• Title/Summary/Keyword: HPF (high pass filter)

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Noise Reduction Method in consideration of bandwidth of Low Pass Filter (저역통과 필터의 대역폭을 고려한 잡음 제거 방법)

  • Yang, Jeong-Ju;Jang, Won-Woo;Kwak, Boo-Dong;Kang, Bong-Soon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2010.05a
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    • pp.157-159
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    • 2010
  • Most digital cameras apply a Charge Coupled Device(CCD) Sensor or a Complementary Metal Oxide Semiconductor(COMS) Sensor. And the images captured these sensors include unwanted noises. In this paper, we proposed a method of the Noise Reduction(NR) about noise reduction or recovery in the image. The proposed NR method is related to Bandwidth of the Low Pass Filter(LPF). For improvement of NR, we were changing the filter coefficient of the LPF. The results of simulations with various filter coefficients, [1 2 1] in the LPF and [-1 2 -1] in the High Pass Filter(HPF) have ideal frequency bandwidth and high performance. We proposed a filter coefficient [1 2 1] and [-1 2 -1] in the LPF and the HPF respectively.

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Phase Image of Susceptibility Weighted Image Using High Pass Filter Improved Uniformity (위상영상 획득 시 영상의 균일도 향상을 위한 high pass filter의 적용)

  • Lee, Ho-Beom;Choi, Kwan-Woo;Son, Soon-Yong;Na, Sa-Ra;Lee, Joo-Ah;Min, Jung-Whan;Kim, Hyun-Soo;Ma, Sang-Chull;Jeong, Yeon-Jae;Jeong, Yeon-Gyu;Yoo, Beong-Gyu;Lee, Jong-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.11
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    • pp.6702-6709
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    • 2014
  • In this study, a susceptibility weighted image (SWI) showed a wrapped phase and a non-uniformity of the rapid susceptibility difference. Consequently, the bandwidth limits at low frequency were improved by applying HPF. From November 2013 to March 2014, a three-dimensional SWI was obtained from patients and compared with the existing images and HPF phase images. The maximum and minimum signal intensity differences and non-uniformity were analyzed. As a result, a high pass filter before and after applying the maximum and minimum of the signal intensity difference was decreased by 274.16% (498.98), and the non-uniformity was decreased by 439.55% (19.83). After applying the HPF, a comparison with the existing phase images revealed the HPF phase images to have high signal and image uniformity of the SWI image. A high pass filter method can effectively remove the non-uniformity and improve the overall image quality.

Turbulence-tolerant Manchester On-off Keying Transmission for Free-space Optical Communication

  • Qian-Wen Jing;Pei-Zheng Yu;Han-Lin Lv;Yanqing Hong
    • Current Optics and Photonics
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    • v.7 no.4
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    • pp.345-353
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    • 2023
  • We propose a turbulence-tolerant Manchester on-off keying (M-OOK) transmission for free-space optical (FSO) communication. At the transmitter end, a M-OOK signal featuring a spectrum with low-frequency components absent is modulated and transmitted into a turbulent channel. At the receiver end, a low-pass filter (LPF) -based adaptive-threshold decision (ATD) with LPF-extracted channel-state information (CSI) and a high-pass filter (HPF)-based fixed-threshold decision (FTD) are employed to compensate for the effects of turbulence, owing to the low-frequency spectral characteristics of the turbulent channel. The performance of LPF-based ATD and HPF-based FTD are evaluated for various cutoff frequencies for the LPF and HPF. Besides, the proposed M-OOK transmission is compared to conventional non-return-to-zero OOK (NRZ-OOK) for different data rates. The proposed technique is verified in simulation. The simulation results show that the proposed M-OOK detection with optimized cutoff frequencies of LPF and HPF has better bit-error-rate (BER) performance compared to NRZ-OOK, and it is close to the theoretical ATD with the knowledge of precise CSI under various degrees of turbulence effects.

Research About Filter Association and Clinical Effect Noise Reduction of Digital Medical Imaging System (디지털 의료영상에서 Noise감소를 위한 필터조합과 임상적 효과에 관한 연구)

  • Min, Jung-Whan;Kim, Jung-Min;Jeong, Hea-Won;Ok, Chi-Il
    • Journal of radiological science and technology
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    • v.30 no.4
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    • pp.329-334
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    • 2007
  • This paper is for investigation of the noise reduction effect all 20 filters by combining Low Pass Filter(LPF) 5 kinds, High Pass Filter(HPF) 4 kinds, Median Filter(MF) 11 kinds. Noise is added to reduce noise and minimize the quality degradation in medical imaging system. We also compared Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE) for all the combinations of different filters. As a result, noise decrease appeared in the LPF3*3#1 + HPF3*3#1 + Vertical3*1 of highest filter. We confirmed noise reduction effect by applying the proposed filter combination in many fields of medical imaging applications.

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Implementation of Sharpness-Enhancement Algorithm based on Adaptive-Filter for Mobile-Display Apparatuses (Mobile Display 장치를 위한 Adaptive-Filter 기반형 선명도 향상 알고리즘의 하드웨어 구현)

  • Im, Jeong-Uk;Song, Jin-Gun;Lee, Sung-Jin;Min, Kyoung-Joong;Kang, Bong-Soon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2007.10a
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    • pp.109-112
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    • 2007
  • Definition-Enhancement of the digitalized image has been being made researches continuously due to application a camera to a mobile-apparatus and the advent of a digital camera. In particular, the inputted image from a sensor goes through the process of ISP(Image Signal Process) prior to output as a visual image. The high-frequency components are offset by LPF(Low Pass Filter) that eliminates the noise of high spatial-frequency at the moment. In this paper, we propose an algorithm that outputs more vivid image by using adaptive-HPF(High Pass Filter) that has apt coefficients for diverse conditions of an image edge, nevertheless we do not employ any Edge-Detection algorithm to enhance a blurred image.

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Eliminating Method of Estimated Magnetic Flux Offset in Flux based Sensorless Control of PM Synchronous Motor using High Pass filter with Variable Cutoff Frequency (모터 운전 주파수에 동기화된 차단주파수를 갖는 HPF(High pass filter)를 적용한 영구자석 동기전동기의 자속기반 센서리스 제어의 추정 자속 DC offset 제거 기법)

  • Kang, Ji-Hun;Cho, Kwan-Yuhl;Kim, Hag-Wone
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.3
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    • pp.455-464
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    • 2019
  • The sensorless control based on the flux linkage of PM synchronous motors has excellent position estimation characteristics at low speeds. However, a limitation arises because the integrator of flux estimator is saturated by the DC offset generated during the analog to digital conversion(ADC) process of the measured current. In order to overcome this limitation, HPF with a low cutoff frequency is used. However, the estimation performance is deteriorated (Ed- the verb deteriorate already includes the meaning of 'problem') at high speed due to the low cutoff frequency, and increasing the cutoff frequency of the HPF induces further problems of phase leading and initial starting failure at low speeds. In this paper, the cutoff frequency of HPF was synchronized to the operation frequency of the motor: at low speeds the cutoff frequency was set to low in order to reduce the phase leading of the estimated flux, and at high speeds it was set to high to raise the DC offset removal performance. As a result, the operating range was increased by 200%. Furthermore, a phase compensation algorithm is proposed to reduce the phase leading of the HPF to less than 1.5 degrees over the full operating range. The proposed sensorless control algorithm was verified by experiment with a PM synchronous motor for a washing machine.

Synthetic-heterodyne interferometry for measuring extremely small amplitude of mechanical vibrations (미소 진폭 기계진동의 Synthetic-heterodyne 간섭측정에 대한 연구)

  • Kang, Seong-Gu;La, Jong-Pil;Yoon, Hee-Sun;Park, Kyi-Hwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.373-378
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    • 2007
  • On the homodyne interferometers, high pass filter(HPF) is usually used to remove the electrical noise in the interferent signal. Heterodyne interferometer has modulating frequency is shifted in the frequency region where the electrical noise effect is minimized by HPF effect. However, on the homodyne interferometer, the interferent DC-component of homodyne interferometer is unfortunately eliminated by using a HPF because its shifted frequency does not exist. Moreover, this effect is more serious the vibration amplitude is smaller. So, when unstable interferent signals via HPF are demodulated, a velocity is distorted. In this work, the mathematical explanation for the distortion of the homodyne interferent signal using the HPF is given. New synthetic heterodyne LDV based on the homodyne interferometer by exciting the reference mirror is proposed for the cancellation of the distortion. The optimum excitation condition of the mirror to compensate the distortion is discussed. The numerical simulation using the commercial MATLAB code is provided to show the effect of the proposed synthetic heterodyne LDV. The experimental results are also given and the effect of the proposed LDV is discussed.

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Design and Fabrication of Diplexer using Lumped Elements (집중 소자를 이용한 다이플렉서 설계 및 제작)

  • Park, Yong-Wook
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.1
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    • pp.9-14
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    • 2012
  • In this study, the diplexer used a separator or a combine of signals was designed and its characteristics were investigated. The diplexer consists of two fixed tuned bandpass filter such as low pass filter(LPF) and high pass filter(HPF) sharing a common part and was simulated. The diplexer with micro-strip structure was fabricated. The LPF of diplexer has insertion loss of -0.4 dB, return loss of -30 dB and 1.6 GHz cut-off frequency and HPF has insertion loss of -0.8 dB, return loss of -30 dB and 1.9 GHz cut-off frequency, respectively.

New Design Approach for Grid-Current-Based Active Damping of LCL Filter Resonance in Grid-Connected Converters

  • Gaafar, Mahmoud A.;Dousoky, Gamal M.;Ahmed, Emad M.;Shoyama, Masahito;Orabi, Mohamed
    • Journal of Power Electronics
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    • v.18 no.4
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    • pp.1165-1177
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    • 2018
  • This paper investigates the active damping of grid-connected LCL filter resonance using high-pass filter (HPF) of the grid current. An expression for such HPF is derived in terms of the filter components. This expression facilitates a general study of the actively damped filter behavior in the discrete time domain. Limits for the HPF parameters are derived to avoid the excitation of unstable open loop poles since such excitation can reduce both the damping performance and the system robustness. Based on this study, straightforward co-design steps for the active damping loop along with the fundamental current regulator are proposed. A numerical example along with simulation and experimental results are presented to verify the theoretical analyses.

Fully Analog ECG Baseline Wander Tracking and Removal Circuitry using HPF Based R-peak Detection and Quadratic Interpolation

  • Nazari, Masoud;Rajeoni, Alireza Bagheri;Lee, Kye-Shin
    • Journal of Multimedia Information System
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    • v.7 no.3
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    • pp.231-238
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    • 2020
  • This work presents a fully analog baseline wander tracking and removal circuitry using high-pass filter (HPF) based R-peak detection and quadratic interpolation that does not require digital post processing, thus suitable for compact and low power long-term ECG monitoring devices. The proposed method can effectively track and remove baseline wander in ECG waveforms corrupted by various motion artifacts, whereas minimizing the loss of essential features including the QRS-Complex. The key component for tracking the baseline wander is down sampling the moving average of the corrupted ECG waveform followed by quadratic interpolation, where the R-peak samples that distort the baseline tracking are excluded from the moving average by using a HPF based approach. The proposed circuit is designed using CMOS 0.18-㎛ technology (1.8V supply) with power consumption of 19.1 ㎼ and estimated area of 15.5 ㎟ using a 4th order HPF and quadratic interpolation. Results show SNR improvement of 10 dB after removing the baseline wander from the corrupted ECG waveform.