• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.381-387
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• 2013

Nitrogen and phosphorus removal was investigated in an UASB-ABF (Up-flow anaerobic sludge blanket - aerated bio-filter) anaerobic sewage treatment system. Successful removal of nitrogen and phosphorus with organic matters was possible in the UASB-ABF system from the results of 160 days operation with the influent raw domestic sewage. Removal efficiencies of organic matter (as TCOD) showed 64% in UASB without recycle of the ABF effluent, however, they increased to 92%, 95%, 96% with 120%, 180% and 240% recycle of the ABF effluent, respectively. Increasement of the organic matter removal was not prominent at recycle ratio above 180%. Apparent increase in TN removal occurred with recycle of the ABF effluent. TN removal efficiency was 18% without recycle, but it increased to 82% with 240% recycle of the ABF effluent. And stable nitrification above 95% was possible as a result of efficient removal of organic matter in the UASB with and without recycle of the effluent. Removal of both TP and $PO{_4}^{3-}$-P also increased remarkably with recycle of the effluent. Without recycle of the effluent, that is at strict anaerobic condition in UASB, TP was not removed, however, its removal efficiency increased to 51%, 63%, 71% at recycle ratios of 120%, 180%, 240%, respectively mainly at UASB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1281-1286
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• 2008

The PSK carrier signal recovery circuit using a six-port phase correlator was analyzed and the circuit structure is proposed in this paper. The proposed carrier signal recovery circuit that is made of reflection element and six-port phase correlator, which is comprised of a power divider and three hybrid branch line couplers, give a simple structure and can be fabricated without no difficulty. The circuit recovers the carrier signal of BPSK and QPSK modulation signal. The proposed scheme can be utilized as a basis structure for high-mode PSK carrier signal recovery. By simulation results, the recovered signal by the proposed circuit shows a good carrier signal characteristic with CW signal of a constant phase($23.4^{\circ}$) and ${\pm}0.8^{\circ}$ phase error due to glitch conditions.

• 전기산업
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• v.7 no.3
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• pp.41-51
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• 1996

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.96-107
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• 2011

Recently, studies of 3D HDTV broadcasting technology have been processed actively. Korea is making efforts to modify Advanced Television Systems Committee (ATSC) 8-Vestigial Side Band (8-VSB) systems for terrestrial 3D HDTV broadcasting services. We intend to adopt a new frame structure to use PN (Pseudo-Noise) sequence as frame header, and VSB modulation. PN sequence is used to recover carrier freqeuncy offset, carrier phase error. In this paper, we will describe this system as the modified ATSC systems. The receiver of the modified ATSC system should be able to estimate and recover carrier frequency offset exactly. A existing ATSC systems inserts pilot to recover carrier frequency offset, on the other hand the modified ATSC systems use PN sequence to recovery carrier frequency offset without the use of pilot. In this paper, we introduce carrier frequency recovery (CFR) scheme for the modified ATSC systems. The proposed CFR scheme is composed of coarse CFR scheme using Fitz algorithm and fine CFR scheme using a simple PN sequence correlation algorithm. And, the symbol information of QAM modulated signal is contained in both In-phase (I)channel and Quadrature-phase (Q)channel. However the symbol information of VSB modulated signal is contained in I channel, and Q channel is just Hilbert transform of I channel. For the reason, VSB modulated symbols can not have fixed phase like QAM modulated symbols, and VSB modulated symbols is more sensitive to carrier frequency offset. Therefore we perform phase correction of received PN sequence to improve performance.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.593-599
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• 2013

In this paper, the GPS cycle-slip detection for carrier-phase based positioning of land vehicle is presented. For the carrier phase based positioning, cycle-slip detection is necessary to get the reliability of positioning result. There exists many cycle-slip detection algorithms, but we detect the cycle-slip by using the monitoring value which is defined as residual between the carrier phase measurement and estimated value from low-cost inertial sensor. To achieve goal of paper, low-cost cycle-slip detection system, permissible specification region of inertial sensor is derived. By using the result of permissible region, appropriate inertial sensor of cycle-slip detection can be decided, proper cost and proper specification. To verify the result of this paper, we conduct the rate table test. As a result, required cycle-slip detection performance is satisfied conservatively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.755-761
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• 2007

In this paper the uplink single carrier scheme is proposed for wireless Internet application and its performance is evaluated in terms of PAPR (peak to average power ratio) and ABR (achievable bit rate) compared with the uplink OFDM scheme. There exist constraints regarding the signal amplification because the non-linear amplifier should be exploited instead of the linear amplifier due to its high cost of linear amplifier and power inefficiency at the WiBro terminal. Therefore characteristics in the uplink scheme design are discussed in order to maximize ABR and relieve the requirements for the amplifier specifications.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.47-50
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• 2010

최근 3D HDTV (3-Dimensional High Definition Television)에 대한 연구가 활발히 진행되고 있다. 국내에서도 3D HDTV 방송 서비스를 위하여 기존의 ATSC (Advanced Television Systems Committee) 8-VSB (8-Vestigial Side Band) 시스템을 수정하려는 연구가 진행되고 있다. 그 중에서도 프레임 생성 과정에서 프레임 헤드 부분에 PN (Pseudo-Noise)심볼을 사용하는 새로운 시스템의 개념을 제안하고, 이 시스템을 수정된 ATSC 시스템이라 부를 것이다. 수정된 ATSC 시스템은 기존 ATSC 8-VSB 시스템에서 사용되던 VSB 변조방식을 사용한다. 본 논문에서는 수정된 ATSC 시스템에 적용 가능한 반송파 주파수 복구 방식을 제안한다. 제안된 반송파 주파수 복구 방식은 Fitz 알고리즘을 사용하는 거친 주파수 복구부와 간단한 PN심볼 상관 알고리즘을 사용하는 미세 주파수 복구부로 구성된다. 그리고 진폭만을 변조하여 사용하는 VSB 변조 방식의 경우 심볼 정보가 동위상 채널에만 존재하고, 직교위상 채널은 단순히 동위상 채널의 힐버트 변환된 값에 지나지 않는다. 그러므로 VSB 변조된 심볼은 QAM 변조된 심볼 처럼 일정한 배열을 가지지 않고, 반송파 주파수 옵셋에 더욱 민감하게 된다. 이를 극복하기 위하여 수신된 PN심볼에 대한 위상 보정 과정을 수행하고, 이 과정은 수정된 ATSC 시스템의 반송파 주파수 복구 시 성능을 향상 시킨다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.383-388
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• 1998

본 논문에서는 LMDS(Local Multipoint Distributed Services) 시스템의 역방향 채널에서 TDMA(Time Division Multiple Access) 방식으로 ATM(Asynchronous Transfer Mode) 셀을 효율적으로 전송하기 위해 전치부호를 줄일 수 있는 블록복조 알고리즘을 적용한 $\pi$/4 QPSK 변복조 방식 시스템을 제안하고, 블록복조의 동기성능을 향상시키기 위해 새로운 반송파 동기회로를 설계하였다. 제안한 블록동기복조 알고리즘을 적용한 $\pi$/4 QPSK 변복조 방식 시스템은 LMDS 환경에서 ATM 셀 단위의 버스트 데이터로 반송파 위상동기, 심벌 타이밍 동기, 슬롯 타이밍 동기 둥을 수행할 때 전치부호를 아주 적게 사용하므로 효율적인 프레임 전송을 얻어질 수 있도록 하고 있다. 제안한 방식의 성능평가를 위한 모의실험은 LMDS 채널환경과 프레임 구조의 버스트 모드 전송환경에서 심벌 타이밍 동기, 주파수 오프셋, 반송파 위상동기, 페이딩 채널에 따라 수행하였다. 본 논문에서 제안한 블록동기복조 알고리즘을 적용한 $\pi$/40 QPSK 변복조 방식 시스템을 모의수행을 통하여 분석한 결과, 페이딩 환경에서 심벌 타이밍 동기, 주파수 오프셋, 반송파 위상동기할 때 전치부호를 아주 적게까지 줄이더라도 좋은 성능을 발휘함을 확인할 수 있었다.

• Journal of Broadcast Engineering
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• v.21 no.4
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• pp.552-561
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• 2016

In OFDM system, frequency-domain sub-carriers of a symbol generally consist of data sub-carriers and scattered pilot sub-carriers and in the receiver, channel is estimated through time-axis interpolating pilot sub-carriers of several OFDM symbols. However, time-axis interpolation fails to keep track of rapid channel variation caused by fast moving receiver. Although symbol by symbol channel estimation without time-axis interpolation enables fast estimation, the performance is severely degraded for a long delay spread channel in a single frequency networks (SFNs) because of insufficient pilot sub-carriers. In this paper, a channel estimation scheme for OFDM receiver in a fast mobile SFN channel is proposed. The proposed scheme is applied to DVB-T receiver to improve the Doppler mobile performance in SFN channel.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.85-95
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• 2011

In this paper, we propose an alternative carrier phase independent timing recovery method for VSB receivers. The Gardner algorithm may not estimate a timing offset in VSB systems when the residual carrier phase offset is contained in the signal. We use the conjugate multiplication of received signals for cancelling out the carrier phase offset. Then Gardner algorithm is employed for extracting the spectral line. The proposed method generates a consistent timing error even in the presence of the carrier phase offset.