• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.23-30
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• 2002

The PVDF (Polyvinylidene Fluoride) thin film having P phase is prepared by the vacuum deposition with applying the electric field and its pyroelectric properties are studied by using a dynamic method to examine the possibility of the application to the pyroelectric IR sensor. The pyroelectric responses of the PVDF thin film are characterized as the frequency dispersion in both low and high modulation frequency regions, and their frequency dependences are observed. In the low frequency region (2~10Hzz), the polarization can easily rotate with the increase of modulation frequency and show the maximum since the reorientation rate of domains is higher than the modulation frequency. On the other hand, in the high frequency region (100~1000Hz), the pyroelectric response decreases as the frequency increases, because the reorienatation rate of domains is suppressed and thus, the change of polarization decreases. Pyroelectric coefficient, figure of merits for noise equivalent power and detectivity of the PVDF thin film are measured as 3.2$\times$10$^{-10}$ C/$\textrm{cm}^2$.K, 2.34$\times$10$^{-10}$ C.cm/J and 1.32$\times$10$^{-9}$ C.cm/J, respectively. Also, the noise equivalent and the detectivity are 1.66$\times$10$^{-7}$ W/H $z^{$\sfrac{1}{2}$}$, 6.03$\times$10$^{5}$ cm.H $z^{$\sfrac{1}{2}$}$W, respectively.

• Korean Journal of Optics and Photonics
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• v.34 no.1
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• pp.1-12
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• 2023

In this study, we propose a hybrid phase-control algorithm for multi-channel coherent beam combining (CBC) system by combining the covariant matrix adaption evolution strategy (CMA-ES) and stochastic parallel gradient descent (SPGD) algorithms and analyze its operational performance. The proposed hybrid CMA-ES/SPGD algorithm is a sequential process which initially runs the CMA-ES algorithm until the combined final output intensity reaches a preset interim value, and then switches to running the SPGD algorithm to the end of the whole process. For ideal 7-channel and 19-channel all-fiber-based CBC systems, we have found that the mean convergence time can be reduced by about 10% in comparison with the case when the SPGD algorithm is implemented alone. Furthermore, we analyzed a more realistic situation in which some additional phase noise was introduced in the same CBC system. As a result, it is shown that the proposed algorithm reduces the mean convergence time by about 17% for a 7-channel CBC system and 16-27% for a 19-channel system compared to the existing SPGD alone algorithm. We expect that for implementing a CBC system in a real outdoor environment where phase noise cannot be ignored, the hybrid CMA-ES/SPGD algorithm proposed in this study will be exploited very usefully.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.157-157
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• 2017

To minimize the damage by wild birds and acquire the benefits such as protection against weeds and maintenance of water content in soil, the mulching black color vinyl after seeding should be carried out. Non-contact and non-destructive methods that can continuously determine the locations are necessary. In this study, a crop position detection method was studied that uses infrared thermal image sensor to determine the cotyledon position under vinyl mulch. The moving system for acquiring image arrays has been developed for continuously detecting crop locations under plastic mulching on the field. A sliding mechanical device was developed to move the sensor, which were arranged in the form of a linear array, perpendicular to the array using a micro-controller integrated with a stepping motor. The experiments were conducted while moving 4.00 cm/s speed of the IR sensor by the rotational speed of the stepping motor based on a digital pulse width modulation signal from the micro-controller. The acquired images were calibrated with the spatial image correlation. The collected data were processed using moving averaging on interpolation to determine the frame where the variance was the smallest in resolution units of 1.02 cm. Non-linear integral interpolation was one of method for analyzing the frequency using the normalization image and then arbitrarily increasing the limited data value of $16{\times}4pixels$ in one frame. It was a method to relatively reduce the size of overlapping pixels by arbitrarily increasing the limited data value. The splitted frames into 0.1 units instead of 1 pixel can propose more than 10 times more accurate and original method than the existing correction method. The non-integral calibration method was conducted by applying the subdivision method to the pixels to find the optimal correction resolution based on the first reversed frequency. In order to find a correct resolution, the expected location of the first crop was indicated on near pixel 4 in the inversion frequency. For the most optimized resolution, the pixel was divided by 0.4 pixel instead of one pixel to find out where the lowest frequency exists.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.17-23
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• 2004

The implementation and design of the wideband IFIU using aperture open loop resonator and reversed phase technique to reduce the local oscillator leakage signal was represented in this paper. The local oscillator leakage signal is generated in stage of frequency conversion, especially in frequency conversion of fully digital modulation signal close to DC signal. The leakage signal and spurious signals, which have effects on adjacent channel or in-band channel as interference signals, were reduced below -60 dBc for 45 Mbps and 155 Mbps IF interface units. The group delay for both IFIUs shows low ripple characteristics of 15 ns and 8 ns, respectively. Also, the amplitude ripple characteristic in 150 MHz bandwidth with L-band center frequency satisfies the required specification of 2 dB. The implemented IFIU provides the required specifications for wideband satellite communication system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.65-72
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• 2001

This paper deals with a novel full digital control of the single-phase PWM(Pulse Width Modulation) inviter for UPS(Uninterruptible Power Supp1y). The voltage and current of output filter capacitor as a state variable are the feedback control input. In the proposed scheme a double deadbeat control consisting of minor current control loop and major voltage control loop have been developed In addition, a second order deadbeat currents control which should be exactly equal to its reference in two sampling time without error and overshoot is proposed to remove the influence of the calculation time delay. The load current prediction is achieved to compensate the load disturbance. The simulation and experimental result shows that the proposed system offers an output voltage with THD(Total Harmonic Distortion) less than 5% at a full nonlinear load.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.517-526
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• 2000

In this paper, we propose the trellis coded spread spectrum communication system with one channel signal selection of the subset by the PN code. This paper proposes the Viterbi decoder that have the squared Euclidean distance of the order phase difference as well as 1st order phase difference as the branch metrics by using the multiple symbol detection method. TCM method was developed to overcome limited power and bandwidth efficiently in digital communication. we multiply one of convolution code's output data to PN code for applying TCM to the spread spectrum. We investigated the performance of the direct sequence/spread spectrum communication system with trellis coded modulation. In this system, we could improved the coding gain in the spread spectrum.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.102-108
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• 2010

The photovoltaic system changes solar energy into DC by solar cell and this DC is inverted into AC which is used in general houses by inverter. Recently, the use of power of the photovoltaic system is increased. Therefore, the study of 3 phase solar system to transmit large power is very important. This paper proposes a method that finds simply faults and diagnoses the switch open faults of 3-phase pulse width modulation (PWM) inverter of grid-connected photovoltaic system. The proposed method in $\alpha\beta$ plane uses the patterns of trajectory image as the characteristic parameters and differenciates a normal state and open states of switches. Then, the result is made into tree. The tree is composed of 21 fault patterns and the parameters to classify faults are a shape, a trajectory area, a distributed angle, and a typical vector angle. The result shows that the proposed method diagnosed fault diagnoses, classified correctly them, and made a pattern tree by fault patterns.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.472-480
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• 2009

This paper describes the overmodulative SVPWM technique and harmonics analyses of three phase NPC type three-level inverter to the modulation index. Three phase NPC type three-level inverter adopted SVPWM to extend the linear region to 0.907, moreover, the following voltage compensation using Fourier series was adopted in the region of overmodulation to make it work to six-step level. PD type of multi carrier method is used with the double Fourier series for the analysis of output power harmonics characteristic. Simulation was performed by PSIM, and the harmonics characteristics of 3-level inverter in each region are analyzed. The side band harmonics of carrier frequency are dominant in the linear region, but these harmonic components are decreased as the inveter goes to overmodulation region, and the harmonics due to the fundamental frequency is increased gradually at the same time. The harmonic analyses are verified through the simulation and experimental results under the same condition.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.27-35
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• 2016

A Low jitter dual output frequency synthesizer for smart audio devices is described in this paper. It has been fabricated in a 1.8 V Dongbu $0.18-{\mu}m$ CMOS process. Output frequency is controlled by 3 rd order Sigma-Delta Modulation and digital divider. The frequency synthesizer has a size of $0.6mm^2$, frequency range of 0.6-200 MHz, loop bandwidth of 350 kHz, and rms jitter of 11.4 ps-21.6 ps.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1172-1180
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• 2007

OFDM system has very good high spectral efficiency and the robustness to the frequency-selective fading. Because of the high PAPR, OFDM signals can be distorted in nonlinear HPA(High Power Amplifier). So, to overcome the nonlinear distortion, it is very important to reduce the IMD value. With respect to the BER performance, IMD reduction method is better than the PAPR reduction method. However, IMD reduction method has much more system complexity because of the additional FFT processor in transmitter. In this paper, we study the OFDM communication system based on the IMD reduction method using SPW method. A new IMD reduction method is proposed to reduce the computational complexity. SPW method is to divide the input OFDM data into several sub-blocks and to multiply phase weighting values with each sub-blocks for the reduction of PAPR or IMD. Unlike the conventional method, the system size and computational complexity can be reduced.