• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.11
• /
• pp.83-89
• /
• 2008

The Effect of Space Velocity(SV) on NOx conversion rate was performed to develop NOx reduction after-treatment system. SV is calculated from engine exhaust gas volume and SCR catalyst volume. Found the Urea injection duty of maximum efficiency for NOx conversion if increase SV, NOx Conversion rate is down. Especially, when SV is more than $110,000h^{-1}$, NOx conversion rate decrease suddenly. Same case, if SV is lower than $40,000h^{-1}$, NOx conversion rate is down. Also, the characterization of Urea-SCR system was performed. Three candidate injectors for injecting Urea were tested in terms of 속 injection rate and NOx reduction rate. The performances of SCR catalytic converter on temperature were investigated. The performance of Urea-SCR system was estimated in the NEDC test cycle with and without EGR. It was found that nozzle type injector had high NOx conversion rate. SCR catalytic converter had the highest efficiency at the temperature of $350^{\circ}C$. EGR+Urea-SCR system achieved NOx reduction efficiency of 73% through the NEDC test cycle.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.1 no.1
• /
• pp.23-31
• /
• 1976

When Television signal of VHF and UHF channel is retransmitted at the relay system with 6MHz Bandwidth including video and aural signals, the image is often affected with the unnatural changes of output amplitude frequency response within ttle region of dual sideband near to the carrier frequency. These phenomena are caused by the unnecessary lower sideband due to the spurious emission at the local oscillator, the nonlinear distortion in the linear amplifier, the intermoudulation distortion with the components of neighboring signal, the AM-PM conversion, and the envelope delay distortion. From the output characteristics, considering above results, the chief cause is caused by nonlinear response and has an effect on the bias states. Finally, it is confirmed that the effects on neighboring signal appear high in case of Down conversion than Up conversion and obtained the method for reducing the effects on the system.

• Proceedings of the IEEK Conference
• /
• 2003.07b
• /
• pp.827-830
• /
• 2003

This paper proposes an area-efficient FIR filter architecture for sampling rate conversion of hi-fi audio data. Sampling rate conversion(SRC) block converts audio data sampled at 96KHz down to 48KHz sampled data and vice versa. 63-tap FIR filter coefficients have been synthesized that gives 100dB stop band attenuation and 5.2KHz transition bandwidth. Time-shared filter architecture requires only one multiplier and accumulator for 63-tap filter operation. This results in huge hardware saving of up to 10~19 times smaller compared with traditional FIR structure.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.3
• /
• pp.433-437
• /
• 2015

We have designed and fabricated a low power and high linearity up down convertor for wireless repeaters using $0.35{\mu}m$ SiGe Bipolar CMOS technology. Repeater is composed of a wideband up/down converting mixer, programmable gain amplifiers (PGA), input buffer, LO buffer, filter driver amplifier and integer-N phase locked loop (PLL). As of the measurement results, OIP3 of the down conversion mixer and up conversion mixer are 32 dBm and 17.8 dBm, respectively. The total dynamic gain range is 31 dB with 1 dB gain step resolution. The adjacent channel leakage ratio (ACLR) is 59.9 dBc. The total power consumption is 240 mA at 3.3 V.

• Journal of Power Electronics
• /
• v.14 no.2
• /
• pp.203-216
• /
• 2014

In the conventional dc-dc converter, a pair of additional diode and the adjacent passive component capacitor/inductor can be added to the circuit with an X-shape connection, which generates a family of new topologies. The novel circuits, also called diode-assisted dc-dc converter, enhance the voltage boost/buck capability and have a great potential for high step-up/step-down power conversions. This paper mainly investigates and compares conventional dc-dc converter and diode-assisted dc-dc converter in wide range power conversion from the aspects of silicon devices, passive components requirements, electro-magnetic interference (EMI) and efficiency. Then, a comprehensive comparison example of a high step-up power conversion system was carried out. The two kinds of boost dc-dc converters operate under the same operation conditions. Mathematical analysis and experiment results verify that diode-assisted dc-dc converters are very promising for simultaneous high efficiency and high step-up/step-down power conversion in distributed power supply systems.

• Korean Journal of Materials Research
• /
• v.25 no.9
• /
• pp.475-479
• /
• 2015

$YNbO_4:Yb^{3+}/Er^{3+}$ is synthesized using a solid-state reaction process with a LiCl flux. The effects of the Er/(Yb+Er) ratios ($R_{Er}$) on the up-conversion (UC) and down-conversion (DC) spectra are investigated. The XRD data confirm that the $Yb^{3+}$ and $Er^{3+}$ ions are fully substituted for the $Y^{3+}$ sites. The UC emission spectra activated by 980 nm consists of green and red emission bands, which originate from the $Er^{3+}$ ions through an energy transfer (ET) process from $Yb^{3+}$ to $Er^{3+}$. The UC emission intensity depends on the $R_{Er}$ value, and the findings demonstrate that $R_{Er}{\leq}0.14$ is suitable for an effective UC process. The DC emission spectra under 269 nm radiation of the synthesized powders exhibits not only a strong blue emission assigned to the $[NbO_4]^{3-}$ niobates, but also green peaks that originate from the $Er^{3+}$ ions through an ET process between $[NbO_4]^{3-}$ and $Er^{3+}$.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.835-839
• /
• 2002

Stoichiometric $LiNbO_3$(LN) single crystals of 1 mm diameter and 30∼40 mm length with co-doped the $Er_2O_3$ and MgO were grown by the Micro-Pulling Down(${\mu}$-PD) method. The grown crystals were investigated for the change of the up-conversion property by the $Er_2O_3$ and MgO addition and the optical damage by the MgO concentration. Also, the crystals were studied the defects using the optical microscope and it is identified the homogeneities of the distribution of the $Er_2O_3$ and MgO concentration by the Electron Probe Micro Analysis(EPMA).

• KIEE International Transactions on Electrophysics and Applications
• /
• v.2C no.5
• /
• pp.273-278
• /
• 2002

Even though the modulating signal frequency of the light is too high to detect directly, the signal can be extracted by frequency conversion at the same time as the detection by means of the non-linearity of the APD. An analysis is presented for super-high-speed optical demodulation by an APD with electronic mixing. A normalized gain is defined to evaluate the performance of the frequency conversion demodulation. The nonlinear effect of the internal capacitance was included in the small signal circuit analysis. We showed theoretically and experimentally that the normalized gain is dependent on the down converted difference frequency component. In the experiment, the down converted different frequency outputs became larger than the directly detected original signal for the applied local signal of 20㏈m.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.1
• /
• pp.65-70
• /
• 2001

This paper presents a Receiver MMIC for the CDMA terminal. The complete circuit is composed of Low Noise Amplifier, Down Conversion Mixer, Intermediate Frequency Amplifier and Bias circuit. The Bias circuit implementation, which allows for compensation for threshold voltage and power supply voltage variation are provided. The proposed topology has high linearity and low noise characteristics. Results of the designed circuit are as follows: Overall conversion gain is 28.5 dB, input IP3 of LNA is 8 dBm, input IP3 of down conversion mixer is 0 dBm and total DC current consumption is 22.1 mA.

• ETRI Journal
• /
• v.46 no.2
• /
• pp.238-249
• /
• 2024

Equivalent-time sampling can improve measurement or sensing systems because it enables a broader frequency band and higher delay resolution for periodic signals with lower sampling rates than a Nyquist receiver. Meanwhile, a digital down-conversion (DDC) technique can be implemented using a straightforward radio frequency (RF) circuit. It avoids timing skew and in-phase/quadrature gain imbalance instead of requiring a high-speed analog-to-digital converter to sample an intermediate frequency (IF) signal. Therefore, when equivalent-time sampling and DDC techniques are combined, a significant synergy can be achieved. This study provides a parameter design methodology for optimal equivalent-time sampling using DDC.