• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.974-982
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• 2009

Photomixing techniques beating two optical signals with different wavelengths and strong correlations are also very useful techniques to make a continuous wave(CW) signals in the range of millimeter(mm) and terahertz(THz) frequencies. An optical double sideband-suppressed carrier(DSB-SC) technique is one of the popular techniques to generate two optical signals with different wavelengths and strong correlations. DSB-SC signals with strong correlations are generated by a CW modulation of an optical carrier with a local oscillator and an optical modulator. In the previous parers related the DSB-SC for producing the CW signals within the range of mm and THz frequencies, there have been no reports why the optical carrier should suppress. In order to clear that, we have analyzed and measured the characteristics of the mm-wave CW signals made by the DSB-SC photomixing in this paper. From our analysis and measurement results, compared with the case of the DSB with the maximized optical carrier, the power and phase noise have improved about 23.9 dB and 21 dBc/Hz(@ 1 MHz offset frequency) in the case of the DSB with the minimized optical carrier (that is to say, the DSB-SC). Consequently, it is evident reason that the optical carrier should sufficiently suppress to obtain the mm-wave CW signals with the high power and low noise. This paper has given very helpful data to make mm- and THz-wave CW signals using photomixing techniques with the DSB-SC because the reason why the optical carrier should be suppressed is reported in this paper based on the numerical and experimental results.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.328-334
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• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.28-33
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• 2017

In this paper, new signal model for bio-signal detection, i.e heart beat and respiration, using CW radar. Most research on this similar topic are based on the conventional signal model which is not correct in envisaging reflected signal from the human body. The system developed based on this conventional model can not predict exact performance of the system. So in this paper modified signal model for bio-radar is proposed and then simulation for detecting heartbeat and respiration signal in AWGN, multipath environment. The detection performance difference between two signal models are discussed.the modified

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.35-42
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• 2008

Since Bianchi's 2-D Markov Chain Model considers collision problem only in ideal channel condition, it does not reflect real channel impaired by fading, interference, and noise. Distributed Coordination Function(DCF) doubles its contention window(CW) when transmission fails regardless of collision or transmission error. Increase of CW caused by transmission error degrade throughput and increase the delay. In this paper, we present quantitative analysis of the impact of the parameters such as contention window size(CW), transmission probability for a given time slot(${\Im}$), transmission failure probability($p_f$), on the system performance and provide a method how to decrease the initial CW to achieve equivalent performance.

• The Journal of the Acoustical Society of Korea
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• v.23 no.7
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• pp.514-520
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• 2004

There are many techniques for underwater source localization. These are the methods based on TDOA (Time Difference Of Arrival) estimation. beamforming techniques and high resolution techniques, etc. In this Paper we estimate the underwater source position using MCPSP (Modified Cross Power Spectrum Phase) function that is calculated on frequency domain using sensors of small number. However, the performances of the localizing method based on MCPSP function drops greatly in the case of CW (Continuous Wave) signal . In this Paper we proposed the TDOA estimation method for pulsed CW signal. In the Proposed method we composed of new segment including a edge of ping. This segment was computed by short-time energy detection. With theoretical representation the performances of the proposed method were analyzed under various environment.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.482-489
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• 2009

This paper proposes a CW(Continuous-Wave) bio-radar applying a new adaptive noise canceller based on ALE(Adaptive Line Enhancer) which can remove the Gaussian noise and system noise. Recently the research works on this CW bio-radar which can be used to detect heartbeat and respiration are advanced by the university and research facility. Although the researches describe CW bio-radar not only is vulnerable for the Gaussian noise but also has a disadvantage of decreasing the heart-rate accuracy due to the noise, the researches do not demonstrate the effective method for removing the noise component in a baseband signal. In this paper, a CW bio-radar applying the new adaptive noise canceller based on ALE which can remove the noise component is proposed. This paper compares and analyzes the performance for increasing the heart-rate accuracy according to removing the Gaussian noise and system noise in the baseband signal through the quadrature receiver which can alleviate the demodulation sensitivity to target position.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.80-87
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• 2013

This paper proposes a CW (Contention window) allocation scheme for real-time data transmission of emergency data on VANET (Vehicle to vehicle Ad hoc Network, V2V) protocol. The proposed scheme reduces the probability of packet collisions on V2V protocol and provides bandwidth efficiency with short delay of emergency sporadic data. In the case of high density traffic, the proposed scheme provides a decrease of recollision probability using dynamic CW adjustments. For the performance analysis, a throughput, end-to-end delays, and network loads were investigated on highway traffic. Simulation results show the performance enhancements in terms of the throughput, end-to-end delays, and network loads.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.866-869
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• 2015

In this paper, we propose a device for detect front object using low-price the CW Doppler sensor to prevent safety accident such as a bicycle, an electric wheelchair users. For this propose, we develop a signal process board and the object motion detect algorithm using to analyzing output signal of the CW Doppler sensor. Output signal from CW Doppler sensor is analog I and analog Q. The CW Doppler sensor shows phase I and phase Q of object differently when the object approach, stop, drop by sensor. We develop an algorithm that can detect object by discrimination information of phase using the CW Doppler sensor. The verification use firmware of applied hardware and algorithm. Then, the motion information can be confirming output depending on motion object by experiment normally. As a result, we check that the sensing information output by following motion of object and confirm an algorithm and motion of signal processing board.

• Food Engineering Progress
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• v.14 no.1
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• pp.27-34
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• 2010

Multilayer edible coatings was applied to lemon with beeswax-hydroxypropyl methylcellulose (BW-HPMC), soybean oil-carboxymethyl cellulose (SBO-CMC), and carnaubawax-shellac-locust bean gum (CW-SL-LBG), respectively. The multilayer was composed of two layers of the same material, but the outer layer only contained vitamins C and E as antioxidants. Coating amounts built on lemon peel were measured to be large in the order of CW-SLLBG> BW-HPMC> SBO-CMC. The coated lemons were stored at 30${^{\circ}C}$ for 12 days. CW-SL-LBG showed the least change during the storage in weight loss, rotten rate, firmness, and browning. Whereas SBO-CMC had the least change in pH, soluble solid amount, and titratable acidity. In a sensory test, CW-SL-LBG was evaluated to be the best in the attributes such as spoilage, glossiness, color, firmness, and flavor. Overall CW-SL-LBG was judged to be the best for multilayerd coating with vitamin C and E on lemon.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.379-387
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• 2013

In order to improve practical utility of agro-microorganisms (AMs) which had been cultured and disseminated to promote plant growth and to control crop diseases, 51 isolates of AMs were collected from 18 agricultural extension centers in local government and screened for multi-functions such as antifungal activity, activities of phosphorus solubilization, IAA and siderophore production, nitrogen fixation, and hydrolytic enzyme activity. Finally we selected one isolate showing good antifungal activity and multi-functions related to plant growth and disease control. The selected isolate, Paenibacillus polymyxa CW, showed good inhibitory effect against plant pathogens, Pyricularia gresea, Colletotrichum acutatum, Fusarium oxysporum, Phomopsis sp., Aspergillus niger, Rhizoctonia solani and Phytophthora capsici. Suppressive effect of P. polymyxa CW against the used plant pathogens except for R. solani was much higher than that of P. polymyxa AC-1 storing in National Academy of Agricultural Science. We found P. polymyxa CW isolate showed good activity in siderophore and IAA formation, and nitrogen fixation. With P. polymyxa CW isolate, siderophore formation activity was similar to that of P. polymyxa AC-1, but IAA formation and nitrogen fixation activity was much higher than that of P. polymyxa AC-1. However neither P. polymyxa CW nor P. polymyxa AC-1 showed hydrolytic enzyme (chitinase, pectinase and cellulase) activity. The treatment of P. polymyxa CW with culture suspension of different cell density ($10^8$, $10^7$. $10^6$ cfu/ml) showed that the highest density reduced incidence of red pepper powdery mildew by 68.3% after 10 days of application. As application density of P. polymyxa CW was decreased, its control efficacy was proportionally decreased. In addition, when P. polymyxa CW was treated to control tomato powdery mildew at the same concentrations and their control effects were investigated after 7 days of inoculation, disease incidence was 0.03, 19.5, 45.7%, respectively, compared to 56.3% that of untreated check. Like red pepper powdery mildew, increase of application density of P. polymyxa CW resulted in increase of its control efficacy proportionally. P. polymyxa CW showed a density-dependent control efficacy against red pepper and tomato powdery mildews. Therefore we think that mode of action of the antagonist for suppressing two powdery mildew diseases might be antibiosis and density of more than $10^8cfu/ml$ was needed to control effectively the two diseases. On this basis, we think that P. polymyxa CW can be a promising control agent for suppressing powdery mildews of red pepper and tomato.