• Proceedings of the Optical Society of Korea Conference
• /
• 2002.11a
• /
• pp.178-179
• /
• 2002

We generate optical millimeter-waves by double-sideband suppressed carrier (DSB-SC) modulation using a Mach-Zehnder (MZ) modulator biased at the minimum power. The DSB-SC modulation allows the high-frequency intensity modulation for millimeter-wave generation at the twice of the MZ modulator driving frequency.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.4
• /
• pp.375-387
• /
• 2015

This study investigates an economic and highly efficient power-converter topology and its modulation scheme for 60 kW rapid EV charger system. The target system is a three-phase three-switch buck-type rectifier topology. A new carrier-based PWM scheme, which is characterized by simple implementation using logic gates, is introduced in this paper. This PWM scheme replaces the diode rectifier equivalent switching state with an active switching state to produce the same effective current flowing path. As a result, the distortion of input current during the polarity reversal of capacitor line voltage can be mitigated. The proposed modulation technique is confirmed through simulation verification. The proposed modulation technique and its implementation scheme can expand the operation range of the three-phase three-switch buck-type rectifier with high-quality AC input and capacitor ripple current.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.37 no.1
• /
• pp.27-34
• /
• 2000

In this paper, carrier transport mechanism and modulation response for SCH(Separate Confinement Heterostructure) SQW(Single Quantum Well) laser diodes were studied. In order to explain carrier transport mechanism, both carrier density and current density were calculated. The recombination current density in the quantum well as a function of the SCH length was also calculated. For the modulation response, linearizing the rate equation, we calculated the bandwidth, relaxation oscillation frequency, damping factor, and the K-factor.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.1
• /
• pp.56-62
• /
• 2011

A Satellite transponder is mounted on the Satellite and performs radio communications with the ground station. A Digital transponder compared to The analog transponder is made easy and accurate performance prediction. Also Modulation Scheme, Data Rate, Loop Bandwidth, Modulation Index and etc. can be changed on orbit, by implementing FPGA can reduce the weight and volume. The core technology of digital transponder is Carrier Recovery loop. Dynamic Range, Frequency Tracking Range, Frequency Tracking Rate and Coherent performance are determined by the performance of the Carrier Recovery loop. In this paper, we proposed the structure of Carrier Recovery loop for the Satellite digital transponder, then tested and verified the structure.

• Proceedings of the KIEE Conference
• /
• 1997.07f
• /
• pp.2058-2061
• /
• 1997

A main research topic in PWM inverter drive system is to reduce the generated acoustic noise. One method to reduce the acoustic noise is to cause the switching pattern to be random. This RPWM(Random Pulse Width Modulation) technique for voltage controlled inverters is a kind of good solutions for reduction of acoustic noise and suppression of vibration. This paper describes a carrier frequency modulated real-time RPWM inverter. Changing the carrier frequency randomly, the power spectrum of tile acoustic noise was spread over the wide-band area. And experimental results showed that emitted noise is much more comportable and less annoying

• Journal of information and communication convergence engineering
• /
• v.7 no.3
• /
• pp.304-308
• /
• 2009

This paper proposes a new concept of a signal constellation of the recently introduced half-symbol-rate-carrier phase-shift keying (HSRC-PSK) modulations for bandwidth-efficient high speed data communications. Since the HSRC-PSK modulations contain different symbol energies representing the same bit sequences due to the loss of orthogonality of their HSRC signals, it is very hard to represent the symbol using the conventional signal constellation. To resolve the problem, two different energies are assigned to represent one symbol for the HSRC offset quadrature phase shift keying (OQPSK) modulation. Similarly, the different energies exist to display the different symbol for HSRC minimum shift keying (MSK) modulation. With the proposed signal space representation, HSRC-PSK symbol can easily be shown with a two-dimensional scatter plot which provides helpful information of evaluating HSRC-PSK signal's quality.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.397-400
• /
• 1990

All the existing PWM voltage-controlled inverters, regardless of the advantages of the operation, have produced serious problems such as acoustic noise. In this raper, the PMW technique for acoustic noise reduction is implemented using randomly modulated carrier modulation. By modulating the triangular carrier in sinusoidal PWM with band-limited white noise, it is shown that the acoutic noise level and spectral density is reduced in a tone. This method shows great merit in application the AC motor drive system to particularly environment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.11
• /
• pp.100-105
• /
• 2014

In this paper, Uninterruptible Power Supply(UPS) Inverter system using Carrier Frequency Modulated PWM (CFM-PWM) is proposed to reduced harmonics and electromagnetic noise. Power conversion of UPS system is executed by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI which deteriorate the reliability of the UPS system. This Problems improved by Random PWM switching method. The simulation results of the proposed system was compared with the system using conventional method using Matlab/Simulink. The results show that the output voltage and current harmonics of the proposed UPS system significantly decreased and spread into wide band area by the proposed Carrier Frequency Modulated PWM(CFM-PWM) method based on the Space Vector Modulation.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.758-761
• /
• 2005

This paper describes the acoustic noise spectra of the pseudo-random carrier modulation technique according to the different PRBS(Pseudo Random Binary Sequence) bits. To confirm the validity of the proposed method, a 130v three-phase 5-level inverter motor drives was implemented. The harmonics spectra broadening effect of pseudo random carrier and the acoustic noise radiated from the inverter drives were discussed and verified according to the different bits of shift resister operating as PRBS.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.20 no.4
• /
• pp.30-35
• /
• 1983

Numerical calculations have been made about the phase differences of the short circuit current in a solar cell according to the variation of the modulation frequency. The phase differences in short circuit current of the solar cell exposed to the modulated light source is measured experimentally. From the above two results, the minority carrier lifetime has been determined. Also, minority carrier lifetime has been determined from the observed photo-induced open circuit voltage decay wave form that follows termination of the excitation.