• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.1
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• pp.54-62
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• 1988

For code division multiple access, a frequency synthesizer of elementary components is necessary in the system application of frequency hopped spread spectrum communication. This paper proposes the model of N-loop PLL frequency synthesizer to be adaptied for generating the output frequency resultes in the frequency hopping pattern and to be easy in practical application of the system. It was analyzed how the frequency divider ratio distribute, what the method to decide frequency divider ratio is and what relationship of bandwidth of BPF and degree of multiple have is also analyzed in order to hop the desired frequency output.

• 전기의세계
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• v.29 no.9
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• pp.584-593
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• 1980

Conventional radar antenna systems are susceptible to performance degradation caused by unwanted signals received via the antenna sidelobes and/or mainlobes. Adaptive array systems offer possible solution to this interference problem by automatically steering nulls to unwanted signals providing significant system performance improvement. Another important andvantage of the adaptive array is its self-optimization capability which uses the collective incoming noise data for the nulling purposes. This paper provides a tutorial introduction to adaptive arrays as well as some new development of recent research in this area. Optimum link between the antenna theory and signal processing has been sought by illustrating the gain patterns and output signal-to-noise ratio. Signal acqusition methods are shown including a new attempt of the use of spread-spectrum techniques in conjuction with array systems.

• Journal of Communications and Networks
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• v.1 no.2
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• pp.81-85
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• 1999

The regrowth of OQPSK power spectral sidelobes from AM/AM and AM/PM amplifier nonlinearity is analyzed. The time-domain expression for amplifier output shows how spectral re-growth will depend on the cubic coefficient of the Taylor's series of the amplifier nonlinearity as well as input amplitude ripple. Closed form spectrum calculations show that the spectral sidelobes produced by AM/PM take the same form as those produced by AM/AM. The rate of growth of AM/PM sidelobes is, however, not as great as for AM/AM.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.8
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• pp.867-873
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• 1988

The degradation due to channel distortion in a quadrature modulation system from the ideal constant values over the bandwidth of a direct sequence spread spectrum signal are considered. Through using series expansion for the channel gain and phase response, the degradation in the correlator output at the receiver is found as a function of the parameters involved , including phase error, delay error, linear gin variation, quadratic gain variation, and quadratic phase variation.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.45-48
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• 1999

The demands of WLAN(Wireless Local Area Network) systems increase rapidly in whole society and this phenonenon has been expected that WLAN wi11 substitute for wired-LAN. The FHSS(Frequency Hopped Spread Spectrum) method using the WLAN is changed to the performance of Frequency synthesizer. In this paper, we proposed pipeline-accumulator using ring-counter method instead of constant accumulator that has demerits of size and power consumption. Designed DDFS generated operating frequency of 167MHz and maximum output frequency of 83.5MHz.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1738-1740
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• 1996

Laser Doppler Vibrometer using heterodyne method with a 632.8 nm He-Ne laser, has been developed for the measurement of small displacement and velocity. The measurement uses heterodyne method can be made insensitive to undesired vibration effect acting the system and can yield the sign of Doppler shift at the expense of increased complexity. A Bragg cell gives a frequency shift of 40MHz for heterodyne method. Frequency Modulated output is detected by spectrum analyzer.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.226-227
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• 1999

In the fiber-optic gyroscope employing the erbium-doped fiber source, the source excess noise was subtracted through a signal processing to improve the gyroscope sensitivity . As the result, we obtained the improvement of 14 dB(electrical) at the proper frequency, which was measured from the noise floor spectrum . In addition the random walk coefficient in the gyro output was reduced by about factor of three.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.211-212
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• 2008

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2162-2164
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• 2000

In this paper, it is analysed the spectrum of optical fiber output through a sunlight collector system. Also the lighting environments under the optical fiber bundles are predicted when applied to interior lighting by using a simulation program. As the result its feasibility as an interior lighting source shows any serious problem except the system cost.

• Journal of information and communication convergence engineering
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• v.1 no.1
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• pp.1-5
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• 2003

This paper discusses the spectral efficiency and performance of asynchronous direct sequency spread spectrum multiple access systems strict bandwidth limitation by Nyquist filtering. The signal to noise plus interference ratio(SNIR) at the output from the correlation receiver is derived analytically taking the cross correlation characteristics of spreading sequences into account, and also an approximated SNIR of a simple form is presented for the systems employing Gold sequences. Based on the analyzed result of SNIR, bit error rate performance and spectral efficiency are also estimated. and at last, we analyzed improvement rate using RS, convolution as a method for improving functions.