• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.2
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• pp.36-40
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• 1993

In order to improve complicated construction and complex control which are disadvantage of optimal PWM technique aimed at harmonic elimination method, this paper presented MRA(Model Reference Adaptive) PWM technique that gatmg signal of inverter is generated by comparing the reference signal with the induced feedback signal at the reference model of load. Design of controller is composed of microprocessor and analog circuit. MRA PWM technique used in the paper is able to compensate the degradation of voltage efficiency to be generated by the ratio of the output voltage to the DC supply voltage being low for using conventional sinusoidal PWM technique. When the trapezoidal signal is employed as the reference signal. the low order harmonics of line current can be reduced and the switching pattern is made by on-line computation using comparatively simple numerical analysis.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.110-114
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• 2008

In this paper, high efficient class F power amplifier with dual band has been realized. Dual band power amplifier have used modify stub matching for single FET, center frequency 2.14GHz and 5.2GHz respectively. Dual band amplifier is 32.65dBm output power, gain 11dB and PAE 36% at the 2.14GHz, 7dB gain at the 5.2GHz. Design of a dual band class F power amplifier using harmonic control circuit. The measured are 9.9dB gain, 30dBm output power and PAE 55% at the 2.14GHz, 11.7dB gain at the 5.2GHz. This paper is being used the load-pull method and it maximizes output power and it is using the only one transistor in the paper. As a result, this research will obtain a dual band high PAE power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.78-83
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• 2010

In this paper, a novel dual-band power amplifier using metamaterials has been realized with one RF GaN HEMT diffusion metal-oxide-semiconductor field effect transistor. The CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. We have managed only the second- and third-harmonics to obtain the high efficiency with the CRLH TL in dual-band. Also, the proposed power amplifier has been realized by using the harmonic control circuit for not only the output matching network, but also the input matching network for better efficiency. Two operating frequencies are chosen at 900 MHz and 2140 MHz in this work. The measured results show that the output power of 39.83 dBm and 35.17 dBm was obtained at 900 MHz and 2140 MHz, respectively. At this point, we have obtained the power-added efficiency (PAE) and IMD of 60.2 %, -23.17dBc and 67.3 %, -25.67dBc at two operation frequencies, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.190-198
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• 1995

Many industrial servo amplifiers employ power transister as output device. Thyristor converters are not adopted to drive servo motor, although thyristor is superior to power TR in power rating, noise immunity, price, and size. The reason is, thyristor has no ability of self turn - off. Here in this paper line commutation, in which thyristor is turned off naturally since cathode voltage is higher than anode as time goes by, is employed to turn on thyristor with a delicate sequence. We developed thyristor servo amplifier which does not cause any damage on thyristor because it is designed to prevent triggering the two SCRs in the same arm simultaneously. And it was made clearly how to trigger SCR without any power line shorting and also harmonic analysis is carried out with the aid of FFT analyzer and proved that it can be used even severe reactive load. The designed circuit operated as a good DC amplifier in conventinal servomotor and the results can be use as a position control system application.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.91-96
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• 2011

In this paper, a low-power direct-conversion transmitter based on current-mode operation, which satisfies the IEEE 802.15.4 standard, is proposed and implemented in a $0.13{\mu}m$ CMOS technology. The proposed transmitter consists of DACs, LPFs, variable gain I/Q up-conversion mixer, a divide-by-two circuit with LO buffer, and a drive amplifier. By combining DAC, LPF, and variable gain I/Q up-conversion mixer with a simple current mirror configuration, the transmitter's power consumption is reduced and its linearity is improved. The drive amplifier is a cascode amplifier with gain controls and the 2.4GHz I/Q differential LO signals are generated by a divide-by-two current-mode-logic (CML) circuit with an external 4.8GHz input signal. The implemented transmitter has 30dB of gain control range, 0dBm of maximum transmit output power, 33dBc of local oscillator leakage, and 40dBc of the transmit third harmonic component. The transmitter dissipates 10.2mW from a 1.2V supply and the die area of the transmitter is $1.76mm{\times}1.26mm$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.887-894
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• 2007

In this paper, design and fabrication of the LPF with controllable four transmission zeros using electric coupling and added open stub is presented. Pass-band of the LPF is GSM band, and two transmission zeros are generated by the electric coupling at the WiBro and S-DMB band, And the other two transmission zeros are generated by the open stub at the upper frequencies. Harmonic frequency of the stop-band is suppressed by the realization of the filter using quasi-lumped element with small parasitic values. $C_M$, which is the electric coupling element of the equivalent circuit, is realized by the distance control between the open stubs of the filter structure. The fabricated LPF used teflon substrate with relative permittivity of 2.6. And it has a size of $38{\times}20{\times}0.79 mm^3$, which is including a feed line. The measured 3 dB cut-off frequency is 1.55 GHz, and locations of the transmission zeros are 2.20, 2.43, 4.11 and 6.84 GHz, respectively.