• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.620-626
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• 2015

In this paper, a 2~6 GHz wideband GaN power amplifier MMIC is designed and fabricated using a second-order all-pass filter for input impedance matching and an LC parallel resonant circuit for minimizing an output reactance component of the transistor. The second-order all-pass filter used for wideband lossy matching is modified in an asymmetric configuration to compensate the effect of channel resistance of the GaN transistor. The power amplifier MMIC chip that is fabricated using a $0.25{\mu}m$ GaN HEMT foundry process of Win Semiconductors, Corp. is $2.6mm{\times}1.3mm$ and shows a flat linear gain of about 13 dB and input return loss of larger than 10 dB. Under a saturated power mode, it also shows output power of 38.6~39.8 dBm and a power-added efficiency of 31.3~43.4 % in 2 to 6 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.213-218
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• 2007

In this paper, we propose the design and fabrication on high frequency CMOS VCO for DS-UWB(Direct-Sequence Ultra-WideBand) applications using 0.18 ${\mu}m$ process. The complementary cross-coupled LC oscillator architecture which is composed of PMOS, NMOS symmetrically, is designed for improving the phase noise characteristic. The resistor is used instead of current source that reduce the 1/f noise of current source. The high-speed buffer is needed for measuring the output characteristic of VCO using spectrum analyzer, therefore the high-speed inverter buffer is designed with VCO. A fabricated core VCO size is $340{\mu}m{\times}535{\mu}m$. The VCO is tunable between 7.09 and 7.52 GHz and has a phase noise lower than -107 dBc/Hz at 1-MHz offset over entire tuning range. The measured harmonic suppression is 32 dB. The VCO core circuit draws 2.0 mA from a 1.8 V supply.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.356-362
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• 2005

In this paper, in order to develop a simple and high efficient ballast without an external ignitor, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The Internal LC resonance of the buck converter is used to generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and trun off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about 4$\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified nth hardware experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.504-511
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• 2003

In this paper, inverter type neon power supply using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed neon power supply is composed of basic circuit and blocks, such as rectifier part, frequency oscillation part and piezoelectric transformer and resonant half bridge inverters. In this paper for complement the low power limitation, piezoelectric transformer at parallel connected driving by inverter is studied for noon tubes system of high power. When piezoelectric transformer is connected with parallel, LC filter connection method with parallel and selection of inductance L and capacitor C of primary side is suggested for reduce unbalanced current at the terminal of each transformer. Piezoelectric transformers use piezoelectric ceramic devices. Thus it is wireless therefore it has high power density, high Isolation level, low loss, more light, and miniaturization. In addition, high voltage transfer ratio is expected because there is no leakage inductance. Also, it has economic merit that the electrical loss Is low because structure is simple, small and tighter weight.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.8-14
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• 2009

A lamp which is currently employed to LCD(Liquid Crystal Display) Backlight is almost CCFL(Cold Cathod Fluorescent Lamp) and EEFL(External Electrode Fluorescent Lamp). However, the use of these lamps is being restricted as RoHS(the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment) regulation is gradually reinforced. According to this situation, the manufacturing of a lamp which doesn't use mercury is unescapable. Moreover, LCD TV has a defect which take place Motion Blur phenomenon due to response time of LC(Liquid Crystal), and Hold-type characteristic which only exists in LCD differently to CRT, PDP. In this paper, an inverter is proposed to drive a plane light source lamp which is not containing mercury. Driving circuit of proposed inverter is simple because the number of semiconductor device and magnetic device is reduced by using forward topology. Also, Motion Blur phenomenon is decreased by dividing the plane light source lamp to six block along vertical direction, and scanning. Finally, we proved usefulness of proposed inverter through experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.438-445
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• 2001

This paper presents a high frequency modulation electronic ballast for the metal halide lamp. As the proposed ballast operates in high frequency ranges and can start up the lamp using the LC resonant circuit without external igniter, the proposed ballast is very compact and has a good efficiency in comparison with the conventional low frequency electronic ballast. The proposed ballast is controlled with the modulated frequency in the range of 20kHz to 100kHz in order to avoid the acoustic resonance phenomenon. In this paper, a new realtime acoustic resonance detection method is proposed to evaluate the characteristics of the ballast. The no load protection algorithm and power control algorithm through the detection of the DC link current are described. Finally, the experimental results on the proto-type ballast of 150w metal halide lamp with the proposed methods are discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.158-165
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• 2013

In this paper, a new circuit topology of an ultra-wideband (UWB) 3.1-10.6GHz CMOS low noise amplifier is presented. The proposed UWB low noise amplifier is designed utilizing RC feedback and LC filter networks which can provide good input impedance matching. In this design, the current-reused topology is adopted to reduce the power consumption and the inductor-peaking technique is applied for the purpose of bandwidth extension. The performance results of this UWB low noise amplifier simulated in $0.18-{\mu}m$ CMOS process technology exhibit a power gain of 14-14.9dB, an input matching of better than -10.8dB, gain flatness of 0.9dB, and a noise figure of 2.7-3.3dB in the frequency range of 3.1-10.6GHz. In addition, the input IP3 is -5dBm and the power consumption is 12.5mW.

• Macromolecular Research
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• v.17 no.12
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• pp.963-968
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• 2009

Liquid crystal (LC; E7 and/or ML-0249)-embedded, poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based, polymer electrolytes were prepared for use in dye-sensitized solar cells (DSSCs). The electrolytes contained 1-methyl-3-propylimidazolium iodide (PMII), tetrabutylammonium iodide (TBAI), and iodine ($I_2$), which participate in the $I_3^-/I^-$ redox couple. The incorporation of photochemically stable PVdF-co-HFP in the DSSCs created a stable polymer electrolyte that resisted leakage and volatilization. DSSCs, with liquid crystal(LC)-embedded PVdF-co-HFP-based polymer electrolytes between the amphiphilic ruthenium dye N719 absorbed to the nanocrystalline $TiO_2$ photoanode and the Pt counter electrode, were fabricated. These DSSCs displayed enhanced redox couple reduction and reduced charge recombination in comparison to that fabricated from the conventional PVdF-co-HFP-based polymer electrolyte. The behavior of the polymer electrolyte was improved by the addition of optimized amounts of plasticizers, such as ethylene carbonate (EC) and propylene carbonate (PC). The significantly increased short-circuit current density ($J_{sc}$, $14.60\;mA/cm^2$) and open-circuit voltage ($V_{oc}$, 0.68 V) of these DSSCs led to a high power conversion efficiency (PCE) of 6.42% and a fill factor of 0.65 under a standard light intensity of $100\;mW/cm^2$ irradiation of AM 1.5 sunlight. A DSSC fabricated by using E7-embedded PVdF-co-HFP-based polymer electrolyte exhibited a maximum incident photon-to-current conversion efficiency (IPCE) of 50%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.139-145
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• 2024

This paper presents the design of a voltage controlled oscillator (VCO) which is one of the key building blocks in modern wireless communication systems with small VCO gain (K_vco) variation. To compensate conventional large K_vco variation, a series varactor bank has been added to the conventional LC-tank with parallel capacitor bank array. And also, in order to achieve excellent phase noise performance while maintaining wide tuning range, a mixed coarse/fine tuning scheme(series varactor array and parallel capacitor array) is chosen. The switched varactor array bank is controlled by the same digital code for switched capacitor array without additional digital circuits. For use at a low voltage of 1.2V, the proposed current reference circuit in this paper used a current reference circuit for safety with the common gate removed more safely. Implemented in a TSMC 0.13㎛ CMOS RF technology, the proposed VCO can be tuned from 4.4GH to 5.3GHz with the K_vco (VCO gain ) variation of less than 9.6%. While consuming 3.1mA from a 1.2V supply, the VCO has -120dBc/Hz phase noise at 1MHz offset from the carrier of the 5.3 GHz.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.6
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• pp.23-36
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• 2005

PLLs have been widely used for many applications including communication systems. This paper presents a VCO with an improved negative skewed delay scheme and a PLL using this VCO. The proposed VCO and PLL are intended for replacing traditional LC oscillators and PLLs used in communication systems and other applications. The circuit designs of the VCO and PLL are based on 0.18um CMOS technology with 1.8V supply voltage. The proposed VCO employs subfeedback loops using pass-transistors and needs two opposite control voltages for the pass transistors. The subfeedback loops speed up oscillation depending on the control voltages and thus provide a high oscillation frequency. The two voltage controls have opposite frequency gain characteristics and result in low phase-noise. The 7-stage VCO in 0.18um CMOS technology operates from $3.2GHz\~6.3GHz$ with phase noise of about -128.8 dBc/Hz at 1MHz frequency onset. For 1.8V supply voltage, the current consumption is about 3.8mA. The proposed PLL has dual loop-filters for the proposed VCO. The PLL is operated at 5GHz with 1.8V supply voltage. These results indicate that the proposed VCO can be used for radio frequency operations replacing LC oscillators. The circuits have been designed and simulated using 0.18um TSMC library.