• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.65-66
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• 2011

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1407-1413
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• 2000

This paper presents a feedforward linear power amplifier (LPA) using error feedback technique to achieve low intermodulation distortions(IMD) of power amplifiers for base stations. Especially, the proposed linear power amplifier is applied to feedforward technique combined with error feedback technique, which has no loss of amplifier gain unlike typical feedback technique. The proposed LPA is designed by using HP ADS ver. 1.3, fabricated. When two-tone signals at 1850 MHz and 1851.25 MHz with -7 dBm/tone from synthesizers are injected into the main power amplifier with gain of 28 dB and P1dB of 1W, the proposed LPA could reduce more than 35 dB.

• Bulletin of the Korean Mathematical Society
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• v.60 no.5
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• pp.1237-1252
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• 2023

A fundamental problem in coding theory is to find n_q(k, d), the minimum length n for which an [n, k, d]_q code exists. We show that some q-divisible optimal linear codes of dimension 4 over 𝔽_q, which are not of Belov type, can be constructed geometrically using hyperbolic quadrics in PG(3, q). We also construct some new linear codes over 𝔽_q with q = 7, 8, which determine n₇(4, d) for 31 values of d and n₈(4, d) for 40 values of d.

• Bulletin of the Korean Mathematical Society
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• v.37 no.1
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• pp.135-152
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• 2000

For a linear operator Q from $R^{d}\; into\; R^{d},\; {\alpha}\;>0\; and\ 0-semi-stability and the operater semi-stability of probability measures on $R^{d}$ are defined. Characterization of $(Q,b,{\alpha})$-semi-stable Gaussian distribution is obtained and the relationship between the class of $(Q,b,{\alpha})$-semi-stable non-Gaussian distributions and that of operator semistable distributions is discussed.

• The Pure and Applied Mathematics
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• v.16 no.2
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• pp.227-241
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• 2009

Let A be a Banach algebra. Suppose there exists a continuous linear Jordan derivation D : A $\rightarrow$ A such that $[D(x),\;x]D(x)^2[D(x),\;x]\;{\in}\;rad(A)$ for all $x\;{\in}\;A$. Then we have D(A) $\subseteq$ rad(A).

• Journal of the Korean Statistical Society
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• v.16 no.2
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• pp.71-79
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• 1987

The linear and quadratic log contrast model with mixtures on the strictly positive simplex, $$ x_{q-1} = {(x_1, \cdots, x_q):\sum x_, = 1 and \delta \leq \frac{x_i}{x_j} \leq \frac{1}{\delta} for all i,j},$$ are considered. Using the invariance arguments, symmetric D-optimal designs are investigated. The class of symmetric D-optimal designs for the linear log contrasts model is given. Any D-optimal design for the quadratic log contrast model is shown to metric D-optimal designs for q=3 and 4 cases are given.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.917-923
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• 2008

The D-STTD system obtains the diversity gain through the STTD scheme and the Multiplexing gain through parallel structure of the encoder using the STTD scheme known Alamouti Code. We are difficult to use Combining scheme of the STTD scheme for the D-STTD detection in the decoder because the D-STTD system transmits mutually different data in each other STTD encoder for multiplexing gain. Therefore, in this paper we combine the D-STTD system with Linear algorithm, SIC algorithm and OSIC algorithm known multiplexing detection scheme based on MMSE scheme and compare the performance of each system. And we propose the detection scheme of the D-STTD using MAP Algorithm and analyze the performance of each system. The simulation results show that the detector using iterative algorithm has better performance than Linear MMSE Detector. Especially, we show that the detector using MAP algorithm outperforms conventional detector.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.297-301
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• 2003

The binary clipping PW/CDMA system is considered. This system can be constructed with effective cost. leading to reduce the influence of the non-linear amplifier because of converting multi-level signals into constant envelope signals. In addition, the clipping method which is to clip out signal amplitude at some level when multi-level signals are converted into constant envelope signals is used. The multi-level signals are clipped at 1 and -1 to limit the extension of bandwidth and to maintain the bandwidth after clipping. In this paper, the performance of the binary clipping PW/CDMA system with the non-linear amplifier analyzed by simulation over AWGN and flat fading channels respectively. The binary clipping PW/CDMA system with the non-linear amplifier is 2.2dB and 0.9dB better than conventional DS/CDMA system over the flat fading channels when the number of users are 9 and 17 respectively.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.450-453
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• 2003

In this paper, the miniaturization of linear polarization microstrip patch antenna is studied by attached Irises near the square linear polarization microstrip patch antenna which are induced the increase of current path. Microstrip patch antenna having the Irises is designed and fabricated at the resonant frequency of 1.575 GHz. The result is like that the resonant length of patch is reduced 41.5 mm which correspond to 50.9 % of that of plane type(81.5mm). The return loss is -28.5 dBd and -10 dB bandwidth is 103 MHz( 6.5 %). And as the radiation pattern is broad through the size reduction of patch, the gain is 5.9 dBd and -3 dB beamwidth of E-plane is $111.9^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.998-1004
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• 2002

This paper reports a design of feedforward linear power amplifier using pilot tone for IMT-2000 band repeaters accepting multi-carrier. As this time pilot tone is applied to the circuit differently from the existing method. Only one pilot tone is used in both 1-st loop(IMD abstraction loop) and 2-nd loop(IMD cancellation loop) to cancell IMD signals automatically according to variation of frequency or power level of input signals. As an experiment, in range of 2110 MHz - 2170 MHz at LPA output power of $20 W_{avg}$, IMD characteristics of over 20 dB was improved maintaining below -60 dBc considering respective 20 MHz. Therefore the supposed feedforward linear power amplifier can be used for linear power amplifier in IMT-2000 band repeaters.