• 대한음성학회지:말소리
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• 제60호
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• pp.181-190
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• 2006

This paper describes a speech enhancement scheme that leads to significant improvements in recognition performance when used in the ASR front-end. The proposed approach is based on adaptive comb filtering and an MMSE-related parameter estimator. While adaptive comb filtering reduces noise components remarkably, it is rarely effective in reducing non-stationary noises. Furthermore, due to the uniformly distributed frequency response of the comb-filter, it can cause serious distortion to clean speech signals. This paper proposes an improved comb-filter that adjusts its spectral magnitude to the original speech, based on the speech absence probability and the gain modification function. In addition, we introduce the modified comb filtering-based speech enhancement scheme for ASR in mobile environments. Evaluation experiments carried out using the Aurora 2 database demonstrate that the proposed method outperforms conventional adaptive comb filtering techniques in both clean and noisy environments.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.139-142
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• 2001

In this paper, a new CIC filter structure for reduction of passband droop in CIC decimation filter is proposed. For improvement of passband characteristics, the 1st order Generalized Comb Filter(UF) is proposed in addition to the conventional CIC decimation filter. By using this filter, it is shown that passband droop is remarkably reduced and aliasing attenuation is slightly increased. We also propose how to find the optimum filter coefficient Furthermora, it is shown that choices for GCF are possible in terms of the number of Half-Band filter. Passband droops and aliasing attenuations of the proposed structure are compared with those of the CIC structures using conventional sharpening techniques.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.33-37
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• 2010

In this paper, we have demonstrated absolute wavelength tuning in an optical fiber comb filter based on a polarization-diversity loop configuration by controlling the current injected into enameled wires wound on polarization-maintaining fibers (PMF's), that is, adjusting Joule heat generated from enameled wires. The proposed fiber comb filter consists of a polarization beam splitter, a half-wave plate, a quarter-wave plate, and PMF's. And we observed wavelength change of spectral dips in transmission spectra of the fabricated filter by varying an input current applied to enameled wires. The absolute wavelength of the filter could be controlled in proportional to the square of the input current with good linearity, and the rate of the wavelength shift with respect to the input current was measured as 36.79[nm/$A^2$].

• 조명전기설비학회논문지
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• 제26권6호
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• pp.8-15
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• 2012

In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

• 전자공학회논문지
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• 제50권3호
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• pp.139-145
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• 2013

본 논문에서는 스테레오 패닝 시스템에 대해 기존의 진폭 패닝이 가지는 문제점을 분석하였다. 이러한 문제점이 피드포워드 빗형 필터 형태로 발생하는 것을 관찰하고 이를 해결하기 위하여 피드백 빗형 필터를 사용한 스테레오 진폭 패닝 시스템을 제안하였다. 방향 인지에 대해 중요한 단서인 양이간레벨차의 차이가 최소가 되도록 하여 빗형 필터를 설계하였으며 제안된 시스템이 방향 인지에 관련된 대역에 대해 선택적으로 동작하도록 주파수 대역을 설정하였다. 제안된 시스템의 성능을 주관적 음질 평가를 통하여 검증하였다.

• 조명전기설비학회논문지
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• 제29권12호
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• pp.1-7
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• 2015

In this paper, we propose a second-order fiber flexible comb filter based on a polarization-diversity loop(PDL). The proposed filter consists of a polarization beam splitter, four half-wave plates(HWPs), and three high birefringence fiber(HBF) segments. In the previous Solc-type second-order filter based on the PDL, HBF segments were fusion-spliced with a fixed angle offset between their principal axes with each other. But, the proposed filter implemented by inserting two HWPs between three HBF segments has a great flexibility in adjusting relative angular difference between the principal axes of two adjacent HBF segments. Owing to this flexibility, second-order transmission spectra, which had a channel spacing of ~0.8nm, could be interleaved by controlling the orientation angles of four HWPs. The output transmission spectra of the proposed filter were theoretically analyzed and experimentally verified.

• 문화기술의 융합
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• 제6권3호
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• pp.427-430
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• 2020

IoT 분야와 의료 측정기기 분야에서 여러 개의 아날로그 입력 신호를 동시에 디지털 신호로 변환하는 기술 요구가 늘어나고 있다. 기존 단일 또는 2개의 체널 방식을 이용하여 여러 개의 아날로그 신호를 처리하는 방식에서는 하드웨어 크기와 전력소모 면에서 응용 제한을 받게 된다. 본 논문에서는 여러 개의 아날로그 입력을 동시에 받아서, 각각에 대한 24비트 디지털 신호를 출력하는 다채널 24비트 ADC 용 콤필터 설계 및 구현을 기술하였다. 제안된 콤필터의 기능은 매트랩 시뮬레이션과 FPGA 테스트 보드로 검증하였다. SK 하이닉스 0,35㎛ CMOS 표준 공정을 이용하여 칩으로 제작하였다. 미분기/적분기 사용 또는 FIR 구조의 기존 방식과 성능, 칩 면적을 비교하였다. 제안된 콤필터는 6개 이상의 다채널 아날로그 입력, 저 전력 소모, 작은 하드웨어 크기를 요구하는 IoT 제품과 의료 측정기기 활용이 예상된다.

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
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• pp.298-299
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• 2004

We propose and theoretically analyze multi-functional integrated optical device based on figure-eight shaped birefringent Sagnac loops. Our analysis shows that the propose device exhibit many unique features which allows it to operate as a tunable high-Q comb filter with a good channel isolation, and the intensity transmission of the filter can be varied from zero to 100 percent.

• 조명전기설비학회논문지
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• 제29권12호
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• pp.83-87
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• 2015

This paper presents a simple notch filter, which is so suitable for three-phase unbalanced and distorted power line. In the d-q synchronous transformation, three-phase unbalanced and distorted voltages generate lots of ripple voltages on d-q axes. The ripples make disturbances on controllers such as PLL of phase tracking. Unbalanced state makes ripple of double the frequency of power line. Odd harmonics 5th and 7th on the line make even 4th and 6th ripples on d-q axes due to the rotating reference frame, respectively. Cascaded two comb filters, delay lines 1/4T and 1/8T, are adopted for the ripple rejection. The filter rejects harmonics 2nd, 4th, 6th, 10th and so on. They are very effective to remove the ripples of both unbalance and distortion. The filter, implemented by two FIFOs on an experimental system, is adopted on a PLL controller of power line phase tracking. Through the simulation and experimental results, performance of the proposed comb filter has been validated.

• ETRI Journal
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• 제33권2호
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• pp.169-175
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• 2011

This paper presents a double-sharpened decimation filter based on the application of a Kaiser and Hamming sharpening technique for multistandard wireless systems. The proposed double-sharpened decimation filter uses a pre-droop compensator which improves the passband response of a conventional cascaded integrator-comb filter so that it provides an efficient sharpening performance at half-speed with comparison to conventional sharpened filters. In this paper, the passband droop characteristics with compensation provides -1.6 dB for 1.25 MHz, -1.4 dB for 2.5 MHz, -1.3 dB for 5 MHz, and -1.0 dB for 10 MHz bandwidths, respectively. These results demonstrate that the proposed double-sharpened decimation filter is suitable for multistandard wireless applications.