• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1234-1238
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• 2005

As the low power GPS signal is susceptible to interference, interference can seriously degrade the performance of GPS receiver. This paper designs a ANIEF(Adaptive Narrowband Interference Excision in Frequency domain) filter that removes narrow band interferences with low signal loss. This filter uses the pre-correlation technique and attempts to filter out the interference in the frequency domain. The interference excision performance of the designed filter is evaluated for various interferences using the ANIEF filter inserted GPS software receiver and the interference generator. Interferences considered in this paper are single-tone CWI(Continuous Wave Interference), multi-tones CWI, pulsed CWI, and swept CWI. The narrowband interference excision filter in frequency domain is very effective against various interferences and the strong interference with a simple structure. However, the signal power loss is unavoidable while transforming. In this paper, the hamming window and overlap technique are adopted to reduce the signal power loss. Finally, the interference excision performance and the reduced signal power loss of the ANIEF filter are shown.

• 방송공학회논문지
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• 제11권1호
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• pp.100-106
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• 2006

본 논문에서는 지상파 디지털 방송시스템의 단일 주파수망 (SFN; Single Frequency Network) 구성을 위해 DTV (Digital Television)의 TxID (Transmitter Identification)용 저간섭 ZCD (Zero Correlation Duration) 확산코드를 제시하였다. ZCD 확산 코드는 코드발생기의 구현이 용이함과 동시에 ZCD 특성을 가짐으로 인해서, TxID에서 발생되는 인접코드 간섭 (ICI; Inter Code Interference) 및 다중경로 간섭 (MPI; Multi-Path Interference) 문제를 확산코딩기법을 이용하여 근원적으로 해결해주는 역할을 하고 있으며, 주기를 가변적으로 조절할 수 있어 TxID를 위한 워터마킹 (Watermarking)시에 발생하는 Truncated error 를 제거할 수 있다. 본 논문에서는 AWGN (Additive White Gaussian Noise) 잡음 및 ICI, MPI와 같은 다양한 간섭환경을 모의실험에 반영하여 도출된 DER (Detection Error Rate) 특성을 분석함으로써, TxID용 저간섭 ZCD 확산코드의 유용성을 입증하였다.

• Journal of the Optical Society of Korea
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• 제14권1호
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• pp.33-37
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• 2010

The joint transform correlator (JTC) has been the best known technique for pattern recognition and identification. The JTC optically compares the reference image with the sample image then examines match or non-match by acquiring a correlation peak. However, the JTC technique has some problems such as weak correlation discrimination and noise which originates from the interference fringes in the Fourier transform plane. In order to solve these problems, this paper proposes a new technique of modifications of the interference fringes by adopting special iterative filters. Experimental results are presented to show that the proposed technique can successfully improve the correlation peaks and the level of discrimination.

• 한국통신학회논문지
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• 제42권4호
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• pp.819-830
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• 2017

FM 신호 기반 PCL 시스템은 FM 송신탑에서 송신되는 신호를 이용하여 이동하는 표적의 위치를 추적하는 수동형 레이더 기술로서, 송신탑에서 수신기에 LOS (line-of-sight)로 입사되는 직접경로 신호와 표적으로부터 반사된 표적반사 신호의 상호 상관 함수를 유도하여 표적의 위치를 추적한다. 하지만, 직접경로 신호와 지형 및 지표면 등에서 반사되는 간섭 신호가 표적반사 신호 획득을 위한 감시 채널에 동시에 측정되며, 이에 따라 표적의 위치를 정확하게 탐지하지 못하는 문제가 발생한다. 간섭 신호 제거에는 적응 필터가 효과적인 것으로 알려져 있지만, 기존 연구에서는 상호 상관 함수나 적응 필터 입출력 신호의 전력 비율로부터 간섭 신호의 제거 성능을 유도하기 때문에, 정확한 성능 분석이 어려운 문제가 존재하였다. 본 논문에서는 필터 계수의 각 성분이 특정한 간섭 신호를 제거하기 위해 유도된다는 특징을 활용하여, 각 간섭 신호 제거 성능을 적응 필터 계수에 대한 함수로 정리한다. 제안한 성능 분석 방법을 기반으로 적응 필터 기법의 성능을 비교 및 분석하여, 제안한 방법이 간섭 신호 제거 성능 분석에 효과적으로 활용될 수 있음을 보인다.

• 한국위성정보통신학회논문지
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• 제6권2호
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• pp.125-130
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• 2011

본 논문은 T-DMB 재난방송에서 데이터 전송 기술 향상을 위해 확산코드를 이용하여 각 코드들의 자기상관특성(Auto Correlation Feature) 성능을 비교해 보았다. 일반적으로 DMB와 같은 무선 이동 통신 환경은 수신기에서 송신기의 식별 과정에서 발생하는 인접코드 간섭(Inter Code Interference) 및 다중경로 간섭(Multi-Path Interference)이 일어난다. 이러한 문제점을 해결하기 위해서 확산코드 기법을 이용하여 비화 특성을 개선시킬수 있고, 코드의 주기를 조절하여 가변시킬수가 있어 신호처리 다분야에서 활용 할 수가 있다. 이에 본 논문은 직교성이 우수한 Golay코드와 Kasami코드, ZCD(Zero Correlation Duration)코드에 성능을 비교하는 연구를 하였다.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.181-190
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• 2014

This paper reports a cognitive radio network architecture based on overloaded multicarrier direct sequence code division multiple access (O-MC-DS-CDMA). The O-MC-DSCDMA technique combines CDMA with a multicarrier modulation technique to overcome the channel fading effects. In this technique, secondary users are enabled to share the available bandwidth with the existing primary users. Two sets of orthogonal Gold codes are used to support the primary and secondary users simultaneously. The orthogonality between the spreading codes is lost due to the non-zero cross correlation between the codes and the timing synchronization error in the uplink transmission, which causes interference between primary and secondary users. This paper proposes two modified hybrid parallel/successive interference cancellation techniques for primary and secondary user base station receivers with multiple antennas to suppress the interference among users. Interference among the same group of users is cancelled by parallel interference cancellation and the interference among groups is cancelled using successive interference cancellation. The simulation results confirmed that the proposed modified interference cancellation techniques show better BER performance over conventional interference cancellation techniques.

• ETRI Journal
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• 제31권5호
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• pp.500-505
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• 2009

The detrimental effect of short-term fading and shadowing can be mitigated using microdiversity and macrodiversity systems, respectively. In this paper, implementation of selection combining at both micro and macro levels to improve system performance is analyzed. An assessment of the performance of such a system is carried out by considering the desired signal as Rician fading with lognormal shadowing and cochannel interference signal as Rayleigh fading superimposed over lognormal shadowing. The proposed analysis is complemented by various performance evaluation results, including the effects on overall system performance of fading severity, shadowing spreads and branch correlation existing at the base station, and correlation between base stations.

• 한국통신학회논문지
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• 제41권1호
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• pp.23-36
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• 2016

본 논문에서 제안하는 새로운 유형의 상향링크 OFDM-CDMA 기법은 ZCZ(Zero Correlation Zone) 부호와 블록 확산 기법을 함께 이용하여 사용자간의 넓은 접속시간 동기오차 허용범위를 가진다. 또한, 제안하는 기법은 OFDM 신호에 보호구간을 삽입하지 않아 주파수 효율을 최대화 한다. 넓은 사용자간 접속시간 동기오차 허용범위를 가지려면 보호구간의 길이를 늘여야 하는 기존 기법과 달리, 본 논문에서 제안하는 기법은 보호구간을 삽입하지 않아도 아주 넓은 사용자간 접속시간 동기오차 허용범위를 가진다. 제안하는 보호구간이 없는 상향링크 OFDM-CDMA 기법은 다중경로 페이딩 환경에서 수신단의 역확산 과정을 통해 모든 사용자간 간섭이 사라지는 특성을 가진다. 더욱이, 제안하는 기법은 복수개의 OFDM 심볼 길이만큼의 사용자간 동기오차 환경에서도 모든 사용자간 간섭이 없다. 보호구간이 없기 때문에 자기 신호의 부반송파간 간섭은 존재하지만, 제안하는 블록 확산 방식으로 인한 블록의 첫 번째 심볼이 ISI(Inter Symbol Interference)가 없는 특성을 이용하여 간단한 SIC(Successive Interference Cancellation)를 통해 첫 번째 이후 심볼의 간섭도 효과적으로 억제할 수 있다.

• Journal of Oral Medicine and Pain
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• 제18권1호
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• pp.31-43
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• 1993

To evaluate the correlationship between sign/symptoms of craniomandibular disorder(CMD) and possible contributing occlusal factors, the author analyzed craniomandibular index(CMI), clinical dysfunction index(CDI) and occlusal index(Oi) obtained from 88 subjects (32 males, 56 females, mean age 28.7) consisted of 49 CMD patients(15 males, 34 females, mean age 28.7) and 39 non-CMD patients (17 males, 22 females, mean age 24.5). The obtained results were as follows : 1. There was very high significant correlation bebween CMI and CDI in total subjects (r=0.83, p<0.01) 2. There was very low correlation between working-side interference and TMJ noise which was observed as a statistically significant value(p<0.05). And also there ws very low correlation between nonworking side interference and muscle tenderness, CDI, dysfunction index(DI), palpation index(PI) which were observed as statistically significant value (p<0.01) 3. There was very low correlation between as ymmetry of tetruded contact position(RCP)-intercuspal position(ICP) slide and muscle tenderness, TMJ tenderness, TMJ noise, CMI, DI, PI which were observed as statistically significant values(p<0.05) 4. In general there was low correlation between Oi and muscle tenderness, CDI, CMI, DI, PI which were observed as statistically significant values (p,0.05). But Oi had a relatively higher correlation with muscle tenderness, PI than whith CDI, DI.

• 대한임베디드공학회논문지
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• 제11권1호
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• pp.29-37
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• 2016

We propose vehicular spread spectrum (SS) radar robust to mutual interference using zero correlation zone (ZCZ) code. SS radar schemes have been employed for vehicular radar systems due to their outstanding correlation property. However, this superiority is based on a premise that timing among codes is completely synchronized. In the practical driving environment, timing mismatch among radar signals is inevitable because the radar signals of several vehicles are independently transmitted at each different location and each timing and thus each radar signal is received at different timing. This timing offset is the main cause of orthogonality destruction among codes and thus radar signals from other vehicles become mutual interference. In order to solve this problem, we find out the new property of ZCZ code which maintains the complete orthogonality except to timing offset corresponding to chips (pulses) of multiple of 4 and employ ZCZ code to SS radar systems. Simulation results show the proposed scheme achieve better performance compared with the conventional SS radar scheme using pseudo code or gold code.