• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.437-442
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• 2000

An alternative inverse feedback structure for adaptive active control of periodic noise is introduced for systems with nonminimum phase cancellation path. To obtain the inverse model of the nonminimum phase cancellation path, the cancellation path model can be factorized into a minimum phase term and a maximum phase term. The maximum phase term containing unstable zeros makes the inverse model unstable. To avoid the instability, we alter the inverse model of the maximum phase system into an anti-causal FIR one. An LMS predictor estimates the future samples of the noise, which are necessary for causality of both anti-causal FIR approximation for the stable inverse of the maximum phase system and time-delay existing in the cancellation path. The proposed method has a faster convergence behavior and a better transient response than the conventional FX-LMS algorithms with the same internal model control structure since a filtered reference signal is not required. We compare the proposed methods with the conventional methods through simulation studies.

• 제어로봇시스템학회논문지
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• 제7권11호
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• pp.891-895
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• 2001

An alternative inverse feedback structure for adaptive active control of periodic noise is introduced for systems with nonminimum phase cancellation path. To obtain the inverse model of the nonminimum phase cancellation path, the cancellation path model can be factorized into a minimum phase term and a maximum phase term. The maximum phase term containing unstable zeros makes the inverse model unstable. To avoid the instability, we alter the inverse model of the maximum phase system into an anti-causal FIR one. An LMS predictor estimates the future samples of the noise, which are necessary for causality of both anti-causal FIR approximation for the stable inverse of the maximum phase system and time-delay existing in the cancellation path. The proposed method has a faster convergence behavior and a better transient response than the conventional filtered-x LMS algorithms with the same internal model control structure since a filtered reference signal is not required. We compare the proposed methods with the conventional methods through simulation studies.

• 소음진동
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• 제6권6호
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• pp.851-856
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• 1996

The active noise cancellation system showing the effective convergence and stability has been studied by simplifying the controller structures using the weighting factors of control error path to the multi-channel filtered-x LMS algorithm which needs a lot of calculations and the performance has been verified experimentally. Besides, to implement the system performance in a vehicle cabin, experimental work for selecting the suitable numbers and positions of the microphones and speakers was accomplished. Effectively combining a TMS 320C 31 main processor conducting real number calculations and having various functions with other components, the purpose-built system board for active noise cancellation has been designed and with this board, car active noise cancellation system showing maximum stable 10dB noise reduction has been obtained at the car idling conditions above 3000rpm range.

• Transactions on Control, Automation and Systems Engineering
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• 제1권1호
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• pp.69-74
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• 1999

Adaptive algorithms based on gradient adaptation have been extensively investigated and successfully joined with active noise/vibration control applications. The Filtered-X LMS algorithm became one of the basic feedforward algorithms in such applications, but is not fully understood yet. Effects of cancellation path model on the Filtered-X LMS algorithm have investigated and some useful properties related to stability were discovered. Most of the results stated that the error in the cancellation path model is undesirable to the Filtered X LMS. However, we started convergence analysis of Filtered-X LMS based on the assumption that erroneous model does not always degrade its performance. In this paper, we present a way of optimizing the cancellation path modern in order to enhance the convergence speed by introducing intentional phase error. Carefully designed intentional phase error enhances the convergence speed of the Filtered X LMS algorithm for pure tone noise suppression application without any performance loss at steady state.

• 한국통신학회논문지
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• 제25권5A호
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• pp.602-610
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• 2000

본 논문에서 무선 ATM LAN 환경에서 기지국 기반 기법의 루프 제거 및 경로 최적화 알고리즘을 제안한다. 제안하는 경로 최적화 알고리즘은 다각 루프 제거법과 삼각 루프 제거법의 두 단계로 이루어져 있다. 단말기의 이동각을 고려한 순서쌍의 기념을 도입하여 핸드오버하는 단말기의 위치를 표현하고, 계산된 순서쌍을 이용하여 경로 최적화를 수행한다. 우리는 핸드오버 지연 시간, 통신 단절 시간, 버퍼 요구량, 그리고 총시그널링 교환 시간 등을 이용하여 제안하는 기법과 앵커 재라우팅 기법을 비교하였다. 이러한 비교 평가를 통하여 제안하는 기법이 경로 확장 기법의 장점인 빠른 핸드오버를 보장하면서 경로 상에서 발생하는 루프의 제거와 경로의 최적화를 효과적으로 수행할 수 있음을 보였다.

• 한국소음진동공학회논문집
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• 제13권7호
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• pp.499-507
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• 2003

This paper presents a method for active noise control (ANC) in a duct by using a ring-tyPe smart foam. The ring-type smart foam consists of an elastic porous material of lining shape and a PVDF film embedded In the material. The PVDF element acts as a secondary sound source to reduce the noise. Active noise control using a ring-type smart foam is only effective locally because of the way to excite radially. To enlarge the quiet zone, the duct Is lined with additional acoustic foam between the smart foam and the error microphone. When cancellation path ks optimized by the LMS/RLS algorithm, the computation power is reduced while control performance Is maintained. The filtered-x LMS algorithm is used to minimize the error signal.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.525-529
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• 2002

ANC technic can overcome the limited performance of passive noise control at the low frequency range. But it has the local quiet control region in general. In this paper, it is discussed that the global noise control in a circular duct using a ring type smart foam and a porous material. LMS algorithm and RLS algorithm are used to find optimal orders of cancellation path. Experiments are performed to compare the efficiency of RLS algorithm with that of LMS algorithm.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권10호
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• pp.639-642
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• 2005

In this paper, a robust nonlinear echo cancellation is proposed, where a third-order adaptive Volterra filtering is employed along with an expanded correlation LMS (ECLMS) algorithm to compensate for nonlinear distortion in the echo path. (e.g., DAC of the hybrid network). Finally, the robustness in the echo cancellation of the proposed approach is demonstrated using computer simulations, where high attenuation of echo signals is achieved even in the double-talk situation (e.n., BdB improvement in ERLE).

• 한국통신학회논문지
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• 제21권4호
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• pp.1027-1037
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• 1996

This paper presents an impulse response of the multi-path channel using KS-GCR(Korean Standard Ghost Cancel Reference) signal. Using the property of the KS-GCRsignal, we can get the impulse response of the multi-path channel from circular cross correlation of the received DS-GCR signal and the orginal KS-GCR ternary sequence. Therefore impulse response of the multi-path channel can be used to design the the ghost cancellation filter if it is designed to have inverse characteristics of multi-path channel. This paper shows that the ghost occurred from the multi-path channel can be cancelled by using the impulse response and preceding ghost cancellation algorithm.

• 전기전자학회논문지
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• 제24권2호
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• pp.550-558
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• 2020

Polar code의 복호 기법 중에 하나인 연속 제거 (successive cancellation; SC) 복호는 순차적으로 복호를 수행해야하는 특성으로 인해 지연시간이 길고, 복호를 위해 필요한 하드웨어 면적이 크다. 이를 극복하기 위하여 다수의 연구들이 진행되었으며, 본 논문에서는 연속 제거 복호를 기반으로 한 복호 기법을 가지치기 (pruning) 복호 기법들과 다중-경로 (multi-path) 복호기법들로 나누어 정리하였다. 가지치기 복호기법에는 SSC (simplified SC), fast-SSC, 신드롬 판단 기반 복호 등이 있으며, 다중-경로 복호 기법에는 2-비트 연속 제거 복호와 redundant-LLR 표현 기반의 복호가 있다. 본 논문에서는 SSC, fast-SSC, 신드롬 판단, 2-비트 연속 제거, 그리고 redundant-LLR 표현 기반의 복호 기법들을 지연시간과 하드웨어 면적 측면에서 비교했으며, 비교 결과 신드롬 판단 기반 복호기법이 지연시간이 가장 짧고, redundant-LLR 표현 기반의 복호가 하드웨어 면적이 가장 작은 복호 기법이다.