• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.2
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• pp.123-128
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• 2020

A low phase noise phase locked loop (PLL) with negative feedback loop including frequency variation sensing circuit (FVSC) has been proposed. The FVSC senses the frequency variation of voltage controlled oscillator output signal and controls the volume of electric charge in loop filter capacitance. As the output frequency of the phase locked loop increases, the FVSC reduces the loop filter capacitor charge. This causes the loop filter output voltage to decrease, resulting in a phase locked loop output frequency decrease. The added negative feedback loop improves the phase noise characteristics of the proposed phase locked loop. The size of capacitance used in FVSC is much smaller than that of loop filter capacitance resulting in no effect in the size of the proposed PLL. The proposed low phase noise PLL with FVSC is designed with a supply voltage of 1.8V in a 0.18㎛ CMOS process. Simulation results show the jitter of 273fs and the locking time of 1.5㎲.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.167-172
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• 2023

A low-noise phase-locked loop(PLL) with three negative feedback loops has been proposed. It is not easy to improve noise characteristics with a conventional PLL. The added negative feedback loops reduce the input voltage magnitude of voltage controlled oscillator which determines the jitter characteristics, enabling the improvement of noise characteristics. Simulation results show that the jitter characteristics are improved as a negative feedback loop is added. In the case of power consumption, it slightly rises by about 10%, but jitter characteristics are improved by about two times. The proposed PLL was simulated with Hspice using a 1.8V 180nm CMOS process.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.345-348
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• 2000

In this paper, A Feedforward Linear Power Amplifier for IMT-2000 which IMD characteristics was improved was designed and fabricated. To improve the main power amplifier IMD characteristics, the Feedback loop was added to basic Feedforward Power Amplifier structure. Therefore, the output power of error amplifier can be reduced, and it is easy to control the linearization circuit to cancel total IMD. The designed power amplifier represented the 40㏈m(l0W) output power and -55㏈C 3rd IMD at Center frequency 2.14㎓ (@5㎒).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2176-2182
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• 2014

In this paper, a phase locked loop with suppressed power supply noise has been proposed. The added negative feedback loop of voltage controlled oscillator(VCO) and power noise detector suppresses the power noise induced jitter variation of VCO down to 1/3. The power noise detector is the modified circuit of frequency voltage converter. The proposed PLL has been designed based on a 1.8V 0.18um CMOS process and proved by HSPICE simulation.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1245-1254
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• 2018

The stability of a grid-connected system (GCS) has become a critical issue with the increasing utilization of renewable energy sources. Under grid faults, however, a grid-connected inverter cannot work efficiently by using only the traditional droop control. In addition, the unbalance factor of voltage/current at the common coupling point (PCC) may increase significantly. To ensure the stable operation of a GCS under grid faults, the capability to compensate for grid imbalance should be integrated. To solve the aforementioned problem, an improved voltage-type grid-connected control strategy is proposed in this study. A negative sequence conductance compensation loop based on a positive sequence power droop control is added to maintain PCC voltage balance and reduce grid current imbalance, thereby meeting PCC power quality requirements. Moreover, a stable analysis is presented based on the small signal model. Simulation and experimental results verify the aforementioned expectations, and consequently, the effectiveness of the proposed control scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.681-689
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• 2010

We will demonstrate a novel topology for the feedforward amplifier. This amplifier does not use a delay element thus providing an efficiency enhancement and a size reduction by employing a distributed element negative group delay circuit. The insertion loss of the delay element in the conventional feedforward amplifier seriously degrades the efficiency. Usually, a high power co-axial cable or a delay line filter is utilized for a low loss, but the insertion loss, cost and size of the delay element still acts as a bottleneck. The proposed negative group delay circuit removes the necessity of the delay element required for a broadband signal suppression loop. With the fabricated 2-stage distributed element negative group delay circuit with -9 ns of total group delay, a 0.2 dB of insertion loss, and a 30 MHz of bandwidth for a wideband code division multiple access downlink band, the feedforward amplifier with the proposed topology experimentally achieved a 19.4 % power added efficiency and a -53.2 dBc adjacent channel leakage ratio with a 44 dBm average output power.

• The Journal of Information Systems
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• v.25 no.2
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• pp.153-171
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• 2016

Purpose This study suggests the development of forecasting model for local cable TV advertisement. In order to verify the expected effect of the suggestion, using the causal loop map of System Dynamics, the factors affecting the prospects of cable TV commercial market were divided into 5 groups. Then targeting 97 people involved in the cable TV commercial market in Busan, Ulsan, and Gyeongnam, a survey was conducted on their perception of the current status of local advertisement market and future prospect. Design/methodology/approach The analysis of the collected data shows that workers in advertising and advertisers perceive the influence of cable TV as an advertising media to be high, while clearly understanding the problems of cable TV commercial market. Based on this the effects on the prospects of cable TV commercial market were analyzed and a forecasting method called Weighted Moving Average was applied. In order to improve accuracy of the added value of Weighted Moving Average, the 5 factors were divided into qualitative factors and quantitative factors, and using Multi-attribute Decision Making method, all the factors were normalized and weighting factors were deduced. The result of simulating the prospects of cable TV commercial market using Weighted Moving Average, both qualitative and quantitative factors showed downward turn in the market prospect for the following 10 years. Findings The result reflects generally negative perception of advertisement viewers about the prospects of cable TV commercial market. Compared to the previous studies on domestic cable TV commercials that focused on policy suggestions and surveys on perception of current status, this study has its significance in that it used scientific method and simulation for verification.

• Journal of Food Hygiene and Safety
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• v.34 no.3
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• pp.290-295
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• 2019

Salmonella spp. are frequently associated with food and are among the most important foodborne pathogens. The recent Salmonella out breaks in Korea was associated with chocolate mousse cakes served with school meals during September 2018. The objective of this research was to compare the 3M Molecular Detection Assay 2 - Salmonella and the Korean Standard Method of Salmonella in artificially inoculated mousse (chocolate and cheese) and tiramisu cakes. Mousse (chocolate and cheese) and tiramisu cakes were artificially inoculated with S. Typhimurium. Twenty five gram of sample was enriched with 225 mL buffered peptone water for incubation at $37^{\circ}C$ for 24 h. After enrichment, the cultures were analyzed by using the 3M Molecular Detection Assay 2 - Salmonella and the Korean Standard Method. Most of the inoculated samples showed similar results except the chocolate mousse cakes, in which real-time PCR was unable to detect S. Typhimurium even after $10^4CFU/25g$ of inoculation. However, S. Typhimurium inoculated at a concentration of $10^0CFU/25g$ was detected by using 3M Molecular Detection Assay 2 - Salmonella. In chocolate mousse, detection of S. Typhimurium using real-time PCR was partially successful when dark chocolate was added at less than 15%. Negative results in real-time PCR and 3M Molecular Detection Assay 2 - Salmonella were confirmed by gel electrophoresis. The data indicated that dark chocolate could inhibit amplification of the target gene in the PCR reactions. In conclusion, the 3M Molecular Detection Assay 2 - Salmonella was better than the Korean Standard Method (real-time PCR) for the detection of S. Typhimurium in chocolate mousse cakes and chocolate mousse.