• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.3-6
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• 2007

In this paper, a hybrid dual band LNA(Low Noise Amplifier) with a tunable matching circuit using varactor is designed for 433MHz and 912MHz RFID reader. The operating frequency is controlled by the bias voltage applied to the varactor. The measured results demonstrate that S21 parameter is 16.01dB and 10.72dB at 433MHz and 912MHz, respectively with a power consumption of 19.36mW. The S11 are -11.88dB and -3.31dB, the S22 are -11.18dB and -15.02dB at the same frequencies. The measured NF (Noise Figure) is 15.96dB and 7.21dB at 433MHz and 912MHz, respectively. The NF had poorer performance than the simulation results. The reason for this discrepancy was thought that the input matching is not performed exactly and a varactor in the input matching circuit degrades the NF characteristics.

• ETRI Journal
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• v.26 no.4
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• pp.292-296
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• 2004

In this paper we present a new current-mode electronically tunable universal filter using only plus-type current controlled conveyors (CCCII+s) and grounded capacitors. The proposed circuit can simultaneously realize lowpass, bandpass, and highpass filter functions - all at high impedance outputs. The realization of a notch response does not require additional active elements. The circuit enjoys an independent current control of parameters $\omega_0$ and $\omega_0/Q$. No element matching conditions are imposed. Both its active and passive sensitivities are low.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.264-265
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• 2007

In this paper, we deal with a hybrid dual band low noise amplifier with tunable matching circuits for a Radio Frequency Identification(RFID) reader operating at 433MHz and 912MHz. The tunable matching circuit consists of the microstrip line, SMD component and varactor. Simulation results show that the S21 parameter is 17dB and 7.91dB at 433MHz and 912MHz, respectively. The noise figure is also determined to 3.56dB and 5.58dB at the same frequencies with a power consumption of 19.36mW.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.137-139
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• 2013

A compact metamaterial (MTM)-based tunable phase shifter consisting of four unit cells with a simple DC bias circuit has been designed at 2.4 GHz. The variable series capacitors and shunt inductors that are required to be loaded periodically onto a host transmission line are realized employing only chip variable capacitors (varactors). In addition, the proposed phase shifter requires only one DC bias source to control the varactors, with the matching condition of the MTM line automatically satisfied. The measured phase shifting range is $285.2^{\circ}$ (from $-74.2^{\circ}$ to $211^{\circ}$). The measured insertion loss is approximately 1.5 dB. The circuit/electromagnetic-simulated and measured results are in good agreement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.519-527
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• 2010

In this paper, we proposed a 13.56 MHz wireless power transfer system using loop antennas with tunable impedance matching circuits. In general, a wireless power transfer system shows an impedance mismatching due to a reflected impedance, because a coupling coefficient is varied with respect to separation distance between two resonating antennas. The proposed system can compensate the effect of this impedance mismatch owing to tunable impedance matching circuits using varactor diodes. Therefore, transmission efficiency is enhanced, moreover, the center frequency of the system is not changed, regardless of separation distance between two antennas. In order to demonstrate the performance of the proposed system, a wireless power transfer system with tunable impedance matching circuits is designed and implemented, which has a pair of loop antennas with a dimension of $30\;cm{\times}30\;cm$ cm. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to a distance between loop antennas were measured. From measured results, the proposed system shows enhanced performances than the case of the general fixed $50\;{\Omega}$ impedance matching circuits. Therefore, we verified that the proposed wireless power transfer system using the proposed impedance matching scheme will be able to ensure robust operation even when the separation distance of antennas is varied.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.5
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• pp.27-37
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• 1999

A CMOS ReadOut Integrated Circuit (ROlC) for InfraRed Focal Plane Array (IRFPA) detector is presented, which is a key component in uncooled thermal imaging systems. The ROIC reads out signals from $64\times64$ Barium Strontium Titanate (BST) infrared detector array, then outputs pixel signals sequentially after amplifying and noise filtering. Various design requirements and constraints have been considered including impedance matching, low noise, low power dissipation and small detector pitch. For impedance matching between detector and pre~amplifier, a new circuit based on MOS diode structure is devised, which can be easily implemented using standard CMOS process. Also, tunable low pass filter with single~pole is used to suppress high frequency noise. In additions, a clamping circuit is adopted to enhance the signal~to-noise ratio of the readout output signals. The $64\times64$ IRFPA ROIC is designed using $0.65-\mu\textrm{m}$ 2P3M (double poly, tripple metal) N~Well CMOS process. The core part of the chip contains 62,000 devices including transistors, capacitors and resistors on an area of about $6.3-mm\times6.7-mm$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.1
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• pp.42-48
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• 2011

In this paper, a passive load-pull using a GaN HEMT (Gallium Nitride High Electron Mobility Transistor) bare-chip in X-band is presented. To obtain operation conditions that characteristic change by self-heating was minimized, pulsed drain bias voltage and pulsed-RF signal is employed. An accuracy impedance matching circuits considered parasitic components such as wire-bonding effect at the boundary of the drain is accomplished through the use of a electro-magnetic simulation and a circuit simulation. The microstrip line length-tunable matching circuit is employed to adjust the impedance. The measured maximum output power and drain efficiency of the pulsed load-pull are 42.46 dBm and 58.7%, respectively, across the 8.5-9.2 GHz band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1069-1077
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• 2011

In this paper, a design and fabrication of a miniaturized 2.5 GHz 8 W power amplifier using selectively anodized aluminum oxide(SAAO) substrate are presented. The process of SAAO substrate is recently proposed and patented by Wavenics Inc. which uses aluminum as wafer. The selected active device is a commercially available GaN HEMT chip of TriQuint company, which is recently released. The optimum impedances for power amplifier design were extracted using the custom tuning jig composed of tunable passive components. The class-F power amplifier are designed based on EM co-simulation of impedance matching circuit. The matching circuit is realized in SAAO substrate. For integration and matching in the small package module, spiral inductors and single layer capacitors are used. The fabricated power amplifier with $4.4{\times}4.4\;mm^2$ shows the efficiency above 40 % and harmonic suppression above 30 dBc for the second(2nd) and the third(3rd) harmonic at the output power of 8 W.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.100-105
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• 2010

A multi-band low noise amplifier (LNA) is designed in 90 nm RF CMOS process for 3GPP LTE (3rd Generation Partner Project Long Term Evolution) applications. The designed multi-band LNA covers the eight frequency bands between 1.85 and 2.8 GHz. A tunable input matching circuit is realized by adopting a switched capacitor array at the LNA input stage for providing optimum performances across the wide operating band. Current steering technique is adopted for the gain control in three steps. The performances of the LNA are verified through post-layout simulations (PLS). The LNA consumes 17 mA at 1.2 V supply voltage. It shows a power gain of 26 at the normal gain mode, and provides much lower gains of 0 and -6.7 in the bypass-I and -II modes, respectively. It achieves a noise figure of 1.78 dB and a IIP3 of -12.8 dBm over the entire band.