• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.813-820
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode converter is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode converter and guarantee zero-current-switching(ZCS) of the switch over the wide load range. The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. In addition, control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations and experiments.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.3
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• pp.313-321
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• 2014

A low-power low-cost polar transmitter for EDGE is designed in $0.18{\mu}m$ CMOS. A differential delta-sigma modulator (DSM) tunes a three-terminal voltage-controlled oscillator (VCO) to perform RF phase modulation, where the VCO tuning curve is digitally pre-compensated for high linearity and the carrier frequency is calibrated by a dual-mode low-power frequency-locked loop (FLL). A digital intermediate-frequency (IF) pulse-width5 modulator (PWM) drives a complementary power-switch followed by an LC filter to achieve envelope modulation with high efficiency. The proposed transmitter with 9mW power dissipation relaxes the time alignment between the phase and envelope modulations, and achieves an error vector magnitude (EVM) of 4% and phase noise of -123dBc/Hz at 400kHz offset frequency.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.148-162
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• 1996

Bonding wires for high frequency device packaging have dominant parasitic inductances which limit the performance of semiconductor lasers. In this paper, the inductance sof bonding wires are claculated by the method of moments with incorporation of ohmic loss, and the wideband modulation characteristics are analyzed for ddifferent wire lengths and structures. We observed the modulation bandwidth for 1mm-length bonding wire lengths and structures. We observed the modulation bandwidth for 1mm-length bonding wire is 7 GHz wider than that for 2mm-length bonding wire. We also observed th estatic inductance calculation results in dispersive deviation of the parasitic inductance and the modulation characteristics from the wideband moment methods calculations. The angled bonding wire has much less parasitic inductance and improves the modulation bandwidth more than 6 GHz. This calculation resutls an be widely used for designing and packaging of high-speed semiconductor device.

• Journal of Power Electronics
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• v.16 no.2
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• pp.480-489
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• 2016

A novel hybrid carrier-based pulse width modulation (CBPWM) scheme that combines unipolar and dipolar modulations is proposed for single-phase three-level rectifiers, which are widely applied in railway traction drive systems. The proposed CBPWM method can satisfy the volt-second balancing principle in the complete modulation index region through overmodulation compensation. The modulation scheme features two modulation modes: unipolar and dipolar. The operation range limits of these modulation modes can be modified by changing the separation coefficient. In comparison with the traditional unipolar CBPWM, the proposed hybrid CBPWM scheme can provide advantageous features, such as lower high-order harmonic distortion of the line current and better utilization of switching frequency. The separation coefficient value is optimized to achieve the maximum utilization of these advantages. The experimental results verify the feasibility and effectiveness of the proposed hybrid CBPWM scheme.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.228-232
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• 1995

We have made modulation doped SMQW-PBH-DFB-LD for high speed optical communications. The waveguide and barrier layers were doped by Zn with the concentration of $1.2 \times 10^{18}cm^{-1}$. Mean threshold current and slope efficiency were 24.88 mA (minimum 16 mA) and 0.197 mW/mA (maximum 0.275 mW/mA) respectively. Linewidth enhancement factor ($\alpha$) of MD-SMQW-PBH-DFB-LD was reduced than that of SMQW-PBH-DFB-LD. Linewidth enhancement factor of 1.8 owes to the large gain coefficient of modulation doped active layer. The resonance frequency was linearly increased with the square root of optical power. The resonance frequency in small signal modulation was measured as 8 GHz and -3 dB modulation bandwidth was 10 GHzat $46mA(I_{th}+30mA)$..

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1137-1146
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• 2008

OFDM is very effective for the high speed communication system. However, OFDM has the problems of high PAPR and serious ICI, which is different from the single carrier system. Especially, ICI problem caused by phase noise, Doppler effect and frequency offset is main reason for poor performance since it breaks down the orthogonality between subcarriers in OFDM communication system. Therefore, WFMT modulation scheme is studied and the effect of the carrier frequency offset and phase noise is analyzed. WFMT modulation scheme is based on the wavelet theory and complex filter banks for synthesis and analysis of multichannel signal. WFHT modulation scheme keeps on the advantage of filter banks system and can be easily possible for the implementation of filter banks. In this paper, we compare ISI and ICI distortions of the WFMT and OFDM system due to the carrier frequency offset and phase noise. Also, we analyze the PAPR and BER performances in the HPA and ICI situation caused by the Doppler frequency shift and the frequency offset.

• 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 international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.330-335
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• 2012

Brushless doubly-fed machine (BDFM) doesn't use brush and slip ring, and has advantages such as high system reliability, small capacity of its frequency converter, low system cost, adjustable power factor and speed, etc. At the same time, it has good applicable potentials on the variable frequency motors and the variable speed constant frequency generators. However, due to the complicacy and particularity of BDFM in the structure and operating mechanism, the effect of magnetic field modulation directly influences the operating efficiency of BDFM. To study the effect of different cage rotor structures on the magnetic field modulation of BDFM, the rotor magnetomotive force (MMF) of BDFM with cage rotor is studied by the analytical method. The components and features of rotor harmonic MMFs are discussed. At the same time, the method to weaken the higher harmonics is analyzed by the theoretic formulae. Furthermore, the magnetic field modulation mechanism is expounded on in detail and the relationship between the magnetic field modulation effect and the operating efficiency of BDFM is established. And then, a new method for estimating the magnetic field modulation effect is proposed. At last, the magnetic field modulation effects of four BDFM prototypes with different cage rotor structures are compared by the MMF analysis and the efficiency data of electromagnetic design. The results verify the effectiveness of the new method for estimating the magnetic field modulation effect of BDFM with cage rotor.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.10
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• pp.35-42
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• 2002

Modulation frequency dependences of the pyroelectric properties of PLT (P $b_{1-x}$ L $a_{x}$ $Ti_{1-x}$ 4/ $O_3$) thin films with La concentrations of 5, 10 and 15㏖% have been investigated by using the dynamic method. The PLT thin film with 10㏖% of the La concentration (PLT(10) thin film) shows the most excellent pyroelectric properties among the films. For PLT(10) thin film, the pyroelectric coefficient shows the maximum value of 6.6$\times$10$^{-9}$ C/$\textrm{cm}^2$ㆍK without frequency dependence. The figure of merits for the voltage responsivity and specific detectivity are 1.03$\times$10$^{-11}$ Cㆍcm/J and 1.46$\times$10$^{-9}$ Cㆍcm/J, respectively. Voltage responsivity corresponding to the pyroelectric voltage is almost constant at low modulation frequency and decreases in proportional to frequency at high modulation frequency. Voltage responsivity is 5.15 V/W at 8Hz. Noise equivalent power (NEP) and specific detectivity ( $D^{*}$) of the PLT(10) thin film are 9.93$\times$10$^{-8}$ W/H $z^{1}$2/ and 1.81$\times$10$^{6}$ cmH $z^{1}$2/W at the frequency of 100Hz, respectively. The results indicate that PLT(10) thin film is very suitable for pyroelectric IR sensors.s.s.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.203-205
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.