• Title/Summary/Keyword: Cutoff frequency

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The Design of A CMOS Gm-C Lowpass Filter with Variable Cutoff Frequency for Direct Conversion Receiver (직접변환 수신기용 가변 차단주파수특성을 갖는 CMOS Gm-C 저역통과필터 설계)

  • Bang, Jun-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.8
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    • pp.1464-1469
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    • 2008
  • A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is $1.5MHz{\sim}3.5MHz$ and the gain control range is $-2.8dB{\sim}2.6dB$. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using $2.5V-0.25{\mu}m$ CMOS processing parameter.

The reconstruction of Structure Velocity Field Using Nearfield Acoustic Holography (근접음장 음향 홀로그래피를 이용한 평판내의 속도분포 예측)

  • 권오훈;이효근;박윤식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.2
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    • pp.251-259
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    • 1994
  • Nearfield acoustic holography is known as a powerful tool to study sound radiation from a structure. In this work, the so called backward propagation of sound pressure field is studied to obtain the structure velocity distribution. The results, which were obtained using FFT algorithms, are presented for a finite plate excited at the frequencies above and below coincidence. These results illustrate the effect of stand-off distance and noise. An optimum cutoff frequency in wavenumber domain was suggested to reduce the effects of evanescent wave in the backward propagation. The experimental results were also included for a plate to demonstrate the effectiveness of the suggested cutoff frequency. The optimum cutoff frequency to exclude the unwanted noise in the process of reconstruction of the velocity field gives the good results in both simulations and experiments.

High Frequency Noise Reduction in ECG using a Time-Varying Variable Cutoff Frequency Lowpass Filter (시변 가변차단주파수 저역통과필터를 이용한 심전도 고주파 잡음의 제거)

  • 최안식;우응제;박승훈;윤영로
    • Journal of Biomedical Engineering Research
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    • v.25 no.2
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    • pp.137-144
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    • 2004
  • ECG signals are often contaminated with high-frequency noise such as muscle artifact, power line interference, and others. In the ECG signal processing, especially during a pre-processing stage, numerous noise removal techniques have been used to reduce these high-frequency noise without much distorting the original signal. This paper proposes a new type of digital filter with a continuously variable cutoff frequency to improve the signal quality This filter consists of a cutoff frequency controller (CFC) and variable cutoff frequency lowpass filter (VCF-LPF). From the noisy input ECG signal, CFC produces a cutoff frequency control signal using the signal slew rate. We implemented VCF-LPF based on two new filter design methods called convex combination filter (CCF) and weight interpolation fille. (WIF). These two methods allow us to change the cutoff frequency of a lowpass filter In an arbitrary fine step. VCF-LPF shows an excellent noise reduction capability for the entire time segment of ECG excluding the rising and falling edge of a very sharp QRS complex. We found VCF-LPF very useful and practical for better signal visualization and probably for better ECG interpretation. We expect this new digital filter will find its applications especially in a home health management system where the measured ECG signals are easily contaminated with high-frequency noises .

A ladder type 8th-order elliptic low-pass filter using transadmittance amplifiers (트랜스어드미턴스 증폭기를 이용한 사다리형 8차 일립틱 저역-통과 여파기)

  • 김종필;박지만;정원섭
    • Journal of the Korean Institute of Telematics and Electronics C
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    • v.35C no.8
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    • pp.42-51
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    • 1998
  • An 8th-order elliptic low-pass filter with cutoff frequency of 3.13kHz is presented. The design procedure is based on teh 1/s impedance transformation which is applied to a minimum capacitor LC ladder network.The tranformed network is implemented with resistors and high Q frequency-dependent negative resistors (FDNR's). The high Q FDNR is realized with two transadmittance amplifiers. Detailed SPICE simulations show that the iflter has pass-band ripple of 0.18dB, stop-band attenuation over 100dB, cutoff frequency of 3.13 khz, and cutoff frequency temperature coefficient of 8.5ppm/.deg. C at supply voltage of .+-.5V.

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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.

Gate-Length Dependent Cutoff Frequency Extraction for Nano-Scale MOSFET (Nano-Scale MOSFET의 게이트길이 종속 차단주파수 추출)

  • Kim, Joung-Hyck;Lee, Yong-Taek;Choi, Mun-Sung;Ku, Ja-Nam;Lee, Seong-Heam
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.42 no.12
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    • pp.1-8
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    • 2005
  • The gate length-dependence of cutoff frequency is modeled by using scaling parameter equations of equivalent circuit parameters extracted from measured S-parameters of Nano-scale MOSFETs. It is observed that the modeled cutoff frequency initially increases with decreasing gate length and then the rate of increase becomes degraded at further scale-down. This is because the extrinsic charging time slightly decreases, although the intrinsic transit time greatly decreases with gate length reduction. The new gate length-dependent model will be very helpful to optimize RF performances of Nano-scale MOSFETs.

LC Filter Design Considering Voltage Control Performance and PWM Inverter Size for Dynamic Voltage Restorers (동적전압보상기(DVR)의 전압제어특성과 인버터 용량을 고려한 출력필터 설계방법)

  • Kim Hyosung;Kim Jang-Hwan;Sul Seung-Ki
    • The Transactions of the Korean Institute of Power Electronics
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    • v.10 no.2
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    • pp.117-123
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    • 2005
  • The cutoff frequency of a LC output filter for Dynamic Voltage Restorers (DVR) limits the control bandwidth of a DVR system while it attenuates the inverter switching ripples. For a selected cutoff frequency of a LC output filter, infinite number of L-C combinations is possible. Although different L-C combination has different filter characteristics, the filter design on L-C combination has been depended on field experiences without clear analysis. This paper proposes a design criterion and design examples for the L-C filter combination considering the control characteristics and the size of DVRs. An experimental DVR system based on the proposed LC output filter design methodology is built and tested.

Mixed Noise Reduction Filters for CR Images (CR X선 영상의 복합잡음 감소에 관한 연구)

  • Min, Jung-Whan;Jeong, Hea-Won;Kim, Jung-Min
    • Journal of radiological science and technology
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    • v.30 no.1
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    • pp.1-6
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    • 2007
  • This study is to decrease compound noise in x-ray films. This study compared Signal to noise ratio(SNR), Peak signal to noise ratio(PSNR), Mean square error(MSE) to surface of the earth. In addition, we evaluated noise elimination effect according to the kernel size of Median filter. This experiments show that some filters are useful by finding image that is near in circle image comparing circle picture with each processed picture. In noise power value, when cutoff frequency was compared with other filters of cutoff frequency. Cutoff frequency of $2/3\pi{\sim}3/4\pi$ is good and it shows good SNR and PSNR. Therefore, it can display high filter effect. As Median Filter's Kernel size grows SNR value gets bigger, which shows better filter effect. Most pictures are distorted after filter application in medical treatment image. It is important to keep spatial resolution in most medical images. Visual estimation as well as quantitative indicators should be necessary for a better image.

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Identifying Frication and Aspiration Noise in the Frequency Domain: The Case of Korean AIveolar Lax Fricatives

  • Yoon, Kyu-Chul
    • Phonetics and Speech Sciences
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    • v.1 no.2
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    • pp.105-110
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    • 2009
  • This paper introduces the technique of semi-automatically identifying different types of noise in the frequency domain. Given the lower cutoff frequency of the frication noise, and a user-specified constant, the technique identifies the boundary between the frication and aspiration noise in a Korean lax fricative followed by the vowel /a/ by comparing the upper and lower sums of energy with respect to the cutoff frequency. The user-specified constant can be adjusted for different speakers. When the technique was applied to distinguish the two types of noise of Korean lax fricatives from the same speaker, the average and standard deviation of the difference between the manually inserted boundaries and the automatically inserted boundaries were 2.67ms and 1.80ms respectively.

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The inference of minimum temperature of the solar atmosphere from the FISS data

  • Moon, Byeongha;Chae, Jongchul;Kang, Juhyeong;Oh, Suyeon
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.58.1-58.1
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    • 2018
  • In the solar atmosphere, below the region of temperature minimum, temperature decreases with height and above it, temperature increases with height. Therefore the inference of temperature minimum is a basis of the study about the solar atmosphere and heating problem. The temperature of the temperature minimum region can be inferred from acoustic cutoff frequency. According to a recent study the acoustic cutoff frequency is related to the peak frequency of the power spectrum the chromospheric three-minute velocity oscillations. Using this relationship, we infer the temperature of temperature minimum. The three minute velocity oscillation and its power spectrum are obtained for a pore observed with the Fast Imaging Solar Spectrograph (FISS) $H{\alpha}$ band. We present the inferred temperature and compare it with the temperature of Maltby model. We also investigate the effect of the inclination of magnetic field on the temperature minimum.

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