• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.68-73
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• 2011

In this paper, a compact-narrow open stub band-pass filter with parasitic-signal of low frequency range and second harmonics rejected using the parallel coupled line and FLCLM(Frquency Locked Controlled Length Method) is proposed. The characteristic of the parallel coupled line can be rejection for parasitic-signal of low frequency range and second harmonics. In last filter of experimental results show that insertion loss is 1.2 dB and return loss is 14.8 dB, and the fractional bandwidth is 10 % at the center frequency of 5.8 GHz. In additional, the rejection for parasitic-signal of low frequency range and second harmonics are 28.9 dB and 28.8 dB, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.25-33
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• 1999

In this paper, the method of reducing hanmnics and correcting of power factor in single PWM converter associated with diode rectifier and boost converter is studied. In the general diode rectifier there are sorre problems that discontinuous current of reducing power factor and including distortion of hanmnics at the input current affects other sources. To solve the problems of performance degradation due to pulse wavefonn in the input current, the ac-dc converter in which the hanmnic distortion in the input current is reduced using a third-hanmnic-injected PWM is proposed. A lower power loss of switching and easy configuration of circuit are obtained by adopting discontinuous current mode. Simulation and experimental results of ac-dc converter with 5[kHz] switching frequency are presented and correction of power factor and reduction of total hanmnic distortion was established.lished.

• 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.118-125
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• 2007

Harmonic band of bandpass filter(BPF) is suppressed using coupled mushroom structure. Between double positive (DPS) transmission line such as microstrip and double negative(DNG) transmission line such as one dimensional mushroom structure, strong coupling broadly arises in the cross range of dispersion curves of isolated microstrip and mushroom structure because of complex propagation constant in the cross range. Strong coupling inhibits wave propagation, so that this kind of structure can be utilized as bandstop filter(BSF). This BSF utilizes coupled transmission line instead of coupled resonator, resulting in broad bandwidth(>30 %), shan-rejection, and high rejection level. The strong coupling between DPS and DNG transmissionline makes it possible shorten coupling length, resulting in compact size. In this paper, parallel coupled BSF having center frequency of 4 GHz and 3 dB fractional bandwidth of 40 % is designed and utilized to suppressed spurious mode of two bandpass filters.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.109-117
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• 2004

In this paper, a K-band local oscillator composed of a VCDRO(Voltage Controlled Dielectric Resonator Oscillator), GaAs MESFET, and Reflector type frequency doubler has been designed and fabricated. TO obtain a good phase noise performance of a VCDRO, a active device was selected with a low noise figure and a low flicker noise MESFET and a dielectric resonator was used for selecting stable and high oscillation frequency. Especially, to have a higher conversion gain than a conventional doubler as well as a good harmonic suppression performance with circuit size reduced a doubler structure was employed as the Reflector type composed of a reflector and a open stub of quarter wave length for rejecting the unwanted harmonics. The measured results of fabricated oscillator show that the output power was 5.8 dBm at center frequency 12.05 GHz and harmonic suppression -37.98 dBc, Phase noise -114 dBc at 100 KHz offset frequency, respectively, and measured results show of fabricated frequency doubler, the output power at 5.8 dBm of input power is 1.755 dBm conversion gain 1.482 dB, harmonic suppression -33.09 dBc, phase noise -98.23 dBc at 100 KHz offset frequency, respectively. This oscillator could be available to a local oscillator in K-band which used frequency doubler techniques.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.3
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• pp.59-64
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• 2002

In the RFID system using ISM-band, The tag mounted at the object has used the DC power by rectifying the RF signals of the small antenna for operating the micro-controller and memory. The performance of the tag would be reduced because of the second harmonics generated by the nonlinearity of the semiconductor and the spurious signal excited the high order mode of the antenna. This paper has realized the novel type low-pass filter with "the Stub-I type DGS slot structure" to improve the efficiency of the tag by suppressing the harmonics. The optimized frequency character at the pass-band/stop-band has obtained by tuning the stub width and slit width of I type slot. The measured result of the LPF has the cutoff frequency 3.25 GHz, the insertion loss about -0.29~-0.3 dB at pass-band 2.4 GHz~2.5 GHz, the return loss about -27.688~-33.665 dB at pass-band with a good performance, and the suppression character is about -19.367 dB at second harmonics frequency 4.9 GHz. This DGS LPF may be applied the various application as the RFID, WLAN to improve the efficiency of the system by suppressing the harmonics and spurious signals. 

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.123-126
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• 2000

STC(Sinusoidal Transform Coding) 방식은 음성신호의 주파수 영역에서 스펙트럼 피크치들을 정현파로 모델링하여 합성하는 방식을 말한다. 저전송률 STC 방식에서는 전송되는 정보량을 줄이기 위해 스펙트럼 피크를 대신해 음성신호의 스펙트럼 포락선 정보와, 피치정보를 이용하여 얻어지는 고조파 성분들을 정현파로 모델링하여 음성을 합성한다. 본 논문에서는 음성신호의 정현파 모델에 기반하여 2.4kbps 전송속도를 갖는 음성부호화 알고리즘을 제안하였으며, 실험결과로 합성음의 파형과 스펙트럼 특성, 위상특성, 그리고 MOS(Mean Opinion Score) 테스트를 이용한 합성음의 음질을 비교/분석 하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.344-350
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• 2009

The goal of this study is to introduce the theoretical background of acoustic nonlinearity in surface wave and to verify its characteristics by experiments. It has been known by theory that the nonlinear parameter of surface wave is proportional to the ratio of $2^{nd}$ harmonic amplitude and the power of primary component in the propagated surface wave, as like as in bulk waves. In this paper, in order to verify this characteristics we constructed a measurement system using contact angle beam transducers and measured the nonlinear parameter of surface wave in an Aluminum 6061 alloy block specimen while changing the distance of wave propagation and the input amplitude. We also considered the effect of frequency-dependent attenuation to the measurement of nonlinear parameter. Results showed good agreement with the theoretical expectation that the nonlinear parameter should be independent on the input amplitude and linearly dependent on the input amplitude and the $2^{nd}$ harmonic amplitude is linearly dependant on the propagation distance.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.219-221
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• 2009

태양전지 어레이(PV-array)로부터 발전되는 DC 전력을 AC로 변환시켜 계통으로 발전시키는 역할을 하는 태양광 발전 시스템용 PCS의 스위칭 회로 Topology로는 일반적으로 3상 풀브리지 회로가 사용된다. 이러한 3상 풀브리지 회로 시스템의 수명예측을 위해 DC link 단의 커패시터의 커패시턴스를 계산하여 커패시턴스의 감소정도를 이용하여 전체 시스템의 수명을 예측하게 된다. 이러한 커패시터의 상태를 추정하기 위해서는 시스템을 정지시킨 후 커패시터를 분리하여 커패시턴스를 측정하는 방법, 특정 주파수의 전류(일반적으로 저주파)를 주입하고 주입한 전류의 주파수에 해당하는 전류 및 전압을 검출하여 capacitance 연산하는 방식등이 이용된다. 시스템을 정지시킨 후 커패시터를 분리하여 커패시턴스를 측정하는 방법은 번거로우며, 전류 주입을 이용한 방식은 불필요한 고조파 전류가 계통으로 침투하는 단점을 가진다. 그러므로 본 연구에서는 모듈타입 PCS 이용시 계통으로 고조파 침투가 없는 비침투 커패시턴스 계산 알고리즘을 제안한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.3
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• pp.221-228
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• 2000

본 논문에서는 전기·전자 장비의 활용이 확대되면서 더욱 더 관심이 고조되고 있는 전자파장해에 대하여 논하고자 한다. 기존 PWM 직류전원장치에서는 회로 소자 및 배치에 따른 기생소자와 갑작스런 전압/전류의 변화에 의해 전자파장해를 발생시킨다. 본 논문에서는 PWM 직류전원장치에서 발생하는 전자파장해의 특성을 고찰하고, 출력전압 조절에 큰 영향을 주지 않는 범위내에서 PWM 제어가 가능하면서 두 개의 고정된 스위칭주파수로 연속적으로 변조하는 Bi-FM 변조제어방식과 랜덤하게 변화하는 스위칭주파수 변조제어방식을 이용하여 전도잡음을 저감시킬 수 있는 변조방식을 논할 것이다. 또한 이들 변조 방식의 주파수 스펙트럼 특성을 비교·분석하여 설명하고, 제어기를 분석·설계하여 실험을 통하여 스위칭주파수와 그 고조파 주파수들의 측대역으로 전도잡음이 분산되고 전도잡음의 피크치가 감소됨을 확인하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.127-132
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• 2006

This paper presents a dual-mode amplifier which operates as amplifier or frequency multiplier according to the input frequency. It satisfies the 802.11a/b/g frequency band of wireless LAN standard. A conventional dual-band wireless LAN transmitter consists of the separating power amplifiers operating at each frequency band, but the proposed dual-mode amplifier operates as an amplifier for the 802.11b/g signal and as a frequency multiplier for the 802.11a signal according to each LAN bias condition. The amplifier mode shows the gain of 13dB, the PldB of 17dBm and second harmonic suppression of below -37dBc. And the frequency-doubler mode shows the gain of 3.3dB, the output power of 7.3dBm and third harmonic suppression of below -50dBr.