• Smart Media Journal
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• v.4 no.2
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• pp.55-61
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• 2015

A bandwidth-enhanced ultra-wide band (UWB) CMOS balun-LNA is implemented as a part of a software defined radio (SDR) receiver which supports multi-band and multi-standard. The proposed balun-LNA is composed of a single-to-differential converter, a differential-to-single voltage summer with inductive shunt peaking, a negative feedback network, and a differential output buffer with composite common-drain (CD) and common-source (CS) amplifiers. By feeding the single-ended output of the voltage summer to the input of the LNA through a feedback network, a wideband balun-LNA exploiting negative feedback is implemented. By adopting a source follower-based inductive shunt peaking, the proposed balun-LNA achieves a wider gain bandwidth. Two LNA design examples are presented to demonstrate the usefulness of the proposed approach. The LNA I adopts the CS amplifier with a common gate common source (CGCS) balun load as the S-to-D converter for high gain and low noise figure (NF) and the LNA II uses the differential amplifier with the ac-grounded second input terminal as the S-to-D converter for high second-order input-referred intercept point (IIP2). The 3 dB gain bandwidth of the proposed balun-LNA (LNA I) is above 5 GHz and the NF is below 4 dB from 100 MHz to 5 GHz. An average power gain of 18 dB and an IIP3 of -8 ~ -2 dBm are obtained. In simulation, IIP2 of the LNA II is at least 5 dB higher than that of the LNA I with same power consumption.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.11
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• pp.65-71
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• 2010

This paper presents a 14-band LO generator architecture for MB-OFDM UWB systems using 3.1 GHz~10.6 GHz frequency band. The proposed LO generator architecture has been consisted of only one PLL and the fewest nonlinear components to generate 14 LO signals with high purity while consuming low dc power consumption. In addition, major spurious generated from the LO generator have been located in the out of UWB band. The proposed LO generator has been implemented in a $0.13-{\mu}m$ CMOS technology and consumes a dc power consumption of 93~103 mW from a 1.5 V supply. The simulation results show an in-band spurious suppression ratio of more than 41 dBc and a band-switching time of below 3 nsec.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.1
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• pp.28-35
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• 2007

In this paper, an ultra low voltage SRAM design method based on dual-boosted cell bias technique is described. For each read/write cycle, the wordline and cell power node of the selected SRAM cells are boosted into two different voltage levels. This enhances SNM(Static Noise Margin) to a sufficient amount without an increase of the cell size, even at sub 1-V supply voltage. It also improves the SRAM circuit speed owing to increase of the cell read-out current. The proposed design technique has been demonstrated through 0.8-V, 32K-byte SRAM macro design in a $0.18-{\mu}m$ CMOS technology. Compared to the conventional cell bias technique, the simulation confirms an 135 % enhancement of the cell SNM and a 31 % faster speed at 0.8-V supply voltage. This prototype chip shows an access time of 23 ns and a power dissipation of $125\;{\mu}W/Hz$.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.420-427
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• 1993

Dielectric thin film mirrors are embedded in multimode and single-mode fibers by a fusion splicing technique. The fibers with $45{\circ}$ angled embedded mirrors serve as ultra-compact directional couplers with low excess optical loss of 0.2 dB for multimode and 0.5 dB for single mode at 1.3 ${\mu}m$ and excellent mechanical properties. The reflectance is wavelength dependent and strongly polarization depencient. Far-field scans of the reflected output power measured with a white-light source show a pattern which is almost circularly symmetric with aspect ratio of 1.09 at 5% of the peak power. The splitting ratio in a multimode coupler measured with a diode laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers, indicating that these couplers are less susceptible to modal noise occuring in optical fiber communication systems. Spectral properties of multilayer internal mirrors normal to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.181-186
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• 2015

With the rapid growth of semiconductor technologies, small-sized devices with powerful computing abilities are becoming a reality. As this environment has a limit on power supply, NVM storage that has a high density and low power consumption is preferred to HDD or SSD. However, legacy software layers optimized for HDDs should be revisited. Specifically, as storage performance approaches DRAM performance, existing I/O mechanisms and software configurations should be reassessed. This paper explores the challenges and implications of using NVM storage with a broad range of experiments. We measure the performance of a system with NVM storage emulated by DRAM with proper timing parameters and compare it with that of HDD storage environments under various configurations. Our experimental results show that even with storage as fast as DRAM, the performance gain is not large for read operations as current I/O mechanisms do a good job hiding the slow performance of HDD. To assess the potential benefit of fast storage media, we change various I/O configurations and perform experiments to quantify the effects of existing I/O mechanisms such as buffer caching, read-ahead, synchronous I/O, direct I/O, block I/O, and byte-addressable I/O on systems with NVM storage.

• ETRI Journal
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• v.41 no.2
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• pp.254-261
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• 2019

Distinct from conventional energy-harvesting (EH) technologies, such as the use of photovoltaic, piezoelectric, and thermoelectric effects, betavoltaic energy conversion can consistently generate uniform electric power, independent of environmental variations, and provide a constant output of high DC voltage, even under conditions of ultra-low-power EH. It can also dramatically reduce the energy loss incurred in the processes of voltage boosting and regulation. This study realized betavoltaic cells comprised of p-i-n junctions based on silicon carbide, fabricated through a customized semiconductor recipe, and a Ni foil plated with a Ni-63 radioisotope. The betavoltaic energy converter (BEC) includes an array of 16 parallel-connected betavoltaic cells. Experimental results demonstrate that the series and parallel connections of two BECs result in an open-circuit voltage $V_{oc}$ of 3.06 V with a short-circuit current $I_{sc}$ of 48.5 nA, and a $V_{oc}$ of 1.50 V with an $I_{sc}$ of 92.6 nA, respectively. The capacitor charging efficiency in terms of the current generated from the two series-connected BECs was measured to be approximately 90.7%.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.59-64
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• 2024

In this study, we conducted research on a miniaturized transmission system suitable for ultra-compact electric vehicles, such as electric arts or small electric cars. While conventional electric vehicles eliminate multi-gear transmissions and control motor output or secure initial driving force through reducers, in vehicles like electric karts or compact electric cars, which have relatively small battery capacities, the driving range can be reduced or the motor can be stressed epending on the loading state. Therefore, in this study, we developed a low stage ratio 0.625 and high stage ratio 1.6 a two-stage transmission system that can change gears as needed, considering factors such as slope conditions and loading status, by applying the continuously variable transmission (CVT) mechanism. Based on the selected gear ratios, we designed the transmission and created a test rig to verify the power transmission efficiency of the developed transmission. Using the test rig, we varied the rotational speed and load of the transmission to confirm its power transmission characteristics and also examined the heat generation characteristics during shifting and operation. As a result, developed a two-stage transmission with a CVT structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.844-853
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• 2008

This paper describes the design of a FEM(Front End Module) having power detection function for mobile handset application. The designed FEM consists of a MMIC(Monolithic Microwave Integrated Circuits) power amplifier chip, SAW Tx filter and duplexer, diode power detector and stripline matching circuit. An LTCC(Low Temperature Co-fired Ceramics) technology is adopted for miniaturized FEM. The frequency band is $824{\sim}869$ MHz which is the uplink Tx band of the CDMA mobile system. The size of designed FEM is $7.0{\times}5.5{\times}1.5\;mm^3$, which is an ultra-small size even though the power detector circuit is included. All sub-components of FEM have been developed and measured in advance before being integrated into FEM. The measured output power and gain are 27 dBm and 27 dB, respectively. In addition, the measured ACPR characteristics are 46.59 dBc and 55.5 dBc at 885 kHz and 1.98 MHz offset, respectively.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.364-371
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• 2012

Currently, CMMB(China Mobile Multimedia Broadcasting) and the conventional analog TV broadcasting have transmitted by using UHF(Ultra High Frequency : 474MHz~754MHz) band. Normally, the transmission power of the digital TV broadcasting is lower than the conventional analog TV broadcasting to protect the reception quality of the conventional analog TV broadcasting. The reception sensitivity of CMMB receiver has severely deteriorated due to adjacent the conventional analog TV broadcasting signals which called ACI (Adjacent Channel Interference). To improve the reception sensitivity of a CMMB receiver on ACI environment, this paper proposed a simple method which is tuning a cut off frequency of LPF (Low Pass Filter). From the experiment, the reception sensitivity of CMMB receiver was improved as 11.3dB.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.408-413
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• 2008

In this work, the use of LPRTO (low pressure rapid thermal oxidation) and remote plasma oxidation was evaluated for the preparation of ultra thin silicon oxide layer with less than 5 nm. The silicon oxide thickness grown by LPRTO was rapidly increased and saturated. The maximum thickness could be controlled at about 5 nm. As RF power and oxygen flow rate at a remote plasma oxidation increased, the behavior of oxide growth was almost the same as that of LPRTO. The oxide thickness of 4 nm was the maximum obtained by a remote plasma oxidation in this work. The quality of silicon oxide grown by LPRTO was comparable to the thermally grown conventional oxide.