• 한국정보통신학회논문지
• /
• 제6권2호
• /
• pp.151-158
• /
• 2002

본 논문에서는 저 위상잡음과 고안정 특성을 나타내는 디지털 MMDS용 위상고정 발진기를 설계하였으며 전압제어 발진기용 능동소자의 비선형 등가모델에 의하여 저 위상잡음 파라미터와 안정된 전압제어 발진기의 필요충분 조건을 분석하였다. 설계된 전압제어 발진기에 위상고정루프를 적용하여 위상고정 마이크로파 발진기를 구현하였으며 고안정 전압제어 발진기에 대하여 시뮬레이션한 결과 －90dBc/Hz @ 10KHz의 위상잡음을 보였으며 위상고정 마이크로파 발진기에 대한 실험 결과 －85dBc/Hz @ 10KHz의 위상잡음을 얻었다. 고안정도와 저 위상잡음특성을 나타내는 위상고정 마이크로파 발진기의 설계모델을 디지털 MMDS 단말기용 고안정 주파수 합성기로 응용할 수 있음을 보였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.388-395
• /
• 2000

Axial fans are widely used in heavy machines due to their ability to produce high flow rate for cooling of engines. At the same time, the noise generated by these fans causes one of the most serious problems. This work is concerned with the low noise technique of discrete frequency noise. The prediction model, which allowed the calculation of acoustic pressure at the blade passing frequency and it's harmonics, has been developed by Farrasat. This theory is founded upon the acoustic radiation of unsteady forces acting on blade. To calculate the unsteady resultant force over the fan blade. Time-Marching Free-Wake Method are used. The ideas of low noise technique are obtained from Blade-Momentum Methods. In this paper, the discussion is confined to the performance and discrete noise of axial fan in heavy equipments.

• Transactions on Electrical and Electronic Materials
• /
• 제7권1호
• /
• pp.42-50
• /
• 2006

Co-Fe-Al-O nano-granular thin films with high electrical resistivity, fabricated by radio frequency magnetron sputtering under an $Ar+O_2$ atmosphere, are found to show good soft magnetic properties in the GHz frequency range. The real part value of the relative permeability is 260 at low frequencies and this value is maintained up to the GHz frequency range. A non-integrated type noise filter on a coplanar waveguide transmission line is demonstrated by using the Co-Fe-Al-O nano-granular thin film with the dimensions of $4\;mm(l){\times}4\;mm(w){\times}0.1\;{\mu}m(t)$. The insertion loss is very low being less than 0.3 dB and this low value is maintained up to 2 GHz. At a ferromagnetic resonance frequency of 3.3 GHz, the degree of noise suppression is measured to be 3 dB. This level of noise attenuation is small for real applications, but there is much room for further improvement by increasing the magnetic volume and integrating the magnetic thin film into the CPW transmission line.

• 한국산업정보학회논문지
• /
• 제18권5호
• /
• pp.9-14
• /
• 2013

본 논문은 DLL 기술을 사용하여서 낮은 위상잡음을 갖는 주파수 체배기를 설계 하였다. VCDL은 공통모드 잡음을 줄이기 위해서 차동구조를 이용하여 설계 되었다. 이번 설계는 65nm, 1.2V TSMC CMOS 공정을 이용 하였고, 동작 주파수 범위는 10MHz에서 24MHz로 측정되었다. TCXO를 기준 주파수로 사용하여 위상잡음을 측정하였을 때 38.4MHz의 출력에서 1MHz offset 기준으로 -125dBc/Hz가 측정되었다. 총 면적은 $0.032mm^2$을 사용하였고, 출력 버퍼를 포함하여 총 1.8mA의 전류를 칩에서 소비하였다.

• Journal of Information Processing Systems
• /
• 제19권3호
• /
• pp.275-288
• /
• 2023

Many image edge details are easily lost in the image denoising process, and the smooth image regions are prone to produce jagged. In this paper, we propose a wavelet-based image global k- singular value decomposition variational method to remove image noise. A layer of wavelet decomposition is applied to the noisy image first. Then, the image global k-singular value decomposition (IGK-SVD) method is used to remove the random noise of low-frequency components. Furthermore, a constructed variational denoising method (VDM) removes the random noise in the high-frequency component. Finally, the denoised image is obtained by wavelet reconstruction. The experimental results show that the proposed method's peak signal-to-noise ratio (PSNR) value is higher than other methods, and its structural similarity (SSIM) value is closer to one, indicating that the proposed method can effectively suppress image noise while retaining more image edge details. The denoised image has better denoising effects.

• 대한전자공학회논문지TC
• /
• 제47권2호
• /
• pp.62-66
• /
• 2010

본 논문은 높은 Q 특성을 갖는 이중 H자 형태의 메타 전자파구조의 공진기를 적용한 발진기를 제안하였다. 제안된 발진기는 고성능의 주파수합성부에 적용하기 위한 것으로 저위상잡음 및 높은 출력 전력을 요구한다. 특히 이중 H자 형태의 메타 전자파구조(DHM)는 전기장의 커플링을 강하게 하여 발진 주파수에서 높은 Q 값을 갖도록 설계되었다. 이러한 특성을 통해 우수한 위상잡음 특성을 얻을 수 있다. 이중 H자 형태의 메타 전자파구조를 이용한 발진기는 레이더 시스템의 주파수 합성부에 적용하기 위한 X 대역 내 발진을 형성하였으며 출력 전력은 4.33 dBm, 위상잡음은 100 kHz 옵셋에서 -108 dBc를 얻을 수 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.84-85
• /
• 2008

In this paper, differential cross coupled LC VCOs with two noise frequency filtering techniques are proposed. Both VCOs are based on symmetric capacitor with asymmetric inductor tank structure. The VCO using low pass filtering technique shows low phase noise of -130.40 dBc/Hz at 1 MHz offset when the center frequency is 1.619 GHz. And the other VCO using band pass filtering technique shows -127.93 dBc/Hz at 1 MHz offset frequency when center frequency is 1.604 GHz. Two noise frequency filtering techniques are approached with different target.

• 한국전기전자재료학회논문지
• /
• 제20권1호
• /
• pp.1-7
• /
• 2007

In this paper, two kinds of initial oxidation methods i.e., SLTO(Slow Low Temperature Oxidation: $700^{\circ}C$) and RTO(Rapid Thermal Oxidation: $850^{\circ}C$) are applied prior to the plasma nitridation for ultra thin oxide of RPNO (Remote Plasma Nitrided Oxide). It is observed that SLTO has superior characteristics to RTO such as lower SS(Sub-threshold Slope) and improved Ion-Ioff characteristics. Low frequency noise characteristics of SLTO also showed better than RTO both in linear and saturation regime. It is shown that flicker noise is dominated by carrier number fluctuation in the channel region. Therefore, SLTO is promising for nano-scale CMOS technology with ultra thin gate oxide.

• 한국전자파학회논문지
• /
• 제12권3호
• /
• pp.462-469
• /
• 2001

본 논문에서는 저주파 잡음이 상향변환 이득 해석을 이용한 K 밴드 국부발진기를 설계 및 제작하였다. 상향 변환 이득을 해석하고, 그에 따른 위상잡음을 예측하기 위하여 Two Signal Method(TSM)을 확장하였다. 제시된 이론의 유용성을 검증하기 위해 저 상향변환 이득을 갖는 회로의 동작점을 선택하여 free-running 발진기를 설계하였다. 측정결과 발진주파수는 23.42 GHz였고, 위상잡음은 1MHz offset에서 -105.2 dBc/Hz로 우수한 특성을 보였다. 그리고 같은 회로를 부고조파로 주입시켜 부고조파 주입동기 발진기로 동작시켰으며, 이 경우에도 낮은 부고조파 입력 파워에서 이상적인 체배기의 위상잡음 특성을 보였다.

• 한국소음진동공학회논문집
• /
• 제22권8호
• /
• pp.756-762
• /
• 2012

A method of the low-frequency noise reduction in an enclosure by using an array of Helmholtz resonator is presented. An integral form of equation, which represents the acoustical coupling between the internal sound field and the resonator array, is formulated so that the boundary element method can be applied to solve the coupling problem. It is shown that the resonator array on the surface of the enclosure can be regarded as impedance patches on the boundary element. Experiments on a simple enclosure acoustically coupled with an array of resonators are conducted to verify the method. The predicted noise reduction by the boundary element method shows good agreement with the measured one. The effects of the resistance of resonators as well as the number of resonators on the noise reduction are demonstrated. As a practical example, the presented method is applied to the payload fairing of a space launcher with resonator arrays. It is demonstrated that the resistance of resonators affects significantly the required number of resonators to achieve a desired noise reduction.