• 한국통신학회논문지
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• 제30권2A호
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• pp.122-128
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• 2005

본 논문에서는 고조파 억압 특성 개선을 위한 저잡음 병렬 궤환형 발진기 (Parallel feedback oscillator)와 주파수 체배기 (frequency doubler)를 설계 및 제작하였다. 주파수 체배를 위한 발진기의 기본 주파수를 유전체 공진기 (DR: Dielectric Resonator) 여파기와 능동소자 사이에서 얻음으로써 불요 고조파를 현저히 억압하였다. 발진기의 기본 주파수 신호는 고조파 신호를 억압하기 위한 부가적인 대역 통과 여파기가 필요치 않으며 곧바로 주파수 체배기의 입력단으로 인가되어 주파수 체배기의 입력 정합 회로가 간단하다. 측정된 발진기의 고조파 억압 특성은 -47.7 dBc이고 주파수 체배기를 이용하였을 때 24.0 GHz 에서의 기본 주파수 억압 특성은 -37.5 dBc이다. 위상 잡음 특성은 중심 주파수에서 10 KHz와 100 KHz 떨어진 곳에서 각각 -80.3 dBc/Hz와 -93.5 dBc/Hz이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.415.2-415.2
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• 2016

Triboelectric nanogenerator (TENG) is one of ways to convert mechanical energy sound, waves, wind, vibrations, and human motions to available electrical energy. The principal mechanism to generate electrical energy is based on contact electrification on material surface and electrostatic induction between electrodes. The performance of TENG are dependent on amount of the input mechanical energy and characteristics of triboelectric materials. Furthermore, the whole TENG system including mechanical structure and electrical system can effect on output performance of TENG. In this work, we investigated the effect of gear train on output performance and power conversion efficiency (PCE) of TENG under a given input energy. We applied the gear train on mechanical structure to improve the contact rate. We measured the output energy under a constant input energy by controlling the size of the working gear. We prepared gears with gear ratios (rin/rw) of 1, 1.7, and 5. Under the constant input energy, the voltage and current from our gear-based TENG system were enhanced up to the maximum of 3.6 times and 4.4 times, respectively. Also, the PCE was increased up to 7 times at input frequency of 1.5 Hz. In order to understand the effect of kinematic design on TENG system, we performed a capacitor experiment with rectification circuit that provide DC voltage and current. Under the input frequency of 4.5 Hz, we obtained a 3 times enhanced rectifying voltage at a gear ratio of 5. The measured capacitor voltage was enhanced up to about 8 fold in using our TENG system. It is attributed that our gear-based TENG system could improve simultaneously the magnitude as well as the generation time of output power, finally enhancing output energy. Therefore, our gear-based TENG system provided an effective way to enhance the PCE of TENGs operating at a given input energy.

• 전기학회논문지
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• 제62권6호
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.

• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.435-441
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• 2010

To verify the possibility of a power generation system using biogas from the waste of pig farm for rural electric production, a SI gasoline engine is modified to use biogas fuel and was installed in a 20 KVA power generation system. An electronic speed regulation unit is developed to keep the system speed at 1500 rpm. Experimental investigations have been carried out to examine the performance characteristics of power generation system (such as: system frequency, phase output voltage,$\ldots$). In addition, the operating parameters and output emissions ($NO_x$, HC, and $CO_2$) of biogas-fueled engine are preliminary evaluated and analyzed for the change of system load. Results indicated that the researched power generation system shows a high stability of output voltage and frequency with help of speed regulator. Biogas fuel (mainly $CH_4$ and $CO_2$) has an environmental impact and potential as a green alternative fuel for SI engine and they would not require significant modification of existing engine hardware. Output emissions of biogas-fueled engine are found to be relative low. $NO_x$ emission increases with the increase of output electric power of the power generation system.

• 음성과학
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• 제10권2호
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• pp.145-157
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• 2003

Vowels are classified by the shapes of vocal tract. These shapes form constriction points along the tract, which have an influence on such vocal tract resonance as F1, F2, F3, and so on. The formant frequency is influenced by aperture and placement of tongue and the intensity is influenced by air pressure of subglottis. The object of this study compares to characterize the spectral outputs of oral and nasal spectra for the formant frequencies and intensity of Korean oral vowels. Subjects consisted of 20 normal persons (10 male and 10 female) without laryngeal pathology. The speech sample included /a/, /e/, /i/, /o/, /u/ of Korean oral vowels. The spectrum of each vowel was analysed by Nasal View and Real Analysis Program using Dr. Speech. The result showed that nasal intensity is decreased manifestly from F1 to F2. But oral intensity and Intensity is decreased little bit from F1 to F2. The most of values of nasal formant frequency is similarity oral formant frequency and Formant frequency or little bit smaller.

• 한국항행학회논문지
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• 제14권2호
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• pp.176-182
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• 2010

본 논문에서는 역 E-급 증폭기 출력 회로의 병렬 공진기를 주파수에 대해 가변되도록 회로를 구성하여 넓은 주파수 범위에서 높은 전력부가효율과 출력전력을 유지하는 방법을 제안하였다. 여기서 사용된 병렬 공진기는 동작 주파수에 따라서 Q 값은 동일하고, 가변 특성을 얻기 위해서 바렉터 다이오드를 사용하여 인덕터와 캐패시터를 만들었으며, 전류 영점 교차를 위한 인덕턴스 성분은 집중소자로 또, 위상 보상을 위한 캐패시턴스는 분포소자로 구현하였다. 역 E-급 증폭기의 주파수 가변 특성을 통해서 효율과 출력 전력을 확인한 실험 결과는 65-120MHz의 주파수 범위에서 증폭기는 최대 75%의 전력부가효율과 25dBm의 출력전력을 얻었다.

• 전기학회논문지P
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• 제66권2호
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• pp.63-68
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• 2017

This paper proposes a new non-isolated DC conversion circuit topology of the voltage source coupled inductor series resonant high-frequency PFM controlled boost chopper type DC-DC power converter using two in one IGBT power module, which can efficiently operate under a principle of zero current soft switching for wide output regulation voltage setting ranges and wide fluctuation of the input DC side voltage as well as the load variation ranges. Its steady state operating principle and the output voltage regulation characteristics in the open-loop-based output voltage control scheme without PI controller loop are described and evaluated from theoretical and experimented viewpoints. Finally, in this paper the computer-aided simulation steady-state analysis and the experimental results are presented in order to prove the effectiveness and the validity of voltage regulation characteristics of the proposed series resonant zero current soft switching boost chopper type DC-DC power converter circuit using IGBTs which is based on simple pulse frequency modulation strategy more than, 20kHz.

• Journal of Power Electronics
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• 제14권3호
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• pp.531-540
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• 2014

A novel carrier-based PWM (CBPWM) strategy of a three-level NPC converter is proposed in this paper. The novel strategy can eliminate the low-frequency neutral point (NP) voltage oscillation under the entire modulation index and full power factor. The basic principle of the novel strategy is introduced. The internal modulation wave relationship between the novel CBPWM strategy and traditional SPWM strategy is also studied. All 64 modulation wave solutions of the CBPWM strategy are derived. Furthermore, the proposed CBPWM strategy is compared with traditional SPWM strategy regarding the output phase voltage THD characteristics, DC voltage utilization ratio, and device switching losses. Comparison results show that the proposed strategy does not cause NP voltage oscillation. As a result, no low-frequency harmonics occur on output line-to-line voltage and phase current. The novel strategy also has higher DC voltage utilization ratio (15.47% higher than that of SPWM strategy), whereas it causes larger device switching losses (4/3 times of SPWM strategy). The effectiveness of the proposed modulation strategy is verified by simulation and experiment results.

• 한국위성정보통신학회논문지
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• 제1권1호
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• pp.54-58
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• 2006

동작주파수를 쉽게 조절할 수 있는 신호생성용 안테나 (Antenna-Integrated Oscillator) 설계방법을 소개한다. 제안하는 회로는 광대역에서 부성저항을 갖는 능동회로 (Negative-Resistance Circuit)와 패치안테나로 구분되며, 오실레이터의 동작주파수는 안테나의 공진 주파수로 결정된다. 이러한 디자인 방법은 안테나와 오실레이터의 동작주파수 불일치로 인한 출력파워의 감소 가능성을 줄일 수 있다. 또, 제안하는 설계방법에서 안테나의 Feed 지점과 Feed 라인의 길이를 조절하여 최적의 출력파워를 낼 수 있음을 Load-Pull 시뮬레이션으로 확인하였다. C-band, X-band 회로를 각각 제작, 측정하였고 이를 통하여 설계방법의 타당성을 증명하였다.

• 한국광학회지
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• 제11권2호
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• pp.97-101
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• 2000

본 논문에서는 광섬유 자이로스코프에서 자이로 출력으로부터 광원의 과잉잡음 성분을 소거할 수 있는 새로운 방법을 제안하고 실험하였다. 이 방식은 기존의 방식과 달리 광원잡음 검출시에 별도의 지연 광섬유가 필요없다는 장점이 있으며, 신호처리를 통해 자이로 출력에서 광우너 과잉잡음의 적정주파수 성분만을 소거하는 방식으로서, 적정주파수에서 동작하는 광섬유 자이로에 단순하게 적용될 수 있다. 고출력 Erbium 첨가 광섬유 광원을 사용하고 적정주파수로 변조된 광섬유 자리로스코프에 이 방식을 적용한 결과, 자이로 출력 스펙트럼상의 잡음이 12dB 감소하였다. 또한, 회전에 따른 자이로 출력을 측정한 결과, 불규칙잡음 계수가 1/3.5 정도로 감소하였다.