• 전기학회논문지
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• 제63권9호
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• pp.1259-1265
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• 2014

In this paper, the real-time attitude determination based Matlab using low-cost receivers was designed and evaluated. The GNSS attitude determination system was implemented to operation in real-time by TimerCallback in MATLAB. The TTM(Transmission Time Misalignment) of U-blox receiver was confirmed through zero baseline tests and this problem was revised. The computed attitude by the high-cost NovAtel receiver was compared to the computed attitude by the low-cost U-blox receiver. As a result of this, the performance of attitude determination systems by low-cost receiver was confirmed. To determine baseline, LAMBDA and BC-LAMBDA for integer ambiguities search methods were used. To confirm suitable integer ambiguity search method in real-time attitude determination algorithm, determined baselines by two methods were compared, and it was confirmed that BC-LAMBDA is more suitable. As a result of this, the operation of real-time attitude determination system was confirmed using 3 low-cost receivers.

• 한국전자파학회논문지
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• 제8권6호
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• pp.589-599
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• 1997

본 논문에서는 동기 CDMA 환경에서, 사용자간 간섭을 제거하기 위해 결정궤환을 이용한 다중 사용자 수신기 를 설계한다 부가백색 가우시안 잡음(AWGN) 채널인 경우에는 정합여파기 뱅크, 페이딩 채널인 경우는 RAKE 수신기 뱅크 출력으로부터 결정궤환을 이용하여 사용자간 간섭을 제거하고, 결정단에서 사용자 신호를 결정한다. 정합여파기와 RAKE 수신기는 심볼간 간섭과 다경로에 의한 간섭을 제거하고, 결정궤환 구조는 사용 자의 신호간 간섭을 제거한다. 결정궤환 구조의 계수는 Least Mean Square(LMS) 알고리듬에 의해서 적응되 도록한다. 실험 결과를 통해서, 이동 통신 다중 사용자 환경에서 RAKE 수신기만을 사용하는 경우보다 결정궤환을 이용 한 다중사용자 수신기를 사용하는 경우에 더욱 성능이 향상되는 것을 확인할 수 있었다.

• Journal of Communications and Networks
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• 제6권1호
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• pp.26-34
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• 2004

A blind interference canceller in the presence of subchipspaced multipath channels for direct-sequence code division multiple access (DS-CDMA) down-link system is considered. This technique is based on combining the existing blind interference canceller with a technique that involves assigning subchip-tap spacing to the Rake receiver. The proposed receiver minimizes the receiver’s output energy subject to a constraint in order to mitigate the multiple access interference (MAI) along each multipath component, and then suboptimally combining all the multipath components. Moreover, it is able to mitigate the mismatch problem when subchip-spaced multipath components arrive at the blind interference canceller. It is known that optimal combining techniques perform a decorrelation operation before combining, which requires both knowledge and computational complexity. In the following, we have adopted a simpler but suboptimum approach in the combining of the suppressed signals at the output of our proposed receiver. Computer simulation results verify the effectiveness of the proposed receiver to handle subchip-spaced multipath components and still suppresses MAI significantly.

• 전기학회논문지
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• 제61권3호
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• pp.384-393
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• 2012

Railroad signaling systems perform controlling the distance and routes between trains. Signaling methods on the wayside are to control passively the train speed by using signal flags which are installed on the wayside. ATS(Automatic Train Stop) device is used as the signaling method on the wayside in Korea. The ATS device is assistance equipment of engineers. Signal information is transmitted by combining mutual inductance between the wayside transmitter and on-board receiver. The wayside transmitter performs changing oscillation frequency according to the signal information. The on-board receiver performs controlling the train by receiving the frequency. Currently, the oscillation frequency on the on-board receiver is 78[kHz] in case of normal state. When the on-board receiver is over the wayside transmitter, the oscillation frequency is changed by capacitors of the wayside transmitter according to signal flags. In case of changing the oscillation frequency, the waveform is modified in the wayside transmitter and on-board receiver. This phenomenon is that other signals or communication frequency are included. In this paper, electric model between the wayside transmitter and on-board receiver is suggested and frequency response in the wayside transmitter and on-board receiver including other signals is estimated by the coupling coefficient. Also, the value of coupling coefficient is proposed to exclude other signals and demonstrated by using Matlab and PSpice program.

• Journal of Positioning, Navigation, and Timing
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• 제5권3호
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• pp.137-144
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• 2016

In this paper, the performance of ranging measurement, which is generated using two receiver clock offsets in one receiver, was analyzed. A spoofer transmits a counterfeited spoofing signal which is similar to the GPS signal with hostile purposes, so the same tracking technique can be applied to the spoofing signal. The multi-correlator can generate two receiver clock offsets in one receiver. The difference between these two clock offsets consists of the path length from the spoofer to the receiver and the delay of spoofer system. Thus, in this paper, the ranging measurement was evaluated by the spoofer localization performance based on the time-of-arrival (TOA) technique. The results of simulation and real-world experiments show that the position and the system clock offset of the spoofer could be estimated successfully.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.44-49
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• 2013

A transimpedance amplifier (TIA)-optical receiver (Rx) using two intersecting active feedback system with regulated-cascode (RGC) input stage has been designed and implemented for optical interconnects. The optical TIA-Rx chip is designed in a 0.13 ${\mu}m$ CMOS technology and works up to 10 Gbps data rate. The TIA-Rx chip core occupies an area of 0.051 $mm^2$ with power consumption of 16.9 mW at 1.3 V. The measured input-referred noise of optical TIA-Rx is 20 pA/${\surd}$Hz with a 3-dB bandwidth of 6.9 GHz. The proposed TIA-Rx achieved a high gain-bandwidth product per DC power figure of merit of 408 $GHz{\Omega}/mW$.

• 한국전자파학회논문지
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• 제24권10호
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• pp.987-993
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• 2013

카오스 통신 시스템은 신호의 비예측성, 광대역성, 비주기성, 구현의 용이성 등의 특징을 가지고 있다. 또한, 카오스 방정식의 초기 조건이 미세하게 변함에 따라 카오스 신호는 전혀 다른 신호가 되기 때문에, 카오스 통신은 초기 조건에 민감하다는 특징을 갖는다. 이런 특징으로 인해 카오스 통신 시스템은 다른 디지털 통신 시스템보다 보안성이 우수하게 평가된다. 하지만 기존 카오스 통신 시스템의 송수신기는 레퍼런스 신호나 잡음에 많은 영향을 받기 때문에, BER(Bit Error Rate) 성능은 다른 디지털 시스템보다 나쁘게 평가된다. 그래서 카오스 통신시스템의 BER 성능 향상과 관련된 연구는 지속적으로 활발하게 이루어지고 있다. 본 논문에서는 BER 성능 향상을 위한 새로운 CDSK(Correlation Delay Shift Keying) 수신기를 제안한다. 그리고 기존 수신기와 제안한 수신기의 BER 성능 비교를 통해서 제안한 수신기의 BER 성능 향상을 평가한다. 하지만 제안하는 수신기를 사용하는 경우 BER 성능은 크게 향상되지만, 기존의 송신기를 사용하면 제안하는 수신기뿐만 아니라, 비록 BER 성능은 안 좋더라도 기존의 수신기로도 정보 신호를 복원할 수 있다. 따라서 제안하는 수신기의 보안성을 향상시키기 위해서는 제안하는 수신기로만 정보 비트를 복원할 수 있는 새로운 CDSK 송신기를 제안한다. 제안하는 송신기를 이용하여 정보 신호를 전송하는 경우에 기존의 수신기로는 정보 신호를 복원할 수 없고, 제안한 수신기를 사용해야 정보 신호를 복원할 수 있다.

• Journal of electromagnetic engineering and science
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• 제14권2호
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• pp.61-67
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• 2014

This paper presents a zero-IF CMOS RF receiver, which supports three channel bandwidths of 5/10/40MHz for LTE-Advanced systems. The receiver operates at IMT-band of 2,500 to 2,690MHz. The simulated noise figure of the overall receiver is 1.6 dB at 7MHz (7.5 dB at 7.5 kHz). The receiver is composed of two parts: an RF front-end and a baseband circuit. In the RF front-end, a RF input signal is amplified by a low noise amplifier and $G_m$ with configurable gain steps (41/35/29/23 dB) with optimized noise and linearity performances for a wide dynamic range. The proposed baseband circuit provides a -1 dB cutoff frequency of up to 40MHz using a proposed wideband OP-amp, which has a phase margin of $77^{\circ}$ and an unit-gain bandwidth of 2.04 GHz. The proposed zero-IF CMOS RF receiver has been implemented in $0.13-{\mu}m$ CMOS technology and consumes 116 (for high gain mode)/106 (for low gain mode) mA from a 1.2 V supply voltage. The measurement of a fabricated chip for a 10-MHz 3G LTE input signal with 16-QAM shows more than 8.3 dB of minimum signal-to-noise ratio, while receiving the input channel power from -88 to -12 dBm.

• ETRI Journal
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• 제35권5호
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• pp.797-807
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• 2013

In this paper, an input receiver with a hysteresis characteristic that can work at voltage levels between 0.9 V and 5 V is proposed. The input receiver can be used as a wide voltage range Schmitt trigger also. At the same time, reliable circuit operation is ensured. According to the research findings, this is the first time a wide voltage range Schmitt trigger is being reported. The proposed circuit is compared with previously reported input receivers, and it is shown that the circuit has better noise immunity. The proposed input receiver ends the need for a separate Schmitt trigger and input buffer. The frequency of operation is also higher than that of the previously reported receiver. The circuit is simulated using HSPICE at 0.35-${\mu}m$ standard thin oxide technology. Monte Carlo analysis is conducted at different process conditions, showing that the proposed circuit works well for different process conditions at different voltage levels of operation. A noise impulse of ($V_{CC}/2$) magnitude is added to the input voltage to show that the receiver receives the correct logic level even in the presence of noise. Here, $V_{CC}$ is the fixed voltage supply of 3.3 V.

• 한국정보전자통신기술학회논문지
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• 제2권1호
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• pp.59-64
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• 2009

본 논문은 다중 안테나를 사용하는 통신시스템의 수신부에서 사용하는 복잡도가 낮은 신호검출기법을 제안한. 선형검출기법에는 Zero-Forcing (ZF)기법과 minimum mean squared error (MMSE) 기법이 있고, ZF기법은 MMSE 기법에 비해 하드웨어 구현관점에서 더 간단하나 성능이 열등한 것으로 알려져 있다. 일반적으로 통신시스템에서는 채널상황에 따라 modulation coding scheme (MCS)을 적응으로 바꾸어 사용한다. 본 논문에서는 사용되는 MCS 레벨에 따라 ZF기법과 MMSE기법 중 더 적합한 방식을 선택할 필요가 있음을 보인다. 또한 하드웨어 구현을 통해 적응 선형수신기의 복잡도가 기존의 MMSE 기법의 복잡도와 유사함을 보인다.