• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2594-2603
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• 1997

A novel method of adaptive beam forming is presented in this paper. The proposed technique provides for a suboptimal beam pattern that increases the Signal to Noise/Interference Ratio (SNR/SIR), thus, eventually increases the capacity of the communication channel, under an assumption that the desired signal is dominant compared to each component of interferences at the receiver, which is precoditionally achieved in Code Division Multiple Access (CDMA) mobile communications by the chip correlator. The main advantages of the new technique are:(1)The procedure requires neither reference signals nor training period, (2)The signal interchoerency does not affect the performance or complexity of the entire procedure, (3)The number of antennas does not have to be greater than that of the signals of distinct arrival angles, (4)The entire procedure is iterative such that a new suboptimal beam pattern be generated upon the arrival of each new data of which the arrival angle keeps changing due tot he mobility of the signal source, (5)The total amount of computation is tremendously reduced compared to that of most conventional beam forming techniques such that the suboptimal beam pattern be produced at vevery snapshot on a real-time basis. The total computational load for generating a new set of weitht including the update of an N-by-N(N is the number of antenna elements) autocovariance matrix is $0(3N^2 + 12N)$. It can further be reduced down to O(11N) by approximating the matrix with the instantaneous signal vector.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.173-180
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• 2006

An airborne radar is an essential aviation electronic system of the aircraft to perform various missions in all weather environments. This paper presents the design, development, and test results of the multi-mode pulsed Doppler radar system test model for helicopter-borne flight test. This radar system consists of 4 LRU units, which include ANTU(Antenna Unit), TRU(Tx Rx Unit), RSDU(Radar Signal & Data Processing Unit) and DISU(Display Unit). The developed technologies include the TACCAR processor, planar array antenna, TWTA transmitter, coherent I/Q detector, digital pulse compression, DSP based Doppler FFT filtering, adaptive CFAR, IMU, and tracking capability. The design performance of the developed radar system is verified through various helicopter-borne field tests including MTD (Moving Target Detector) capability for the Doppler compensation due to the moving platform motion.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1252-1263
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• 2009

In this paper, in order to improve a service quality and to broaden the service coverage in the mobile communication system a study on a digital RF repeater employed with an Interference Cancellation System(ICS) is performed. The digital RF repeater employed with an ICS is implemented to remove interference and feedback signals which are disadvantages of a conventional(or general) RF repeater. This thesis presents the design and experiments of the new wireless repeater. The proposed wireless repeater consists of a RF repeater mounted with digital engine. The digital ICS engine consists of a DSP and FPGA. The digital engine and RF circuit are designed into a one-piece. After developing hardware through the digital platform they are also designed and fabricated into a one-piece in order to apply a best performance repeater system. The method of removing interference and feedback signals is an adaptive IF technique employed with a LMS algorithm. The powerful performance and fast convergence speed is obtained by using this method.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.4
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• pp.333-339
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• 2017

Transmission signal in wireless environment receives a signal in which a source signal, interference, and noise are mixed. The goal of this study is to estimate the desired signal from the received signal. In this paper, we have studied a method correctly estimating a target in spatial by modified beamformer method. The modified bemaformer uses an adaptive array antenna and perturbation matrix to obtain the optimal weight, and estimate the desired signal by radiating the beam in spatial. We estimate a desired signal of the target by improving resolution with the modified beamformer method which does not have complicated calculation amount. Through simulation, we compare and analyze the modified beamformer method and the MUSIC method with good resolution. In result of simulation, we showed that modified beamformer method has better resolution of 10degree than classical beamformer method and showed similar performance as the MUSIC method. The resolution of this paper was estimated to be about 5 degrees.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.132-137
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• 2003

This performance is motivated to develop a tracking antenna system for receive the satellite broadcasting signal in the coast sailing ship. Therefore, this system is made to small size, light weight and simple operation which is must to low cost system for popularization of small size ship and adaptive possibilities with useful on a ship in the coast using 1 axis Az-mount. The antenna mount structure is a compact size and easy operation to the Az-axis type which is operated by step motor. The antenna unit is a domestic made plate type of patch array and ship's moving detection is using the gyro sensor for ship's moving control. We are designed to algorithm, which walking is abreast for step track and ship's moving compensation. Ship's moving compensation is adapted to the closed loop control method by detection from gyro sensor. This system is consisted of micro processor, ADC, comparative amplifier, step motor driver, mount mechanism and algorithm. We have analysised the tracking performance of prototype on sailing ship board.

• Journal of Astronomy and Space Sciences
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• v.30 no.2
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• pp.79-82
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• 2013

We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of $n_H$ has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.694-701
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• 2003

In this paper, we present a hardware structure and new features of a smart antenna BTS (Base Transceiver Station) for CDMA2000 1X system. The proposed smart antenna BTS is a composite system consisting of many subsystems, i.e., array antenna element, frequency up/down converters, AD (Analog-to-Digital) and DA (Digital-to-Analog) converters, spreading/despreading units, convolutional encoder/Viterbi decoder, searcher, tracker, beamformer, calibration unit etc. Through the experimental tests, we found that the desired beam-pattern in both uplink and downlink communications is provided through the calibration procedure. Also it has been confirmed that the adaptive beamforming algorithm adopted to our smart antenna BTS is fast and accurate enough to support 4 fingers to each user. In our experiments, commercial mobile terminals operating PCS (Personal Communication System) band have been used. It has been confirmed that the smart antenna BTS tremendously improves the FER (Frame Error Rate) performance compared to the conventional 2-antenna diversity system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1130-1137
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• 2003

This performance is motivated to develop a tracking antenna system for receive the satellite broadcasting signal in the coast sailing ship. Therefore, this system is made to small size, light weight and simple operation which is must to low cost system for popularization of small size ship and adaptive possibilities with useful on a ship in the coast using 1 axis Az-mount. The antenna mount structure is a compact size and easy operation to the Az-axis type which is operated by step motor. The antenna unit is a domestic made plate type of patch array and ship's moving detection is using the gyro sensor for ship's moving control. We are designed to algorithm, which walking is abreast for step track and ship's moving compensation. Ship's moving compensation is adapted to the closed loop control method by detection from gyro sensor. This system is consisted of micro processor, ADC, comparative amplifier, step motor driver, mount mechanism and algorithm. We have analysised the tracking performance of prototype on sailing ship board.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.5
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• pp.243-250
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• 2002

In the synthesis of the current source distribution function of an array antenna with the arbitrary radiation pattern, the Woodward-Lawson sampling method has been mainly used for the synthesis of an even function lobe pattern. In this paper, the method is extended to the synthesis of the odd function pattern and then the optimum synthesis method for the nonlinear source distribution function is proposed. The proposed method is applied to the design of nonuniform transmission lines with arbitrary reflection responses. The both dispersive impedance profiles of single and coupled nonuniform lines with arbitrary reflection responses are directly synthesized by the sampled values of a reflected spectral pattern which is optimally shaped by a perturbation of its complex null positions, hence removing the conventional step-by-step segmentation process and global optimization routines. The control problem in the case that all of port impedances are identical is also solved. The generality of the proposed method is verified by a filter design with the controlled arbitrary passband

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.1
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• pp.15-23
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• 2003

This paper proposes a fast direction of arrival (DOA) estimation algorithm that can rapidly estimate incidence angles of incoming signals using a pseudo covariance matrix. The conventional subspace DOA estimation methods such as MUSIC (multiple signal classification) algorithms need many sample signals to acquire covariance matrix of input signals. Thus, it is difficult to estimate the DOAs of signals because they cannot perform DOA estimation during receiving sample signals. Also if the D0As of signals are changing rapidly, conventional algorithms cannot estimate incidence angles of signals exactly. The proposed algorithm obtains bearing response and directional spectrum after acquiring pseudo covariance matrix of each snapshot. The incidence angles can be exactly estimated by using the bearing response and directional spectrum. The proposed DOA estimation algorithm uses only concurrent snapshot so as to obtain covariance matrix. Compared to conventional DOA estimation methods. The proposed algorithm has an advantage that can estimate DOA of signal rapidly.