• Current Optics and Photonics
• /
• 제7권5호
• /
• pp.557-561
• /
• 2023

Ultralow-noise soliton pulse generation over a wider Fourier frequency range is highly desirable for many high-precision applications. Here, we realize a low-phase-noise soliton pulse generation by transferring the low phase noise of a mode-locked laser to a silica microcomb. A 21.956-GHz and a 9.9167-GHz Kerr soliton combs are synchronized to a 2-GHz and a 2.5-GHz mode-locked laser through a fractional optoelectronic phase-locked loop, respectively. The phase noise of the microcomb was suppressed by up to ~40 dB at 1-Hz Fourier frequency. This result provides a simple method for low-phase-noise soliton pulse generation, thereby facilitating extensive applications.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.393-396
• /
• 2003

Conventional method for designing and installing anechoic chambers is to utilize porous wedges for the sound absorbers. As cutoff frequency lowers down such as 63Hz or 50Hz, the corresponding long wedges diminish the free field area of the chamber. In this study, a new broadband compact absorber(BCA) is introduced which absorbs acoustic energy down to 50Hz. Most prominent is that it measures only 250mm thick. A freely vibrating panel between the non-fibrous absorbers allows tuned absorption at the low frequency region in addition to the high frequency absorption resulted from the conventional absorber installed at the front. Standing waves at low frequency range are suppressed as the BCA modules which are tuned to the corresponding modes absorb sound energy effectively, resulting in anechoic condition. Not only the low frequency performances, but the high frequency absorption is measured to meet adequate conditions for the anechoic chamber. Realized BCA chambers are presented.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.919-922
• /
• 2003

The correlation between noise and vibration by a heavy-weight floor impact was studied. The triggering technique was used for increasing the reliability and stability to measure the level of sound pressure, sound intensity and vibration acceleration. The simple finite element and rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The result show that the isolation material adapted to reduce the light-weight floor impact noise, causing the natural frequency lower, make resonance with dominant driving frequency, and increase the noise level very sharply. Therefore the noise level Peak in the region of low frequency, below 63Hz, would be related with the natural frequencies of the floor system.

• 한국정보전자통신기술학회논문지
• /
• 제10권1호
• /
• pp.57-65
• /
• 2017

본 논문은 헤드폰/이어폰에 최적화된 저전력 피드백 능동 소음 제어 필터 설계 방법을 제안하였다. 제약 최적화를 이용하여 높은 샘플링 주파수 환경에서 합리적인 소음 저감 성능을 확보하기 위한 높은 차수의 유한 임펄스 응답소음 제어 필터를 얻은 후 무한 임펄스 응답 근사 기법인 Balanced Model Truncation (BMT)를 이용하여 얻어낸 필터를 헤드폰/이어폰과 같은 저전력 디지털 신호처리 시스템에 적합하도록 낮은 차수의 무한 임펄스 응답 소음 제어 필터로 변환하였다. 성능 확보를 위해 주파수 워핑 기법을 이용하여 기존의 높은 차수의 유한 임펄스 응답 소음 제어 필터와 더욱 유사한 주파수 응답을 가지는 무한 임펄스 응답 필터를 얻었으며, 이를 2차 무한 임펄스 응답 필터들의 종속연결 구조로 재구성하여 시스템 전체의 안정성을 높였다. 백색 잡음을 통한 능동 소음 제어 시뮬레이션과 결과 및 안정성 실험 등을 통해 제안하는 기법이 기존의 기법보다 우수한 소음 저감 성능과 안정성을 가짐을 검증하였다.

• 소음진동
• /
• 제7권4호
• /
• pp.579-588
• /
• 1997

When a membrane couples with compressive fluid, waves on the membrane follow a typical dispersion relations. One of characteristics of this relations is that evanscent waves occur below cutoff frequency. We have attempt to use this spatially decaying characteristics as a low frequency sound absorber. Theoretical development has required to solve membrane-fluid coupled linear differential. The solution has been successfully obtained by using eigenfunctions. To assure the obtained solution, experiment was also performed. The comparison was quite satisfactory. We conclude, based on these theoretical as well as experimental evidences, that it is very likely possible to use a membrane as a low frquency sound control element.

• 한국전자통신학회논문지
• /
• 제11권1호
• /
• pp.23-28
• /
• 2016

본 논문에서는 범 세계적으로 이용가능한 다중대역 디지털 위성방송용 Ku-대역 하향변환기를 설계하였다. 설계된 다중대역 하향변환기는 광대역 잡음 정합에 의한 3단 저 잡음 증폭회로와 10.7~12.75GHz의 입력신호를 VCO-PLL에 의한 저 위상잡음을 나타내는 4개의 국부발진주파수(9.75, 10, 10.75 및 11.3GHz)를 형성하고 디지털 제어에 의하여 4개대역 중 하나의 IF 주파수 채널을 선택할 수 있도록 설계하였다. 개발한 저 잡음 하향 변환기의 전체 변환이득 64dB, 저 잡음 증폭기의 잡음지수는 0.7dB, 출력신호의 P1dB는 15dBm, band 1반송주파수 9.75GHz에서 위상잡음은 -73dBc@100Hz를 나타내었다. 설계한 다중대역 디지털 위성방송용 하향변환기(LNB)는 국제적으로 이동하는 선박 등의 위성방송용으로 사용가능하다.

• 한국전자파학회논문지
• /
• 제27권2호
• /
• pp.115-122
• /
• 2016

본 논문에서는 디지털 위성방송을 수신하기 위하여 Ku-대역 광대역 하향변환기를 설계하였다. 설계된 저 잡음 하향변환기는 잡음 정합에 의한 3단 저 잡음 증폭회로와 10.7~12.75 GHz의 입력신호를 VCO-PLL에 의한 저 위상잡음을 나타내는 4개의 국부발진주파수(9.75, 10, 10.75 및 11.3 GHz)를 형성하고, 디지털 제어에 의하여 4-대역의 IF 주파수 채널을 선택할 수 있도록 설계하였다. 개발한 저 잡음 하향 변환기의 전체 변환이득 64 dB, 저 잡음 증폭기의 잡음지수는 0.7 dB, 출력신호의 P1dB는 15 dBm, band 1 반송주파수 9.75 GHz에서 위상잡음은 -85 dBc@10 kHz를 나타내었다. 설계한 광대역 디지털 위성방송용 하향변환기(LNB)는 국제적으로 이동하는 선박 등의 위성방송용으로 사용가능하다.

• International journal of advanced smart convergence
• /
• 제10권1호
• /
• pp.12-23
• /
• 2021

This paper proposes a low power radio frequency receiver front-end where, in a single stage, single-balanced mixer and voltage-controlled oscillator are stacked on top of low noise amplifier and re-use the dc current to reduce the power consumption. In the proposed topology, the voltage-controlled oscillator itself plays the dual role of oscillator and mixer by exploiting a series inductor-capacitor network. Using a 65 nm complementary metal oxide semiconductor technology, the proposed radio frequency front-end is designed and simulated. Oscillating at around 2.4 GHz frequency band, the voltage-controlled oscillator of the proposed radio frequency front-end achieves the phase noise of -72 dBc/Hz, -93 dBc/Hz, and -113 dBc/Hz at 10KHz, 100KHz, and 1 MHz offset frequency, respectively. The simulated voltage conversion gain is about 25 dB. The double-side band noise figure is -14.2 dB, -8.8 dB, and -7.3 dB at 100 KHz, 1 MHz and 10 MHz offset. The radio frequency front-end consumes only 96 ㎼ dc power from a 1-V supply.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.862-867
• /
• 2000

The auxiliary engine exhaust noise in ships are directly transmitted to bridge wing with the only distance attenuation. It is not so practical that no special treatment can be applied between exhaust pipe and bridge wing in order to reduce the transmission of the exhaust noise. In general, a silencer is fitted to reduce the exhaust noise and also noise of bridge wing. The silencer should be properly designed under the consideration of the frequency component of the exhaust noise and the required insertion loss. In this paper, the frequency component of exhaust noise of various engines are compared and a design and a design and installation of silencer to reduce low frequency is introduced.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2009년도 춘계학술대회
• /
• pp.156-159
• /
• 2009

Speckle noise reduction for 3D power doppler ventricle coherent image for restoration and enhancement using wavelet packet transform with separated thresholding is presented. Wavelet Packet Transform divide into low frequency component image to high frequency component image to be multi-resolved. speckle noise is located on high frequency component in multiresolution image mainly. A ventricle image is transformed and inversed with separated threshold function from low to high resolved images for restoration to be utilize visualization for ventricle diagnosis. The experimental result shows that the proposed method has better performance in comparison with the conventional method.