• Journal of Electrical Engineering and Technology
• /
• 제7권5호
• /
• pp.797-806
• /
• 2012

Fault detection and isolation (FDI) algorithms provide fault monitoring methods in GPS measurement to isolate abnormal signals from the GPS satellites or the acquired signal in receiver. In order to monitor the occurred faults, FDI generates test statistics and decides the case that is beyond a designed threshold as a fault. For such problem of fault detection and isolation, this paper presents and evaluates position domain integrity monitoring methods by formulating various pseudorange prediction methods and investigating the resulting test statistics. In particular, precise measurements like carrier phase and Doppler rate are employed under the assumption of fault free carrier signal. The presented position domain algorithm contains the following process; first a common pseudorange prediction formula is defined with the proposed variations in pseudorange differential update. Next, a threshold computation is proposed with the test statistics distribution considering the elevation angle. Then, by examining the test statistics, fault detection and isolation is done for each satellite channel. To verify the performance, simulations using the presented fault detection methods are done for an ideal and real fault case, respectively.

• Macromolecular Research
• /
• 제11권4호
• /
• pp.267-272
• /
• 2003

The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to $120^{\circ}C$ but phase separations occurred in the early stages of the curing process at higher temperatures than $120^{\circ}C$. According to the rheological measurement results, a rise of G' and G" at the onset of phase separation is seen. A rise of G' and G" is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.

• ETRI Journal
• /
• 제21권2호
• /
• pp.9-21
• /
• 1999

In this paper, to enhance the performance of ${\pi}$/4-DQPSK (${\pi}$/4-differential quadrature phase shift keying), the scheme using nonredundant multiple error correction is proposed and investigated. This scheme for the differential detection of ${\pi}$/4-DQPSK uses the signal output which is delayed for more than two time slots as the parity check bit and applies it to nonredundant multiple error correction. The proposed system was used for studying the performance of ${\pi}$/4-DQPSK with Nonredundant Error Correction (NEC) in additive white Gaussian noise (AWGN) and Nakagami fade modeled mobile communication channel, and it was observed that the performance increased as the error correction capability increased.

• 한국통신학회논문지
• /
• 제24권12A호
• /
• pp.1948-1959
• /
• 1999

본 논문에서는 비용장 다중오류정정을 갖는 $\pi$/4-QPSK의 차동검파 시스템을 이용하여 가산성 가우시안 백색잡음(additive white Gaussian noise: AWGN)과 나카가미 늦은 페이딩(Nakagami slow fading)채널로 모델링된 이동통신채널에서 성능이 분석연구되었다. 비용장 다중오류정정은 두 개 이상의 타임스롯(time slots)만큼 지연되어 수신된 신호를 이용하여 형성된 출력이 패리티체크 비트가 되어 오류정정에 이용되었으며, 비용장연속 다중오류정정(NEC)의 차수가 증가함에 따라 성능이 증가됨을 보이고 나카가미 페이딩 변수가 증가함에 따라도 성능이 증가됨을 보였다.

• 로봇학회논문지
• /
• 제4권4호
• /
• pp.320-326
• /
• 2009

This paper proposed a new magnetic field detection algorithm to detect metal pieces in food producing processes. This algorithm can detect mixed metal pieces by sensing magnetic field. Some metal pieces are passed through an over-current circuit to magnetize them. The magnetic field sensor can detect the change in the magnetic field on theconveyor belt caused by the flow of the metal pieces in the food product. However, such a method detects the output of signals that change their amplitude and phase according to the movement of the conveyor belt with the food product, in which the equilibrium of the positive signal that is created in the receiver coil loses its balance due to the magnetized material. This includes not only the signal elements resulting from the effect of the alternating magnetic fields of the mixed metals, but also the signal elements resulting from the effect of the alternating magnetic fields of the examined object itself.

• 전자공학회논문지A
• /
• 제31A권5호
• /
• pp.1-9
• /
• 1994

In this paper, we analyzed the performances for FH/CPFSK system with limiter-discriminator detection and integrate-and-dump post-detection filtering under thermal noise and partial-band jamming noise. And,we considered intersymbol interference-related SNR and differential phase parameters for all eight of the possible adjacent bit data patterns, FM noise clicks for evaluating FH/CPFSK and CPFSK Systems. In result, the optimum modulation index h was 0.7 and the optimum value of bandwidth-time product D was 1.0 Next, when we considered the thermal noise under the partial-band jamming, the thermal noise significantly influenced the error probability of system below 20dB approximately but could ignore above 20dB.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 D
• /
• pp.2299-2301
• /
• 2001

광 디스크의 용량을 증가시기키 위해선, 레이저 다이오드의 단파장화와 렌즈의 개구수 증가가 수년 동안 시도되어왔다. 불행히도 이러한 노력들은 디스크 틸트(tilt)로 인해 야기되는 코마(coma) 수차로 인한 부작용을 유발하였다. 이런 문제를 해결하기 위해, 램(random access memory, RAM) 디스크의 경우 몇 가지 검출과 보상 방법이 제안되었다. 그러나, 롬(read only memory, ROM) 디스크의 경우 아직까지 뚜렷한 해결책이 제시되지 않고 있다. 본 논문에서는 8분할 광 검출기에 의해 생성되는 차동 위상 검출(differential phase detection, DPD) 신호를 이용한 고밀도 롬 디스크에서 래디얼(radial) 틸트를 검출하는 방법을 제안한다. 3축 렌즈 구동형 액츄에이터(actuator)를 이용하여 개발한 래디얼 틸트 서보로 검출된 래디얼 틸트를 보상한다. 액츄에이터의 회전이 트래킹(tracking) 서보(servo)에 미치는 영향을 소개한다. 끝으로 제안된 방법의 유용성을 고밀도 롬 드라이브에 대한 실험을 통해 검증한다.

• 한국컴퓨터정보학회논문지
• /
• 제3권4호
• /
• pp.78-85
• /
• 1998

본 논문에서는 열잡음과 부분대역 재밍하에서 리미터-변별기 검파와 Integrate - and - Dump 필터링을 고려한 FH/CPFSK시스템의 성능을 분석하였고, 시스템을 평가하는데 있어서 인접한 8개의 Bit 패턴에 대한 심볼간 간섭과 차분위상, FM잡음 클릭을 고려하였다. 그 결과, 최적의 변조지수 h는 0.7이었고, 대역폭과 시간의 곱 D는 1.0이었으며, 부분대역 재밍하에서 열잡음을 고려했을 때, 대략 20dB 이하에서는 시스템의 오류확률에 중대한영향을 미쳤으나 20dB 이상에서는 무시할 수 있었다.

• 융합신호처리학회논문지
• /
• 제10권2호
• /
• pp.136-140
• /
• 2009

The performances of M-ary signals using L-branch maximum ratio combining (MRC) diversity reception in correlated Nakagami fading channels are derived theoretically. The coherent reception of M-ary differential phase shift keying (MDPSK), phase shift keying (MPSK), and quadrature amplitude modulation (MQAM) is considered. It is assumed that the fading parameters in each diversity branch are identical. The general formula for evaluating symbol error rate (SER) of M-ary signals in the independent branch diversity system is presented using the integral-form expressions. Until now, results did not extend to the various M-ary case for a coherent reception. The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.

• 한국통신학회논문지
• /
• 제25권8B호
• /
• pp.1436-1444
• /
• 2000

본 논문에서는 버스트 모뎀에서 반복적인 프리엠블(preamble)과 차등 검출 방식을 이용하여 반송파와 타이밍을 동시에 복원하는 동기 검출 알고리즘을 제안한다 제안된 방식은 짧은 길이의 프리엠블과 낮은 SNR(signal-to-noise ratio)에서도 주파수 편차의 정도에 관계없이 주파수 편차와 심볼 타이밍 오차를 높은 정확도로 추정할 수 있으며 CPFSK(continuous phase frequency shift keying) 방식 및 PSK(phase shift keying) 유형의 방식에 적용이 된다 모의 실험을 통하여 제안된 동기 방식과 기존의 동기 방식들과의 방식들의 프리엠블의 길이에 따른 동기 검출 성능을 비교하고 비트 오류율에 미치는 영향을 분석한다.