• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1782-1792
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• 1994

Ti : $LiNbO_3$ traveling-wave phase optical modulators at wavelength 1.3㎛ have been designed and fabricated, focusing on the optical waveguide and asymmetric coplanar electrode structure. To improve the phase-mismatch of traveling-wave ACPS electrode, the characteristic impedance, effective microwave index, and electrode loss have been presented as a function of geometric parameters including electrode and buffer layer thickness. Low-loss channel optical waveguides on $LiNbO_3$ were fabricated by the Ti diffusion method with $O_2$ water-vapor environment. $2.5{\mu}m$ thick electrode was successfully fabricated by double-spin image reversal process. Modulation bandwidth was limited by a resonance at 2.9 GHz and modulation bandwidth up to 2.5GHz was approxirnately measured.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.94-99
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• 2003

In this paper, a rotation invariant fingerprint identification system is implemented using the circular harmonic filter and phase only correlator. We extracted the phase component from input fingerprint image and correlate it with the circular harmonic filter of the reference fingerprint image by POC. The input image is obtained using a prism operating in the internal full reflection mode. Then the input image is transformed to two dimensional Fourier spectrum in optical way and the phase component is extracted using a digital system from the spectrum. Because composed of the optical system and digital algorithm, the proposed system has the advantages of the two technologies such as realtime parallel processing property of the optics and the flexibility of the digital system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.938-940
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• 2003

고출력 반도체 레이저(500mW)의 출력광 파장 809nm과 반도체 레이저로 여기되는 Nd:YVO4레이저의 출력광 파장 1064nm를 공진기 내부에서 비선형 광학 소자인 KTP(Potassium titanyl posphate : KTPiOPO$_4$)를 사용하여 합주파 발생 실험을 행하여 459nm의 청색레이저를 얻었다. 제2의 위상 정합 정합조건($\psi$=90$^{\circ}$, $\theta$=90$^{\circ}$)에서 반도체 레이저의 입력광 세기가 400mW일 때 청색레이저의 최대 출력 0.95mW를 얻었으며, 청색레이저의 발진문턱입력 세기는 120mW이었다.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.156-157
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• 2001

전계 흡수 광 변조기는 우수한 소광비와 낮은 전력 소모로 넓은 대역폭을 확보할 수 있으며 LD와의 단일 집적인 EML(electro-absorption modulator integrated laser diode)의 제작도 용이하므로 Microwave-Photonics 시스템에 매우 적합한 소자로써 근래에 활발한 연구가 진행되어지고 있다. 전계 흡수 광 변조기의 대역폭을 최대한 확보하기 위해서는 진행하는 마이크로파의 위상속도와 광파의 그룹 속도가 정합 되어야 하며 소자의 임피던스가 50Ω에 정합 되어야 한다. (중략)

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.224-227
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• 2006

We have chained 459nm blue laser radiation generated by intracavity sum frequency generation( SFG ) due to the mixing of the 1064 nm laser output of a Nd:YVO4 pumped by diode and the 809nm radiation from higg-power semiconductor laser(500mW). The maximum blue output power of 0.95 mW was obtained using 400 mW input power of semiconductor laser at the type II phase matching condition (${\psi}=90^{\circ}\;{\theta}=90^{\circ}$). The threshold input power of blue laser generation was 120 mW.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.32-37
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• 2022

As semiconductors become finer, equipment must perform precise and accurate processes to achieve the desired wafer fabrication requirement. Radio frequency power delivery system in plasma system plays a critical role to generate the plasma, and the role of impedance matching unit is critical to terminate the reflected radio frequency power by modifying the impedance of the matching network in the plasma equipment. Impedance matching unit contains one fixed inductor and two variable vacuum capacitors whose positions are controlled two step motors. Controlling the amount of vacuum variable capacitor should be made as soon as possible when the mismatched impedance is detected. In this paper, we present the impedance matching algorithm using the phase sensor.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.23-28
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• 2009

The general six-port phase correlator is comprised of a Wilkinson power divider and three $90^{\circ}$ hybrid coupler, which has less than 10 % bandwidth. In this paper, the six-port phase correlator using two section power divider has 33 % bandwidth and external matching $90^{\circ}$ hybrid coupler with 15 % bandwidth was designed at the center frequency of 2.5 GHz. The simulation result by ADS2003A indicates that RF port and LO port of proposed six-port phase correlator got wide frequency bandwidth of 14 % for VSWR of 1.5. The fabricated six-port phase correlator has a bandwidth of 12 % similar to the simulation result. The maximum phase discrepancy and insertion loss are $6^{\circ}$ and 2.5 dB over a bandwidth, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.661-670
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• 2013

In this paper, we propose the measurement techniques of mixed waveform. Mixed waveform has phase-continuous periodic waveform with fixed frequency signal and Linear Frequency Modulation(LFM) signal. This waveform is generated from a compact radar transmitter with frequency synthesizer and high power amplifier. Frequency synthesizer generates various signal waveform with continuos phase and high power amplifier amplify transmitting signal. First, we describe a compact radar transmitter with the phase-continuos signal and then verify the distortion characteristic of pulse compression by the mismatch of LFM waveform. Second, we describe three kinds of measurement techniques for measuring LFM waveform. These techniques include methods using signal analyzer, signal source analyzer and new methods using RF mixer and phase shifter. Finally, we verify the accuracy of the measurement technique from the pulse compression result of receiving signal.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.3
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• pp.110-116
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• 2008

In this paper, we proposed an improvement technique of image encryption using binary phase computer generated hologram(BPCGH) and multi exclusive-OR(XOR) operations. For the encryption process, a BPCGH that reconstructs the original image is designed, using an iterative algorithm, and the resulting hologram is regarded as the image to be encrypted. The BPCGH is encrypted through the exclusive-OR operation with the random generated phase key image. Then the encrypted image is divided into several slide images using XOR operations. So, the performance of encryption for the image is improved. For the decryption process, we cascade the encrypted slide images and phase key image and interfere with reference wave. Then decrypted hologram image is transformed into phase information. Finally, the original image is recovered by an inverse Fourier transformation of the phase information. If the slide images are changed, we can get various decrypted BPCGH images. In the proposed security system, without a random generated key image, the original image can not be recovered. And we recover another hologram pattern according to the slide images, so it can be used in the differentiated authorization system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1103-1108
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• 2010

In this paper, Frequency Synthesizer which is widely used for FH-SS system is proposed and the experimental results are analyzed. The performance of the DPLL(Digital Phase-Locked-Loop), which is the main part of the Synthesizer is analyzed by the computer program. Using Maxplus-II tool provided by altera. co., ltd, each part of the DPLL is designed and all of them is integrated into EPM7064SLC44-10 chip. And the simulation results are compared with the characteristics of the implemented circuits for analysis. And the experiential results show that the N value of the loop filter is toggled to adjacent N value, which result in phase jitter of the output. It can be resolved by increasing DCO(Digital Controlled oscillator) clock rate.