minimize the effect of temperature variation. Ballast resistors are optimized to prevent a current collapse and a thermal runaway. The fabricated power amplifier exhibited a gain of 17.6 dB, an output P1dB of 30 dBm, and a PAE of 44.9 % at an output P1dB from the one-tone excitation. It also showed a very high OIP3 of 47.3 dBm at an average output power of 20 dBm from the two-tone excitation.

• ETRI Journal
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• v.38 no.2
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• pp.235-243
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• 2016

A low-noise readout integrated circuit (ROIC) for a microelectromechanical systems (MEMS) microphone is presented in this paper. A positive feedback signal amplification technique is applied at the front-end of the ROIC to minimize the effect of the output buffer noise. A feedback scheme in the source follower prevents degradation of the noise performance caused by both the noise of the input reference current and the noise of the power supply. A voltage booster adopts noise filters to cut out the noise of the sensor bias voltage. The prototype ROIC achieves an input referred noise (A-weighted) of -114.2 dBV over an audio bandwidth of 20 Hz to 20 kHz with a $136{\mu}A$ current consumption. The chip is occupied with an active area of $0.35mm^2$ and a chip area of $0.54mm^2$.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.257-260
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• 2017

In this paper, we present the design of a 4.5 V low dropout (LDO) voltage regulator implemented in the 130 nm CMOS process. The design uses a two-stage cascaded operational transconductance amplifier (OTA) as an error amplifier, with a body bias technique for reducing dropout voltages. PMOS is used as a pass transistor to ensure stable output voltages. The results show that the proposed LDO regulator has a dropout voltage of 32.06 mV when implemented in the130 nm CMOS process. The power dissipation is only 1.3593 mW and the proposed circuit operates under an input voltage of 5V with an active area of $703{\mu}m^2$, ensuring that the proposed circuit is suitable for low-power applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.549-554
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• 2003

In this paper, we have designed and implemented by a monolithic microwave integrated circuit(MMIC) of a 5.8GHz-band low noise amplifier (LNA) composed of receiver front-end(RFE) in a on-board equipment system for dedicated short range communication. The designed LNA is provided with two active devices, matching circuits, and two drain bias circuits. Operating at a single supply of 3V and a consumption current of 18mA, The gain at center frequency 5.8GHz is 13.4dB, NF is 1.94dB, Input IP3 is -3dBm, S$_{11}$ is -18dB, and S$_{22}$ is -13.3dB. The circuit size is 1.2 $\times$ 0.7 $\textrm{mm}^2$.>.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.517-520
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• 2008

A voltage-programming pixel circuit, which compensates the threshold voltage shift of TFTs and the degradation of OLED, is proposed for large sized a-Si:H active matrix organic light emitting diode (AMOLED) applications. Considering threshold voltage variation (or shift), OLED degradation and reverse bias annealing, HSPICE simulation results indicate that luminance error of every gray level is less than 0.4 LSB under the condition of +1V threshold voltage shift and from -0.2 LSB to 2.6 LSB within 30% degradation of OLED in the case of 40-inch full HDTV condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1038-1045
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• 2010

The theory for a new electromagnetically biased combined radial and axial magnetic bearing is developed. This combined magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. One dimensional magnetic circuit model for this combined magnetic bearing is developed and analyzed such that flux densities and magnetic forces can be obtained. Three dimensional finite element model for the bearing is also developed and analyzed. Numerical analysis shows that the calculated magnetic forces from 1D model are well matched with those from the finite element model.