• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1262-1270
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• 2007

In this paper, we propose a new distortion cancellation mechanism for a balanced power amplifier structure using the carrier cancellation loop of a feedforward and post-distortion technique. The proposed cross post-distortion balanced linear amplifier can reduce nonlinear components as much as the conventional feedforward amplifier through the output dynamic range and broad bandwidth. Also the proposed system provides higher efficiency than the feedforward. The capacities of power amplifier and error power amplifier in the proposed system are analyzed and compared with those of feedforward amplifier. Also the operation mechanisms of the three kind loops are explained. The proposed cross post-distortion balanced linear power amplifier is implemented at the IMT-2000($f_0=2.14\;GHz$) band. With the commercial high power amplifiers of total power of 240 W peak envelope power fer base-station application, the adjacent channel leakage ratio measurement with wideband code division multiple access 4FA signal shows 18.6 dB improvement at an average output power of 40 dBm. The efficiency of fabricated amplifier Improves about 2 % than the conventional feedforward amplifier.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.143-152
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• 2004

A novel low-power wideband bipolar second-generation current conveyors(CCIIs) and its application to universal instrumentation amplifier(UIA) were proposed. The CCII for accuracy voltage or current transfer characteristics and low current input impedance adopted adaptive current bias circuit into conventional class Ab CCII. The UIA consists of only two CCIIs and four resistors. Three instrumentation function of the UIA can be realized by selection of input signals and resistors. The simulation results show that the CCII has input impedance of 2.0$\Omega$ and the voltage gain of 60㏈ for frequency range from 0 to 50KHz when used as a voltage amplifier. The CCII has also good characteristics of current follower for current range from -100㎃ to ＋100㎃. The simulation results show that the UIA has three instrumentation amplifier functions without resistor matching. The UIA has the voltage gain of 40㏈ for frequency range from 0 to 100KHz when used as a fully-differential instrumentation amplifier. The power dissipations of the CCII and the UIA are 0.75㎽ and 1.5㎽ at supply voltage of $\pm$2.5V, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.174-181
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• 2004

Ultra precision positioning mechanism has widely been used on semiconductor manufacturing equipments, optical spectrum analyzer and cell manipulations. Ultra precision positioning mechanism is consisted of several actuators, sensors, guides and control systems. Its efficiency depends on each performance of components. The object of this study is to design, analysis and manufacture all of the inchworm linear motor system, which is one of the equipments embodied in ultra precision positioning mechanism. Inchworm linear motor system is consisted of a controller system and an inchworm linear motor, and its driving form is similar to a motion of spanworm. A design and manufacture of inchworm linear motor, which is consisted of three PZT actuators, a rod, two columns and a guide plate, are performed. Minimizing the von-Mises stress of the hinge using Taguchi method and simulation by FEM software optimizes the structural design in a column of flexure hinge. The designed columns and guide plates are manufactured by a W-EDM and NC-milling. A controller system, which is an apparatus to drive inchworm linear motor, can easily adjust driving conditions by varying resonance frequency and input-output voltage of actuators and amplifiers. The performance of manufactured inchworm linear motor system is verified and valuated. In the future, inchworm linear motor system will be used to make a more precision positioning by reinforcing a sensor and feedback system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.136-136
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• 2003

In fiber optic networks, system size and cost can be significantly reduced by development of optical components through planar optical waveguides. One important step to realize the compact optical devices is to develop planar optical amplifier to compensate the losses in splitter or other components. Planar amplifier provides optical gain in devices less than tens of centimeters long, as opposed to fiber amplifiers with lengths of typically tens of meters. To achieve the same amount of gain between the planar and fiber optical amplifier, much higher Er doping levels responsible for the gain than in the fiber amplifier are required due to the reduced path length. These doping must be done without the loss of homogeniety to minimize Er ion-ion interactions which reduce gain by co-operative upconversion. Sol-gel process has become a feasible method to allow the incorporation of Er ion concentrations higher than conventional glass melting methods. In this work, Er-doped $SiO_2$-A1$_2$ $O_3$ films were prepared by two different method via sol -Eel process. Tetraethylorthosilicate(TEOS)/aluminum secondary butoxide [Al (OC$_4$ $H_{9}$)$_3$], methacryloxypropylcnethoxysaane(MPTS)/aluminum secondary butofde [Al(OC$_4$ $H_{9}$)$_3$] systems were used as starting materials for hosting Er ions. Er-doped $SiO_2$-A1$_2$ $O_3$ films obtahed after heat-treating, coatings on Si substrate were characterized by X-ray din action, FT-IR, and N-IR fluorescence spectroscopy. The luminescence properties for two different processing procedure will be compared and discussed from peak intensity and life time.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.135-135
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• 2003

The fast evolution in the fold of optical communication systems demands powerful optical information treatment. These functions can be performed by integrated optical systems. A key component of such systems is erbium doped waveguide amplifier(EDWA). The intra 4f radiative transition of Er at 1.5 $\mu\textrm{m}$ is particularly interesting because this wavelength is standard in optical telecommunications. The fabrication of waveguide amplifier for integrated optics using sol-gel process has received an increasing attention. Potential advantage of lower cost by less capital equipment and easy processing makes this process an attractive alternatives to conventional technologies like flame hydrolysis deposition, ion exchange and chemical vapor deposition, etc. In addition, sol-gel process has been found to be extremely suitable for the control of composition and refractive index related directly with optical properties. The main drawback of such an amplifier with respect to the EDWA is the need for a much higher Er3+ concentration to compensate for the smaller interaction length. However, the high doping of Er might be resulted in the non-radiative relaxation by clustering of Er ions End co-operative upconversion. In order to solve this problem, we investigate the possibility of avoiding short Er-Er distances by encapsulation of Er3+ ions in hosts such as organic-inorganic hybrid materials. For inorganic-organic hybrid sols, methacryloxypropyltrimethoxysilane (MPTS), zirconyl chloride octahydrate and erbium(III) chloride hexahydrate were used as starting materials, followed by conventional sol-gel process. It was observed by TEM that nano sols having core/shell toplology were formed, depending on the mole ratio of Zr/Er. The surface roughness for the coatings on Si substrate was investigated by AFM as a function of Zr/Er ratio. The local environment and vibrational Properties of Er3+ ions were studied using Near-IR, FT-IR, and UV/Vis spectroscopy. Nano hybrid coatings derived from polymer and Er doped encapsulation Eave the good luminescence at 1.55$\mu\textrm{m}$.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.565-572
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• 2001

At the most recent years, laser medical instruments, laser applications and laser nuclear fusion need strong visible light and ultraviolet rays. Nonlinear optical devices, such as harmonic generators and parametric oscillators, provide a means of extending the frequency range of available laser sources. Frequency conversion is a useful technique for extending the utility of high-power lasers. It utilizes the nonlinear optical response of an optical medium in intense radiation fields to generate new frequencies. These progresses have been used to generate high-power radiation in all spectral regions, from the ultraviolet to the far infrared. Optical parametric oscillators and amplifiers generate two waves of lower frequency They are capable of generating a range of wavelengths from a single frequency source, in some cases spanning the entire visible and near infrared regions. Consequently, in order to obtain the green light, the pulsed Nd:YAG laser using multiple-mesh PFN(Pulsed Forming Network) method with Nonlinear optical device was adopted. We compared the current pulseshapes with the laser output energy, and conversion efficiency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.1-11
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• 2009

In this paper, a new 1 kW power amplifier with high efficiency and high stability in a RF generator is designed and fabricated for plasma applications. The efficiency of power amplifier is improved by using class-E amplifier that consists of one push-pull MOSFET and high current drive IC instead of class-C amplifier composed of several single ended MOSFET. Switchable damper that allows selecting three different modes of amplifiers for considering efficiency and stability is added into the amplifier for plasma applications. Stable region of an early electronic discharge section is extended to VSWR of 4.5:1 compared to conventional VSWR of 3.8:1 through using switchable damper. The dimension of the amplifier is also reduced to 30 % of conventional amplifier. The 80 % efficiency of power amplifier with switchable damper is obtained the output power of 1 kW in operating frequency of 13.56 MHz. In comparison of conventional power amplifier for plasma applications, 13 % efficiency is improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.571-575
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• 2017

This paper presents a C-band bi-directional T/R chipset in $0.13{\mu}m$ TSMC CMOS technology for phased array antenna. The T/R chipset, which is a key component of phased array antenna, consists of a 6 bit phase shifter, a 6 bit step attenuator, and three bi-directional gain amplifiers. The phase shifter is controlled up to $354^{\circ}$ with $5.625^{\circ}$ phase step for precise beam steering. The step attenuator is also controlled up to 31.5 dB with 0.5 dB attenuation step for the side lobe level rejection. The LDO(Low Drop Output) regulator for stable 1.2 V DC power and the SPI(Serial Peripheral Interface) for digital control are integrated in the chipset. The chip size is $2.5{\times}1.5mm^2$ including pads.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1465-1470
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• 2006

This paper presents a design of low power CMOS LNA(Low Noise Amplifier) for 2.4 GHz ZigBee applications that is a promising international standard for short area wireless communications. The proposed circuit has been designed using TSMC $0.18{\mu}m$ CMOS process technology and two stage cascade topology by current reuse technique. Two stage cascade amplifiers use the same bias current in the current reused stage which leads to the reduction of the power dissipation. LNA design procedures and the simulation results using ADS(Advanced Design System) are presented in this paper. Simulation results show that the LNA has a extremely low power dissipation of 1.38mW with a supply voltage of 1.0V. This is the lowest value among LNAs ever reported. The LNA also has a maximum gain of 13.38dB, input return loss of -20.37dB, output return loss of -22.48dB and minimum noise figure of 1.13dB.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1101-1109
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• 2012

Accelerometers play a key role in the structural assessment. However, the current electric type accelerometers have certain limitations to apply some structures such as heavy cabling labor, installed sea structure and sensitivity to electromagnetic fields. An optical Fiber Bragg Grating (FBG) accelerometer has many advantages over conventional electrical sensors since their immunity to electromagnetic interference and their capability to transmit signals over long distance without any additional amplifiers, and there is no corrosion from sea water. In this paper, we have developed a new FBG-based accelerometer. The accelerometer consists of two cantilevered type beams and a mass and two rollers. A bragg grating element is not directly glued to a cantilever to avoid possible non-uniform strain in the element. Instead, the bragg grating element will be attached to rotation part that rolled inducing vertical movement of the mass and support cantilever beams so that the bragg grating element is uniformly tensioned to achieve a constant strain distribution. After manufacturing, we will prove the performance and the natural frequency of the accelerometer through the experiment with a vibration shaker. The FBG-based accelerometer is developed for measuring the vibration not exceeding 50 Hz for the marine and civil structures.