• 전기학회논문지
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• 제59권4호
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• pp.831-840
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• 2010

In this paper, we propose a hearing impairment simulator considering reduced frequency selectivity and asymmetrical auditory filter of the hearing impaired, and we verified the reduced frequency selectivity and asymmetrical auditory filter affected in speech perception through experiments. The reduced frequency selectivity has made embodied by spectral smearing using LPC(linear prediction coding). The shapes of auditory filter are asymmetrical different with each center frequency. Hearing impaired person which has hearing loss was differently changed with that of normal hearing people and it has different value for speech of quality through auditory filter. The experiments confirmed subjective test and objective test. The subjective experiments are composed of 4 kinds of tests: pure tone test, SRT(speech reception threshold) test, and WRS(word recognition score) test without spectral smearing, and WRS test with spectral smearing. The experiment of the hearing impairment simulator was performed from 9 subjects who have normal ears. The amount of spectral smearing was controlled by LPC order. The asymmetrical auditory filter of proposed hearing impairment simulator was simulated and then some tests to estimate the filter's performance objectively were performed. The objective experiment as simulated auditory filter's performance evaluation method used PESQ(perceptual evaluation of speech quality) and LLR(log likelihood ratio) for speech through auditory filter. The processed speech was evaluated objective speech quality and distortion using PESQ and LLR value. When hearing loss processed, PESQ and LLR value have big difference according to asymmetrical auditory filter in hearing impairment simulator.

• Journal of electromagnetic engineering and science
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• 제7권4호
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• pp.190-194
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• 2007

In this paper, a cross-coupled microstrip combline bandpass filter using stepped-impedance resonators(SIRs) is proposed. In order to improve the selectivity as well as the insertion loss, the SIR configuration is used. The cross coupling is also introduced to enhance the selectivity. The improvement of the insertion loss is demonstrated not only by deriving the quality factor of the SIR but through the measured performances. Both the proposed and the conventional combline bandpass filter with 5 % of fractional bandwidth at 2 GHz were fabricated and tested. Compared to the conventional combline bandpass filter, the proposed one exhibits the improved selectivity as well as the lower insertion loss characteristics.

• Journal of electromagnetic engineering and science
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• 제8권4호
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• pp.144-147
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• 2008

This paper proposes a tunable combline bandpass filter with high selectivity, constant bandwidth, and good stopband performances. A filter with these characteristics is obtained by applying cross-coupling to the conventional combline bandpass filter using stepped-impedance resonators(SIRs). For high selectivity and constant bandwidth, cross-coupling is utilized and the SIR configuration is used for enhanced stopband performances. The proposed combline tunable bandpass filter with 5% of fractional bandwidth at 1.6 GHz was fabricated and tested. The measured results showed 11.6% tunability with constant bandwidth, high selectivity and enhanced stopband characteristics.

• 전기학회논문지
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• 제60권6호
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• pp.1196-1203
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• 2011

The reduced frequency selectivity is a typical phenomenon of sensorineural hearing loss. In this paper, we compared two modeling methods for reduced frequency selectivity of hearing impaired people. The two models of reduced frequency selectivity were made using LPC(linear prediction coding) algorithm and bandwidth control algorithm based on ERB(equivalent rectangular bandwidth) of auditory filter, respectively. To compare the effectiveness of two models, we compared the result of PESQ (perceptual evaluation of speech quality) and LLR(log likelihood ratio) using 36 Korean words of two syllables. To verify the effect on noise condition, we mixed white and babble noise with 0dB and -3dB SNR to speech words. As the result, it is confirmed that the PESQ score of bandwidth control algorithm is higher than the score of LPC algorithm, on the other hands, and the LLR score of LPC algorithm is lower than the score of bandwidth control algorithm. It means that both non-linearity and widen auditory filter characteristics caused by reduced frequency selectivity could be more reflected in bandwidth control algorithm than in LPC algorithm.

• 센서학회지
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• 제30권6호
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• pp.446-450
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• 2021

Non-dispersive infrared (NDIR) gas sensors typically use an optical filter that transmits a discriminating 4.26 ㎛ wavelength band to measure carbon dioxide (CO2), as CO2 absorbs 4.26 ㎛ infrared. The filter performance depends on the transmittance and full width at half maximum (FWHM). This paper presents the fabrication, sensitivity, and selectivity characteristics of a distributed Bragg reflector (DBR)-based Fabry-Perot filter with a simple structure for CO2 detection. Each Ge and SiO2 films were prepared using the RF magnetron sputtering technique. The transmittance characteristics were measured using Fourier-transform infrared spectroscopy (FT-IR). The fabricated filter had a peak transmittance of 59.1% at 4.26 ㎛ and a FWHM of 158 nm. In addition, sensitivity and selectivity experiments were conducted by mounting the sapphire substrate and the fabricated filter on an NDIR CO2 sensor measurement system. When measuring the sensitivity, the concentration of CO2 was observed in the range of 0-10000 ppm, and the selectivity was measured for environmental gases of 1000 ppm. The fabricated filter showed lower sensitivity to CO2 but showed higher selectivity with other gases.

• Journal of Power Electronics
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• 제13권5호
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• pp.861-876
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• 2013

Instead of extracting every selected harmonic component, the current reference of selective active power filter (APF) can be also obtained by filtering out the fundamental component from distorted load current for computation efficiency. This type of mixed current reference contains kinds of harmonic components and easily involves noises. In this condition, selective harmonic compensation must be realized by the current controller. With regard that selectivity is the most significant feature of controller, this paper presents specific comparison analysis between two types of resonant controllers: proportional-resonant (PR) controller and vector-resonant (VR) controller. The comparison analysis covers the relations, performances, and stability of both controllers. Analysis results conclude that the poorer selectivity of the PR controller could be relatively improved, but limitations from system stability make the improvement hardly realized. By contrast, the VR controller exhibits excellent selectivity and is more suitable for selective APF with mixed current reference. Experimental results from laboratory prototype validate the reasonability of analysis. And the features of each resonant controller are concluded.

• 한국통신학회논문지
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• 제23권4호
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• pp.1051-1058
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• 1998

광굴절결정에서 두 기록빔의 입사각에 따른 파장선택성을 이용해 원하는 통과대역과 중심파장을 갖는 대역통과필터로의 응용을 제안하였다. 2광파결합을 통해 Fe가 0.02Wt.% 도핑된 $LiNbO_3$ 결정의 회절특성을 실험함으로써, 가장 우수한 회절효율을 갖는 조건을 도출하고, 이러한 조건에서 원하는 대역 및 파장을 선택해 낼 수 있는 대역통과필터를 전광학적으로 구현하였다. 또한, 기록빔의 입사각을 변화시킴으로써, 임의의 원하는 필터 특성을 얻을 수 있음을 실험적으로 증명하였다.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3425-3430
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• 2013

최근 이동통신 시장의 급속한 증가에 따라 단말기 설계는 다표준 방식으로 발전하고 있다. 본 논문에서는 다표준 이동통신 시스템에 적용할 수 있는 주파수 가변형 능동 RC 대역통과 필터를 능동 인덕터를 사용하여 설계하였다. 기존의 대역통과 필터 설계법에서는 저지대역의 감쇠 특성과 통과대역의 주파수 선택도를 향상시키기 위하여 필터의 차수를 높게 하거나 극점 Q를 증가시키는 설계법을 사용한다. 본 논문에서는 극점 Q가 높은 능동 인덕터로 대역통과 필터를 설계하여 주파수 특성이 향상되었다. 또한 설계된 대역통과 필터는 튜닝 회로를 이용하여 필터의 중심주파수와 이득을 간단히 조절할 수 있도록 제안하였다. 설계된 능동 RC 대역통과 필터 특성은 TSMC $0.18{\mu}m$ 공정 파라미터를 이용하여 해석하였다. 시뮬레이션 결과, Q=20.5를 갖는 능동 인덕터를 이용한 필터는 1.86GHz 중심주파수에서 90MHz의 대역폭을 갖고, 튜닝 회로의 커패시터 값으로 중심주파수를 1.86~2.38GHz 범위까지 튜닝이 가능하여 다표준 무선통신 시스템에 적용할 수 있다.

• 전자공학회논문지D
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• 제36D권6호
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• pp.79-86
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• 1999

Fe가 0.015wt.% 도핑된 $LinbO_3$ 결정에서 형성된 홀로그래픽 부피격자 필터의 각 선택성 및 역다중화 특성을 이용하여 WDM 통신 시스템에 적용하기 위한 새로운 광굴절 역다중화기를 제안하였다. 결정에 입사되는 두 기록빔의 교차각, 판독빔의 입사각 및 기록빔의 크기에 따른 광굴절 필터의 파장 선택 특성을 해석하고 실험하였으며, 동일한 회절효율을 갖는 다중-노출 필터 기록을 위한 다중화 기법을 적용하여 DMUX 소자로 활용하기 위한 예비 실험 결과를 제시했다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.567-570
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• 1988

This paper describes the design of FIR filtering DSP-chip that can be operated without programming. The proposed DSP-chip has not only the improvement of execution time but also selectivity of filter length from N=1 to N=128. Hilbert Transformer can be designed from this chip. FIR filter system is composed of Data memory/Control Unit, external memory and multiplier-accumulator. Data memory/Control Unit is laid out in this paper.