• Proceedings of the KIEE Conference
• /
• 2001.10a
• /
• pp.150-156
• /
• 2001

This paper describes an implementation of the DSP(Digital Signal Processor) based triangular carrier frequency modulated RPWM inverter drive system. The power spectrum of the noise emitted from the induction motor was measured in the anechoic chamber. The analysis of the sources for the acoustic noise and the effects of the noise reduction are confirmed by the measured spectra of the noise. Real-time RPWM along with the speed control was achieved by high speed DSP. By changing the center frequency and the bandwidth of the carrier, the proposed real-time RPWM scheme can be used as an efficient switching frequency band acoustic noise reduction method for the inverter drive system with variant load conditions.

• International Journal of Computer Science & Network Security
• /
• v.23 no.10
• /
• pp.1-10
• /
• 2023

This paper proposes a method to extend Inter-Carrier Interference (ICI) canceling Orthogonal Frequency Division Multiplexing (OFDM) receivers for 5G mobile systems to spatial multiplexing 2×2 MIMO (Multiple Input Multiple Output) systems to support high-speed ground transportation services by linear motor cars traveling at 500 km/h. In Japan, linear-motor high-speed ground transportation service is scheduled to begin in 2027. To expand the coverage area of base stations, 5G mobile systems in high-speed moving trains will have multiple base station antennas transmitting the same downlink (DL) signal, forming an expanded cell size along the train rails. 5G terminals in a fast-moving train can cause the forward and backward antenna signals to be Doppler-shifted in opposite directions, so the receiver in the train may have trouble estimating the exact channel transfer function (CTF) for demodulation. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceller is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number n to receiver sub-carrier number l is generated. In case of n≠l, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 8 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, 2×2MIMO QPSK and 16QAM modulation schemes, BER (Bit Error Rate) improvement was observed when the number of taps in the multi-tap equalizer was set to 31 or more taps, at a moving speed of 500 km/h and in an 8-pass reverse doppler shift environment.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2006.10a
• /
• pp.243-254
• /
• 2006

[ $\bullet$ ] Miniaturization of packaging size is a key for system performance. $\bullet$ Fundamental density increase of joint and carrier wiring are required in near future.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.11
• /
• pp.38-45
• /
• 1998

A new set of MQW LD rate equations is proposed that include the interwell carrier transport effect assuming it is dominated by holes. Solving the rate equations, the DC transient response of MQW was obtained and it was shown that uneven carrier concentrations exist due to the interwell carrier transport effect. In addition, it was found that the large number of quantum wells can limit the LD modulation speed and InGaAlAs barriers with smaller valence band offsets can have larger modulation speeds. It is expected that the proposed rate equations can find useful applications in designing the optimal MQW LD structures for high speed applications.

• Advances in concrete construction
• /
• v.7 no.1
• /
• pp.23-30
• /
• 2019

Five key items were used to create an economical and physically small impact test device for concrete panels subject to high speed collision: an air-compressive system, carbon steel pipe, solenoid valve, carrier and carrier-blocking, and velocity measurement device. The impact test device developed can launch a 20 mm steel spherical projectile at over 200 m/s with measured impact and/or residual velocity. Purpose for development was to conduct preliminary materials tests, prior to large-scale collision experiments. In this paper, the design process of the small impact test device was discussed in detail.

• Journal of the Korean Vacuum Society
• /
• v.13 no.1
• /
• pp.14-21
• /
• 2004

It is essential to increase the switching speed of power devices to reduce the energy loss because high frequency is commonly used in power device operation these days. In this work electron irradiation has been conducted to reduce the lifetime of minority carriers and thereby to increase the switching speed of a$p^+- n^-$ junction diode. Effects of electron irradiation on the electrical properties of the diode are reported The switching speed is effectively increased. Also the junction leakages and the forward voltage drop which are anticipated to increase are found to be negligible in the $p^+- n^-$ junction diodes irradiated with the optimum energy and dose. The analysis results of DLTS and C-V profiling indicate that the defects induced by electron irradiation in the silicon substrate are donor-like ones which have the energy levels of 0.284 eV and 0.483 eV. Considering all the experimental results in this study, it might be concluded that electron irradiation is a very useful technique in improving the switching speed and thereby reducing the energy loss of $p^+- n^-$ junction diode power devices.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.512-517
• /
• 1998

In a matrix converter, input side and output side are coupled with each other through switching elements. Since disturbances on either side affect directly on the other side, it requires a high-speed on-line control system to compensate them. We proposed in previous papers a new control strategy and an on-line control circuit for a matrix converter. The control circuit could keep the output voltage at commanded value against fluctuation in the supply voltage. Furthermore wave forms of the output voltage and the input current were always kept sinusoidal. The switching pattern was generated by comparing modified voltage references with a carrier. The carrier was synchronized with the supply voltage using a PLL system, which made the control circuit complicated and costly. This paper discusses on the possibility of an asynchronized carrier. Experiment results show the input current distortion in case of asynchronous carrier is bigger than that of synchronous carrier. However, the deterioration can be minimized by increased carrier frequency.

• Journal of the Korean Professional Engineers Association
• /
• v.31 no.6
• /
• pp.35-39
• /
• 1998

• Journal of Navigation and Port Research
• /
• v.34 no.3
• /
• pp.181-187
• /
• 2010

The performance of underwater wireless communication system is influenced on channel characteristic. Especially, a delay spread cause by reverberation and multi-path happen the ISI (Inter Symbol Interference) and reduces the communication performance. In this paper, we study the application of high speed data transmission in underwater to use the OFDM (Orthogonal Frequency Division Multiplexing) technique for robust the reverberation and multi-path. we confirm the performance of communication in underwater to use the model for actually underwater channel simulation model. As a result, we acquired the BER of modulation techniques. The BER of single carrier is $2{\times}10^{-1}$ and BER of multi carrier is $8{\times}10^{-2}$ in 1000m.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.1
• /
• pp.93-102
• /
• 1994

This paper, presents SECRET(SEC REliability Tool), which predicts reliability problems related to the hot-carrier and electromigration effects on the submicron MOSFETs and interconnections. To simulate DC and AC lifetime for hot-carrier damaged devices, we have developed an accurate substrate current model with the geometric sensitivity, which has been verified over the wide ranges of transistor geometries. A guideline can be provided to design hot-carrier resistant circuits by the analysis of HOREL(HOT-carrier RFsistant Logic) effect, and circuit degradation with respect to physical parameter degradation such as the threshold voltage and the mobility can also be expected. In SECRET, DC and AC MTTF values of metal lines are calculated based on lossy transmission line analysis, and parasitic resistances, inductances and capacitances of metal lines are accurately considered when they operate in the condition of high speed. Also, circuit-level reliability simulation can be applied to the determination of metal line width and-that of optimal capacitor size in substrate bias generation circuit. Experimental results obtained from the several real circuits show that SECERT is very useful to estimate and analyze reliability problems.