• Title/Summary/Keyword: Reference signals

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Identification of Flaw Signals Using Deconvolution in Angle Beam Ultrasonic Testing of Welded Joints (용접부 초음파 사각 탐상에서 디컨볼루션을 이용한 균열신호와 기하학적 반사신호의 식별)

  • Song, Sung-Jin;Kim, Jun-Young;Kim, Young-H.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.4
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    • pp.422-429
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    • 2002
  • The identification of ultrasonic flaw signals is a truly difficult task in the angle beam testing of welded joints due to non-relevant signals from the geometric reflectors such as weld roots and counter bores. This paper describes a new approach called "technique for identification of flaw signal using deconvolution(TIFD)" in order to identify the flaw signals in such a problematic situation. The concept of similarity function based on the deconvolution is introduced in the proposed approach. The "reference" signals from both flaws and geometric reflectors and test signals are acquired and normalized. The similarity functions are obtained by deconvolution of test signals with reference signals. The flaw signals could be identified by the patterns of similarity function. The initiative results show great potential of TIFD to distinguish notch comer signals from the geometric reflections.

A Robust Frequency-Domain Multi-Reference Narrowband Adaptive Noise Canceller (여러 개의 참고입력 신호를 사용하는 강인한 주파수 영역 협대역 잡음 제거기)

  • Kim, Seong-Woo;Seo, Ji-Ho;Ryu, Young-Woo;Park, Young-Cheol;Youn, Dae Hee
    • The Journal of the Acoustical Society of Korea
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    • v.34 no.2
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    • pp.163-170
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    • 2015
  • In this paper, it is shown that the performance of the frequency-domain multi-reference narrowband noise canceller is determined by the narrowband component to the broadband disturbance power ratio in the reference signals. To overcome this problem, a new narrowband ANC is proposed, where the update of the adaptive filter is determined based on SNR of the reference inputs being measured using the magnitude squared coherence (MSC) between the primary and the reference signals. Simulation results show that the proposed ANC has superior performance over the conventional one.

An acoustic echo canceler robust to noisy environment (잡음환경에 강건한 음향반향제거기)

  • 박장식;손경식
    • Proceedings of the IEEK Conference
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    • 1998.06a
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    • pp.623-626
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    • 1998
  • NLMS algorithm is degraded by the ambient noises and the near-end speech signals. In this paper, a robust acoustic echo cancellation algorithm is proposed. To enhance the echo cancellation performance, the step size of the proposed algorithm is normalized by the sum o fthe power of the reference signals and the primary signals. as results of comparing the excess mean square errors, it is shown that the proosed algorithm can enhance the performance of cancelling the echo signals. Some experiments, which is used multimedia personal computer, are carried out. As results of experiments, the proposed algorithm shows better performance than conventional ones.

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TOA-Based Ranging Method using CRS in LTE Signals (LTE 신호의 CRS를 이용한 TOA 기반 거리 측정 방법)

  • Kang, Taewon;Lee, Halim;Seo, Jiwon
    • Journal of Advanced Navigation Technology
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    • v.23 no.5
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    • pp.437-443
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    • 2019
  • In this paper, a new algorithm for the calculation of the range between an LTE base station (BS) and a user equipment (UE) using time-of-arrival (TOA) measurements of LTE signals is proposed. First, the cell identity (cell ID) of the received signal is acquired using the primary synchronization signal (PSS) and secondary synchronization signal (SSS) to identify the BS transmitted the signal. The proposed algorithm exploits the cell-specific reference signal (CRS), the reference sequence inserted in commercial LTE signals, to estimate the time delay using 2D cross-correlation. The obtained TOA estimations can be used to calculate the range employed from the known BS location. The performance of the proposed algorithm is evaluated with the experiment performed using real LTE signals transmitted from the commercial BS.

Color coding of MF(model failure) object using hybrid coding method in object based coding (객체기반 부호화에서 혼합형 부호화방식을 이용한 MF(Model Failure) 객체의 색신호 부호화)

  • 김동하;이지훈;고성제;이태원
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.5
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    • pp.45-51
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    • 1997
  • To trnsmit moving image signals by using an object vased coding technique at the rate of 8kbps~11kbps, it is very important to minimize the bit rates used for the compression of the color information of MF-objects. This paper proposes a hybrid coding method which uses the shpae adaptive coding method and the interframe reference method selectively. Gilge's shape adaptive orthogonal coidng method is utilized for shpae adaptive coding. The interfarame reference method approximates the low-passed signals of the image by gilge's shpae adaptive orthogonalization method and then refers the approximation error signals from the high frequency signal components of th eprevious frame. The proposed method achives the bit rates reduction of 17% compared to the gilge's shape adaptive orthogonalization method and 30% rduction compared to the shape adaptive DCT in average.

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A Study on the Ultrnsonic Distance Amplitude Characteristics Curve for Weld Defects Evaluation of Titanium Weld Zone (티타늄 용접부의 용접결함평가를 위한 초음파거리진폭특성곡선에 관한 연구)

  • Yi, Won;Park, Hee-Dong;Yun, In-Sik
    • Journal of the Korean Society of Safety
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    • v.23 no.4
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    • pp.7-12
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    • 2008
  • This study proposes integrity evaluation method of weld zone in titanium using titanium distance amplitude characteristics curve(TDACC) and ultrasonic signals. For these purposes, the ultrasonic signals for porosity defects of weld zone in titanium are acquired in the type of time series data and echo strength. 4 lines in the DACC indicated damage evaluation standard of weld zone in titanium. The acquired ultrasonic signals agree fairly well with the measured results of reference block and sensitivity block(defect location, bean1 propagation distance, echo strength, etc). The proposed TDACC in this study agree fairy well with the measured results of weld zone in titanium(weld defects as porosity). The proposed TDACC in this study can be used for integrity evaluation of weld zone in titanium.

Construction of Through Transmission Scanning System for Weld Defects Detection of Rail Weld Zone (레일용접부의 용접결함검출을 위한 투과주사시스템의 구축)

  • Yun, In-Sik
    • Journal of the Korean Society of Safety
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    • v.20 no.1 s.69
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    • pp.30-35
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    • 2005
  • This study proposes construction of through transmission for weld defects detection of rail weld zone from ultrasonic signals. For these purposes, the ultrasonic signals for defects(porosity and crack) of weld zone in rails are acquired in the type of time series data and echo strength. 6 lines in the distance amplitude characteristics curve(DACC) indicated damage evaluation standard of weld zone in rails. The acquired ultrasonic signals agree flirty well with the mesured results of reference block and sensitivity block(defect location beam propagation distance, echo strength, etc). The proposed construction of through transmission in this study can be used for weld defects detection of rail weld zone.

Improved Attenuation Estimation of Ultrasonic Signals Using Frequency Compounding Method

  • Kim, Hyungsuk;Shim, Jaeyoon;Heo, Seo Weon
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.430-437
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    • 2018
  • Ultrasonic attenuation is an important parameter in Quantitative Ultrasound and many algorithms have been proposed to improve estimation accuracy and repeatability for multiple independent estimates. In this work, we propose an improved algorithm for estimating ultrasonic attenuation utilizing the optimal frequency compounding technique based on stochastic noise model. We formulate mathematical compounding equations in the AWGN channel model and solve optimization problems to maximize the signal-to-noise ratio for multiple frequency components. Individual estimates are calculated by the reference phantom method which provides very stable results in uniformly attenuating regions. We also propose the guideline to select frequency ranges of reflected RF signals. Simulation results using numerical phantoms show that the proposed optimal frequency compounding method provides improved accuracy while minimizing estimation bias. The estimation variance is reduced by only 16% for the un-compounding case, whereas it is reduced by 68% for the uniformly compounding case. The frequency range corresponding to the half-power for reflected signals also provides robust and efficient estimation performance.

Differential- Average Transmitted Reference Ultra Wide Band Communication System (Differential - Average Transmitted Reference Ultra Wide Band 통신 시스템)

  • Kim, Se-Kwon;Kim, Jae-Woon;Shin, Yo-An;Roh, Don-Suk
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.1C
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    • pp.81-89
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    • 2009
  • We propose a D-ATR UWB (Differential-Average Transmitted Reference Ultra Wide Band) system based on impulse radio. The TR-UWB systems including traditional TR (Transmitted Reference) and ATR (Average TR), exhibit a problem of reduced data rate, since reference signals are additionally transmitted. To tackle this issue, the transmitter of the proposed D-ATR system employs a differential coding like the conventional D-TR system. In addition, the receiver of the proposed system has the structure that can improve signal-to-noise ratio of the reference template used in the correlation process, by recursively averaging the received reference signals like the conventional ATR system. The simulation results in the IEEE 802.15.4a UWB multipath channel models reveal that the proposed D-ATR system achieves much better bit error rate performance as compared to the conventional D- TR system.

The torque distribution algorithm of driving wheels using 2D joystick in the electric wheel-chair (2D 조이스틱에 기반한 전동휠체어의 토크 분배 알고리즘)

  • Park, Sung-Jun;Park, Je-Wook;Kim, Jang-mok
    • Proceedings of the KIPE Conference
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    • 2013.07a
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    • pp.212-213
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    • 2013
  • This paper proposes the algorithm of torque distribution in the electric wheel-chair using 2D joystick for drive safety. For the accurate driving performance, the specific and precise torque distribution is required in both wheels depending on signals of X-Y axis that is generated from 2D joystick. The signals of X-Y axis from joystick are transformed into the propulsion force and the torque reference. And the torque reference can be generated through the dynamic model of wheel-chair. The optimal dynamic characteristics of the electric powered wheelchair can be obtained, by adjusting the sensitivity coefficients of propulsion force and torque reference, In addition, the system takes smooth and stable control characteristics due to continuous torque output at all directions of joystick. The several simulations verify the usefulness of the proposed algorithm about torque distribution.

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